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Factors Influencing Tremor Occurrence in Subduction Zones

BROWN, J. R., Stanford University, Stanford, CA,; BEROZA, G. C., Stanford University, Stanford, CA,

Tectonic tremor from multiple circum-Pacific subduction zones has been shown to consist of repeating low frequency earthquakes on the plate interface. Tremor/LFE occurrence in some areas exhibits episodic behavior down-dip of previous great mega-thrust earthquakes suggesting that the tremor may delimit the lower edges of large earthquake rupture. We investigate where and why tremor does (and does not) occur. We compare observations of LFE locations in five subduction zones: southwest Japan, Cascadia, Alaska-Aleutian Arc, Costa Rica and Mexico. We compare the LFE location patterns among the five areas with subduction parameters such as incoming sediment thickness, plate age, convergence rate and temperature. A preliminary conclusion is that temperature exerts a strong influence on LFE depth; warmer subduction zones (e.g. southwest Japan, Cascadia) experience tremor activity around 30-40 km depth, whereas cooler subduction zones (e.g. the Alaska-Aleutian Arc) experience tremor between 45-55 km depth. In addition, sediment thickness seems to play little to no role in tremor/LFE depths. This may be attributable to the amount of shear and chemical alterations that occur in the primary seismogenic zone up-dip from the tremor zone.


Last Modified: 2011 Aug 10