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Published October 1980 | Published
Journal Article Open

Modeling the long-period body waves from shallow earthquakes at regional ranges


A procedure for modeling P and PL waves recorded on long-period WWSSN instruments at ranges 1° to 12° is presented. Following the experience gained by modeling explosions (Helmberger, 1972), we demonstrate that these long-period phases are adequately treated by a single crustal layer for most of Western United States. After generating the Green's functions at the various ranges for the three fundamental dislocation types, we need only construct linear combinations of these vectors to represent any arbitrary oriented earthquake. The waveform patterns produced from the various fault types are quite diagnostic with the dip-slip orientations showing a strong ringing nature which is caused by the vertical SV lobes. To test the usefulness of this technique, we construct synthetics for some well-studied west coast earthquakes where the orientation, time history, and moment have been determined independently. Comparing the predicted seismograms with observations, we find good agreement in waveshapes and amplitudes.

Additional Information

© 1980 Seismological Society of America. Manuscript received February 4, 1980. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force of Scientific Research under Contract F49620-77-C-0022.

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