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Science 9 July 1993:
Vol. 261. no. 5118, pp. 177 - 183
DOI: 10.1126/science.261.5118.177
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Articles

Teleseismic Detection of a Slow Precursor to the Great 1989 Macquarie Ridge Earthquake

Pierre F. Ihmlé 1, Paolo Harabaglia 1, and Thomas H. Jordan 1

1 Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139

Low-frequency spectra for the 1989 Macquarie Ridge earthquake (magnitude 8.2) show an amplitude increase and a phase-delay decrease below 6 millihertz that require a short-term slow precursor. This earthquake can be modeled as a compound event in which a fast-rupturing, ordinary earthquake was initiated by an episode of slow, smooth deformation that began more than 100 seconds before the main shock. The moment released in the slow precursor was large, about 3 x 1020 newton-meters, equivalent to an event of magnitude 7.6. The data are consistent with the precursor being generated in a region of the oceanic upper mantle below the main rupture.

Submitted on March 17, 1993
Accepted on June 1, 1993


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Low-Frequency Properties of Intermediate-Focus Earthquakes.
(2002)
Bulletin of the Seismological Society of America 92, 2434-2448
Continuous monitoring of seismic energy release associated with the 1994 Northridge earthquake and the 1992 Landers earthquake.
S. Kedar and H. Kanamori (1996)
Bulletin of the Seismological Society of America 86, 255-258
   Abstract »    PDF »
Beginnings of earthquakes in the Mexican subduction zone on strong-motion accelerograms.
J. G. Anderson and Q. Chen (1995)
Bulletin of the Seismological Society of America 85, 1107-1115
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Seismic Evidence for an Earthquake Nucleation Phase.
W. L. Ellsworth, W. L. Ellsworth, and G. C. Beroza (1995)
Science 268, 851-855
   Abstract »    PDF »
Teleseismic Search for Slow Precursors to Large Earthquakes.
P. F. Ihmle, P. F. Ihmle, and T. H. Jordan (1994)
Science 266, 1547-1551
   Abstract »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)