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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.

International audienceTime series analysis of spaceborne synthetic aperture radar (SAR) data, GPS measurements, and fi eld observations reveal that the central section of the Izmit (Turkey) fault that slipped with a supershear rupture velocity in the A.D. 1999, Mw7.4, Izmit earthquake began creeping aseismically following the earthquake. Rapid initial postseismic afterslip decayed logarithmically with time and appears to have reached a steady rate comparable to the preearthquake full fault-crossing rate, suggesting that it may continue for decades and possibly until late in the earthquake cycle. If confi rmed by future monitoring, these observations identify postseismic afterslip as a mechanism for initiating creep behavior along strike-slip faults. Long-term afterslip and/or creep has signifi cant implications for earthquake cycle models, recurrence intervals of large earthquakes, and accordingly, seismic hazard estimation along mature strike-slip faults, in particular for Istanbul which is believed to lie adjacent to a seismic gap along the North Anatolian fault in the Sea of Marmara

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Geodetic measurements following the 23 October 2011, M w = 7.2 Van (eastern Turkey) earthquake reveal that a fault splay on the footwall block of the coseismic thrust fault was reactivated and slipped aseismically for more than 1.5 years following the earthquake. Although long-lasting aseismic slip on coseismic ruptures has been documented following many large earthquakes, long-lasting, triggered slip on neighboring faults that did not rupture during the earthquake has not been reported previously. Elastic dislocation and Coulomb stress modeling indicate that the postseismic deformation can be adequately explained by shallow slip on both the coseismic and splay fault and is likely driven mostly by coseismic stress changes. Thus, the slip deficit on the shallow section of the coseismic fault indicated by interferometric synthetic aperture radar-based models has been partially filled by aseismic slip, suggesting a lower likelihood for a large earthquake on the shallow section of the Van fault than suggested by previous studies.