Mechanisms of Mantle Wedge and Intraslab Earthquakes Beneath Southwestern Colombia From Analysis of Earthquake Source Properties

地震发生在50公里以下的深度，以及700公里的深度，是出乎意料的，因为这些深度的高压和高温。这种深源地震占全球所有地震的25%，发生在俯冲带，偶尔会造成地表破坏，因此更好地了解它们发生的原因将有助于地震危险性分析和准备。它还将帮助我们更好地了解地震发生的各种条件。这项工作将通过研究南美洲西北部地下发生的一组独特地震的性质，对此类地震的可能机制提供新的限制。该项目使社会受益，因为它关注地震的发生和危害，并且通过培训地震学博士后来加强STEM教育。位于哥伦比亚地下50-200公里深处的考卡中深度地震群每年发生约58次地震，当地震级ML大于或等于2.5。这些地震既位于俯冲板块中的平面地震带，也位于两个不同的柱状物或指状物中，垂直于俯冲板块并在俯冲板块上方延伸30-40公里，并进入地幔楔。 利用哥伦比亚国家地震网络2010年至今的地震数据，考卡地震群的特点是精确地重新定位地震，反演波形以计算许多较大地震的震源机制，并估计地震的静态和动态震源特性。 这些分析将提供有史以来第一次地幔楔地震的特征和地震的震源特性在两个设置的比较，从而使不同的假设-如脱水脆化，剪切不稳定性，水力压裂，和崩溃的流体传播途径-为这些地震发生的测试。 对中深地震机制和通过地幔楔的流体迁移路径的新限制将适用于所有俯冲带。该奖项反映了NSF的法定使命，并被认为值得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来支持。

The occurrence of earthquakes below 50 kilometers depth, and as deep as 700 kilometers depth, is unexpected because of the high pressure and temperature at those depths. Such deep earthquakes, which represent ~25% of all earthquakes globally, occur in subduction zones and occasionally cause damage at the surface, so better understanding of why they occur will help with seismic hazard analysis and preparation. It will also help us to better understand the variety of conditions under which earthquakes can occur. This work will provide new constraints on the possible mechanisms of such earthquakes by studying the properties of a unique cluster of earthquakes that occur beneath northwestern South America. This project benefits society because of its focus on earthquake occurrence and hazard and because it enhances STEM education by training a postdoctoral fellow in seismology. The Cauca cluster of intermediate-depth earthquakes, which is located beneath Colombia between at depths of 50-200 kilometers, has ~58 earthquakes per year with local magnitude ML greater than or equal to 2.5. The earthquakes are located both in a planar seismic zone in the subducting slab and in two distinct columns, or fingers, extending 30-40 kilometers normal to and above the slab and into the mantle wedge. Using seismic data from 2010 to the present from the Colombian National Seismic Network, the Cauca cluster earthquakes will be characterized by precisely relocating the earthquakes, inverting waveforms to calculate focal mechanisms for many of the larger earthquakes, and estimating static and dynamic source properties for the earthquakes. These analyses will provide the first-ever characterization of mantle wedge earthquakes and a comparison of the source properties of earthquakes in two settings, thus enabling the testing of different hypotheses --- such as dehydration embrittlement, shear instability, hydrofracture, and collapse of fluid propagation pathways --- for why these earthquakes occur. The new constraints on the mechanisms of intermediate-depth earthquakes and fluid migration pathways through the mantle wedge will be applicable to all subduction zonesThis 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.