Earthquake processes and symptoms What is an earthquake? Fault ...
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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
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
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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
Environmental Geology – Earthquake processes and symptoms
Seismic wavesEarthquake processes
Environmental Geology – Earthquake processes and symptoms
Locating earthquakesEarthquake processes
3
Environmental Geology – Earthquake processes and symptoms
Current earthquake activityEarthquake processes
Environmental Geology – Earthquake processes and symptoms
Magnitude and frequencyEarthquake processes
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
4
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
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
5
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
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
6
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
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