Enhanced Observations with Borehole Seismographic Networks. The Parkfield, California Experiment

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The data acquired in the Parkfield, California experiment are unique and they are producing results that force a new look at some conventional concepts and models for earthquake occurrence and fault-zone dynamics. No fault-zone drilling project can afford to neglect installation of such a network early enough in advance of the fault-zone penetration to have a well-defined picture of the seismicity details (probably at least 1000 microearthquakes--an easy 2-3 year goal for the M<0 detection of a borehole network). Analyses of nine years of Parkfield monitoring data have revealed significant and unambiguous departures from stationarity both in the seismicity characteristics ... continued below

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4 pages

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McEvilly, T.V.; Karageorgi, E. & Nadeau, R.M. January 2, 1997.

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Description

The data acquired in the Parkfield, California experiment are unique and they are producing results that force a new look at some conventional concepts and models for earthquake occurrence and fault-zone dynamics. No fault-zone drilling project can afford to neglect installation of such a network early enough in advance of the fault-zone penetration to have a well-defined picture of the seismicity details (probably at least 1000 microearthquakes--an easy 2-3 year goal for the M<0 detection of a borehole network). Analyses of nine years of Parkfield monitoring data have revealed significant and unambiguous departures from stationarity both in the seismicity characteristics and in wave propagation details within the S-wave coda for paths within the presumed M6 nucleation zone where we also have found a high Vp/Vs anomaly at depth, and where the three recent M4.7-5.0 sequences have occurred. Synchronous changes well above noise levels have also been seen among several independent parameters, including seismicity rate, average focal depth, S-wave coda velocities, characteristic sequence recurrence intervals, fault creep and water levels in monitoring wells. The significance of these findings lies in their apparent coupling and inter-relationships, from which models for fault-zone process can be fabricated and tested with time. The more general significance of the project is its production of a truly unique continuous baseline, at very high resolution, of both the microearthquake pathology and the subtle changes in wave propagation.

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4 pages

Notes

OSTI as DE00842021

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  • 1st workshop on the development of a multiborehole observatory at the Gulf of Corinth, Athens (GR), 10/25/1997--10/28/1997

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  • Report No.: LBNL--44990
  • Grant Number: AC03-76SF00098
  • Office of Scientific & Technical Information Report Number: 842021
  • Archival Resource Key: ark:/67531/metadc781313

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • January 2, 1997

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  • Dec. 3, 2015, 9:30 a.m.

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  • Sept. 25, 2017, 4:08 p.m.

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McEvilly, T.V.; Karageorgi, E. & Nadeau, R.M. Enhanced Observations with Borehole Seismographic Networks. The Parkfield, California Experiment, article, January 2, 1997; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc781313/: accessed December 11, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.