The Distribution of Aseismic Slip and Partitioning of Deformation on Multiple Parallel Strike-slip Faults in the Chaman Fault System from InSAR

Abstract:

The Chaman fault marks the western border of the ~100 km wide transform plate boundary between the Eurasian and Indian tectonic plates in Pakistan and Afghanistan. This fault system links the Makran subduction and accretionary wedge system to the Southwest with the Himalayas to the Northeast. Although global pate models predict 20-35 mm/yr of left-lateral movement, very few large earthquakes were recorded or described in historical catalog in the region. In addition, aseismic processes have been described in the area. Using Interferometric Synthetic Aperture Radar (InSAR), we quantify the partitioning of deformation between major transform faults in the region, as well as the spatial distribution of aseismic slip along the Chaman and neighboring faults. We map the distribution of surface slip, which locally reaches up to 4 mm/yr, along the Chaman fault. We obtain a first order description of slip at depth and its distribution between faults using a Bayesian exploration of slip at depth between latitudes 27.5 and 31. Finally, we precisely identify the geometry of the active plate boundary, notably the role of the Ghazaband fault and we find that a major fault in the northern prolongation of the Ornach-Nal fault accommodates a significative part of the relative displacement between India and Eurasia.