3-DIMENSIONAL SEISMIC VELOCITY ANOMALIES AND THEIR RELATION TO LOCAL SEISMICITY

This is a brief review of recent results on three-dimensional seismic velocity structures, determined by the method of Aki, Christoffersson and Husebye, using the teleseismic and local earthquake P-time data. Particular attention was given to the relation between the velocity structure and local seismicity. We found that seismic activity may be associated with either low- or high-velocity anomalies, presumably depending on whether the structural weakness, which invites stress concentration, or the ductility, which cannot sustain the tectonic stress, is causing the velocity low. © 1979.