Spectral Shapes and Amplifications for the Loma Prieta Earthquake of October 17, 1989by Bijan Mohraz, Southern Methodist Univ, Dallas, United States,
Mehran Tiv, Southern Methodist Univ, Dallas, United States,
Abstract: The 1971 San Fernando earthquake provided engineers and seismologists with the largest number of strong motion accelerograms ever recorded for an earthquake at that time. Those records together with similar data from previous earthquakes were used in numerous studies to investigate the influences of soil condition, earthquake magnitude, epicentral distance and duration of strong motion on peak ground motion, response amplifications, and spectral shapes. Some of the studies showed that amplifications and spectral shapes for alluvium and rock differ. These findings were ultimately incorporated in ATC 3-06 and in the Uniform Building Code. This paper examines the amplifications and spectral shapes from the records in the Loma Prieta, California, Earthquake of October 17, 1989, and compares them with the amplifications and spectral shapes from previous earthquakes and with the spectral shapes recommended by the UBC. The study shows that while the amplifications and spectral shapes for alluvium from the Loma Prieta earthquake are very similar to those from previous earthquakes, the spectral shapes for rock are significantly different.
Subject Headings: Earthquakes | Ground motion | Rocks | Alluvium | Seismic tests | Seismic effects | Building codes | North America | California | United States
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