Collaborative Research: Geodetic imaging of the interplay between creep, locking, earthquakes and land subsidence along the Chaman plate boundary

在过去的5000万年里，地球深处的过程迫使印度次大陆与亚洲大陆相撞。在北部，高山和喜马拉雅的地震就是这种持续碰撞的证据。研究较少的是，卡拉奇和喀布尔之间700英里长的次大陆西部边缘，有几个大断层，同样受到破坏性地震的困扰。尽管最近没有发生任何地震，但预计未来将发生地震的几个关键地区。多亏了卫星图像和干燥的地形，研究人员可以非常详细地量化导致未来地震的地区的应力演变。他们将利用卫星雷达观测建立一个详细的模型，说明板块边界断层目前被锁定在哪里，以及它在哪里缓慢爬行，从而表明地震风险降低。然而，使这些研究复杂化的是，在过去20年里，当地人口增加了10倍，增加了对水的需求。通过从六个地下含水层抽水来满足这一需求，但带来了灾难性的后果。地下压力降低导致地面下沉，城市出现裂隙，在某些情况下导致学校和医院被拆除。地下压力的这些变化也有可能改变预计会发生地震的断层上的应力。该项目量化了导致地震的不断变化的构造作用力，以及该地区史无前例的地下水开采对这些作用力的修正。在该项目中，将利用卫星大地测量技术，包括卫星雷达干涉测量和全球导航卫星系统数据，以及蠕变仪，研究2014至2023年期间整个查曼断裂系统的地面变形的时空分布。重点是以下科学目标：1)量化地震间耦合、断层蠕变、地震和地下水开采引起的地面沉降引起的查曼断层沿线的地表变形速率；2)反演查曼断层系统中主要断层的断层滑动速率和锁定深度，识别查曼和加扎班德断层上地震间应变累积和断层蠕变的相关空间分布和时间变化；3)研究构造载荷、时变断层蠕变速率与地震之间的基本关系；4)根据对断层滑移率的估计，并强调区域含水层迅速枯竭引起的水文储存变化的影响，评估区域地震和水文变化的危害。研究人员的形变量化和建模将根据过去的地震发生和当前的水文卸载对未来地震的可能性提供新的限制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.