Multiscale Dynamics of Aseismic Slip on Central San Andreas Fault

Abstract

Understanding the evolution of aseismic slip enables constraining the fault's seismic budget and provides insight into dynamics of creep. Inverting the time series of surface deformation measured along the Central San Andreas Fault obtained from interferometric synthetic aperture radar in combination with measurements of repeating earthquakes, we constrain the spatiotemporal distribution of creep during 1992–2010. We identify a new class of intermediate‐term creep rate variations that evolve over decadal scale, releasing stress on the accelerating zone and loading adjacent decelerating patches. We further show that in short‐term (<2 year period), creep avalanches, that is, isolated clusters of accelerated aseismic slip with velocities exceeding the long‐term rate, govern the dynamics of creep. The statistical properties of these avalanches suggest existence of elevated pore pressure in the fault zone, consistent with laboratory experiments.

Strain Rate Distribution in South‐Central Tibet From Two Decades of InSAR and GPS

“…As geodetic data improve and time series lengthen, there are examples where geodetic strain rates have been observed to vary in time. For example, long‐term accelerating slip was observed preceding the 2011 Tohoku‐oki earthquake (Mavrommatis, Segall & Johnson, ; Mavrommatis, Segall, Uchida, et al, ) and on the creeping segment of the Central San Andreas Fault (Khoshmanesh & Shirzaei, ). In addition, there are a number of locations where the geodetic strain rate has shown to be inconsistent with the long‐term tectonic strain rate, for example, Garlock Fault, California (Dolan et al, ; Peltzer et al, ).…”

Shallow Creep Along the 1999 Izmit Earthquake Rupture (Turkey) From GPS and High Temporal Resolution Interferometric Synthetic Aperture Radar Data (2011–2017)

“…The maximum amplitude (~10 mm in our case, whereas it was~20 mm along the Ismetpasa section) and duration of these shallow bursts (~1 month) are similar. The growing number of evidence for such creep bursts along the North Anatolian Fault, as also suggested by long time series of creepmeter measurements (Altay & Sav, 1991;Bilham et al, 2016), and along other major strike-slip faults worldwide (De Michele et al, 2011;Jolivet, Simons, et al, 2015;Khoshmanesh & Shirzaei, 2018;Pousse-Beltram et al, 2016), suggest that continuously decaying afterslip or steady interseismic creep may not be the rule for creep behavior. New mechanical models are required to account for coupling temporal variations at shallow depth and recurrent creep bursts triggering.…”

“…A recent review by Harris (2017) discussed the earthquake potential of shallow creeping continental faults using worldwide data. Reported cases include the Hayward fault (Savage & Lisowski, 1993;Schmidt et al, 2005), the Supersitition Hills fault (Bilham, 1989;Wei et al, 2009), and the Central San Andreas Fault in California (De Michele et al, 2011, Jolivet, Candela, et al, 2015, Khoshmanesh & Shirzaei, 2018, the Longitudinal Valley fault in Taiwan (Champenois et al, 2012;Thomas et al, 2014), the Ismetpasa segment of North Anatolian Fault in Turkey (Ambraseys, 1970;Bilham et al, 2016;Cakir et al, 2005;Cetin et al, 2014;Kaneko et al, 2013;Rousset et al, 2016), the Izmit and Marmara segment of the North Anatolian Fault (Cakir et al, 2012;Ergintav et al, 2014;Hussain et al, 2016), the Haiyuan fault in China (Jolivet et al, 2012, Jolivet, Simons, et al, 2015, the El-Pilar fault in Venezuela (Jouanne et al, 2011, Pousse-Beltram et al, 2016, and the Chaman fault in Pakistan (Barnhart, 2017;Fattahi & Amelung, 2016). These studies show that the spatial patterns (rate and rate-change distribution along strike and with depth) vary significantly.…”

The Transient and Intermittent Nature of Slow Slip

“…Complementing this observed temporal complexity of slow slip, the spatial complexity of slow slip becomes evident with InSAR observations of aseismic slip along continental faults (Figure ). Along the Haiyuan fault and the San Andreas Fault, the along‐strike evolution of aseismic slip suggests creep is not steady in time and rather occurs in bursts with potency distributed following a power law distribution (Jolivet et al, ; Khoshmanesh & Shirzaei, ). The probability distribution of slip rates during the events peaks near the plate rate (i.e., the loading rate) and shows an excess of fast events that can be interpreted as the signature of interaction between events.…”