Mapping Active Magma Chambers by b-Values

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9614783 Wyss This research involves testing and development of the hypothesis that the b-value, the Gutenberg-Richter earthquake frequency magnitude distribution, is significantly different in crustal volumes associated with volcanic magma chambers. Small volumes (radii of 1 to 3 km) with high b-values of about 1.7 are embedded in background activity in the crust with b-values of about 0.8. Under several volcanos, where the locations of magma chambers are known from other evidence, the crustal volumes with anomalously high b-values map out the magma chambers. This work involves the testing of this hypothesis and the investigation of other possible causes of high b-values such as active dikes and magma vesiculation along with their associated temporal variations. This research is a component of the National Earthquake Hazard Reduction Program. ***