Fmds0102 Earthquakes

July 2011Page 1 of 85

EARTHQUAKES

Table of ContentsPage

1.0 SCOPE ................................................................................................................................................... 31.1 Changes ............................................................................................................................................ 3

2.0 LOSS PREVENTION RECOMMENDATIONS ....................................................................................... 32.1 Introduction ...................................................................................................................................... 32.2 Earthquake Considerations for New Construction .......................................................................... 3

2.2.1 Site Considerations ............................................................................................................... 32.2.2 Design Standards .................................................................................................................. 32.2.3 Other New Design Considerations ........................................................................................ 4

2.3 Earthquake Considerations for Existing Facilities ........................................................................... 42.4 Occupancy, Equipment and Processes ........................................................................................... 52.5 Protection ......................................................................................................................................... 52.6 Operation and Maintenance ............................................................................................................ 52.7 Human Element ............................................................................................................................... 6

2.7.1 Earthquake Emergency Response Team .............................................................................. 63.0 SUPPORT FOR RECOMMENDATIONS ............................................................................................... 6

3.1 General ............................................................................................................................................ 64.0 REFERENCES ....................................................................................................................................... 6

4.1 FM Global ........................................................................................................................................ 64.2 Others .............................................................................................................................................. 6

APPENDIX A GLOSSARY OF TERMS ........................................................................................................ 7APPENDIX B DOCUMENT REVISION HISTORY ...................................................................................... 11APPENDIX C SUPPLEMENTAL INFORMATION ...................................................................................... 13

C.1 Earthquakes and Seismicity ......................................................................................................... 13C.1.1 General ............................................................................................................................... 13C.1.2 Faults .................................................................................................................................. 14C.1.3 Seismic Waves ................................................................................................................... 14C.1.4 Ground Motion .................................................................................................................... 16C.1.5 Earthquake MeasurementMagnitude ................................................................................ 17C.1.6 Earthquake MeasurementIntensity ................................................................................... 17

C.2 Site Specific Geologic Considerations .......................................................................................... 19C.3 Building Codes .............................................................................................................................. 20

C.3.1 Building Code Design Philosophy ...................................................................................... 20C.3.2 Building Code Provisions .................................................................................................... 21C.3.3 Meeting and Exceeding Minimum Building Code Provisions ............................................. 22

C.4 Earthquake Performance of Buildings .......................................................................................... 29C.4.1 General ............................................................................................................................... 29C.4.2 Foundations ........................................................................................................................ 30C.4.3 Generic Building Types ....................................................................................................... 31C.4.4 Effects of Building-Specific Features on Generic Building Performance ........................... 34

C.5 Earthquake Performance of Contents .......................................................................................... 35C.6 Emergency Action .......................................................................................................................... 35C.7 Maps of FM Global Earthquake Zones ......................................................................................... 36

C.7.1 Scope ................................................................................................................................... 36C.7.2 General ................................................................................................................................ 36

FM GlobalProperty Loss Prevention Data Sheets 1-2

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C.7.3 Earthquake Zone Maps ...................................................................................................... 43

List of FiguresFig. 1. Types of fault movement. ................................................................................................................ 15Fig. 2. Earthquake zones, North America, for engineering purposes ......................................................... 44Fig. 2A. Earthquake zones, United States for engineering purposes ......................................................... 45Fig. 2A. (part 2) Western United States. ...................................................................................................... 46Fig. 2A. (part 3) Midwest United States ....................................................................................................... 47Fig. 2A. (part 4) Eastern United States ........................................................................................................ 48Fig. 2A. (part 5) California/Nevada. .............................................................................................................. 49Fig. 2B. Earthquake zones, Canada, for engineering purposes ................................................................. 50Fig. 2B. (part 2) Southeast Canada .............................................................................................................. 51Fig. 2B. (part 3) Southwest Canada ............................................................................................................. 52Fig. 2B. (part 4) Northwest Canada .............................................................................................................. 53Fig. 2C. Earthquake zones, Alaska, for engineering purposes ................................................................... 54Fig. 2D. Earthquake zones, Mexico, for engineering purposes .................................................................. 55Fig. 3. Earthquake zones, South America, for engineering purposes ........................................................ 56Fig. 3A. Earthquake zones, Central America, for engineering purposes .................................................... 57Fig. 3B. Earthquake zones, northern South America and Caribbean, for engineering purposes .............. 58Fig. 3C. Earthquake zones, southern South America, for engineering purposes ...................................... 59Fig. 4. Earthquake zones, Africa, for engineering purposes ....................................................................... 60Fig. 5. Earthquake zones, Europe, for engineering purposes .................................................................... 61Fig. 5A. Earthquake zones, Eastern Europe, for engineering purposes ..................................................... 62Fig. 5A. (part 2) ............................................................................................................................................ 63Fig. 5A. (part 3) ............................................................................................................................................. 64Fig. 5B. Earthquake zones, Portugal, Spain and Gibraltar, for engineering purposes ............................... 65Fig. 5C. Earthquake zones, France, Monaco, Belgium, Netherlands and Andorra,

for engineering purposes ............................................................................................................... 66Fig. 5D. Earthquake zones, Germany, Liechtenstein, Luxemburg and Switzerland,

for engineering purposes ............................................................................................................... 67Fig. 5E. Earthquake zones, Italy, San Marino and Vatican City, for engineering purposes ....................... 68Fig. 5F. Earthquake zones, Czech Republic, Austria and Slovenia, for engineering purposes ................. 69Fig. 5G. Earthquake zones, Hungary, Slovakia, Croatia, Serbia, Montenegro, Bosnia &

Herzegovina, for engineering purposes .......................................................................................... 70Fig. 6 Earthquake zones, Asia, for engineering purposes ........................................................................... 71Fig. 6. (part 2) Earthquake zones, West Asia, for engineering purposes ................................................... 72Fig. 6. (part 3) Earthquake zones, Central Asia, for engineering purposes ............................................... 73Fig. 6. (part 4). Earthquake zones, East Asia, for engineering purposes ................................................... 74Fig. 7. Earthquake zones, China and Mongolia, for engineering purposes ............................................... 75Fig. 7. (part 2) Eastern China and Mongolia, for engineering purposes ...................................................... 76Fig. 8. Earthquake Zones, Oceania, for engineering purposes .................................................................. 77Fig. 8. (part 2) ............................................................................................................................................... 78Fig. 8A. Earthquake zones, Australia, for engineering purposes ................................................................ 79Fig. 8A (part 2) Earthquake zones, Australia, for engineering purposes .................................................... 80Fig. 8A (part 3) Earthquake zones, Australia, for engineering purposes .................................................... 81Fig. 8A (part 4) Earthquake zones, Australia, for engineering purposes ..................................................... 82Fig. 8B. Earthquake zones, New Zealand, for engineering purposes ........................................................ 83Fig. 8C. Earthquake zones, Taiwan, for engineering purposes .................................................................. 84Fig. 8D. Earthquake zones, Hawaii, for engineering purposes ................................................................... 85

List of TablesTable 1. Modified Mercalli Intensity Scale, 1956 Version ............................................................................ 18Table 2. Site Classification from the 2003 International Building Code Based on Soil Type ...................... 20Table 2A. Approximate Allowable Capacities vs. Earthquake Loading for a Single Post-Installed

Concrete Expansion or Wedge Anchor in 2500 psi (17.2 MPa) Normal Weight Concrete1 ...... 28Table 3. Data Sheet 1-2 Seismic Zoning Summary ..................................................................................... 39

1-2 EarthquakesPage 2 FM Global Property Loss Prevention Data Sheets

2000-2011 Factory Mutual Insurance Company. All rights reserved.

1.0 SCOPEThe text of this data sheet is limited to general discussion of the subject with references as necessary madeto other publications covering certain complex technical areas. Loss examples and recommendations areincluded.

1.1 ChangesJuly 2011. Made the following changes related to earthquake zones in Central Asia and Africa:

Revised FM Global earthquake zones in the Central Asian countries of Bangladesh, Bhutan, China, India,Kazakhstan, Kyrgyzstan, Mongolia, Nepal, North Korea, Pakistan, Russia (east of 50 longitude), SouthKorea, Tajikistan, Turkmenistan, and Uzbekistan; and in the African countries of Algeria, Burundi,Democratic Republic of the Congo, Djibouti, Eritrea, Ethiopia, Kenya, Libya, Malawi, Morocco and WesternSahara (including Ceuta and Melilla), Mozambique, Rwanda, Somalia, Sudan, Tanzania, Tunisia, Uganda,Zambia, and Zimbabwe.

The changes have been documented in Table 3 and in maps showing the rezoned areas including Figure 4 (Africa); Figure 5 (Europe); Figure 5A (Eastern Europe); Figure 5A, Part 3 (Middle East); Figure 6 (Asia); Figure 6, Part 2 (West Asia); Figure 6, Part 3 (Central Asia); Figure 6, Part 4 (East Asia); Figure 7 (Western China and Mongolia); Figure 7, Part 2 (Eastern China and Mongolia); and Figure 8 (Oceania).

