Abstract
We apply a new analysis technique using earthquake focal mechanisms
to infer the 3-D fluid pressure field at depth in the source region
of the A.D. 2009 L'Aquila earthquake/aftershock sequence. The technique,
termed focal mechanism tomography, inverts for fluid pressure by
examining the fault orientation relative to the regional tectonic
stress pattern. We identify three large-scale pockets of high fluid
pressure (up to 50 MPa above hydrostatic pressure) at depths of 7-10
km that strongly correlates with an independent data set of well-located
foreshocks and aftershocks. The shape of overpressured regions and
the evolution of seismicity indicate a plausible scenario that this
sequence is being driven in part by the poro-elastic response of
trapped reservoirs of high-pressure fluid, presumably CO2, and postseismic
fluid flow initiated by the main shock.
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