UC San Diego

In this dissertation, I study two fundamental topics in seismology, tidal triggering of earthquakes and attenuation and scattering structure. Studies of tidal triggering help constrain earthquake nucleation models and relate to earthquake predicability and forecasting. Resolving

attenuation and scattering behavior can provide more physically realistic models for strong ground motion prediction equations (GMPEs) and improve our understanding of the physical properties of rocks in the lithosphere. Chapter 1 is an introduction, providing background and motivation for each of the following chapters. Chapters 2 & 3 focus on the topic of tidal triggering of earthquakes. Chapter 2 studies tidal triggering in the central Japan region using M>3 earthquakes and finds no clear evidence for tidal triggering. Chapter 3 analyzes seismicity in the Coso region of California and finds strong tidal triggering but an absence of remote triggering at the Coso geothermal field, constraining earthquake triggering sensitivities at different time scales of stress perturbations. Chapters 4-6 study the inelastic properties of the crust and upper mantle in southern California using both coda and direct-wave observations. Chapter 4 stacks coda envelope functions across southern California and synthesizes them using a two-layer model, composed of a shallow crustal

layer with strong wide-angle scattering and high P and S intrinsic attenuation and a deeper layer with weaker scattering and lower intrinsic attenuation. Chapter 5 describes improvements to the conventional coda-Q method to solve for coda attenuation, site amplification and source radiated energy simultaneously. Chapter 6 models focal-sphere-dependent S/P amplitudes assuming a

whole-space intrinsic and scattering attenuation model around the San Bernardino region.