Confirmed, and documented in Table 3, that no change to the previous FM Global earthquake zones isneeded for the Central Asian country of Sri Lanka; and for the African countries of Angola, Benin, Botswana,Burkina Faso, Cameroon, Central Africa Republic, Chad, Comoros (including Mayotte), Republic of theCongo, Cote dIvoire (Ivory Coast), Equatorial Guinea, Gabon, The Gambia, Ghana, Guinea, Guinea-Bissau, Lesotho, Liberia, Madagascar, Mali, Mauritania, Namibia, Niger, Nigeria, Sao Tome and Principe,Senegal, Sierra Leone, South Africa, Swaziland and Togo.

2.0 LOSS PREVENTION RECOMMENDATIONS

2.1 Introduction

Recommendations are applicable to FM Global 50-year through 500-year earthquake zones. Appendix C,Supplemental Information, provides further details regarding recommendations.

2.2 Earthquake Considerations for New Construction

2.2.1 Site Considerations2.2.1.1 Assess site seismic hazards and their consequences to facility operation during the initial site selectionto determine the earthquake-related risk and methods to reduce that risk.

2.2.1.2 Do not locate new construction on sites where the potential for earthquake-caused ground rupture,liquefaction, landslide, dam failure, etc. is significant.

2.2.2 Design Standards2.2.2.1 Have new buildings and equipment, piping-system bracing, mezzanines, nonstructural elements,etc., designed by an engineer registered to practice structural design in the jurisdiction in which the projectis located.

2.2.2.1.1 For locations in the United States, Puerto Rico, the Virgin Islands, and Guam, ensure designearthquake forces are in accordance with the requirements of SEI/ASCE 7 (ASCE 7), Minimum Design Loadsfor Buildings and Other Structures, Structural Engineering Institute/American Society of Civil Engineers, ora building code based on this standard (e.g., the International Building Code).2.2.2.1.2 Outside the geographical areas designated in Section 2.2.2.1.1, design buildings, and equipmentand content load-resisting elements and anchorage using the provisions of Section 2.2.2.1.1 and earthquakeacceleration parameters appropriate for the location. If these parameters are not available, use the valuesof SDS and SD1 provided below:

FM Global 50-year earthquake zone: SDS = 1.3 (g) SD1 = 0.8 (g)


Earthquakes 1-2FM Global Property Loss Prevention Data Sheets Page 3




Where:

SDS = the site (soil) adjusted, 5% damped, design spectral response acceleration at a short (0.2- second)period, expressed as a portion of the gravitational acceleration (g).

SD1 = the site (soil) adjusted, 5% damped, design spectral response acceleration at a period of 1 second,expressed as a portion of the gravitational acceleration (g).

2.2.2.1.3 Use only post-installed concrete anchors that are prequalified for seismic applications in accordancewith American Concrete Institute (ACI) Standard 355.2, Qualification of Post-Installed Mechanical Anchorsin Concrete, and designed in accordance with ACI 318, Building Code Requirements for Structural Concrete,Appendix D, or equivalent local building code. Design post-installed concrete anchors and establish qualitycontrol procedures (e.g., special inspection during installation) based on building code and manufacturersrequirements. For post-installed concrete anchors, use an embedment of at least 6 times the bolt diameter(6Db), anchor spacing of at least 8Db, and distance from concrete edges of at least 12Db, unless smallervalues are allowed by the manufacturer and the calculated capacity of the anchor is more than required.

See Appendix C for further information regarding post-installed concrete anchor bolts.

2.2.2.2 Use suction tanks that are FM Approved (see Appendix A for definition) to FM Approval StandardClass Number 4020/4021, and ensure their foundations are designed to resist the calculated seismic forceswithout sliding or rocking.

2.2.2.3 Ensure fire protection systems, including piping, fire pumps and fire pump controllers meet theearthquake protection requirements in FM Global Property Loss Prevention Data Sheet 2-8, EarthquakeProtection for Water-Based Fire Protection Systems.2.2.2.4 Ensure gravity tank installations meet all local code requirements, including earthquake provisions,with respect to the tank itself, tower, and foundation.

2.2.2.5 Follow provisions to prevent fire following earthquake, including pipe bracing, equipment anchorage,and seismic shut off valves, etc., in Data Sheet 1-11, Fire Following Earthquake.2.2.2.6 Design Maximum Foreseeable Loss (MFL) fire walls to meet the earthquake protection requirementsin Data Sheet 1-22, Maximum Foreseeable Loss.

2.2.2.7 Ensure earthquake requirements specific to certain occupancies/facilities that are contained in otherFM Global data sheets are met (see section 4.1 for references).

2.2.3 Other New Design Considerations2.2.3.1 Design vital buildings and equipment, such as hospital structures, fire stations, and fire protectionsuction tanks (as well as those critical to the facility, even if not considered essential by traditional buildingcode criteria) with increased seismic safety to resist damage and remain operational during and after anearthquake. Incorporate procedures to ensure quality design and construction, including peer review,submittal review, and frequent site observation by the engineer of record.

2.2.3.2 Where practical, equipment and piping that can leak fluid, corrosive gas, etc. if damaged should belocated so as to limit the consequences of the leak (e.g., away from cleanrooms, valuable and damageablestorage, etc.).

2.2.3.3 Ensure buildings housing on-premises fire services are earthquake-resistant and have very lightweightvehicle doors.

2.2.3.4 Provide a single common monolithic foundation pad to support interconnected equipment, such asdrivers and pumps.

2.2.3.5 When settlement would result in disorientation of equipment that must remain plumb:

a) Incorporate a self-contained manual leveling mechanism into the equipment.

b) Establish a contingency plan for achieving efficient realignment.



2.3 Earthquake Considerations for Existing Facilities2.3.1 Prior to making modifications to a structure (such as mounting heavy objects on or suspending themfrom roofs, removing braces, or cutting openings in walls), have the structure evaluated by a registeredstructural engineer.

2.3.2 Include requirements for earthquake anchorage of the equipment in specifications for new equipmentitems.

2.4 Occupancy, Equipment and Processes2.4.1 Keep heavier items on storage racks on the lower shelves or on pallets on the floor (but not in aisles).

2.4.2 Secure valuable storage kept on open shelves by installing a lip or horizontal barrier of appropriateheight on the shelf.

2.4.3 Chain or fasten valuable or vital equipment used or stored on workbenches to the supporting surface.Brace or anchor the benches themselves to limit movement.

2.4.4 Store hazardous chemicals in unbreakable containers and, when practical, at or near floor level. If glasscontainers must be used, locate them where the chemical would do the least harm in case of breakage. Ifpossible, place the glass container within a second, fixed container that is restrained from movement. Inaddition, store chemicals that would react violently with one another as far apart as practical.

2.4.5 Ensure dip tanks and other open containers for corrosive or flammable liquids have sufficient freeboardto prevent spillage from sloshing.

2.4.6 Equip hazardous liquid storage in tanks without permanent roofs with internal baffles to minimizedamage caused by sloshing of the contents.

2.4.7 Provide tanks that contain hazardous chemical liquids with trenches or diked areas to contain a possiblespill.

2.4.8 Where process pipes carry very expensive or hazardous liquids, or where pipe breakage would resultin extended interruption to production, take as many of the following precautions as is practical:

a) Provide seismic shutoff valves or seismic switch-operated shutoff systems.

b) Provide arrangements similar to that of sprinkler piping, including flexible couplings, flexibility acrossseismic joints and sway bracing. (Note: sway bracing should already have been provided as part of thedesign since restraint of piping is a requirement in building codes.)

c) Provide adequate clearance where the piping passes through walls and floors.

d) Consider flexible piping and welded, rather than threaded, connections

2.4.9 Provide an integrated seismic protection system that will withstand the effects of a severe earthquakeand function to shut down major equipment in a safe condition.

2.4.10 Provide a safe, remote shutoff for electrical service.

2.4.11 Avoid the use of automatic-starting process equipment.

2.5 Protection

2.5.1 Fire pumps should be diesel-powered and located in a structure that is earthquake-resistant. If pumpsare electric-powered, furnish an automatically activating emergency power supply and ensure it is properlyprotected against earthquakes.

2.6 Operation and Maintenance2.6.1 Have a qualified person inspect the following at least annually to detect damage and identify neededrepairs or maintenance:

a) Significant buildings and structures

b) Fire protection systems

c) Warehouse storage racks



d) Other significant equipment

2.7 Human Element

2.7.1 Earthquake Emergency Response TeamThis organization should be a part of the overall emergency response team (ERT).

2.7.1.1 Establish a comprehensive earthquake emergency plan to provide guidelines for control of hazards,fire safety, repairs, and salvage (see Appendix C for more information).

