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Seismic attenuation monitoring of a critically stressed San Andreas fault

November 20, 2020

We show that seismic attenuation ( ) along the San Andreas fault (SAF) at Parkfield correlates with the occurrence of moderate‐to‐large earthquakes at local and regional distances. Earthquake‐related  anomalies are likely caused by changes in permeability from dilatant static stress changes, damage by strong shaking from local sources, and pore unclogging/clogging from mobilization of colloids by dynamic strains. We find that, prior to the 2004 M6 Parkfield earthquake, prefailure conditions for some local events of moderate magnitude correspond to positive anomalies of  on the Pacific side, with local and regional earthquakes producing sharp attenuation reversals. After the 2004 Parkfield earthquake, we see higher  anomalies along the SAF, but low sensitivity to local and regional earthquakes, probably because the mainshock significantly altered the permeability state of the rocks adjacent to the SAF, and its sensitivity to earthquake‐induced stress perturbations.

Publication Year 2020
Title Seismic attenuation monitoring of a critically stressed San Andreas fault
DOI 10.1029/2020GL089201
Authors Luca Malagnini, Thomas E. Parsons
Publication Type Article
Publication Subtype Journal Article
Series Title Geophysical Research Letters
Index ID 70216684
Record Source USGS Publications Warehouse
USGS Organization Pacific Coastal and Marine Science Center