ABSTRACT

For the past 50 million years, processes deep within the Earth have forced the Indian subcontinent to collide with the Asian continent. In the north the high mountains and earthquakes of the Himalaya are evidence of this continued collision. Less well studied, the 700-mile-long western edge of the subcontinent between Karachi and Kabul is marked by several large faults similarly plagued by damaging earthquakes. Although none have occurred recently, several key areas where future earthquakes are anticipated. Thanks to satellite imagery and the dry terrain, the researchers can quantify the evolution of stresses in the region responsible for these future earthquakes in remarkable detail. They will use satellite radar observations to develop a detailed model of where the plate boundary fault is currently locked and where it is slowly creeping, suggesting reduced earthquake hazard. However, complicating these studies, a tenfold increase in local populations in the past two decades has increased the demand for water. This demand has been met by pumping water from a half dozen subsurface aquifers, but with catastrophic consequences. Lowered underground pressures have caused surface subsidence and open fissures in cities, leading in some cases to the demolition of schools and hospitals. These changes in subsurface pressure also have the potential to alter stresses on faults where earthquakes are anticipated. This project quantifies both the changing tectonic forces responsible for earthquakes, and the modification of these forces by unprecedented groundwater withdrawal in the region.

In this project, satellite geodesy techniques, including satellite radar interferometry and Global Navigation Satellite System data, and creepmeters will be used to study the spatial and temporal distributions of ground deformation along the entire Chaman fault system during the time period from 2014 to 2023. The focus is on the following scientific targets: 1) quantify the surface deformation rates along the Chaman fault arising from interseismic coupling, fault creep, earthquakes, and ground subsidence due to groundwater extraction; 2) invert for the fault slip rates and locking depths of major faults in the Chaman fault system and identify the associated spatial distribution and temporal variation of interseismic strain accumulation and fault creep along both the Chaman and Ghazaband faults; 3) investigate the fundamental relationships between tectonic loading, time-variable fault creep rates, and earthquakes; 4) assess the hazards of regional earthquakes and hydrological changes based on estimates of fault slip rates and stressing influences from hydrological storage changes due to rapid depletion of regional aquifers. The researchers? deformation quantification and modeling will provide new constraints on the potential for future earthquakes based on past earthquake occurrences and current hydrologic unloading.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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