2.7.1.2 Assign emergency response team members specific duties relating to each action necessitated bythe earthquake emergency plan. Because of the possibilities of difficult access, general panic, and personalinjury, assign at least two people to each major duty.

2.7.1.3 Coordinate the plan with local authorities and conduct annual meetings and training of the earthquakeemergency response team.

2.7.1.4 In the emergency plan, include all shifts as well as periods when the plant is not fully staffed.

2.7.1.5 Keep emergency equipment, such as tools, firefighting equipment, portable electric generators, andmedical supplies, on hand in readily available locations. If practical, keep emergency equipment andsupplies, as well as food and communication equipment, in a separate, very lightweight or earthquake-resistant structure. Use this structure as the control center during an emergency.

3.0 SUPPORT FOR RECOMMENDATIONS

3.1 GeneralRefer to Appendix C, Supplemental Information, for general comments on recommendations.

4.0 REFERENCES

4.1 FM GlobalApproval Standard Class Number 1950, Approval Standard for Seismic Sway Brace Components forAutomatic Sprinkler SystemsApproval Standard Class Number 4020/4021, Approval Standard for Ground Supported, Flat Bottom SteelTanks for Fire Pump SuctionData Sheet 1-6, Cooling TowersData Sheet 1-11, Fire Following EarthquakesData Sheet 1-22, Maximum Foreseeable LossData Sheet 1-40, FloodData Sheet 2-8, Earthquake Protection for Water-Based Fire Protection SystemsData Sheet 2-0, Installation Guidelines for Automatic SprinklersData Sheet 3-2, Water Tanks for Fire ProtectionData Sheet 3-7, Fire Protection PumpsData Sheet 5-14, TelecommunicationsData Sheet 7-7/17-12, Semiconductor Fabrication FacilitiesData Sheet 7-54, Natural Gas and Gas PipingData Sheet 7-55, Liquefied Petroleum GasData Sheet 10-2, Emergency Response

4.2 OthersAmerican Concrete Institute (ACI). Building Code Requirements for Structural Concrete and Commentary.ACI 318.

American Concrete Institute (ACI). Qualification of Post-Installed Mechanical Anchors in Concrete andCommentary. ACI 355.2.American Water Works Association. Factory Coated Bolted Steel Tanks for Water Storage. Standard AWWAD103.



American Water Works Association. Welded Steel Tanks for Water Storage. Standard AWWA D100.Federal Emergency Management Agency (FEMA). Installing Seismic Restraints for Duct and Pipe. FEMA414/January 2004.

Federal Emergency Management Agency (FEMA). Installing Seismic Restraints for Electrical Equipment.FEMA 413/January 2004.

Federal Emergency Management Agency (FEMA). Installing Seismic Restraints for Mechanical Equipment.FEMA 412/December 2002.

Federal Emergency Management Agency (FEMA). Reducing the Risks of Nonstructural Earthquake Damage.FEMA 74/June 2009.

International Code Council, USA. International Building Code.International Conference of Building Officials, USA. Uniform Building Code.Mercalli, G. 1902. Earthquake intensity scale. Modified by H. Wood and F. Neuman, 1931, and Richter, 1956.

National Research Council of Canada. National Building Code of Canada.Structural Engineering Institute/American Society of Civil Engineers. Minimum Design Loads for Buildingsand Other Structures. Standard SEI/ASCE 7.

APPENDIX A GLOSSARY OF TERMSAcceleration: rate of change in velocity with respect to time resulting from earthquake ground motion.

Accelerometer: a seismograph designed to measure earth particle accelerations.

Active Fault: a fault that has experienced displacements in recent geological time (within the last11,000 years), and the potential for future displacement is great enough for concern.

Allowable Stress Design (ASD): a method of designing structural members such that computed stressesproduced by normal gravity design loads (e.g., the weight of the building and usual occupancy live loads)do not exceed allowable stresses that are typically below the elastic limit of the material (e.g., in steel theseare typically well below the yield point). Normal allowable stresses are commonly increased by a factor (oftena one-third increase is used) when design includes extreme environmental loads such as earthquakes. (Alsocalled working stress design or elastic design).

Alluvial Soil (Alluvium): soils carried and deposited by water, such as those found at the deltas of riversreaching lakes or oceans.

Amplitude: the distance that a point on the earths surface moves from its origin during each (ground)oscillation.

FM Approved: references to FM Approved in this data sheet mean the products or services have satisfiedthe criteria for FM Approvals. Refer to the Approval Guide, a publication of FM Approvals, for a completelisting of products and services that are FM Approved.

Attenuation: the decrease in seismic energy, or amplitude of seismic waves, with distance from its sourcethrough absorption and scattering.

Base Shear: total design lateral force or shear at the base of a building.Bearing Wall: when a wall carries floor or roof loads, this load-carrying wall is defined as a bearing wall. Ifonly supporting itself, it is termed a nonbearing wall.

Bond Beam: a horizontal course of U-shaped (lintel) masonry with steel reinforcement embedded in concretecore fill to provide structural integrity to a masonry wall.

Braced Frame: an essentially vertical truss system having bracing to resist lateral forces and in which themembers are subjected primarily to axial stresses.

Creep: fault movement without recorded earthquakes.Damping: the decreasing of ground or building earthquake motions due to friction generated within the earthscrust or within a building.



Dead Fault (Inactive): a fault that has shown no evidence of movement in recent geological time.Design Acceleration: a specific ground acceleration at a site; used for the earthquake-resistant design of astructure.

Design Earthquake Ground Motion: a specific seismic ground motion at a site; used for theearthquake-resistant design of a structure.

Design Spectra: a set of response spectrum (acceleration, velocity and/or displacement) used for design.Diaphragm, Horizontal: the wood sheathing, concrete slab or fill, or metal deck at a roof or floor capable oftransferring earthquake forces to vertical lateral force-resisting elements (e.g., shear walls, braced frames,or moment frames).

Displacement: change in (earth particle) position relative to former position, resulting from earthquake groundmotion or relative movement of two sides of a fault.

Diving Plates: the earths crustal rock masses driven downward by collision with other masses.Drift (Story Drift): relative movement between one floor and the floor or roof above it.Ductile Detailing: special requirements (usually in building codes) needed so that an element remains ductile.In concrete and masonry, for example, closely spaced hoops around longitudinal reinforcement confine theconcrete core so that it can still resist forces after being severely cracked.

Ductile Element: a (structural) element capable of sustaining large cyclic deformations and stresses(e.g., beyond the yield point) without any significant loss of strength.

Earthquake: a sudden motion in the earth caused by the abrupt release of energy in the earths lithosphere(crust and upper mantle).

Elastic: a mode of structural behavior in which a structure displaced by a force will return to its original stateupon release of the force.

Elastic Design: see allowable stress design.Epicenter: the point on the earths surface directly over the focus or hypocenter.

Equivalent Lateral Force Seismic Design Procedure: a simplified method of earthquake design in which asingle seismic response coefficient is determined and multiplied by the building mass to determine the designbase shear. The seismic response coefficient is based mainly on building characteristics (e.g., use, lateralforce-resisting system and natural period) and the design earthquake ground shaking at the site.

Essential Facility: a facility where buildings and equipment are intended to remain operational in the eventof extreme environmental loading from flood, wind, snow, or earthquakes.

Fault (see also active and dead faults): a fracture or fracture zone of the Earths crust along which therehas been movement of the sides relative to one another.

Focal Depth: the depth to the focus (hypocenter) below the earths surface.

Focus (Hypocenter): the point below the earths surface where an earthquake starts (always below groundsurface, presumably on a fault).

Frequency. The number of oscillations (cycles) in a second, expressed in Hertz. The frequency is the inverseof the period of a cyclic event.

Geologic Hazard: landsliding, liquefaction soils, or active faulting that, during an earthquake event, mayproduce adverse effects in structures.

Gravity (g): acceleration due to the earths gravity.Hypocenter: see focus.

Importance Factor: a factor used in building codes to increase, for example, the usual wind or earthquakedesign forces for important or essential structures, tending to make them more resistant to those phenomena.

Inactive Fault: see dead fault.



Inelastic: a mode of structural behavior in which a structure displaced by a force exhibits permanentunrecoverable deformation upon release of the force.

Intensity: a qualitative measure of the observed effects of an earthquake at a specific location or site(e.g., Modified Mercalli Intensity and Rossi-Forel Intensity).

Isoseismal Lines: lines separating areas on a map experiencing different seismic intensities.

Lateral Force-Resisting System: a structural system for resisting horizontal forces due, for example, toearthquakes or wind (as opposed to the vertical load-resisting system, which provides support against gravity).

Lateral Spread: landslides having a rapid, fluid-like flow that occur on mildly sloping sites due to liquefactionof soil.

