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Series1

Exam 1 Results

Average: 59

Celepration of survival of the Bolognesi EQ1650National Geographics

Picture Of The Day

P-wave: always the champ!

LAST LECTURE

Richter vs. MercalliLAST LECTURE LAST LECTURE

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Causes for Earthquakes

• Earthquake: Sudden release of strain energy caused by rock rupture (faulting)

LAST LECTURE

Causes for Earthquakes

• Earthquake: Sudden release of strain energy caused by rock rupture (faulting)

• Earthquakes induced by human activitiesMuch smaller magnitudeReservoir-induced earthquakesDeep waste disposal and earthquakeNuclear explosions

Human-caused earthquakes. Rocky Mountain Arsenal Well Relationship between earthquake frequency and the rate of injection of liquid waste

Material Amplification• Seismic waves travel differently through different

rock materials

• Propagate faster through dense and solid rocks

• Material amplification: Intensity (amplitude of vertical movement) of ground shaking more severe in unconsolidated materials

• Seismic energy attenuated more and propagated less distance in unconsolidated materials

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Ancient lake deposits amplified shaking in Mexico City. 1985 (M 8.1) Mexico City Earthquake

1989 Loma Prieta earthquake (M 7.1), San Francisco Bay area.

Severe shaking occurred in bay fill and mud (freeway collapsed and Marina district was damaged.

Collapse of a freeway during 1989 Loma Prieta quake

Collapsed freeway. 1989 earthquake

Collapsed freeway. 1989 earthquake

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Marina District, San Francisco 1989 (M 7.1) earthquake

• Primary effectsGround shaking,

tilting, and ground rupture

Loss of life and collapse of infrastructure

Landslides, liquefaction, and tsunamis

• Secondary effectsFires, floods, and

diseases

Effect of Earthquakes

Earthquake Destruction

• Amount of structural damage attributable to earthquake vibrations depends on

• Intensity and duration of the vibrations

• Nature of the material upon which the structure rests

• Design of the structure

Earthquake Destruction

• Ground shaking– Regions within 20 to 50

kilometers of the epicenter will experience about the same intensity of ground shaking

– However, destruction varies considerably mainly due to the nature of the ground on which the structures are built

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Earthquake destruction

• Destruction from seismic vibrations• Liquefaction of the ground

– Unconsolidated materials saturated with water turn into a mobile fluid

• Seiches– The rhythmic sloshing of water in lakes,

reservoirs, and enclosed basins – Waves can weaken reservoir walls and

cause destruction

Liquefaction (1964 Niigata, Japan, earthquake)

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Sand blow at bay bridge

Sand blow at Orkland International Airport

Collapse of beach road

Liquefaction caused by the 1989 Loma Prieta earthquakeEarthquake destruction

• Landsliding– 70,000 people killed in the 1970 Peru

earthquake (Mw=7.7 ); 20,000 of them were killed by a giant landslide that buried several towns.

Landslide of the great Alaska (03/28/1964, Mw-9.2) earthquake

Earthquake-triggered landslide. M 7.9 Alaskan earthquake, partially covering Black Rapids Glacier. This is one of thousands!

Earthquake destruction

• Fire – ~80% of the damage in the 1906 San

Francisco earthquake was caused by fire – the quake was known as the San Francisco fire.