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Environmental Geology – Earthquake processes and symptoms

Earthquake processes and symptoms

Reading: This week: Ch 4Next week: Ch 5

Internal processes:

Environmental Geology – Earthquake processes and symptoms

What is an earthquake?…the release of built-up stress along faults

1. Stress builds up due as tectonic plates move past one another

2. Friction along the fault prevents slip, elastic deformation instead

3. Stress exceeds rupture strength, fault slips …earthquake

Earthquake processes

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Environmental Geology – Earthquake processes and symptoms

Fault slip

Movement along the fault: San Francisco 1906 about 6 meters in places

Earthquake processes

Environmental Geology – Earthquake processes and symptoms

Vertical fault motion

Thrust faults form mountain belts

Earthquake processes

3

Environmental Geology – Earthquake processes and symptoms

Vertical fault motionEarthquake processes

Chi-chi earthquake, Taiwan 1999up to 9 meters vertical offset

Environmental Geology – Earthquake processes and symptoms

Radiated energyEarthquake processes

4

Environmental Geology – Earthquake processes and symptoms

Seismic wavesEarthquake processes

Environmental Geology – Earthquake processes and symptoms

Locating earthquakesEarthquake processes

5

Environmental Geology – Earthquake processes and symptoms

Current earthquake activityEarthquake processes

Environmental Geology – Earthquake processes and symptoms

Magnitude and frequencyEarthquake processes

6

Environmental Geology – Earthquake processes and symptoms

Intensity

Describes the effect on the surface and

buildings

Northridge intensity map

Earthquake processes

Environmental Geology – Earthquake processes and symptoms

Ground motionEarthquake symptoms

Permanent displacement along the fault

Transient ground shaking in earthquake region

India 2001

Taiwan 1999

San Francisco

1906

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Environmental Geology – Earthquake processes and symptoms

ShakingEarthquake symptoms

From the 1995 Kobe earthquake in Japan

Environmental Geology – Earthquake processes and symptoms

Stable ground?Earthquake symptoms

Ground motion is amplified on soft sediment

Loma Prieta 1989

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Environmental Geology – Earthquake processes and symptoms

San Francisco Marina District

Earthquake symptoms

The Marina District is landfill

Loma Prieta

damage 1989

Environmental Geology – Earthquake processes and symptoms

LandslidesEarthquake symptoms

El Salvador

Peru

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Environmental Geology – Earthquake processes and symptoms

LiquefactionEarthquake symptoms

Niigata Japan 1964

Izmit Turkey 1999

Environmental Geology – Earthquake processes and symptoms

TsunamisEarthquake symptoms

Tsunamis can occur when there is an offshore earthquake which

vertically displaces the seafloor

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Environmental Geology – Earthquake processes and symptoms

TsunamisEarthquake symptoms

Japan 1993

Alaska 1964

Environmental Geology – Earthquake processes and symptoms

TsunamisEarthquake symptoms

Tsunamis early warning system detects earthquakes around the Pacific rim and monitors ocean surface for tsunamis

Able to issue several hours of

warning

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Environmental Geology – Earthquake processes and symptoms

Coastal subsidenceEarthquake symptoms

Alaska 1964

Environmental Geology – Earthquake processes and symptoms

FireEarthquake symptoms

San Francisco 1906

Northridge 1994Kobe 1995

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Environmental Geology – Earthquake processes and symptoms

DiseaseEarthquake symptoms

Causes of disease• Population movement• Poor sanitation• Contaminated water• Cramped living space• Public health programs

disrupted

cholera malaria

dengue fever