Title: Fault Zone Imaging and Earthquake Detection with Dense Seismic Arrays

Committee members: Zhigang Peng (advisor), Andrew Newman, Josef Dufek, Ken Ferrier, James McClellan (ECE)

Abstract: Natural earthquakes occur on faults. The relationship between fault zone properties and earthquake behaviors remains one of the core problems in modern seismology. As an important tool to study earthquakes and fault zone properties, seismic arrays have been widely used since the 1960s. Recordings from closely spaced uniform seismometers significantly enhance observation reliability and provide valuable resources for studying the Earth’s structure and tectonic processes. Increase in array density (more sensors and smaller interstation spacing) has significantly improved the imaging resolution of the Earth’s interior and enhanced the detection completeness of small-magnitude earthquakes. However, the following increase in data size also poses a challenge in the way of handling and processing seismic data; in particular, visual inspection and manual selection is becoming less practical.

My PhD research primarily focuses on seismic anisotropy and velocity contrast in major fault zones in western Turkey and southern California, using multi-scale dense seismic arrays. To process large-size seismic data and reduce laborious human intervention, I developed several processing tools to automatically pick P, S and fault zone head waves. In the later stage of my doctoral study, I studied on the earthquake detection, with the goal to improve the detection resolution of earthquakes near noise level. Specifically, I developed a new technique, termed local similarity, to detect weak microseismicsignals, utilizing the emerging ultra-dense arrays. These studies share the same features of using automatic techniques to extract earthquake and structure information from big seismic data recorded by dense arrays. The results are expected to provide valuable constraints on the properties of fault zones and the behavior of microearthquakes. The tools developed in these studies can be applied to a wide range of research topics.