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This Article Figures Only Full Text Full Text (PDF) Supplemental figures and table of empirical MMI site corrections. Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Bakun, W. H. Search for Related Content GeoRef GeoRef Citation

Estimating Locations and Magnitudes of Earthquakes in Southern California from Modified Mercalli Intensities

¹ U.S. Geological Survey
Earthquakes Hazards Team
Menlo Park, California 94025-3591

Modified Mercalli intensity (MMI) assignments, instrumental moment magnitudes M, and epicenter locations of thirteen 5.6 M 7.1 "training-set" events in southern California were used to obtain the attenuation relation MMI = 1.64 + 1.41M – 0.00526 * _h – 2.63 * log _h, where _h is the hypocentral distance in kilometers and M is moment magnitude. Intensity magnitudes M_I and locations for five 5.9 M 7.3 independent test events were consistent with the instrumental source parameters. Fourteen "historical" earthquakes between 1890 and 1927 were then analyzed. Of particular interest are the M_I 7.2 9 February 1890 and M_I 6.6 28 May 1892 earthquakes, which were previously assumed to have occurred near the southern San Jacinto fault; a more likely location is in the Eastern California Shear Zone (ECSZ). These events, and the 1992 M 7.3 Landers and 1999 M 7.1 Hector Mine events, suggest that the ECSZ has been seismically active since at least the end of the nineteenth century. The earthquake catalog completeness level in the ECSZ is M 6.5 at least until the early twentieth century.

Online material: Figures and table of empirical MMI site corrections.

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