Lift Slab Construction: a construction process whereby reinforced concrete floor and roof slabs are cast oneupon another, then lifted into place.

Liquefaction: water-saturated sands, silts, and other very loosely consolidated soils, when subject to seismicground motions, may be re-arranged, losing their supporting power, and behave as dense fluids (liquefied).

Load and Resistance Factor Design (LRFD): a method of designing structural members such that computedstresses produced by service design loads multiplied by load factors do not exceed the theoretical nominalmember strength multiplied by a strength reduction (resistance) factor. (Also called strength design orultimate strength design).

Long Period: more than a one-half second time period to complete one oscillation of ground motion or buildingvibration.

Magma: molten rock material within the earth.Magnitude: a quantitative measure of the total energy released by an earthquake independent of the placeof observation (commonly designated with M as in M6.6). Currently the most commonly used measureis the moment-magnitude (Mw). C. F. Richter devised the original magnitude scale (also known as the localmagnitude [ML]). Other magnitude scales are body and surface wave magnitudes (mb and MS, respectively).

Masonry: brick, stone, tile, or concrete block bonded together with mortar (with reinforcing steel, it is definedas reinforced masonry; without reinforcing steel it is defined as unreinforced masonry [URM]).

Mean Recurrence Interval: the average time between events (e.g., earthquakes of magnitude 7 on a givenfault).

Moment-Resisting Frame (Moment Frame): a vertical structural frame comprised of beams and columns inwhich the members and beam-column joints are capable of resisting lateral forces primarily by flexure (alsocalled a rigid frame).

Natural Period: a constant interval of time required for an oscillating body in free (i.e., unforced) vibrationto complete a cycle.

Non-Ductile Elements: elements lacking ductility or energy absorption capacity due to the lack of ductiledetailingthe element is able to maintain its strength only for smaller deflections and/or fewer cycles (bycomparison to ductile elements).

Peak Ground Acceleration (PGA): the maximum amplitude of recorded acceleration at ground level duringan earthquake.

Period: the interval of time, usually in seconds, required for an oscillating body to complete a cycle. The periodis the inverse of the frequency of a cyclic event.

Plasticity: The property of a soil (or other material) which allows it to deform continuously under a constantload and to retain its deformed shape when the load is removed.

Pounding: the collision of adjacent buildings during an earthquake due to insufficient lateral clearance.Resonance: an abnormally large response of a system having a natural vibration period to a stimulus ofthe same frequency.



Response Spectrum: a set of curves calculated from an earthquake accelerogram that plot maximumamplitudes of acceleration, velocity, or displacement of a single-degree-of-freedom oscillator as a functionof its period of vibration and damping.

Rigid Frame: see moment-resisting frame.Scarp: a line of cliffs caused by ground raising at a fault.Seiche: oscillations of confined bodies of water due to earthquake shaking.Seismic: pertaining to or produced by earthquake or earth vibrations.Seismic Design Category: A category used in building codes to classify buildings based on their use andthe expected seismic acceleration at a site. In the American Society of Civil Engineers Standard SEI/ASCE7, Mininmum Design Loads for Buildings and Other Structures, these are designated as Seismic DesignCategories A to F (not to be confused with Site Class A to F based on soil type). The building code provisionsfor a lower Seismic Design Category (e.g., Category A) are typically less restrictive than those for highercategories. Ordinary buildings at sites with small expected accelerations are in the lowest Seismic DesignCategory; essential facilities at sites with high expected accelerations are in the highest.

Seismic-Design-Load Effects: the actions (axial forces, shears, or bending moments) and deformationsinduced in a structural system due to a specified criteria (time history, response spectrum, or base shear)of seismic design ground motion.

Seismic-Design Loading: the prescribed criteria (time history, response spectrum, or equivalent static baseshear) of seismic ground motion to be used for the design of a structure.

Seismic Hazard: any physical phenomenon (e.g., ground shaking, ground failure) associated with anearthquake that may produce adverse effects on human activities.

Seismic Risk: the probability that social or economic consequences of earthquakes will equal or exceedspecified values at a site, at several sites, or in an area, during a specified exposure time.

Seismic Waves: three basic types originate from an earthquake, two of which travel through the rock withinthe earth while the third travels along the earths surface.

Seismic Zone: a generally large area within which seismic design requirements for structures are constant.Seismograph: an instrument for recording the motion of the earths surface as a function of time.Sensitive (Quick) Clay: a clay soil that has a very low strength when disturbed (e.g., by earthquake shaking)and so fails or flows.

Shear Wall: a wall designed to resist lateral (e.g., earthquake) forces parallel to the plane of the wall.Short Period: ground motion periods of less than 0.5 second (in some definitions 0.2 seconds or less).Sinkhole: an underground hole which develops when underground rocks that are water soluble to water(typically limestone) dissolve. Development of a sinkhole is a non-seismic occurrence, but collapse of theoverlying soils into the sinkhole may be hastened by an earthquake.

Snubbers: resilient and strong anchored blocks placed next to equipment to prevent earthquake forces frommoving it laterally.

Soft Story: a story of a building significantly less stiff than adjacent stories (some codes define this as a lateralstiffness 70% or less than that in the story above, or 80% of the average stiffness of the three stories above).

Strength Design: see load and resistance factor design.Subduction Zone: a region where one of the earths crustal plates descends beneath another crustal plate.Tectonics: forces or conditions within the earth that cause movements of the earths crust.

Tilt-Up Construction: reinforced concrete walls that are cast horizontally, usually on a concrete floor slab,then lifted (or tilted up) into place.

Tsunami: long period ocean waves, usually generated by large-scale seafloor displacements associated withlarge earthquakes or major submarine slides.

Ultimate Strength Design: see load and resistance factor design.



Unreinforced Masonry: masonry construction (e.g., bricks, concrete blocks) that does not incorporate steelreinforcement.

Velocity: the rate of change in (earth particle) displacement with respect to time resulting from earthquakeground motion.

Vertical Load-Resisting System: the structural system providing support against gravity (as opposed to thelateral force-resisting system, which resists horizontal forces from earthquakes or wind).

Working Stress Design: see allowable stress design.Yield Point: the stress at which there is a decided increase in the deformation or strain without a correspondingincrease in stress. The strain is inelastic resulting in permanent deformation.

APPENDIX B DOCUMENT REVISION HISTORYApril 2011. For the following countries in Europe, the Middle East, Asia and Africa, and near Australia:

Revised FM Global earthquake zones in Afghanistan, Armenia, Azerbaijan, Bahrain, Belarus, Brunei,Burma, Cambodia, Egypt, Georgia, Indonesia, Iran, Iraq, Kuwait, Laos, Malaysia, Moldova, Oman,Papua-New Guinea, Philippines, Russia (west of 50E longitude), Saudi Arabia, Singapore, SolomonIslands, Thailand, Ukraine, United Arab Emirates (UAE), Vietnam and Yemen. Revised Table 3 and mapsshowing the rezoned area including Figure 4 (Africa); Figure 5 (Europe); Figure 5A (Eastern Europe);Figure 5A, Part 2 (East Europe); Figure 5A, Part 3 (Middle East); Figure 6 (Asia); Figure 6, Part 2 (WestAsia); Figure 6, Part 3 (Central Asia); Figure 6, Part 4 (East Asia); Figure 8 (Oceania); and Figure 8A(Australia) to reflect the change.

Confirmed that no change to the previous FM Global earthquake zones is needed for Estonia, Finland,Latvia, Lithuania, Qatar and Timor-Leste, and revised Table 3 to reflect this.

April 2010. The following changes were made:

Revised FM Global earthquake zones for Australia. Revised the maps showing the rezoned area, includingFigure 6, Part 1 (Asia); Figure 8 (Oceania); and Figure 8A, Part 1 (Australia). Added Figures 8A, Parts2, 3, and 4 (Australia).

Revised Table 3 entries for Australia to reflect earthquake zone changes.

Revised Table 3 entries for Japan to reflect confirmation of current earthquake zones.

Modified Section 2.2.2.1.3 regarding post-installed concrete anchors.

Modified Section 2.2.2.2 regarding suction tanks.

Updated Section 4.0, References.

Updated Appendix A, Glossary of Terms

Revised Section C.3.3 regarding equipment/nonstructural component anchorage and post-installedconcrete anchors.

Revised terminology in Sections C.7.1 through C.7.3.

January 2009. Revised FM Global Earthquake Zones for Taiwan. Revised maps showing the rezoned areaincluding: Figure 6 (Asia), Figure 6-part 4 (East Asia), Figure 8 (Oceania) and Figure 8C (Taiwan). RevisedTable 3 to reflect the above change.

May 2008. Revised FM Global Earthquake Zones for the following countries/territories in Asia and Oceania:Bangladesh, Bhutan, China, India, Kazakhstan, Kyrgyzstan, Mongolia, Nepal, New Zealand, North Korea,Pakistan, Russia (east of 60E longitude), South Korea, Tajikistan, Turkmenistan and Uzbekistan. Confirmedthat no change to the previous FM Global Earthquake Zones is needed for Sri Lanka.

