Elucidating the Mechanics of Tsunami Generating Earthquake Rupture with Long Period Seismology

海底地震能够产生异常巨大的海啸，极大地增加了目前生活在沿海地区的世界上大多数人口所面临的危险。目前用于研究海底地震的技术是昂贵的，不能应用于大多数感兴趣的地震。缺乏观测妨碍了人们对地震是否会使海底移位和增加产生重大海啸的可能性的理解。本项目发展的理论将为海底地震研究提供一个新的基础工具，具有重要的科学和社会意义。将开发一个新的框架，克服以前的理论限制，使我们能够开发一种易于使用，价格低廉的工具，它将允许仅从遥远的地面运动记录中检测海底滑动。然后，这个工具将被用来检查过去15年里产生毁灭性海啸的大地震，以及最近世界各地发生的中等规模地震。通过使用新开发的工具研究大量地震，将更好地了解为什么有些地震会使海底位移，而另一些则不会。该项目可为海啸灾害评估提供改进。该项目支持培养一名博士后研究员。该项目的第一个组成部分将建立理论和观测框架，以区分滑动到达和未到达地表的事件。这一理论将提供一种简单的地震诊断工具，并具有补充数值模型、海底仪器、钻井或海洋调查的额外好处。该项目的第二个组成部分将提供必要的观测，通过对全球地震网记录的大量事件的长周期地震数据进行诊断，确定控制海底表面破裂的物理机制。新的框架将通过2011年东北大地震期间测量到的大量浅层滑动来验证。在2010年和2015年智利地震、2004年和2010年苏门答腊海啸地震以及最近的中等规模地震中，这种类型的浅层滑动在多大程度上被观察到，将被确定。利用大地震和中地震的调查结果，将尝试确定控制板块边界最浅部分破裂的断裂带的性质（例如，增生楔的存在、俯冲沉积物的厚度、断层倾角等）。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。

Submarine earthquakes are capable of generating uncharacteristically large tsunamis, and drastically increase the hazard facing most of the world's population, which currently lives along the coastlines. Current techniques used to study submarine earthquakes are expensive and cannot be applied to most earthquakes of interest. The lack of observations has hindered the understanding of whether an earthquake will displace the seafloor and increase the likelihood of generating a significant tsunami. The theory developed in this project will provide a new fundamental tool for the study of submarine earthquakes with significant scientific and societal implications. A new framework will be developed that overcomes previous theoretical limitations and allows us to develop an easily utilized, inexpensive tool which will allow for the detection of slip on the seafloor from distant recordings of ground motion alone. This tool will then be used to examine giant earthquakes in the last 15 years that produced devastating tsunamis, as well as recent moderate-size earthquakes from around the world. By studying a large number of earthquakes with the newly developed tool, a better understanding will be obtained of why some earthquakes displace the seafloor while others do not. This project could provide an improvement for tsunami hazard assessment. The project supports the training of a postdoctoral investigator.The first component of this project will establish the theoretical and observational framework required to distinguish events for which slip reached and did not reach the surface. This theory will provide a simple seismological diagnostic tool, and has the added benefit of complementing numerical models, seafloor instrumentation, drilling, or marine surveys. The second component of this project will provide the necessary observations required to determine the physical mechanisms controlling submarine surface rupture by applying the diagnostic to long-period seismic data from a large number of events recorded by the Global Seismographic Network. The new framework will be validated using the large amount of shallow slip that was measured to have occurred during the 2011 Tohoku-Oki Earthquake. To what extent this type of shallow slip is observed in giant megathrust earthquakes, such as the 2010 and 2015 Chile and the 2004 and 2010 Sumatra tsunami earthquakes, as well as recent moderate-size earthquakes will be determined. Using the outcome of the survey of large and moderate-size earthquakes, an attempt will be made to determine the properties of fault zones (e.g., presence of accretionary wedge, subducted sediment thickness, fault dip-angle, etc.) that govern the rupture of the shallowest part of plate boundary.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.