Schedule Oct 28, 2005
Long-Range Earthquake Triggering
Dr. Emily Brodsky, UCLA

Long-range triggering of earthquakes provides a window into earthquake initiation processes. In this talk, I review the observational facts about long-range triggering and discuss their implications for the start of slip in general. We observe that seismic shaking make earthquakes, long-range triggering is more often observed in geothermal areas, seismicity persists and other long-range triggered phenomena occur such as deformation and water level change. The last observation motivates a detailed investigation of the coupling between seismic waves and pore pressures. Based on water well records in Grants Pass, OR, I conclude that unclogging of fractures results in pore pressure redistribution during earthquakes which can in turn trigger earthquakes. This redistribution of pore pressure is consistent with triggering thresholds in Long Valley Caldera. As further evidence of the macroscopic effects of very small shaking, I also discuss large permeability changes as a result of small seismic stresses at Pinon Flat Geophysical Observatory.

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