Before you jump into this slide show, you should view the Presentation on
EarthquakeSeismologySee notes for link.
Earthquake Intensity is what you feel.What controls ground shaking and earthquake
damage?Magnitude — More energy released by larger earthquakeDistance — Shaking decreases with distanceGeology — Local geology can amplify the shakingBuilding style — Strength and building designDuration of shaking — Increases with earthquake magnitudeExample:
1994 Northridge EQ, M=6.7
Seismic intensity is affected by rock type.
Amplitude of oscillation
How would you expect the houses to react during an EQ?
Seismic intensity is affected by rock type.
Amplitude of oscillation increasing
Amplification of Ground Motion
Damage from Loma Prieta EQ 1989
West of Oakland.Marina District
of San Francisco.
Santa Cruz.
Landslides
El Salvador January 2001 M7.6
Liquefaction experimentWhat happens to a structure built on a weak
foundation when an earthquake strikes?
Photos: Lily RodriguezFrom website below
For the description of this liquefaction activity:http://www.exploratorium.edu/faultline/activezone/liquefaction.html
Niigata, Japan 1964Source: National Geophysical Data Center
Building design: If the resonant frequency of a building is equal to the frequency of ground oscillation, then damage or collapse is likely.
What is resonant frequency?
Discussion: Why is building damage selective?
ResonanceOscillating buildings demonstration—3 methods.
BOSS model
Links to video demonstrations by John Lahr are in notes.
Two similar demonstrations use simpler methods:
Spaghetti & Manilla file raisins……. “Boss lite”…
During earthquakes, buildings experience vertical AND horizontal accelerations. NOT a simple problem
to engineer earthquake resistance .. BUT can be done.
“Earthquakes don’t kill people. Buildings that collapse during earthquakes kill people.”
Building design is critical to earthquake safety
Resistance to shear is critical.
See the video lecture on Building Strength available through link provided in Notes.
Seismic Retrofit
1942 North Portland HouseWood frame NOT attached to
foundation.
Seismic Retrofit
Bolting frame to foundation on exterior.
Seismic Retrofit
Post & beam reinforcement.
Base Isolation