A comparison of broadband source spectra, seismic energies, and stress drops of the 1989 Loma Prieta and 1988 Armenian earthquakes

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Geophysical Research Letters (American Geophysical Union); (USA)

DOI:https://doi.org/10.1029/GL017i009p01413· OSTI ID:6400561

Houston, H ^[1]

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1. Univ. of California, Santa Cruz (USA)

Broadband source spectra of the 1989 Loma Prieta (M{sub W} = 6.9) and 1988 Armenian (M{sub W} = 6.7) earthquakes are computed at periods from 1 to 50 sec using digitally-recorded teleseismic P body waves. The effects of attenuation, geometrical spreading, and radiation pattern are removed from the spectra of individual stations, which are then averaged. The source spectra of the Loma Prieta and Armenian earthquakes are higher for their seismic moments than the spectra of 11 intraplate earthquakes studied by Zhuo and Kanamori (1987), which in turn are 2 to 4 times larger than average spectra of interplate subduction zone earthquakes. The seismically radiated energy can be computed from the source spectrum using Haskell's (1964) formulation assuming a point source with no directivity. An Orowan stress drop can be obtained from the seismic energy and moment. The Orowan stress drops for the Loma Prieta and Armenian earthquakes are both about 20 bars, significantly higher than Orowan stress drops of recent large interplate earthquakes. There is a positive correlation between the Orowan stress drops and the estimated repeat times, consistent with the notion that mechanical fault strength increases with increasing interseismic period.

• OSTI ID: 6400561
• Journal Information: Geophysical Research Letters (American Geophysical Union); (USA), Vol. 17:9; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
EARTHQUAKES
COMPARATIVE EVALUATIONS
USSR
ATTENUATION
DATA ANALYSIS
EARTHQUAKE MAGNITUDE
GEOLOGIC FAULTS
SEISMIC P WAVES
SEISMIC SOURCES
SLIP
STRESS ANALYSIS
ASIA
EASTERN EUROPE
EUROPE
FEDERAL REGION IX
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
NORTH AMERICA
SEISMIC EVENTS
SEISMIC WAVES
USA
580000* - Geosciences