The earthquake cycle Loma Prieta and seismic gaps

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Environmental Geology – Earthquakes vs. humankind

Earthquakes vs. humankind

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

Internal processes:

QUESTION

Environmental Geology – Earthquakes vs. humankind

Global seismicity

Environmental Geology – Earthquakes vs. humankind

The earthquake cycle

Environmental Geology – Earthquakes vs. humankind

Loma Prieta and seismic gaps

Locked

Creeping

2

Environmental Geology – Earthquakes vs. humankind

San Andreas and North Anatolian faults

Environmental Geology – Earthquakes vs. humankind

North Anatolian slip history

Environmental Geology – Earthquakes vs. humankind

North Anatolian slip history

Izmit1999

Environmental Geology – Earthquakes vs. humankind

Learning the lessons

QUESTION

3

Environmental Geology – Earthquakes vs. humankind

Earthquake forecasting

Earthquake forecast issued 1988

Northridge?

Environmental Geology – Earthquakes vs. humankind

The Parkfield experiment

Parkfield on the San Andreas Fault

In 1985 the USGS predicted an earthquake at Parkfield in

January 1988 ± 5 years

…still waiting

Environmental Geology – Earthquakes vs. humankind

Seismic hazard

Environmental Geology – Earthquakes vs. humankind

Building codesEarthquakes don’t kill people, buildings do

4

Environmental Geology – Earthquakes vs. humankind

Building codes

Turkey, 1999:Poor building standards blamed for much of the death

Environmental Geology – Earthquakes vs. humankind

Insurance

Environmental Geology – Earthquakes vs. humankind

The cycle goes on…

Istanbul earthquake 1556

Environmental Geology – Earthquakes vs. humankind

Earthquake prediction

“There will be an earthquake a week from Wednesday at Parkfield”

What is a useful prediction?

There will be an earthquake……in the first week of May…in LA in the first week of May …in LA on Wednesday…in LA on Wednesday greater than magnitude 8…in an hour…in a minute…in 5 seconds

Earthquake early warningan active area of research

5

Environmental Geology – Earthquakes vs. humankind

Earthquake prediction in China

Possible earthquake precursors:• Rapid surface deformation• Rapid increase in small earthquake activity• Changes in physical properties of rocks e.g. conductivity, P-velocity• Change in the level of water in wells• Strange animal behavior

Environmental Geology – Earthquakes vs. humankind

Earthquake prediction in China

Success: Haicheng, NE China, February 1975• predicted an imminent earthquake,

evacuation ordered• nine hours later a large earthquake

struck destroying many homes but there was little loss of life

Failure: Tangshan, NE China, 1976• predicted an earthquake in the Tangshan region over the “next

two months”• no immediate precursors, no evacuation• more then 250,000 people died

But, what of false alarms?

Environmental Geology – Earthquakes vs. humankind

The future of earthquake prediction

This is currently being pursued in the US, Russia, China and Japan

…don’t expect results in the foreseeable future

When we are ready to try predictions consider:

• legal implications• political implications• property values• practical implications

…we would need a serious educational campaign

Environmental Geology – Earthquakes vs. humankind

Earthquake warning

Could provide a few to tens of seconds of warning

This is a research effort here at UW!

6

Environmental Geology – Earthquakes vs. humankind

“Earthquake control”

Unlocking faults

• fluid injection to “smooth” fault motion

• nuclear explosion to trigger stress release on the fault