What is an earthquake anyway? An earthquake by definition is a
sudden movement of the Earth's lithosphere. They are natural
geologic phenomena causing the sudden and rapid movement of a large
volume of rock. Due to rupture and slippage along faults, or
fractures in Earths crust, violent shaking and many times
destruction occur. Earthquakes originate at the focus or hypocenter
which occurs at any depth between 5 and 700 kilometers (3.1 and
434.9 miles) below the Earths surface. Directly above the
hypocenter, on the surface is the epicenter. This is the point on
the Earths surface where the earthquake begins.
Slide 3
How do earthquakes cause damage? Ground shaking is the cause
for damage done by earthquakes. The magnitude or size (energy
release) of an earthquake, distance to the epicenter, depth of the
hypocenter, type of faulting, and type of rock and mass material
are important factors in determining the amount of ground shaking
that might be produced at any particular site.
http://www.history.navy.mil/photos/events/ev-1900s/ev-
1908/messina.htm
Slide 4
How do we measure earthquakes? During an earthquake, large
amounts of energy are released in the form of heat and seismic
waves. Sensitive instruments, seismographs, located around the
world can quickly pick up on the rapidly dissipating seismic waves
and energy. We take the measure the magnitude of an earthquake by
using the Richter Scale, with 1 being We measure the intensity of
an earthquake by using the modified Mercalli scale, which starts
with I being the lowest intensity and XII being the most
intense.
Liquefaction Liquefaction occurs when earthquake vibrations
cause the loose or saturated soil particles to lose contact with
one another. As a result, the soil behaves like a liquid, has an
inability to support weight and can flow down very gentle slopes.
Causing a lot of significant damage in many earthquakes.
http://www.ndmc.gov.za/Hazards/Natural/Seismic/Liquefaction.aspx
Slide 8
Can Earthquakes be predicted? There are no definite ways of
predicting earthquakes in either the short term or long term. The
movement of tectonic plates and faults is so unpredictable, that
there is no sure way of knowing exactly when and where an
earthquake will strike. Many factors contribute to how large and
devastating an earthquake will be, depending on what type of fault
it is, how much energy is released, how structurally sound the
buildings and structures are in the surrounding area, how prepared
the cities surrounding are prepared to deal with the earthquake,
etc.
Slide 9
Earthquake Safety It is important in the event of an earthquake
to be prepared, and since we are unable to predict earthquakes, it
is necessary to be prepared at all times The following slides show
how FEMA suggests we prepare ourselves when faced with an
unpredictable natural disaster, in this case earthquakes.
Slide 10
FEMAs 7 Steps to Earthquake Preparedness PREPARE (before) 1.
Secure your spaces 2. Create a plan 3. Prepare disaster kits 4.
Strengthen your home SURVIVE (during) 5. Drop, cover, and hold on
RECOVER (after) 6. Check for injuries and damage 7. Follow your
plan
Slide 11
STEP 1: Secure your space 1) Hang plants in lightweight pots
with closed hooks, well secured to a joist or stud and far away
from windows. 2) Install strong latches on kitchen cabinets. 3) Use
flexible connections where gas lines meet appliances. 4) Remove or
lock refrigerator wheels, secure to studs. 5) Secure valuable
electronics items such as computers and televisions. 6) Keep
breakables in low or secure cabinets with latches. 7) Move heavy
plants and other large items to floor or low shelves. 8) Hang
mirrors and pictures and pictures on closed hooks. 9) Secure
free-standing woodstove or fireplace insert. 10) Keep heavy
unstable objects away from doors and exit routes. 11) Place bed
away from windows or items that may fall. 12) Secure knick knacks
and other small valuables with museum putty. 13) Brace overhead
light fixtures. 14) Place only light weight/soft items over bed.
15) Secure top-heavy furniture to studs. 16) Secure water heater
with metal straps attached to studs. 17) Trim hazardous tree
limbs.
Slide 12
STEP 2:Create a plan 18) Store fire extinguisher (type ABC) in
easily accessible location. 19) Keep several flashlights in easily
accessible places around the house. 20) Keep wrench or turn-off
tool in water proof wrap near gas meter. 21) Know the location of
your main electrical switch (fuse box or circuit breaker). 22) Have
your emergency plan accessible and discuss with all family members.
23) Know whether you live, work, or play in a tsunami hazard zone.
24) Obtain a NOAA Weather Radio with the Public Alert feature to
notify you of tsunamis and other hazards. 25) Keep flashlight,
slippers and gloves next to beds. 26) Keep gas tank at least half
full. STEP 3: Prepare disaster kits 27) Keep an emergency backpack
with copies of important documents near the door to grab and go.
28) Store emergency food and water supplies in a dry accessible
area. Include first aid kit, extra cash, portable radio, extra
batteries, medications and other necessary supplies. STEP 4:
Strengthen your home 29) Use anchor bolts every 4 to 6 feet to
secure home to foundation. 30) Reinforce brick chimneys.
Slide 13
During an Earthquake Its important to properly protect yourself
by Dropping to the floor Covering yourself under or parallel to a
large stable object Hold on, and ride out the earthquakes
vibrations
http://kendrah4.edublogs.org/files/2011/01/drop-cover-hold-on-20mmb06.jpg
Slide 14
A Few Famous Earthquakes San Francisco, California: April 18,
1906 (Magnitude: About 8) Tokyo, Japan: September 1, 1923
(Magnitude: About 8.25) Chile: May 22, 1960 (Magnitude: About 9)
Anchorage, Alaska: March 27, 1964 (Magnitude: About 8.5) Tangshan,
China: July 27, 1976 (Magnitude: About 7.5) Sumatra, Indonesia,
Dec. 26, 2004. (Magnitude: About 9.0)
Slide 15
Sources http://earthquake.usgs.gov/earthquakes/
http://www.earthquakescanada.nrcan.gc.ca/info-gen/faq-eng.php#cause
http://library.thinkquest.org/22360/Earthquakes.html Earth: An
Introduction to Physical Geology, 10 th Edition by Edward J.
Trabuck, Frederick K. Lutgens, and Dennis Tasa. 2011