Revised maps showing, or overlapping into, the rezoned countries/territories identified above including: Figure2 (North America), Figure 5A Part 3 (Middle East), Figure 6 Part 1 (Asia), Figure 6 Part 2 (West Asia), Figure7 Parts 1 and 2 (China and Mongolia), Figure 8 (Oceania) and Figure 8B (New Zealand). The mapped areain Figure 6 Parts 1 and 2 has been revised from the previous version of this data sheet.



Added new maps: Figure 6 Part 3 (Central Asia) and Figure 6 Part 4 (East Asia). Deleted maps: Figure 7Parts 3 and 4 (Eastern China).

Revised Table 3 to reflect the above changes.

July 2007. Revised FM Global Earthquake Zones for the following countries/territories in South America andthe Caribbean: Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Falkland Islands (Islas Malvinas),Guyana, Paraguay, Peru and Venezuela (all in South America); and Anguilla, Aruba, Bahamas, CaymanIslands, Cuba, Dominican Republic, Haiti, Navassa Island, Netherlands Antilles, Puerto Rico, St. Kitts & Nevis,St. Lucia, St. Vincent & the Grenadines, Trinidad & Tobago, Turks & Caicos Islands, and the Virgin Islands(all in the Caribbean).

Confirmed that no change to the previous FM Global Earthquake Zones is needed for the followingcountries/territories in South America and the Caribbean: French Guiana, Suriname and Uruguay (all in SouthAmerica); and Antigua & Barbuda, Barbados, Dominica, Grenada, Guadeloupe, Jamaica, Martinique, andMontserrat (all in the Caribbean).

Revised maps showing, or overlapping into, the rezoned countries identified above including: Figure 2 (NorthAmerica), Figure 3 (South America), Figure 3A (Central America), Figure 3B (Northern South America andthe Caribbean) and Figure 3C (Southern South America). The mapped area in Figures 3B and 3C has beenrevised from previous version of DS/OS 1-2.

Revised Table 3 to reflect the above changes.

May 2007. Revised FM Global Earthquake Zones for the following countries/territories in Europe andAsia/Middle East: Bulgaria, Cyprus, Israel (includes Gaza Strip, Golan Heights and West Bank), Jordan,Lebanon, Romania, Syria and Turkey. Confirmed the FM Global Earthquake Zone (>500-year) determinedpreviously for the European countries of Finland, Norway and Sweden. Revised FM Global Earthquake Zonesfor the following countries in Central America: Belize, Guatemala, Honduras, Nicaragua and Panama.Confirmed the FM Global Earthquake Zone (50-year) determined previously for the Central Americancountries of Costa Rica and El Salvador. Revised maps showing, or overlapping into, the rezoned countriesidentified above including: Figure 3 (South America), Figure 3A (Central America), Figure 4 (Africa), Figure5A (Eastern Europe), Figure 5A part 2 (East Europe), Figure 5A part 3 (Middle East) and Figure 6 (Asia).

January 2007. The following changes were made for this revision:

Section 2.2.2.1 Design requirements have been made more specific and seismic parameters have beendefined that correspond to FM Global earthquake zones. These requirements are the basis for buildingand equipment anchorage seismic design.

Section C3.3 of Appendix C Technical details used in the design of equipment and storage-rack anchoragehave been added.

Table 3 - corrected the effective dates of FM Zones for Denmark, Ireland, Luxembourg and United Kingdom.

May 2006. Revised FM Global Earthquake Zones for the following countries/territories in Europe: Albania,Andorra, Austria, Belgium, Bosnia and Herzegovina, Croatia, Czech Republic, Denmark, France, Germany,Gibralter, Greece, Guernsey, Hungary, Ireland, Italy, Jersey, Liechtenstein, Luxembourg, Macedonia, Man(Isle of), Monaco, Netherlands, Poland, Portugal, San Marino, Serbia and Montenegro, Slovakia, Slovenia,Spain, Switzerland, United Kingdom and Vatican City. Updated and changed the mapped area shown inFigure 5, Figure 5B, Figure 5C, Figure 5D, Figure 5E and Figure 5F. Revised Figure 5A and Figure 5A -part 2. Deleted Figure 5D - part 2. Added Figure 5G. Revised Figure 4 (Africa) and Figure 6 (Asia) wherethey show the countries/territories identified above. Revised Table 3 and Section C.7.2.

July 2005. Updated maps for Mexico (including Figures 2, 2D, 3 and 3A), Table 3 and section C.7.2.

March 2005. Updated maps for Canada (Figures 2 and 2B [Parts 1 to 4]), maps for Australia (Figures 8 [Part 1]and 8A) and Table 3. Made editorial changes.

November 2004. Updated with editorial changes.

September 2004. The previous FM Global zones used to define relative earthquake hazards worldwide havebeen replaced by FM Global zones based on recurrence intervals of ground shaking. Legends for all mapshave been revised to reflect the new earthquake zone designations. The map color scheme for portrayingthe new zones has also been revised. For most areas, earthquake zones have not been reevaluated. In these



areas, earthquake zone boundaries shown on the maps remain unchanged, but old earthquake zones havebeen converted to new zones based on an approximate correlation (see section C.7).

Earthquake zones in the continental United States, Alaska, Hawaii, and the area around Vancouver, Canadahave been reevaluated using a revised methodology and the latest seismicity information available. For theseareas only, earthquake zone boundaries shown on the maps differ from those in the previous version of thisdata sheet.

In addition to updating the maps, the text throughout the document has been revised to reflect the new zonesand has also been extensively updated. Sections have been renumbered. Some information previouslymissing from Appendix B has been added.

September 2001. Some of the earthquake zones maps were clarified by completing zone hatching wheremissing and adding cross-references. Figure 9 and 9A were renumbered as Figures 8 (part 2) and 8D,respectively. Figure references in C.14.2 were changed to agree with the revised figure numbers of theredrawn maps for May 2001 revision.

May 2001. All earthquake zones maps were redrawn for improved resolution and mapping accuracy.

January 2001. Revision of earthquake zones for New Zealand and Southeast Canada were added. Thezoning note in Figure 8 was revised.

September 2000. The document was reorganized and revisions of earthquake zones for Andorra, Canada,France, Germany, Monaco, Portugal, Spain and Switzerland were added.

May 2000. Revisions of earthquake zones for the United States, Alaska and Hawaii were added.

1999. Revisions of earthquake zones for Taiwan, Mexico, Venezuela and Colombia were added.

1996. Earthquake zones were revised for much of Europe, Eurasia, and the Middle East, including Albania,Belarus, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, Georgia,Germany, Greece, Hungary, Italy, Latvia, Lithuania, Luxembourg, Macedonia, Moldova, Norway, Poland,Romania, San Marino, Serbia and Montenegro (Yugoslavia), Slovakia, Slovenia, Sweden, Ukraine, VaticanCity (Holy See), Russia, Turkey, Armenia, Azerbaijan, and Cyprus.

1992. Australia earthquake zones were revised.

February 1987. The following changes were made:

1. A glossary of earthquake related terms was added.

2. Earthquake zones where recommendations apply were added.

APPENDIX C SUPPLEMENTAL INFORMATION

C.1 Earthquakes and Seismicity

C.1.1 GeneralEarthquakes are essentially oscillating ground movements, having horizontal and vertical components,caused by sudden breaking of adjacent strained rock masses.

The majority of earthquakes are explained by the recently developed theory of global plate tectonics. Thistheory proposes that the crust of the earth consists of seven large and several smaller crustal plates, whichare drifting over the surface of the earth. The propelling force is the slow upwelling of magma from the mantle,or interior, of the earth through great submarine rifts at some plate boundaries. This upwelling generallyoccurs at crack or rift zones in the ocean basins, and is similar to a great elongated volcano. It is further actedupon by forces caused by the rotation of the earth. The upwelling is believed to be related to thermalconvection currents in the mantle, but is not yet fully understood.

The drifting crustal plates collide with other plates. Where collisions occur, two plates may grind against eachother, or one plate may be driven down under the other. About 90% of the worlds earthquakes occur at theboundaries of adjacent plates that are in conflicting relative motion. Shallow-focus (5 miles [8.0 km])earthquakes generally occur where plates are sliding past each other. This action results in horizontal slidingand occasional mountain building.



Intermediate and deep-focus earthquakes are usually associated with diving plates and generally occur insubduction zones. The diving plate compresses the adjacent plate, thrusting the rock material upward intomountains and forming deep trenches offshore. As the diving plate descends, it becomes heated. Lightermaterials become fractionated and rise to the surface within the adjacent plate, producing volcanoes andalso large masses of granite rock intrusions. This entire process is known as subduction of continental plates.

