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Detailed Reference Information |
Johnson, P.A. and McEvilly, T.V. (1995). Parkfield seismicity: Fluid-driven. Journal of Geophysical Research 100: doi: 10.1029/95JB00474. issn: 0148-0227. |
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Characteristics of microearthquake occurrence along the locked-to-creeping transition of the San Andreas fault at Parkfield in central California are reviewed for evidence that fault zone fluids play a critical role in slip dynamics there. Previous studies at Parkfield have defined a low-velocity, anisotropic, attenuating fault zone and a high VP/VS ratio in the nucleation zone of the repeating M 6 earthquakes. Most of the ongoing seismicity is organized into a temporally-evolving checkerboard pattern of alternating high and low seismic slip regions divided on the fault zone at 3--6 km spacings. Much of the seismicity is further confined to a few hundred small (20--30 m radius) cells of densely clustered microearthquakes that exhibit periodic recurrence. Space-time development of small (tens to hundreds of meters), transient (minutes to days) earthquake sequences reveals diffusivelike outward spreading along the fault zone. There is some evidence for anomalous source mechanisms in sequence-initiating events, possibly indicative of hydraulic fracturing. The data are consistent with a model in which some microearthquake clusters and confined sequences occur by the cyclic pressurization of fluid within localized patches of the fault zone. The consequent modulation of the effective normal stress leads to fluid-driven slip manifested both as the highly periodic earthquake clusters and as localized earthquake sequences observed at Parkfield. ¿ American Geophysical Union 1995 |
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Abstract |
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Keywords
Tectonophysics, Plate boundary—general, Seismology, Earthquake dynamics and mechanics, Structural Geology, Role of fluids, Seismology, Earthquake parameters |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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