Earthquake Prediction - STEPS TOWARDS EARTHQUAKE PREDICTION...

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STEPS TOWARDS EARTHQUAKE PREDICTION
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Earthquake Prediction? OUTLINE Long-term earthquake forecasting / seismic hazard analysis (covered in previous lectures) Short-term EQ prediction Precursors Haicheng example Research on foreshocks and the USGS seismic alert system Earthquake triggering: How earthquakes affect each other Early warning systems
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Seismic Hazard Analysis How likely? --how often? -- last EQ? How big? -- how long? How strong? --How far away? San Andreas San Jacinto Cucamonga (SBdno+Coachella) (SBdno Val.) 59% 31% ??? 150-160 yr 230 yr 600-700 yr 1812 (199 yr ago) ~ 200 yrs ago ??? M7.8 M7.3 M6.7 290 km 90 km 27 km 1 km 6 km 9 km 0.8 g 0.5 g 0.3 g
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Seismic Hazard Analysis See pp. 8-9 in Putting Down Roots in Earthquake Country Level of shaking with a 10% probability of exceedance within 50 years 0.1-0.2 g 0.2-0.3 g 0-0.1 g 0.3-0.4 g 0.4-0.5 g 0.5-0.6 g 0.6-0.7 g 0.7-0.8 g >0.8 g CSUSB What does this map say about the seismic hazard at point A? A
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What good is seismic hazard analysis? Informs individuals and government about the level of seismic hazard so that they can take appropriate action, such as determining appropriate building codes and zoning laws knowing what forces engineers need to design buildings to resist prioritization of retrofit projects
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Earthquake Prediction? OUTLINE Long-term earthquake forecasting / seismic hazard analysis (covered in previous lectures) Short-term EQ prediction Precursors Haicheng example Research on foreshocks and the USGS seismic alert system Earthquake triggering: How earthquakes affect each other Early warning systems
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Short-term earthquake prediction Possible earthquake precursors: Foreshocks 50% of earthquakes are preceded by foreshocks
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What is a foreshock? Foreshock: a relatively small earthquake that precedes a larger earthquake by a few days or weeks and originates at or near hypocenter of the larger earthquake. Example: March 9 th , 2011 M7.2 Hypocenter close to Tohoku hypocenter March 11 th , 2011 M9.0
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Short-term earthquake prediction Possible earthquake precursors: Foreshocks 50% of earthquakes are preceded by foreshocks Emission of Radon gas Changes in water temperature in wells Changes of water level in wells Compression, tilting or extension of the Earth’s crust
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Radon concentration in well water Water temperature in wells Water level in wells Strain (extension, compression or tilting) date of earthquake 1977 Sept Oct Nov Dec Jan Feb 1978 Izu-Oshima-kinkai earthquake 14 January 1978 (M7.0) Precursors identified in hind-sight :
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Short-term earthquake prediction Possible earthquake precursors: Foreshocks 50% of earthquakes are preceded by foreshocks Emission of Radon gas Changes in water temperature in wells Changes of water level in wells Compression, tilting or extension of the Earth’s crust Changes in electromagnetic fields
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Short-term earthquake prediction Extremely low frequency (ELF) electromagnetic waves ELF levels 20 times higher than normal were detected 2 weeks prior
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