Earthquakes occurring along plate boundaries, known as tectonic earthquakes, can cause damage andsignificant geological changes. About 80% of the earthquakes occurring in the world take place around therim of the Pacific Ocean.

Current theory of global plate tectonics does not yet explain all known facts. Theory development may benecessary to account for the earthquakes that occur within crustal plates (intraplate tectonics), such as atCharleston, South Carolina; New Madrid, Missouri; along the St. Lawrence Valley; and elsewhere within theAmerican plate. Some of these intraplate earthquakes may be due to residual stresses from plate tectonicprocesses terminated as much as 200 million years ago. Another concept for the American plate may be therebounding of the earth that was compressed by the weight of the great ice layers of the last Ice Age, some10,000 years ago.

C.1.2 FaultsNearly all earthquakes are associated with observed faults. A fault is a fracture zone along which the twosides (walls) are displaced relative to each other. Most faults are readily recognizable by trained geologists.Not all faults are active, and there is currently no method of predicting the future activity of a given fault ina precise sense.

Displacement along a fault may be vertical, horizontal, or a combination of both. Movement may occur verysuddenly along a stressed fault, producing an earthquake, or it may be very slow, the rock undergoing whatis called creep, unaccompanied by seismographic evidence. Permanent displacement of the terrain duringan earthquake might be several inches, or it might be tens of feet. The Assam, India Earthquake of 1897produced 35 ft (10.7 m) of vertical displacement; the 1906 San Francisco earthquake produced 21 ft (6.4 m)of horizontal displacement.

The total length of a fault varies with magnitude. A magnitude (M) 6 earthquake may produce as little asfive miles (8.0 km) of surface rupture, whereas an M8.8 earthquake may produce as much as 1000 miles(1610 km) of surface rupture.

Faults are frequently described by the way one side, or wall, moved with relation to the other. When therehas been no lateral movement, the fault is normal, or reverse, according to whether the overlying wallslipped down or was thrust upward. If there has been lateral movement, the fault is termed a strike-slipfault. The fault is left lateral if the opposite wall moved to the left when the viewer faces the fault.Combinations of normal or reverse and lateral faults are possible (see Fig. 1).

The width of the fault zone varies widely with different types of faults. Major strike-slip faults are usually severalhundred feet wide. For other types, the fault zone can be as much as 0.5 miles (0.8 km) wide. A majorearthquake also can produce displacement on branch faults many miles away.

C.1.3 Seismic WavesWhen a fault ruptures, seismic waves are propagated in all directions, causing the ground to vibrate atfrequencies ranging from about 0.1 to 30 Hertz. There are three basic wave types: P and S waves that travelthrough the rock within the earth (body waves), and surface waves that travel along the earths surface.

The P and S waves are known as compression and shear waves, respectively. These waves causehigh-frequency (greater than 1 Hertz) vibrations, which are more effective than low-frequency waves incausing low buildings to vibrate. Surface waves are produced by P waves striking the ground surface. Surfacewaves may be subdivided into Love (L) waves and Rayleigh (R) waves. These waves mainly cause lowfrequency vibrations, which are more effective than high frequency waves in causing tall buildings to vibrate.Amplitudes of low frequency vibrations decay less rapidly than those of high frequency vibrations; therefore,tall buildings located at a relatively great distance from a fault, e.g., 250 miles (400 km), may be damaged.

The hypocenter is instrumentally determinable on seismographs by measuring the time interval betweenarrival of the P wave and arrival of the S wave. The velocity of seismic waves varies with the density andelastic characteristics of the rock through which it travels. The P waves followed next by S waves are thefastest traveling seismic waves. L waves are defined as the first surface waves to arrive at the seismograph.



Fig. 1. Types of fault movement. (a) Names of some of the components of faults. (b) Normal fault, in which the hangingwall has moved down relative to the foot wall. (c) Reverse fault, sometimes called thrust fault, in which the hanging wallhas moved up relative to the foot wall. (d) Lateral fault, sometimes called strike-slip fault, in which the rocks on either sideof the fault have moved sideways past each other. It is called left lateral if the rocks on the other side of the fault havemoved to the left, as observed while facing the fault, and right lateral if the rocks on the other side of the fault have movedto the right, as observed while facing the fault. (e) Left lateral normal fault, sometimes called a left oblique normal fault.Movement of this type of fault is a combination of normal faulting and left lateral faulting. (f) Left lateral reverse fault, some-times called a left oblique reverse fault. Movement of this type is a combination of left lateral faulting and reverse fault-ing. Two types of faults not shown are similar to those shown in (e) and (f). They are a right lateral normal fault and a rightlateral reverse fault (a right oblique normal fault and a right oblique reverse fault, respectively).



C.1.4 Ground MotionThe ground shaking in an earthquake depends mainly on the strength of the earthquake (magnitude andrelated duration), the distance from the fault and local geologic conditions. The important characteristics ofground vibration due to earthquakes include acceleration, velocity, displacement or amplitude, and frequencyor period. These can be measured with strong-motion accelerographs, which record the ground accelera-tion at the location of the instrument. By mathematically integrating this record, values of velocity anddisplacement can be obtained. A very useful engineering tool, the response spectrum, can then be derived byplotting spectral values of acceleration, velocity, and displacement against varying periods to determinemaximum peaks at differing levels of damping for a given natural period of vibration.

Ground acceleration during earthquakes can range from barely perceptible to slightly in excess of gravity (g),depending on the size of the earthquake and proximity to the fault.

Most strong earthquakes will produce accelerations from 10% to 20% of g at considerable distances awayfrom the fault. Acceleration near the fault can be substantial, from 30% to 50% g or more, but more than 50% gis infrequent. Damage to each individual item will vary, depending on its inherent strength, natural frequency,and built-in damping capability.

Vertical acceleration in most earthquakes is from one-third to two-thirds the horizontal acceleration, andusually is of higher frequency, or about double the number of horizontal pulses.

Occasional sharp peaks of acceleration can result in a high reported peak ground acceleration, but mightnot be damaging. A true measure of damage potential is the area under the accelerograph curve, which isan indicator of maximum ground velocities. Sustained high acceleration will produce high velocities, perhapsin excess of 3 ft (1 m) per second. Integrating the acceleration record with respect to time will give the recordof velocity. Peaks of the latter curve will give maximum velocities.

The amplitude of ground motion or displacement during an earthquake will vary considerably. Maximumamplitudes in strong earthquakes can range from 3 to 10 in. (76-254 mm) or more.

The frequency content and periods of acceleration impulses also vary throughout the duration of an earth-quake. Near the epicenter of a strong earthquake, ground shaking will consist of a random array ofacceleration impulses, most of which will have periods of from 0.1 to 3 seconds, but possibly as long as10 seconds.

It is a characteristic of ground energy absorption that high frequency energy is largely absorbed by soilsnear the fault zone. Therefore, the intensity of shaking in both the high and low frequency wave range is verystrong near the fault. However, long-period energy does not necessarily quickly attenuate, and accelera-tion impulses of a long period, e.g., from 1 to 3 seconds, will be sustained, and potentially damaging, quitesome distance from the epicenter. These long-period acceleration forces may predominate and produceserious damage to any building having a correspondingly long natural period, whose resonant period coin-cides closely with that of the long period. For example, the 1952 Kern County, California earthquake damagedtall buildings in downtown Los Angeles some 75 miles (121 km) from the epicenter.

Damage in Los Angeles, caused by the Kern County event, was generally confined to steel and concreteframe structures more than five stories high. The explanation for this is that short-period ground motions dieout more rapidly with distance than do long-period motions. Additionally, long-period ground motion tendsto adversely affect taller buildings that have longer natural periods than those of low, rigid buildings. Acontributing factor was damage to these tall buildings from past shocks, particularly the Long Beach,California, earthquake of 1933, because effective repairs had generally not been made. No cases of structuraldamage were noted and principal damage was to partitions, masonry curtain walls, ceilings, marble trim,veneer, and exterior facing. The buildings under discussion are the older ones without special earthquakebracing. The newer earthquake-resistant structures behaved well, except one flexible design that suffereddamages of (US)$150,000 to interior partitions and trim.

Local geologic conditions affect the strength and characteristics (e.g., frequency or period) of shaking. Softground shakes more strongly than firm soil or bedrock. Thicker sediment layers amplify shaking more thanthinner layers. An extreme example of this exists in Mexico City, Mexico, where unconsolidated lakebedsediments amplified motions from a distant (about 250 miles [400 km] away) M8.1 earthquake in 1985.Several hundred buildings collapsed and several thousand buildings were damaged in Mexico City. A largepercentage of the buildings damaged in Mexico City were between 8 and 18 stories high, indicating possibleresonance effects with long period horizontal ground accelerations.



