NSF/EAR-BSF:Aftershock Productivity in Context of Rupture Kinematics

在当前数据丰富的时代，余震研究蓬勃发展。在经验预测地震后会产生多少余震方面已经取得了实质性进展。虽然预测余震的时间和大小在历史上受到了更多的关注，但预测余震的总次数同样是一种可靠的观察。一般来说，7级地震产生的余震是6级地震的10倍，而且这种模式对所有震级都是持续的，也就是说，每增加一个震级，余震的次数就增加10倍。该项目的问题是，为什么余震的产生遵循这种模式？它包含了什么关于地震力学的信息？为什么有些地震，比如2017年的恰帕斯地震，会产生很多余震，而另一些地震，比如2017年的墨西哥城地震，只会产生几次余震？最重要的是，在灾难发生后的关键日子里，这些信息能否用于预测余震的产生？这个项目对我们对地震危害的理解有更广泛的影响，并增加了美国和以色列的科学伙伴关系。这项工作还将支持研究生和一名本科生作为项目的一部分进行研究。利用统计地震学的工具对这些问题进行了大量的研究。许多研究都集中在区域地震上，那里的统计数据最可靠。分离出余震产生的原因可以从单个主震的滑动模式信息中受益，这些信息可以从全球地震数据中得到。以前的研究努力通过将余震数据与有关滑动的时间和分布的信息相结合来解决这个问题。这些研究很有见地，但通常缺乏统计分析所需的主震数量。这种缺乏的部分原因是，直到最近，滑动图都非常困难，只能用于少数病例。因此，由于不同的模型存在不同的偏差，因此很难对余震与主震破裂之间的关系提出疑问。随着最近出版的用单一方法统一完成的大型破裂序列汇编，这种情况发生了巨大变化。这项工作开创了一个新时代，结合了运动学断裂及其随后的余震的信息。研究人员将利用这一能力，并通过以下方式攻击余震生产力：(1)利用相对于高分辨率同震滑动图的余震空间分布来澄清震级依赖的物理根源；(2)研究区域生产力的变化；(3)研究余震生产力与区域强度之间的相互关系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Aftershock studies have blossomed in the current data-rich era. Substantial progress has been made in empirically predicting how many aftershocks are produced in the aftermath of an earthquake. Although predicting the timing and size of aftershocks have received more attention historically, the expected total number of aftershocks is just as robust an observation. In general, a magnitude 7 earthquake produces 10 times as many aftershocks as a magnitude 6 and the pattern continues for all magnitudes, i.e., the number of aftershocks increases by a factor of 10 for each magnitude unit. The project asks why does aftershock production follow this pattern? What information does it contain about earthquake mechanics? Why do some earthquakes, like the 2017 Chiapas earthquake produce many aftershocks, while others, like the 2017 Mexico City earthquake produce only a few? And most importantly, can this information be used to anticipate the aftershock production in the critical days following a disaster? This project has broader implications for our understanding of earthquake hazards, and adds to the US-Israel scientific partnership. The work will also support graduate students and an undergraduate researcher to conduct research as part of the project. Significant effort has been spent on these questions utilizing tools from statistical seismology. Many studies have focused on regional earthquakes, where statistics are most robust. Separating out the causes of aftershock production can benefit from information of the slip patterns of individual mainshocks that can be derived using global seismic data. Previous studies have strived to attack this problem by combining aftershock data with information about the timing and distribution of slip. The studies have been insightful, but have generally lacked the number of mainshocks required for statistical analysis. This lack has been, in part, because until recently slip maps were sufficiently difficult that they were only available for a small number of cases. Therefore, it was difficult to ask questions about the relation between aftershocks and mainshock rupture since different models are biased in different ways. This situation has changed dramatically with recently published large compilations of rupture sequences done uniformly with a single method. This work exploits a new era of combining information from kinematic ruptures and their ensuing aftershocks. The researchers will capitalize on this capability and attack aftershock productivity by: (1) using the spatial distribution of aftershocks relative to well-resolved coseismic slip maps to clarify physical origins of the magnitude dependence, (2) investigating regional variations in productivity, and (3) examining the interrelationship between aftershock productivity, regional strength, and arrest criteria for mainshock rupturesThis 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.