Seismicity Precursors of the M6.0 2004 Parkfield and M7.0 1989Loma Prieta Earthquakes

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The M6.0 2004 Parkfield and M7.0 1989 Loma Prietastrike-slip earthquakes on the San Andreas Fault (SAF) were preceded byseismicity peaks occurring several months prior to the main events.Earthquakes directly within the SAF zone were intentionally excluded fromthe analysis because they manifest stress-release processes rather thanstress accumulation. The observed increase in seismicity is interpretedas a signature of the increasing stress level in the surrounding crust,whereas the peaks and the subsequent decrease in seismicity areattributed to damage-induced softening processes. Furthermore, in bothcases there is a distinctive zone of low seismic activity that surroundsthe epicentral region in the pre-event period. The increase of ... continued below

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Korneev, Valeri A. March 9, 2006.

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The M6.0 2004 Parkfield and M7.0 1989 Loma Prietastrike-slip earthquakes on the San Andreas Fault (SAF) were preceded byseismicity peaks occurring several months prior to the main events.Earthquakes directly within the SAF zone were intentionally excluded fromthe analysis because they manifest stress-release processes rather thanstress accumulation. The observed increase in seismicity is interpretedas a signature of the increasing stress level in the surrounding crust,whereas the peaks and the subsequent decrease in seismicity areattributed to damage-induced softening processes. Furthermore, in bothcases there is a distinctive zone of low seismic activity that surroundsthe epicentral region in the pre-event period. The increase of seismicityin the crust surrounding a potential future event and the development ofa low-seismicity epicentral zone can be regarded as promising precursoryinformation that could help signal the arrival of large earthquakes. TheGutenberg-Richter relationship (GRR) should allow extrapolation ofseismicity changes down to seismic noise level magnitudes. Thishypothesis is verified by comparison of seismic noise at 80 Hz with theParkfield M4 1993-1994 series, where noise peaks 5 months before theseries to about twice the background level.

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  • Report No.: LBNL--60012
  • Grant Number: DE-AC02-05CH11231
  • DOI: 10.2172/901226 | External Link
  • Office of Scientific & Technical Information Report Number: 901226
  • Archival Resource Key: ark:/67531/metadc891334

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  • March 9, 2006

Added to The UNT Digital Library

  • Sept. 22, 2016, 2:13 a.m.

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  • Sept. 29, 2016, 6:58 p.m.

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Korneev, Valeri A. Seismicity Precursors of the M6.0 2004 Parkfield and M7.0 1989Loma Prieta Earthquakes, report, March 9, 2006; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc891334/: accessed August 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.