The idea of earthquake prediction
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The Idea of Earthquake Prediction. Time-independent hazard- random process in time: used for building design, planning, insurance, probability

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The Idea of Earthquake Prediction

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The idea of earthquake prediction

The Idea of Earthquake Prediction

  • Time-independent hazard-random process in time: used for building design, planning, insurance, probability

  • Time-dependent hazard-a degree of predictability, enable authorities to prepare for an event-false alarms- loss of public confidence, China- shut down of public services during false alarms


Earthquake predictions

Earthquake Predictions

  • The 1960’s- descriptions of physical changes

  • 1970’s- 1975, successful prediction; 1976, 250,000- people died in Tangshen, China

  • 1980s- Jim Berkland, fluctuations of missing dogs in local newspapers, increase number of calls to satellite TV companies

  • Greek scientists, electrical signals


Haichen china 1975

Haichen, China, 1975

  • An evacuation warning was issued the day before

  • The local rural population was educated and aided in the monitoring

  • changes in land elevation and ground water

  • reports of peculiar animal behavior- snakes coming out of the ground in January, livestock not going into their barns

  • an increase in small earthquakes


The idea of earthquake prediction or forecasting

The Idea of Earthquake Prediction or Forecasting

  • 1977- National Earthquake Hazards Reduction Program (NEHRP)

  • 1. Precursor detection instruments at the site

  • 2. Detect and recognize precursors

  • 3. Get colleagues to agree, accept and put out a warning


Earthquake forecasts

Earthquake Forecasts

  • Earthquake forecasting- some connection between the level of chance between observation and event; probabilities and errors involved

  • Scientists cannot predict earthquakes

    • Evacuation before an event since 1975 has not occurred


Long term forecasts

Long-term Forecasts

  • Retrofitting

  • Building codes

  • Legislation

  • Insurance

  • Emergency plans

  • Education to the public

  • Preparedness


Long term forecasting methods

Long-term Forecasting Methods


Paleoseismicity

Paleoseismicity

  • Identify fault trace

  • Trench

  • Analyze sedimentary layers and offsets

  • Date organic material


Historical seismicity patterns

Historical Seismicity Patterns

  • Large Bay Area earthquakes are more frequent at some times more than others

  • 1836-1911; 1911-1979 (68 years of no events)


Recurrence interval

Parkfield Seismic Area

1988-90% probability for a M6 earthquake

1901

1922: 21 years

1934: 12 years

1966: 32 years

2004: 38 years

Statistical Method of historic earthquakes

Shortest interval:

Longest interval:

Average: 25.5 years

Problems with this method?

Recurrence Interval


Paleoseismology and recurrence interval

Pallet Creek offset

1857

1745: 112 years

1470: 275 years

1245: 225 years

1190: 55 years

965: 225 years

865: 100 years

545: 320 years

Shortest interval?

Longest interval?

Average?

187 years

Strengths of this method:

Shortcomings?

Paleoseismology and recurrence interval


Seismic gaps areas on a larger fault system that lack seismicity

Seismic Gaps -areas on a larger fault system that lack seismicity


Variation of average movement on known faults

Variation of average movement on known faults

  • Bay Area faults belong to the San Andreas fault system

  • Movement varies

  • Right-lateral strike-slip faults

  • 1868- Hayward fault

  • 1906-San Andreas fault

  • 1989-San Andreas fault


The idea of earthquake prediction 1351920

Variation of average movement on known faults

  • Bay Area faults move at different rates to accommodate the total amount of slip of the San Andreas fault system

  • Total+ 34 mm/year

  • SAF 19 mm/yr

  • Hayward fault 9 mm/yr


Earthquake prediction and probability

Variation of average movement on known faults

Earthquake Prediction and Probability

  • Each vector represents the amount of movement on each fault

  • Variations may indicate an imminent earthquake


Pattern of seismicity

Pattern of Seismicity


Earthquake forecasting and probability

Earthquake Forecasting and Probability

  • Working Group on California Earthquake Probabilities

  • Group of 100 geologists, engineers, government officials evaluated all information

  • Came up with a probability of a magnitude 7 or greater in the next 30 years

  • 1988. 1999, 2003, 2008


Earthquake forecasting and probability1

Assumes a random distribution of earthquakes

In the Bay Area, 5 earthquakes greater or equal to M 6.75 occur approximately every 30 years

50% probability-just as likely to happen as not to happen

Earthquake Forecasting and Probability


The idea of earthquake forecasting

The Idea of Earthquake Forecasting

  • Loma Prieta- 30% probability in 1988- eq, 1989

  • Parkfield -90% probability in 1988-eq, 2004

  • Landers, Northridge, Kobe- earthquake on a little known fault


Short term prediction based on precursors

Short-term Prediction based on precursors


The idea of earthquake prediction 1351920

All the described precursors sometimes occur but as of yet do not occur in a manner that successfully predict earthquakes


What should be expected

What should be expected?

  • A reasonable time period

  • The location- fault or fault segment

  • Magnitude or amount of energy released


Ground deformations

Ground Deformations

  • Ground deformation

  • Preceding the 1906 earthquake in Marin County-elastic rebound theory

  • The Palmdale bulge- monitoring began in the 1960’s , associated with the SAF


Radon gas emissions

Radon Gas Emissions

  • Radon emission- a radioactive gas that sometimes shows an increase preceding an earthquake-

  • There was a ten-fold increase 30 kilometers away from the epicenter 9 days preceding the earthquake.

  • Problem with this method?


Parkfield experiment

Parkfield Experiment

  • Examining precursors or those events that sometimes occur before a main event

  • Changes in physical properties in close proximity to the fault


Parkfield experiment1

Parkfield experiment

  • Magnitude 6 earthquake occurred on average every 22 years from 1857-2004

  • Similar location

  • Similar seismic wave pattern recorded

Hopes of documenting an earthquake before, during, and after the main shock in order to produce a short-term prediction technique.


Precursors expected to observe

Precursors expected to observe

  • Foreshocks

  • Ground deformation

Surface cracks associated with the 2004 earthquake


The idea of earthquake prediction 1351920

San Andreas Fault Observatory at Depth: 2004

Examining physical changes to the rocks at depth


Animal prediction

Animal Prediction

  • Unusual animal behavior prior to a disaster

  • Greece, 373 BC, rats, snakes and weasels deserted days before an earthquake

  • Advanced vibrations?

  • Change in electrical charges?

  • Change in magnetic field?

  • So far, unable to use unusual animal behavior to predict earthquakes


Chi chi earthquke taiwan 1999

Chi Chi Earthquke,Taiwan, 1999

  • Initial smaller earthquake during the first 4 seconds have higher frequency waves than larger earthquake

  • The warning could be sent

  • Seismic waves travel at about 2 miles per second


Early warning system

Detect P-wave arrival

Warning system

Emergency centers, hospitals, railways

Depends on distance to how helpful

Japan-March , 2011, M9, Tokyo-stopped trains; cell phone notification; 8-10 minutes tsunami

Kobe-fault under city

Mexico-11 warnings, M6 or greater

Early Warning System


Early warning system u s

Early Warning System: U.S.

  • $80 dollars over 5 years

  • Arrival of P-waves

  • 3-4 minutes: Cascadia Subduction Zone

  • 1 minute warning for SAF

  • 30 seconds:

    • doctors stop surgery;

    • Duck and cover

    • Trains stop


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