Depths to Larger Earthquakes Associated with Crustal Loading

Twenty-eight earthquakes associated with reservoir filling at Koyna (Western India), Kariba (Rhodesia) and Kremasta (Greece) are with one exception relocated at mid-crustal depths or deeper. Depth resolution is achieved by a master earthquake technique. Nearly equal down-dip and strike dimensions can be inferred for ruptures initiated at the times of main shocks provided larger aftershocks mark the deepest penetration of these ruptures. Ancillary faulting is inferred from some aftershock locations. An unexpected and as yet unexplained result is that foreshocks, of which only five are relocated, are also deeper than their main shocks. In contrast to our results published locations based on local recordings reveal, with varying degrees of certainty, concentrations of activity above foci of main shocks. Larger magnitude activity at depth may result from higher levels of deviatoric stress or different source processes or both.