Location
St. Louis, Missouri
Presentation Date
10 Mar 1991, 1:00 pm - 3:00 pm
Abstract
The amplitudes of strong ground motions from the Loma Prieta earthquake recorded in the San Francisco and Oakland areas exceeded the levels predicted by standard empirical attenuation relations. Preliminary analysis of accelerograms having known trigger times suggests that the elevation of ground motion amplitudes in the distance range of approximately 40 to 100 km was due to critical reflections from the base of the crust. These reflections were large and occurred at relatively close range because of the deep focal depth of the earthquake and the strong velocity gradient at the base of the crust, and were enhanced by rupture directivity. These motions were further amplified, presumably by impedance contrast effects, at soft soil sites in San Francisco and Oakland. The effect of the critical reflections in amplifying peak accelerations of the Loma Prieta earthquake in the San Francisco and Oakland regions was as large as the effect of soft soil site conditions.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
2nd International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics
Publisher
University of Missouri--Rolla
Document Version
Final Version
Rights
© 1991 University of Missouri--Rolla, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
Somerville, P. G. and Smith, N. F., "Source, Path and Site Effects on Loma Prieta Strong Motions" (1991). International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. 14.
https://scholarsmine.mst.edu/icrageesd/02icrageesd/session12/14
Included in
Source, Path and Site Effects on Loma Prieta Strong Motions
St. Louis, Missouri
The amplitudes of strong ground motions from the Loma Prieta earthquake recorded in the San Francisco and Oakland areas exceeded the levels predicted by standard empirical attenuation relations. Preliminary analysis of accelerograms having known trigger times suggests that the elevation of ground motion amplitudes in the distance range of approximately 40 to 100 km was due to critical reflections from the base of the crust. These reflections were large and occurred at relatively close range because of the deep focal depth of the earthquake and the strong velocity gradient at the base of the crust, and were enhanced by rupture directivity. These motions were further amplified, presumably by impedance contrast effects, at soft soil sites in San Francisco and Oakland. The effect of the critical reflections in amplifying peak accelerations of the Loma Prieta earthquake in the San Francisco and Oakland regions was as large as the effect of soft soil site conditions.
