Seismic investigation of subduction in Cascadia and Alaska and Simulating the ability of MyShake networks to detect and locate earthquakes
This study has two major focuses, which are united by the theme of applying data processing and imaging techniques to extract valuable information from large volumes of seismic data.
The first focus is on the use of seismic imaging to improve our understanding of the tectonic settings of two of North-America's subduction zones; namely Cascadia and Alaska. Both exhibit enigmatic features and provide insight into fundamental seismotectonic processes relating to the interplay between subduction, mantle flow, volcanism and continental crust growth. Cascadia, for example, represents the final stages of subduction of the once giant Farallon plate. Using data collected from an ambitious deployment of ocean bottom seismometers across the entirety of the Juan-de-Fuca and Gorda plates offshore Oregon and Washington, this study maps the geometry of upper mantle flow in the region, which has important tectonic implications.
The Alaskan subduction zone contrasts with Cascadia because the downgoing oceanic lithosphere here is older and more seismically active. This study uses data from an unprecedented seismic survey of Alaska to construct high resolution, three dimensional models of the velocity structure from the surface down to about 400km depth. These elucidate many fascinating features of this region, including the geometry of the downgoing material and its relationship to several enigmatic volcanic provinces.
The second focus of this study is concerned with earthquake early warning. This is a technology that aims to provide seconds to minutes of warning to people before the onset of severe shaking during an earthquake, potentially allowing them to take life-saving actions. MyShake is a smartphone application developed by the U.C Berkeley Seismological Laboratory that allows mobile devices to detect earthquakes. MyShake is available for public download and is providing a rich dataset for investigation. This study describes an algorithm designed to use networks of MyShake devices to quickly locate and issue warnings about earthquakes, and a simulation workflow designed to test this approach. The results indicate that MyShake networks have exciting potential to issue useful earthquake early warnings worldwide.