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 earthquake

Distance — Shaking decreases with distance

Geology — Local geology can amplify the shaking

Building style — Strength and building design

Duration 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