Separating rapid relocking, afterslip, and viscoelastic relaxation: An application of the postseismic straightening method to the Maule 2010 cGPS. Issue 10 (30th October 2016)

• Record Type: Journal Article
• Authors: Bedford, Jonathan; Moreno, Marcos; Li, Shaoyang; Oncken, Onno; Baez, Juan Carlos; Bevis, Michael; Heidbach, Oliver; Lange, Dietrich
• Is Part Of: Journal of geophysical research. Volume 121:Issue 10(2016:Oct.)
• Page Start: 7618
• Page End: 7638
• Publication Date: 2016-10-30
• Subjects: postseismic -- subduction -- afterslip -- locking -- viscoelastic -- relaxation; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2016JB013093
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: The postseismic deformation captured with continuous Global Positioning System (cGPS) monitoring following many recent megathrust events has been shown to be a signal composed of two dominant processes: afterslip on the plate interface and viscoelastic relaxation of the continental and oceanic mantles in response to the coseismic stress perturbation. Following the south central Chile 2010 Maule M w 8.8 earthquake, the time series from the regional cGPS network show a distinct curvature in the pathway of the horizontal motion that is not easily fit by a stationary decaying pattern of afterslip in combination with viscoelastic relaxation. Here we show that with realistic assumptions about the long‐term decay of the afterslip signal, the postseismic signal can be decomposed into three first‐order contributing processes: plate interface relocking, plate interface afterslip, and mantle viscoelastic relaxation. From our analyses we conclude that the plate interface recovers its interseismic locking state rapidly (model space ranges between an instant recovery and a period of 1 year), a finding that supports laboratory experimental evidence as well as some recent studies of aftershocks and postseismic surface deformation. Furthermore, relocking is the main cause of the curvature in the cGPS signal, and this study presents a plausible range of geodetic relocking rates following a megathrust earthquake. Key Points: The postseismic straightening method facilitates the parameterization of relocking, afterslip, and viscoelastic relaxation Plate interface relocking is the dominant process that causes the veering of cGPS displacements The isolated afterslip time function is in good agreement with the time function of cumulative aftershock number