Aftershock Distribution as a Constraint on the Geodetic Model of Coseismic Slip for the 2004 Parkfield Earthquake |
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Authors: | Ninfa Bennington Clifford Thurber Kurt L Feigl Jessica Murray-Moraleda |
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Institution: | (1) Department of Geoscience, University of Wisconsin-Madison, Madison, USA;(2) US Geological Survey, Menlo Park, CA, USA |
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Abstract: | Several studies of the 2004 Parkfield earthquake have linked the spatial distribution of the event’s aftershocks to the mainshock
slip distribution on the fault. Using geodetic data, we find a model of coseismic slip for the 2004 Parkfield earthquake with
the constraint that the edges of coseismic slip patches align with aftershocks. The constraint is applied by encouraging the
curvature of coseismic slip in each model cell to be equal to the negative of the curvature of seismicity density. The large
patch of peak slip about 15 km northwest of the 2004 hypocenter found in the curvature-constrained model is in good agreement
in location and amplitude with previous geodetic studies and the majority of strong motion studies. The curvature-constrained
solution shows slip primarily between aftershock “streaks” with the continuation of moderate levels of slip to the southeast.
These observations are in good agreement with strong motion studies, but inconsistent with the majority of published geodetic
slip models. Southeast of the 2004 hypocenter, a patch of peak slip observed in strong motion studies is absent from our curvature-constrained
model, but the available GPS data do not resolve slip in this region. We conclude that the geodetic slip model constrained
by the aftershock distribution fits the geodetic data quite well and that inconsistencies between models derived from seismic
and geodetic data can be attributed largely to resolution issues. |
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