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The Origin of the Tsunami Excited by the Earthquake – Faulting or Slumping

Ma, Kuo-Fong and Satake, Kenji and Kanamori, Hiroo (1994) The Origin of the Tsunami Excited by the Earthquake – Faulting or Slumping. In: The Loma Prieta, California, Earthquake of October 17, 1989 - Hydrologic Disturbances. U.S. Geological Survey professional paper. No.1551-E. United States Geological Survey , Washington, DC, pp. 3-9.

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The first arrival of the tsunami recorded at Monterey, California, was about 10 min after the origin time of the earthquake. Using an elastic half space, we computed vertical ground displacements for many different fault models for the Loma Prieta earthquake and used them as the initial condition for computation of the tsunami in Monterey Bay. The synthetic tsunami computed for the uniform dislocation model determined from seismic data can explain the arrival time, polarity, and amplitude of the beginning of the tsunami. However, the period of the synthetic tsunami is too long compared with the observed. We tested other fault models with more localized slip distribution. None of the models could explain the observed period. The residual waveform, the observed minus the synthetic waveform, begins as a downward motion at about 18 min after the origin time of the earthquake and could be interpreted as due to a secondary source near Moss Landing. If the large-scale slumping near Moss Landing suggested by an eyewitness observation occurred about 9 min after the origin time of the earthquake, it could explain the residual waveform. To account for the amplitude of the observed tsunami, the volume of sediments involved in the slumping is approximately 0.012 km^3. Thus the most likely cause of the tsunami observed at Monterey is the combination of the vertical uplift of the sea floor due to the main faulting and a large-scale slumping near Moss Landing.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Satake, Kenji0000-0002-3368-3085
Kanamori, Hiroo0000-0001-8219-9428
Alternate Title:The Loma Prieta, California, Earthquake of October 17, 1989: Earthquake Occurrence
Additional Information:© 1994 USGS. This work was supported by National Science Foundation grant EAR 89-15987 and U.S. Geological Survey grant 14-08-001-G1832. Contribution No. 4949, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.
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NSFEAR 89-15987
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences4949
Series Name:U.S. Geological Survey professional paper
Issue or Number:1551-E
Record Number:CaltechAUTHORS:20141111-140457823
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51594
Deposited By: Tony Diaz
Deposited On:11 Nov 2014 22:18
Last Modified:09 Mar 2020 13:19

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