Effect of critical reflections from the Moho on the attenuation of strong ground motion

Paul G. Somerville, Nancy F. Smith, Robert W. Graves

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The peak accelerations from the Loma Prieta earthquake showed a more gradual attenuation with distance than predicted by standard attenuation relations. By analyzing profiles of main-shock and aftershock recordings with absolute times, and by generating profiles of synthetic strong-motion records, evidence has been examined for the effects of wave propagation in a layered crust on the attenuation of strong ground motions. At distances within about 50 km, the motions with the largest amplitudes were due to waves traveling directly upward from the source. Analysis of arrival time and phase velocity, however, indicates that the motions with the largest amplitudes at distances beyond about 50 km were critical reflections from interfaces beneath the source, predominantly the Moho. Further support for this interpretation is provided by recordings in San Francisco of explosions fired in the Loma Prieta epicentral area, which also show strong critical reflections from the Moho. -from Authors

Original languageEnglish
Pages (from-to)67-75
Number of pages9
JournalUS Geological Survey Professional Paper
Volume1551 A
Publication statusPublished - 1994
Externally publishedYes

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