Extent and distribution of aseismic slip on the Ismetpaşa segment of the North Anatolian Fault (Turkey) from Persistent Scatterer InSAR

Abstract

We use the Persistent Scatterer InSAR (PSI) technique with elastic dislocation models and geology along the creeping section of the North Anatolian Fault (NAF) at Ismetpas¸a, to map and deduce the velocity field and the aseismic slip distribution. Revealing the spatiotemporal nature of the creep helped us associate the creep with potential lithological controls, hence providing a new perspective to better understand the underlying causes and mechanisms. The PSI analysis of Envisat ASAR images between 2003 and 2010 reveals a clear picture of surface creep along the fault and a new interseismic velocity field transitioning gradually between the creeping and the locked fault sections. The creep rate is found to fluctuate along a 100 km long section of the fault in a manner similar to that along the Hayward fault, reaching a maximum of 20 6 2 mm/yr, close to the far field plate velocity (25 6 1.5 mm/yr). At Ismetpas¸a, it is in the range of 8 6 2 mm/yr, consistent with the previous geodetic observations. The creeping section appears to extend 30 km further east than those previously reported. Modeling of the PSI data reveals a heterogeneous creep distribution at depth with two main patches confined mostly to the uppermost 5 km portion of the seismogenic crust, releasing annually 6.2 3 10 16 Nm (Mw 5 5.1) geodetic moment. Our analysis combined with previous studies suggests that creep might have commenced as postseismic deformation following the 1944 earthquake and has evolved to stable fault creep with time. There is a correlation between aseismic surface creep and the geology along the fault as it is in major part associated to rocks with low frictional strength such as the andesitic-basaltic, limestone, and serpentine bodies within the fault zone.

Long‐Term Afterslip of the 2004M 6.0 Parkfield, California, Earthquake—Implications for Forecasting Amount and Duration of Afterslip on Other Major Creeping Faults

“…Therefore, in most cases we have been unable to confirm how quickly afterslip was completed for other historical events. One sparse postseismic slip record from a 1944 M 7.4 earthquake on the creeping section of the NAF from the Ismetpasa site appeared to indicate that significant afterslip might have continued for decades (Çakir et al, 2005;Cetin et al, 2014). However, a more recent analysis indicates that the significant 1944 afterslip at Ismetpasa was likely finished more rapidly than for the Parkfield 2004 event (Bilham et al, 2016;Fig.…”

A Maxwell elasto-brittle rheology for sea ice modelling

“…Active faults in the Earth crust have been known to deform in two distinct ways: either abruptly, causing earthquakes, or in a transient, aseismic manner (Scholz, 2002;Gratier et al, 2014;Cakir et al, 2012;Cetin et al, 2014). Similar to sea ice, co-seismic fracturing activates aseismic creep, leading to deformations that can be much larger than that associated with the fracturing itself and to the relaxation of a significant amount of elastic strain (Cakir et al, 2012;Cetin et al, 2014). A further justification of the introduction of such pseudo-viscosity comes from the rheology of granular media.…”

Interseismic strain accumulation across the central North Anatolian Fault from iteratively unwrapped InSAR measurements

“…In order to understand the role that the NAF plays in regional tectonics and seismic hazard, there have been numerous estimates of the fault slip rate for the NAF using present‐day deformation measured with Global Navigation Satellite Systems (GNSS) [e.g., Straub et al , ; Reilinger et al , ; Ergintav et al , ] or offset geological features [e.g., Hubert‐Ferrari et al , ; Pucci et al , ; Kozaci et al , ]. There have also been several interferometric synthetic aperture radar (InSAR)‐derived estimates of the fault slip rate, which have focused on the western or eastern regions of the NAF where the InSAR coherence is better [e.g., Wright et al , ; Cakir et al , ; Walters et al , ; Kaneko et al , ; Cakir et al , ; Cetin et al , ; Walters et al , ; Cavalié and Jónsson , ; Hussain et al , ].…”