Depth of the earthquake also affects surface ground motion. Where soils are homogeneous, ground motionsattenuate (decrease) as the distance from the earthquake hypocenter increases. The difference betweenthe distance to the epicenter and the distance to the hypocenter is not as great for a shallow earthquake asit is for a very deep earthquake. The deeper the energy release, the less energy is available per unit surfacearea. The 1949 and 1965 Puget Sound, Washington earthquakes (magnitudes 7.1 and 6.5) had focal depthsof about 35 miles (56 km) and produced maximum Modified Mercalli Intensity (MMI) levels of VIII and VII,respectively. The 1971 San Fernando, California, Earthquake (M6.6) had a focal depth of about 8 miles(13 km), and produced a maximum MMI of XI.

C.1.5 Earthquake MeasurementMagnitudeHistorically, the most common quantitative method of measuring earthquakes has been by Richter Magnitude(also known as the local magnitude [ML]). In 1935 Dr. Charles Richter developed the Richter MagnitudeScale, and he explained it in 1958 as follows: magnitude is intended to be a rating of a given earthquake,independent of the place of observation. Because it is calculated from measurements on seismograms, it isproperly expressed in ordinary numbers and decimals. Magnitude was originally defined in 1935 as the loga-rithm of the maximum amplitude on a seismogram written by an instrument of specified standard type ata distance of 100 kilometers (62 miles) from the epicenter. Because the scale is logarithmic, every upwardstep of one magnitude unit means multiplying the recorded amplitude by 10.

The magnitude also can be related to the earthquakes energy. A 1-unit increase in magnitude correspondsroughly to a 30-fold increase in energy. The magnitude scale necessarily relates only with energy radiatedas seismic waves. Additional energy is converted into heat by friction along the fault.

The magnitude scale has been further developed since its inception. Several kinds of instrumentally-derived magnitudes are now in use by seismologists (e.g., surface-wave magnitude [MS], body-wavemagnitude [mb] and moment magnitude [MW]). ML, MS and mb each use different earthquake characteris-tics (e.g., distance from the earthquake, the frequency of shaking, etc.) to measure magnitude and each hasan upper earthquake magnitude beyond which it cannot measure (i.e., saturates). ML and mb saturate atabout magnitude 6.2 to 6.5, MS saturates at about magnitude 7.5 to 8. Currently earthquake magnitudes arecommonly given in terms of moment magnitude (MW). This scale is derived from the seismic moment (whichis based on the area of fault rupture, the average amount of slip, and the force that was required to over-come the friction between the rocks on either side of the fault). Moment magnitude is uniformly applicable toall sizes of earthquakes and is the most reliable magnitude scale but is more difficult to compute than theother types. Below their saturation points, the reported ML, MS and mb will be roughly equal and approxi-mately the same as MW. For large earthquakes, the reported MW is the most accurate. Because they saturate,ML, MS and mb will typically underestimate the magnitude of large earthquakes. Although magnitude scalesare open-ended, the upper magnitude of earthquakes is limited by the strength of crustal rocks. The largestknown earthquakes are near MW9.5.

The number of earthquakes decreases rapidly as the magnitude increases. Richter found that, for the worldat large, the frequency of shocks at any given magnitude level was roughly 810 times that of about onemagnitude higher. A more recent worldwide study by J.P. Rothe, covering the period 19531965, found:

Magnitude Earthquakes Per Year6.0-6.9 195.07.0-7.9 15.5

8.0 and over 0.7

For an earlier period, Richter found 150, 18, and 2+ earthquakes for the same magnitudes, respectively.

Earthquakes of M6.0 or greater generate ground motions sufficiently severe to be damaging to well-built struc-tures, whereas the threshold for damaging poorly-built structures (e.g., unreinforced masonry walls) maybe as low as M5.0.

C.1.6 Earthquake MeasurementIntensityAnother term commonly used to describe the size of an earthquake is intensity. Intensity and magnitudeare often confused, and it is important to understand the difference.



In the absence of any instrument recordings of ground motion, seismologists describe the severity of theground shaking by assigning intensity numbers, always expressed in Roman numerals (i.e., I through XII).Intensity is an indication of an earthquakes apparent severity at a specific location, as determined by observ-ers. The earthquake intensity scale presently used in the United States was developed first by G. Mercalliin 1902 and modified by H. Wood and F. Neumann in 1931 and Richter in 1956. It is known today as the(abridged) Modified Mercalli Intensity (MMI) scale. This scale is based on the observed effects of earth-quakes determined through interviews with persons in the quake-stricken area, damage surveys, and studiesof earth movement. Because intensity is not determined instrumentally, but rather by observers reviewingthe effects, the MMI scale is subjective and relative. Difficulties frequently are encountered in using the MMIscale. Of special note is the effect of long-period motion on certain types of soil and tall structures; anobserver might be inclined to overrate the intensity.

Despite its many shortcomings, this subjective intensity scale is an important consideration in areas whereno seismographs have been installed, and they afford the only means for interpreting historical information.Generally speaking, Modified Mercalli Intensity of VIII is the threshold of serious damage to well-built struc-tures. Damage to unreinforced masonry structures, unbraced fire protection sprinkler piping and similarsystems built with little or no consideration for earthquake resistance begins at about Modified Mercalliintensity of VI and becomes significant at an intensity of VII. Isoseismic intensity maps for earthquakes areprepared and issued by various agencies, such as the United States Geological Survey (USGS).

A description of the Modified Mercalli Intensity scale as rewritten by Richter in 1956 appears in Table 1, withRichters masonry definitions inserted in brackets.

Magnitude and maximum intensity of an earthquake are interdependent to some degree, but there is noclose correlation between them. For example, an earthquake might have relatively low magnitude but,because of shallow focus, poor soil condition, or poor building construction, it might cause a great deal ofdamage. Thus, it would have a relatively high intensity.

While an earthquake can have only one magnitude, it can have several intensities. The intensity is typi-cally highest near the epicenter and, if geologic conditions are uniform, it gradually decreases as distancefrom the epicenter increases. However, intensity may vary considerably at two points that are equidistant fromthe epicenter because it is so dependent on the particular ground (i.e., local soil conditions) and structuralconditions of a particular area. For this reason it is difficult to equate magnitude with estimated intensity.

Crude correlations have been developed for the relationship of an earthquakes magnitude with its maxi-mum intensity. When the ground conditions vary, as they usually do, the error introduced when using theserelationships becomes exceedingly gross. In other regions, where focal depths may be greater, extrapolationof the relationships introduces much greater error.

Table 1. Modified Mercalli Intensity Scale, 1956 VersionI Not felt. Marginal and long-period effects of large earthquakes.II Felt by persons at rest, on upper floors, or favorably placed.III. Felt indoors. Hanging objects swing. Vibration like passing of light trucks. Duration estimated. May not be

recognized as an earthquake.IV. Hanging objects swing. Vibration like passing of heavy trucks; or sensation of a jolt, like a heavy ball

striking the walls. Standing motor cars rock. Windows, dishes, doors rattle. Glasses clink. Crockeryclashes. In the upper range of IV, wooden walls and frames crack.

V. Felt outdoors; direction estimated. Sleepers wakened. Liquid disturbed, some spilled. Small unstableobjects displaced or upset. Doors swing, close, open. Shutters, pictures move. Pendulum clocks stop,start, change rate.

VI. Felt by all. Many frightened and run outdoors. Persons walk unsteadily. Windows, dishes, glasswarebroken. Knick-knacks, books, etc. off shelves. Pictures off walls. Furniture moved or overturned. Weakplaster and masonry D [weak materials, such as adobe; poor mortar; low standards of workmanship, weakhorizontally] cracked. Small bells ring (church, school). Trees, bushes shaken (visibly, or heard to rustle).

VII. Difficult to stand. Noticed by drivers of motor cars. Hanging objects quiver. Furniture broken. Damage tomasonry D, including cracks. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles,cornices (also unbraced parapets and architectural ornaments). Some cracks in masonry C [ordinaryworkmanship and mortar; no extreme weaknesses, like failing to tie in at corners, but neither reinforcednor designed against horizontal forces]. Waves on ponds, water turbid with mud. Small slides and cavingin along sand or gravel banks. Large bells ring. Concrete irrigation ditches damaged.



VIII. Steering of motor cars affected. Damage to masonry C; partial collapse. Some damage to masonry B[good workmanship and mortar; reinforced, but not designed in detail to resist lateral forces]; none tomasonry A [good workmanship, mortar, and design; reinforced, especially laterally, and bound together byusing steel, concrete, etc.; designed to resist lateral forces]. Fall of stucco and some masonry walls.Twisting, fall of chimneys, factory stacks, monuments, towers, elevated tanks. Frame houses moved onfoundations if not bolted down, loose panel walls thrown out. Decayed piling broken off. Branches brokenfrom trees. Changes in flow or temperature of springs and wells. Cracks in wet ground and on steepslopes.

