EAR-PF: Properties of the shallow crust around the San Jacinto Fault Zone characterized by joint geodetic and seismic analysis

克里斯托弗·W·约翰逊博士获得了NSF EAR博士后奖学金，在加州大学圣地亚哥分校和南加州大学开展研究和教育计划。该项目的目标是使用波形参数开发地震、微震和环境噪声的分类器，并利用统计学习技术训练计算机程序，以识别地壳上部1公里处以前未检测到的微震事件。近地表的性质需要进一步探索，以限制产生地震的过程，并描述地震和大地测量记录的时间变化。该项目的预期结果将促进对地震地面运动、地表变形、瞬时变形信号以及整个社区的弹性和水文地壳属性的了解。这项研究为应用于区域地震台网的新兴地震检测技术提供了框架。在调查期间，约翰逊博士将对本科生和研究生进行互动和培训。沿太平洋-北美板块边界的主要断层系统是圣安德烈亚斯断层(SAF)，该断层将加州海岸沿线人口稠密的城市中心一分为二。加州洛杉矶东南部的SAF分支进入圣哈辛托断裂带(SJFZ)，那里每天都会发生微震事件，在过去的35年里，有6次5级地震破裂。充分描述SAF和SJFZ的特征对于基础设施规划和减灾非常重要。最近部署了1,100个地震仪的密集阵列，记录了SJFZ长达5周的地面运动。该数据集提供了一个独特的机会，可以开发新的技术来表征0-1公里深的浅层地下，并充分描述从地表到~18公里深的脆韧性过渡带的断裂带环境。部署的初步结果显示，阵列数据一天内发生120次小震，明显多于区域地震台网检测到的15次地震。标记尽可能多的数据特征将有助于有效地处理大量数据，从而降低微震地震检测的计算成本。对连续数据的详细分类还应对噪声中的模式进行定性描述，并突出可能代表地壳最浅部分以前未探索的破裂过程的相干能量事件。这是一项利用地球望远镜PBO网络数据来进一步推进对板块边界断层系统的理解的新研究。

Dr. Christopher W. Johnson has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at the University of California San Diego and the University of Southern California. The objective of this project is to develop classifiers for earthquakes, microseisms, and ambient noise using parameters of the waveforms and utilize statistical learning techniques to train a computer program to identify previously undetected microseismic events in upper 1 km of the crust. The properties of the near surface require further exploration to constrain processes that generate earthquakes and characterize the temporal variations in seismic and geodetic records. The expected results from this project will advance the understanding of seismic ground motion, surface deformation, transient deformation signals, and elastic and hydrologic crustal properties for the community at large. This study provides the framework for nascent earthquake detection techniques applicable to regional seismic networks. During the investigation, Dr. Johnson will interact and train undergraduate and graduate students.The dominant fault system along the Pacific-North American plate boundary is the San Andreas Fault (SAF) that bisects dense urban city centers along the California coast. Southeast of Los Angeles, CA the SAF bifurcates into the San Jacinto Fault Zone (SJFZ), where microseismic events occur daily and six M5 earthquakes have ruptured in the past 35 years. Fully characterizing the SAF and SJFZ are of great importance to infrastructure planning and hazard mitigation. A recent dense array deployment of 1,100 seismometers recorded ground motions at the SJFZ for 5 weeks. The data set provides a unique opportunity to develop new techniques that characterize the shallow subsurface from 0-1 km depth and fully describe the fault zone environment from the surface to the brittle-ductile transition zone at ~18 km depth. Preliminary results from the deployment indicate 120 small events in one day of the array data, significantly more than the 15 earthquakes detected by the regional seismic network. Labeling as many features of the data as possible will aid in efficiently processing large volumes of data, thereby reducing the computational expense of microseismic earthquake detection. The detailed classification of continuous data should also produce a qualitative description of patterns in the noise and highlight episodes of coherent energy that may represent previously unexplored failure processes in the shallowest portions of the crust. This is a novel study utilizing data from the Earthscope PBO networks to further advance the understanding of plate boundary fault systems.