EPS C20 Lecture 16: Lecture 16
22 Oct 2016
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Document Summary
The shaking ground peak acceleration (pga) measured in % of g. 1g = gravitational acceleration everything > 1g: weightlessness. They are sick of saying i don"t know . The public wants eq prediction and we can"t deliver. To be useful, we have to pinpoint: when, where, how strong. These are scientifically very stringent and challenging requirements. We need to have at least one measureable precursor, which consistently occurs before each eq: foreshocks, seismic swarms, change in velocity of seismic waves, ground uplift, radon gas, electrical conductivity, animal behavior. Success: haicheng, ne china, february 1975: predicted an imminent earthquake, evacuation order, nine hours later a large earthquake struck destroying many homes but there was little loss of life. Failure/false alarm: kwangtung province, august 1976: predicted an imminent earthquake, evacuation ordered, people slept in tents for nearly 2 months no earthquake. Failure/missed alarm: tangshan, july 1976: no immediate precursors, no evacuation, more than 250,000 people died one of the deadliest earthquakes.