IX. General panic. Masonry D destroyed; masonry C heavily damaged, sometimes with complete collapse;masonry B seriously damaged. (General damage to foundations.) Frame structures, if not bolted, shiftedoff foundations. Frames racked. Serious damage to reservoirs. Underground pipes broken. Conspicuouscracks in ground. In alluviated areas, sand and mud ejected, earthquake fountains, sand craters.

X. Most masonry and frame structures destroyed with their foundations. Some well-built wooden structuresand bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown onbanks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and fault land. Railsbent slightly.

XI. Rails bent greatly. Underground pipelines completely out of service.XII. Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into

the air.

C.2 Site Specific Geologic ConsiderationsUnfavorable site specific geologic conditions include close proximity to known active faults, soft soil condi-tions, and high potential for major geologic deformation (e.g., liquefaction, landslide, lateral spreading,sinkholes, etc.). There are many sources that can provide information on the hazard these conditions presentin a general area. An investigation by a geotechnical engineer is usually needed to confirm the actual hazardat the site and to determine design parameters (i.e., soil bearing capacities, appropriate types of foundations,etc.).

General geological information can be obtained from geologic maps and some seismic risk maps, pub-lished by countries, states, U.S. Geological Survey, and others. These maps give general soil types,expressed as sediments or rocks of differing geological periods or eras. The scale of these maps usually doesnot permit representation of local soil variations or small pockets of weaker soil. Maps showing approximatefault locations also are available.

The best sources for local geological information of a particular occupied or unoccupied site are soil explo-ration or foundation reports, prepared by a geotechnical engineer during the site investigation. In somecases, a record of site soil borings is included in the plans or specifications for a building site or development.

Most faults are actually zones of movement that can be hundreds of yards (meters) in width. The hazardto a site located close to a fault can be higher than the hazard to sites further away. First, sites located directlyover traces of faults can be damaged from the relative movement of the ground on either side of the fault(due to non-earthquake fault creep or fault rupture during an earthquake). The second hazard for sites locatedclose to faults is the higher expected intensity of shaking that occurs near the earthquake source. Nearis a difficult term to define. However, some modern building codes require increases to design forces for siteslocated within 9 miles (15 km) of certain faults; these increases are very significant for sites within 3 miles(5 km) of the fault.

There are at least two generic types of soil that could lead to settlement or other poor response: alluviumand loess. Alluvium is clay, silt, sand, or gravel that has been deposited by water or glaciers. Loess is softsoil deposited by wind. Flat areas of alluvial soil adjacent to rivers or valleys filled with unconsolidated glacialdebris or loess, generally will respond at least one point higher in Modified Mercalli Intensity than otherwise.Highly water-saturated soft soils may respond two points higher. Tertiary (geologically older) sedimentsgenerally are fairly well consolidated and should give a more favorable response than Quaternary (geologi-cally newer) sediments. The depth of the soil is also a factor. Shallow soil beds on rock generally give goodresponse.

Soils of man-made fill are very dangerous unless scientifically compacted with heavy earth-rolling equip-ment. Many such fills have been placed by hydraulic pumping methods, without compaction. They may settleor lurch during strong earthquakes, thus causing severe damage to buildings. Many waterfront areas along



coastal zones have been enlarged with hydraulic fill, which is a poor building foundation, particularly in seis-mic areas, that typically requires the use of deep foundations (i.e., piles). Even when appropriate founda-tions are used to support structures, damage to grade-supported items (such as concrete slabs, asphaltpaving, cranes, and utilities) can be great.

Alluvial soils can lose their capacity to support loads if they are nearly or completely water saturated (thatis, the space between individual soil particles is completely filled with water) and are strongly shaken. Thewater exerts a pressure on the soil particles that influences how tightly the particles themselves are pressedtogether. Earthquake shaking can cause some of the loose soil to compact, displacing and pressurizing thewater in other areas to the point where the soil particles can readily move with respect to each other. Thisessentially produces quicksand. Buildings may then sink into the soil and settle differentially, making repairsvery difficult. A classic example of soil liquefaction problems was in the 1964 Niigata, Japan, Earthquake,which involved large-scale flooding from soil-water ejection and also severe building settlements, includingone four-story concrete building which sank, tilted, and fell onto its side.

Alluvial soil should be considered suspect to potential liquefaction when the water table is near the surface,or surface layers have a high moisture content. It is difficult, however, to predict the probability or degreeof potential vibration. Some alluvial soils may lurch or be displaced horizontally (lateral spread) or form cracks,fissures, and sags during extremely strong ground motion. Buildings may suffer from differential settlement.

Structures built on hillsides need special consideration, as a landslide could occur to the soil on which theyrest. Retaining walls of concrete, sheet piling, etc. can be utilized to stabilize the foundation soil downhill ofthe building, or to prevent landslide uphill.

A geotechnical engineer can determine the soil classification and the potential for seismically induced soilfailures (e.g., liquefaction, landslide, lateral spread, sinkholes, etc.). The site classification based on soil profilecommonly used in the United States, taken from the 2003 International Building Code (IBC), is shown inthe table below (see the 2003 IBC for more information):

Table 2. Site Classification from the 2003 International Building Code Based on Soil TypeSite Class

(Not to be Confusedwith Seismic DesignCategories A to F) Soil Profile Name Soil Profile Description (For Unnamed Soil Profiles)

A Hard rockB RockC Very dense soil and soft rockD Stiff soilE Soft soil

Unnamed More than 10 ft (3 m) of soil having high plasticity, highmoisture content or very low strength

F Unnamed Soils vulnerable to potential failure or collapse under seismicloading (e.g., liquefiable, highly sensitive [quick] clays,collapsible weakly cemented soils)Peats and highly organic clays greater than 10 ft (3 m) thickVery high plasticity clays greater than 25 ft (7.6 m) thickVery thick soft/medium clays (greater than 120 ft [36.6 m])

Sites ideally should be located in areas of firm soils (site class A [hard rock] to D [stiff soil]). Soft soil andsoil subject to failure (site classes E and F) are very undesirable. Site selection should be made to limit thepotential for damage to the facility due to fault rupture or creep and other soil failures (landslide, etc.).

C.3 Building Codes

C.3.1 Building Code Design PhilosophyMinimum building code provisions are intended mainly to safeguard against collapse or failure that can resultin loss of life in a major earthquake. Minimum code provisions will not necessarily limit damage or limitbusiness interruption, or allow for easy repair.



The design earthquake ground motion set by building codes has a low probability of occurrence during thelife of the structure. Historically, an earthquake ground motion having a mean recurrence interval of 500 yearshas commonly been used as a basis for design. Currently, some codes base design on an earthquake groundmotion with a 2500-year return period (when actual design forces are determined, the theoretical forces fromthis more severe earthquake ground motion are reduced by a larger factor than the 500-year return periodearthquake ground motionsee below).

While it is possible to design a structure to respond in the elastic range for these earthquake ground motions,building codes are based on the assumption that it is impractical to do so in most cases. The code-required lateral design forces typically are a fraction of the theoretical forces that would be developed forthe design earthquake ground motion in recognition that this ground motion is a rare event. Because thismeans buildings will respond in the inelastic range for the design earthquake ground motion (and possibly forother more frequent events), building codes also have detailing provisions to ensure the required level ofinelastic capacity is available. The level of force reduction and special detailing required varies dependingon the return period of the design earthquake ground motion (e.g., 500-year, 2500-year, etc.), the type oflateral force-resisting system, the building use, the likelihood that damage to lateral force-resisting elementswill result in building instability (damage to shear walls that are also bearing walls is more likely to triggera vertical collapse), and observed performance of similar buildings in past earthquakes.

C.3.2 Building Code ProvisionsBuilding codes establish the seismic design criteria through formulas and provisions that specify:

the strength and stiffness of the structural system required to resist the seismic design loading (which issome fraction of the theoretical maximum forces from the design earthquake).

the requirements for structural detailing that will allow the expected level of inelastic behavior to occur.

It is the designers responsibility to design into the structures sufficient strength, stiffness, and detailing.Competent structural engineers are aware of the potential effects of strong earthquakes on buildings andequipment, and will make allowances for the special problem areas in their static or dynamic analyses anddesigns.

Many countries develop and enforce their own earthquake code provisions; often these are based on earth-quake requirements in codes established in the United States (e.g., the Uniform Building Code and itsreplacement, the International Building Code), Japan (Building Standards Law), New Zealand (BuildingStandards Law), and Europe (Eurocode 8).In the United States, the Uniform Building Code (UBC) has historically been the most commonly used codein seismically active areas; in 1997 the last edition of this code was issued. Currently, the Building SeismicSafety Council (BSSC) develops the National Earthquake Hazard Reduction Program (NEHRP) Recom-mended Provisions for Seismic Regulations for New Buildings and Other Structures. The NEHRP provi-sions are then used to develop the earthquake requirements in the Structural Engineering Institute/AmericanSociety of Civil Engineers (SE

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