Post on 27-Dec-2015
Thailand Training Program in Seismology and Tsunami Warnings, May 2006
Forecasting Earthquakes
Forecasting Earthquakes
・ Difference between Predictions and Forecasts
・ Early Efforts in Earthquake Prediction
・ Long-term Forecasting
Earthquake Predictions versus Forecasts
Predictions have specific times, locations, and magnitudes for future earthquakes.
Forecasts are more long-term estimates of earthquake occurrences with probability information.
Short-term (minutes to weeks)
Intermediate (months to 10 years )
Long-term (> 10 years)
Forecast Loading Cycle
Interseismic
Preseismic
Coseismic
Postseismic
1. Time 2. Location 3. Magnitude
What is needed in an earthquake prediction ?
Allen, 1996
Frequency of Occurrence of Earthquakes
Descriptor Magnitude
Average Annually
Great 8 and higher
1
Major 7 - 7.9 17
Strong 6 - 6.9 134
Moderate 5 - 5.9 1319
Light 4 - 4.9 13,000
(estimated)
Minor 3 - 3.9 130,000
(estimated)
Very Minor 2 - 2.9 1,300,000(estimated)
1. Time 2. Location 3. Magnitude
4. Indication of confidence (window) 5. Prediction must be presented in accessible form for later evaluation 6. Chance earthquake occurs anyway as a random event
What is needed in an earthquake prediction ?
Allen, 1996
‘Now, when will earthquake prediction be possible and an efficient Forewarning service available ? …if we start the project presented here we should be able to answer the question with sufficient certainty within ten years.’ The Japanese Blueprint (Tsuboi et al, 1962)
‘Based on an assessment of worldwide observations and findings over the past few years, it is the panel’s unanimous opinion that the development of an effective earthquake prediction capability is an achievable goal. …with appropriate commitment and level of effort, the routine announcement of reliable predictions may be possible within ten years…’
Panel of the US National Research Council (Allen et al., 1976)
Optimism in the 1960’s and 1970’s
In actuality: Can only forecast earthquakes and mitigate hazard
‘Predicted’ ・ 1973 Blue Mountain Lake ・ 1975 Haicheng, China ・ 1978 Oaxaca, Mexico ・ 1978 Izu, Japan
‘Not Predicted’ ・ 1976 Tangshan, China (M7.7 650,000 est. casualties) ・ 2004 Parkfield, California
Successes and Failures
Blue Mountain Lake, NY
‘Dilatancy’
Scholz et al., 1973Dilatancyhardening
Prediction of the 1975 Haicheng, ChinaEarthquake (M7.3)
Prediction based on foreshocksand animal behavior saved many lives
Short-Term Crustal Deformation Precursor(M 8.1 Tonankai Earthquake 1944)
Mogi, 1984
Short-Term Electromagnetic Precursor1989 Loma Prieta Earthquake
Fraser-Smith, et al., 1990
1978 Oaxaca, Mexico (Ohtake et al., 1981)
Intermediate-Term:Seismicity Patterns
‘Mogi Doughnut’
Dilatancy Hardening
Mogi, 1985
Intermediate-Term:Crustal Deformation
1964 Niigata earthquake
Wakita, 1981
Intermediate-Term:Water and Chemical
M 7.0 Izu earthquake 1978
‘Successfully’ Predicted
・ 1973 Blue Mountain Lake
・ 1975 Haicheng, China
・ 1978 Oaxaca, Mexico
・ 1978 Izu, Japan
Parkfield Earthquake Prediction Experiment
95% probability thatM5.5 to 6 will occur1985-1993.
Based on •Recurrence pattern•Characteristic waveforms
Bakun and McEvilly, 1979
- Repeating Characteristic Earthquakes- M5 foreshock 17 minutes before 1934 and 1966 events
Not Predicted ・ 1976 Tangshan, China (M7.7 650,000 est. casualties) ・ 2004 Parkfield, California
For short-term prediction, there have been more negative results than positive results:
Other precursors have not been consistently seen
Why has there been lack of continued success in observing precursors?
•Animal experiments have failed•Original observations were hindsight• Instrumentation •Geology dependent (including lights and piezoelectric effects)• Predictive algorithms have not worked (at least short-term)•Earthquakes may be non-characteristic• No connection to tides or planetary alignment• No psychics have made consistent predictions
Short-term minutes to weeks
Intermediate-term months to 10 years
Long-term > 10 years
Earthquake Forecasting
Recurrence times of earthquakes to forecast future earthquakes
• Using historic data• Using geologic data
Shimazaki and Nakata, 1980
Earthquake Cycle
Periodic Time-predictable Slip-predictable
History of Nankai Earthquakes
PALEOSEISMOLOGY
Trenching faults to find geological evidence of past earthquakes
Pallet Creek site on the San Andreas fault
Periodic Time-predictable Slip-predictable
Shimazaki and Nakata, 1980
Earthquake Cycle
100 years
Conditional Probability
Probability
Well defined recurrence interval
Wide range of recurrence intervals (Large variability)
(Small variability)
Variability in Repeating Earthquakes
Probabilistic Earthquake Forecasting for California
Hector Mines Landers 1992
Parkfield 2004
Loma Prieta 1989
http://geohazards.cr.usgs.gov/eq/
USGS National Hazard Maps
Earthquake Hazards
• Ground Shaking
• Surface Faulting
• Landslides and Liquefaction
• Avalanches and soil (mud flows)
NEIC Catalog Seismicity (M>4.5) 1964-2005
What about Thailand?
・ Low Seismicity・ No Historical Earthquakes・ Active Faults (?)
・ Probability is low for future earthquakes
But earthquakes can happen in low probability regions and offshore
Will we be able to predict earthquakes in the future ? Long-term: Probably Intermediate term: Maybe Short-term: Maybe
Future Outlook
Don’t forget that the precursorto a tsunami is the earthquake.
Parkfield Earthquake Prediction Experiment
Loading or deformation cycle
– Four phases• Interseismic• Preseismic• Coseismic• Postseismic
For short-term precursors, there are currently more ‘negative’ results than ‘positive’results.
Kanamori et al., 1996Johnston and Linde, 2002
Distance Measurements on theSan Andreas fault
Matsushiro strainmeter
Earthquake Prediction Research in the 1970’s
Laser Distance Measurements
M 6.8 Nisqually 2001Ground Shaking
Surface faulting
Bei-Fung Bridge near Fung-Yan city, 1999 Chi-Chi, Taiwan earthquake
1964 Niigata EarthquakeLiquefaction