Abstract

Earthquake source theories of Haskell, Brune, and Savage have been drawn upon to develop a description of an earthquake as a major slip accompanied by many smaller tensional and slip events. We find natural explanations of several previously unexplained observations, such as:

Robustness of the MS: mb discriminant,

P corner frequency higher than S corner frequency for shallow earthquakes,

High-frequency P/S amplitude ratio higher for shallow earthquakes than previous theories predict,

Increase of complexity as a function of third moment,

Small mb relative to MS for transform faults.

(This can also be explained by emergent short-period P wave forms or by a low-Q region underlying the source).

The theory predicts that MS:mb populations of earthquakes and explosions will not converge at small magnitudes. The theory also suggests that the standard interpretations of corner-frequency measurements can provide only a lower limit to fault-plane dimensions and, in combination with the moment, only an upper limit on stress drop.

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