Thomas E. Parsons
Luca Malagnini
2020
<p><span>We show that seismic attenuation ( </span><img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/fe6e1bba-0f11-4326-9d90-0344d44a07b8/grl61586-math-0001.png" alt="urn:x-wiley:00948276:media:grl61586:grl61586-math-0001" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/fe6e1bba-0f11-4326-9d90-0344d44a07b8/grl61586-math-0001.png"><span>) along the San Andreas fault (SAF) at Parkfield correlates with the occurrence of moderate‐to‐large earthquakes at local and regional distances. Earthquake‐related </span><img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/a89f08da-3eff-4c9e-95a4-b39accaeac3b/grl61586-math-0002.png" alt="urn:x-wiley:00948276:media:grl61586:grl61586-math-0002" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/a89f08da-3eff-4c9e-95a4-b39accaeac3b/grl61586-math-0002.png"><span> 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 </span><i>M</i><span>6 Parkfield earthquake, prefailure conditions for some local events of moderate magnitude correspond to positive anomalies of </span><img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/999ff49d-0c63-413d-a3d3-7163e4f59927/grl61586-math-0003.png" alt="urn:x-wiley:00948276:media:grl61586:grl61586-math-0003" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/999ff49d-0c63-413d-a3d3-7163e4f59927/grl61586-math-0003.png"><span> on the Pacific side, with local and regional earthquakes producing sharp attenuation reversals. After the 2004 Parkfield earthquake, we see higher </span><img class="section_image" src="https://agupubs.onlinelibrary.wiley.com/cms/asset/4d674cda-5354-4c8d-a1a4-54b743103370/grl61586-math-0004.png" alt="urn:x-wiley:00948276:media:grl61586:grl61586-math-0004" data-mce-src="https://agupubs.onlinelibrary.wiley.com/cms/asset/4d674cda-5354-4c8d-a1a4-54b743103370/grl61586-math-0004.png"><span> 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.</span></p>
application/pdf
10.1029/2020GL089201
en
American Geophysical Union
Seismic attenuation monitoring of a critically stressed San Andreas fault
article