Publication Date:
2016-10-14
Description:
The postseismic deformation captured with continuous Global Positioning System (cGPS) monitoring following many recent mega-thrust 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 Mw 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 re-locking, 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, re-locking is the main cause of the curvature in the cGPS signal, and this study presents a plausible range of geodetic re-locking rates following a megathrust earthquake.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
