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Published March 14, 1980 | public
Journal Article

The Oaxaca, Mexico, Earthquake of 29 November 1978: A Preliminary Report on Aftershocks

Abstract

Aftershocks of the 29 November 1978 Oaxaca, Mexico, earthquake (surface-wave magnitude M_s = 7.8) define a rupture area of about 6000 square kilometers along the boundary of the Cocos sea-plate subduction. This area had not ruptured in a large (M_s ≥ 7), shallow earthquake since the years 1928 and 1931 and had been designated a seismic "gap". The region has also been seismically quiet for small to moderate (M ≥ 4), shallow (depth ≤ 60 kilometers) earthquakes since 1966; this quiet zone became about six times larger in 1973. A major earthquake (M_s = 7.5 ± 0.25) was forecast at this location on the basis of the quiescence that began in 1973. The aftershock data indicate that an area approximately equivalent in size to the seismic gap has now broken.

Additional Information

© 1980 American Association for the Advancement of Science. 13 November 1979. We thank A. Capella for support in obtaining the field data; D. Resendiz, J. Prince and I. Galindo for logistical support; H. Kanamori and J. B. Minster for ongoing interest and suggestions; A. Uribe, D. Novelo, J. Bonifaz, A. del Castillo, J. Gonzalez, L. Morales, F. Nuiiez, E. Vazquez, C. Jiminez, Z. Jimenez, and F. Medina for help in the collection of data; J. Lower for engineering assistance; and M. French, M. Guzman, R. Castro, and L. Astiz for help in data processing. Partial support for this project was provided by U.S. Geological Survey contract 14-08-0001-17631. Contribution 3225, Division of Geological and Planetary Sciences, California Institute of Technology.

Additional details

Created:
August 19, 2023
Modified:
October 20, 2023