Fault creep rates of the Chaman fault (Afghanistan and Pakistan) inferred from InSAR

Abstract

The Chaman fault is the major strike‐slip structural boundary between the India and Eurasia plates. Despite sinistral slip rates similar to the North America‐Pacific plate boundary, no major (>M7) earthquakes have been documented along the Chaman fault, indicating that the fault either creeps aseismically or is at a late stage in its seismic cycle. Recent work with remotely sensed interferometric synthetic aperture radar (InSAR) time series documented a heterogeneous distribution of fault creep and interseismic coupling along the entire length of the Chaman fault, including an ~125 km long creeping segment and an ~95 km long locked segment within the region documented in this study. Here I present additional InSAR time series results from the Envisat and ALOS radar missions spanning the southern and central Chaman fault in an effort to constrain the locking depth, dip, and slip direction of the Chaman fault. I find that the fault deviates little from a vertical geometry and accommodates little to no fault‐normal displacements. Peak‐documented creep rates on the fault are 9–12 mm/yr, accounting for 25–33% of the total motion between India and Eurasia, and locking depths in creeping segments are commonly shallower than 500 m. The magnitude of the 1892 Chaman earthquake is well predicted by the total area of the ~95 km long coupled segment. To a first order, the heterogeneous distribution of aseismic creep combined with consistently shallow locking depths suggests that the southern and central Chaman fault may only produce small to moderate earthquakes (<M7).

Kinematics and Dynamics of the Pamir, Central Asia: Quantifying the Roles of Continental Subduction in Force Balance

“…Our modeled slip rate along the northern Chaman Fault agrees with Fattahi and Amelung (; 6.1 ± 1.1 mm/year; based on InSAR), but not with Szeliga et al (; 16.8 ± 2.7 mm/year; also based on InSAR). It also agrees with Barnhart's () InSAR‐derived estimate of 7–9 mm/year just to the south of our model at 30.4–30.6°N latitude.…”

Kinematics and dynamics of the Pamir, Central Asia: Quantifying surface deformation and force balance in an intracontinental subduction zone

“…Our modeled average slip rate for the Chaman Fault (~10 mm/yr) is lower than geodetic estimates by Szeliga et al [] (16.8 ± 2.7 mm/yr) and Mohadjer et al [] (upper bound of 18.1 ± 1 mm/yr), which may include slip on multiple faults in the area, and a geologic estimate by Ul‐Hadi et al [] (33.3 ± 3 mm/yr). Our Chaman slip rate is slightly higher than interferometric synthetic aperture radar estimates by Fattahi and Amelung [] (6.6 ± 1.2 mm/yr at 32°N) and Barnhart [] (~7–9 mm/yr creep around 30.5°N). Along the Darvaz‐Karakul fault, Ischuk et al [] estimate 10 ± 1 mm/yr of shear that might be localized on the fault and Mohadjer et al [] established an upper bound of 11.4 ± 2 mm/yr.…”

Large earthquakes and creeping faults

“… Fattahi and Amelung [] infer 340 km of fault creep and interspersed locked sections; Barnhart [] image 125 km of creep. The other values in the table are from Barnhart [].…”

“…[] used InSAR data to infer that a 35 km long portion of the Haiyuan fault, at the northeastern boundary of the Tibetan Plateau in northern China, creeps, down to 20 km depth. Fattahi and Amelung [] and Barnhart [] examined the Chaman fault system in Pakistan and Afghanistan using InSAR, and Barnhart [] inferred that 125 km of the Chaman fault creeps, in an amount that relieves most of its tectonic strain. Duquesnoy et al .…”