Reevaluation of the macroseismic effects of the 1887 Sonora, Mexico earthquake and its magnitude estimation

Geo-UNAM : boletín informativo del área de ciencias de la tierra
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Abstract

The Sonora, Mexico, earthquake of 3 May 1887 occurred a few years before the start of the instrumental era in seismology. We revisit all available accounts of the earthquake and assign Modified Mercalli Intensities (MMI), interpreting and analyzing macroseismic information using the best available modern methods. We find that earlier intensity assignments for this important earthquake were unjustifiably high in many cases. High intensity values were assigned based on accounts of rock falls, soil failure or changes in the water table, which are now known to be very poor indicators of shaking severity and intensity. Nonetheless, reliable accounts reveal that light damage (intensity VI) occurred at distances of up to ~200 km in both Mexico and the United States. The resulting set of 98 reevaluated intensity values is used to draw an isoseismal map of this event. Using the attenuation relation proposed by Bakun (2006b), we estimate an optimal moment magnitude of Mw7.6. Assuming this magnitude is correct, a fact supported independently by documented rupture parameters assuming standard scaling relations, our results support the conclusion that northern Sonora as well as the Basin and Range province are characterized by lower attenuation of intensities than California. However, this appears to be at odds with recent results that Lg attenuation in the Basin and Range province is comparable to that in California.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Reevaluation of the macroseismic effects of the 1887 Sonora, Mexico earthquake and its magnitude estimation
Series title Geo-UNAM : boletín informativo del área de ciencias de la tierra
Year Published 2008
Language English
Publisher Universidad Nacional Autónoma de México
Publisher location México, D.F.
Contributing office(s) Earthquake Science Center
Description 16 p.
Larger Work Type Article
Larger Work Subtype Journal Article
First page 1
Last page 15
Country Mexico, United States
Other Geospatial Northern Sonora, Basin and Range province
Online Only (Y/N) N
Additional Online Files (Y/N) N
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