Surface creep on the North Anatolian Fault at Ismetpasa, Turkey, 1944–2016

Abstract

We reevaluate the 72 year history of surface slip on the North Anatolian Fault at Ismetpasa since the Mw = 7.4 1944 Bolu/Gerede earthquake. A revised analysis of published observations suggests that days after the earthquake the fault had been offset by 3.7 m and 6 years later by an additional 0.74 m. Creep was first recognized on the fault in 1969 as a 0.13 m offset of a wall constructed in 1957 that now (2016) has been offset by 0.52 m. A carbon rod creep meter operated across the fault in the past 2 years confirms results from an invar wire creep meter operated 1982–1991 that surface slip is episodic. Months of fault inactivity are interrupted by slow slip (≤10 µm/d) or multiple creep events with cumulative amplitudes of 2–10 mm, durations of several weeks, and with slip rates briefly exceeding >2.5 mm/h. Creep events accommodate 80% of the surface slip and individually release ≈ 10−6 shear strain on the flanks of the uppermost 3–7 km of the fault. GPS and interferometric synthetic aperture radar methods yield a current fault slip rate of 7.6 ± 1 mm/yr suggesting that creep meters incompletely sample the full width of the surface shear zone. The slip rate has slowed from >10 mm/yr in 1969 to 6.1 mm/yr at present, 4.65 mm/yr of which appears to be due to steady interseismic creep driven by plate boundary stressing rates. We calculate that a further 1 m of aseismic surface slip will precede the next major earthquake on the fault assuming an ≈ 260 year main shock recurrence interval on this segment.

Fault Creep and Strain Partitioning in Trinidad‐Tobago: Geodetic Measurements, Models, and Origin of Creep

“…Time‐variable slip partitioning has also been observed on segments of the San Andreas fault system (e.g., the southern San Andreas and San Jacinto Faults) (Bennett et al, ). Similar spatial and temporal variability in interseismic coupling behavior has been reported for the Alpine, North Anatolian, Chaman, Haiyun, Longitudinal Valley, and Sumatra strike‐slip fault systems (Barth et al, ; Bilham et al, ; Fattahi & Ameling, ; Ito et al, ; Jolivet et al, ; Le Pichon et al, ; Thomas et al, ). Understanding and quantifying these complexities in continental transform fault systems are paramount for understanding earthquake potential and how plate motion is accommodated.…”

Slow Slip Event On the Southern San Andreas Fault Triggered by the 2017 Mw8.2 Chiapas (Mexico) Earthquake

“…The comparison of surface displacements that occurred over different epochs (e.g., Figure ; Lindsey, Fialko, et al, ) suggests a complex spatiotemporal evolution of slip in the shallow conditionally stable layer, with triggered and spontaneous slip events occurring at variable depths and locations along strike. This is similar to the shallow slip histories reported at other locations (e.g., Bilham et al, ; Jolivet et al, ; Linde et al, ; Murray & Segall, ; Shirzaei & Bürgmann, ; Simpson et al, ; Wei et al, ). Alternatively, the observed variations in the effective width of the shear zone may be indicative of time‐dependent strain localization within the shallow crust during the interseismic period.…”

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

“…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. 8).…”

“…Continuous monitoring of fault creep in this region occurs only along the Hayward fault on five creepmeters (Bilham et al, 2004). These instruments are designed to record up to 2.2 m of accumulated coseismic and postseismic slip (Bilham et al, 2016). More than 30 alignment arrays are surveyed annually on the Hayward fault McFarland et al, 2016).…”