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Estimation of strong ground motions from hypothetical earthquakes on the Cascadia subduction zone, Pacific Northwest

Heaton, Thomas H. and Hartzell, Stephen H. (1989) Estimation of strong ground motions from hypothetical earthquakes on the Cascadia subduction zone, Pacific Northwest. Pure and Applied Geophysics, 129 (1-2). pp. 131-201. ISSN 0033-4553. doi:10.1007/BF00874626.

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Strong ground motions are estimated for the Pacific Northwest assuming that large shallow earthquakes, similar to those experienced in southern Chile, southwestern Japan, and Colombia, may also occur on the Cascadia subduction zone. Fifty-six strong motion recordings for twenty-five subduction earthquakes of M_s ≥ 7.0 are used to estimate the response spectra that may result from earthquakes M_w <8 1/4. Large variations in observed ground motion levels are noted for a given site distance and earthquake magnitude. When compared with motions that have been observed in the western United States, large subduction zone earthquakes produce relatively large ground motions at surprisingly large distances. An earthquake similar to the 22 May 1960 Chilean earthquake (M_w 9.5) is the largest event that is considered to be plausible for the Cascadia subduction zone. This event has a moment which is two orders of magnitude larger than the largest earthquake for which we have strong motion records. The empirical Green's function technique is used to synthesize strong ground motions for such giant earthquakes. Observed teleseismic P-waveforms from giant earthquakes are also modeled using the empirical Green's function technique in order to constrain model parameters. The teleseismic modeling in the period range of 1.0 to 50 sec strongly suggests that fewer Green's functions should be randomly summed than is required to match the long-period moments of giant earthquakes. It appears that a large portion of the moment associated with giant earthquakes occurs at very long periods that are outside the frequency band of interest for strong ground motions. Nevertheless, the occurrence of a giant earthquake in the Pacific Northwest may produce quite strong shaking over a very large region.

Item Type:Article
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URLURL TypeDescription DOIArticle
Heaton, Thomas H.0000-0003-3363-2197
Additional Information:© 1989 Birkhäuser Verlag, Basel. Received August 5, 1986, accepted July 14, 1987. We thank Hiroo Kanamori and C. B. Crouse for helpful discussions and we thank C. B. Crouse for his help in collection of the digitized strong motion data used in this report. We thank Bob Page, Bill Joyner, and Heidi Houston for their comments on this manuscript. This work was partially supported by the United States Nuclear Regulatory Commission.
Funding AgencyGrant Number
Nuclear Regulatory Commission (NRC)UNSPECIFIED
Subject Keywords:Earthquake, strong motion, subduction, Cascadia, Washington, Oregon
Issue or Number:1-2
Record Number:CaltechAUTHORS:20130305-094649151
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37297
Deposited By: Tony Diaz
Deposited On:05 Mar 2013 23:56
Last Modified:09 Nov 2021 23:28

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