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quake prediction needs what 3 things?
epicenter, fault segment, magnitude
2 types of prediction
- -short(w/in hrs of quake)
- -long(years,decades, called “forecasting”
cannot predict short term (used to think precursers could tell us)
- -expected quake at Parkfield but it was late
- -foreshock swarms-small “soon to be” earthquakes in the epicenter area—rocks that are under stress and will soon rupture
- -Tilting of land-rocks may expand prior to rupture
- -changes in water
- -abnormal animal behavior
Long Term Prediction
called “forecasts”, give probabilities of quakes, of a certain size (such as richter value), not useful if people depend upon warnings and resulting evacuation ptior to quake, helpful for buildings esp in hazard zones
estimating recurrence times of major earthquakes on segments of the San Andreas faults, how?
-use historical records to work out averages
- - trenching and finding geological evidence, San Andreas has earthquake cycles
- -did not predict loma prieta but the quake occurred on a segment of the San Andreas Fault which was a seismic gap
stress-triggering: long term prediction?
- -suggests that although the stress in the rocks, in a segment of a fault in which the epicenter of an earthquake occurs, is decreased by that earthquake that neighboring segments may have their stress actually INCREASED, thus making it MORE likely that they will experience a major quake.
- -May not be immediate
Landers quake and stress
- -relieved stress in some areas near the quake which increased the stress in other areas
- -quake increased the possibility of a quake on certain faults & fault segments
- -decreased the time until the next major earthquake