Results from two studies in seismology: I. Seismic observations and modeling in the Santa Clara Valley, California. II. Observations and removal of the long-period noise at the Monterey ocean bottom broadband station (MOBB)

Results from two projects are presented in this work. Following brief introductory Chapter 1 that provides general background, Chapter 2 describes the influence of the Santa Clara Valley (SCV) basin structure on the propagation of teleseismic waves. Teleseismic P-waves recorded during the 1998 deployment of the 41-station seismic array are used in the analysis. Observations are compared to synthetics computed by 3D finite-difference simulations using the University of California, Berkeley (UCB) and the U.S. Geological Survey (USGS) 3D velocity models.; Chapter 3 includes further study of the ground-motion amplification in the SCV using microseisms recorded by the SCV seismic array in 1998. The obtained results are compared to the local earthquake amplification. Chapter 4 presents results of the 3D simulations using the most recent version of the USGS velocity model for the greater San Francisco Bay Area. Results are compared to 1998 SCV seismic array observations and to simulations presented in Chapter 2.; Results presented in Chapters 2 to 4 all show strong correlations between basin depth reported in the USGS 3D seismic velocity model and different relative measures of ground motion parameters. The teleseismic, local earthquake and microseism observations are also found to be strongly correlated with one another. Since the results suggest that all three datasets are sensitive to the basin structure, they can be used to improve the 3D velocity model. I started to develop a simultaneous inversion of the teleseismic, local, and microseism observations to refine the seismic velocity model. Chapter 5 presents preliminary results and future plans.; Results from the second project are included in Chapters 6 to 9. Chapter 6 provides information about the Monterey ocean bottom broadband seismic station (MOBB). It explains why seismology is moving into the oceans, describes the MOBB location, provides details about the instruments that comprise the MOBB, and describes the deployment. Examples of data and preliminary analysis are also included.; Chapter 7 presents observations of infragravity waves at MOBB. Combined with the information from the ocean buoys, the MOBB data show that the infragravity waves in the longer than 20 s period band are mainly locally generated from shorter-period ocean waves. Two types of the observed infragravity band signal modulation are presented and possible mechanisms for the modulation are discussed. Also included is the analysis of the ocean bottom seismic data from the temporary Oregon ULF/VLF deployment that also indicates that the infragravity waves are primarily locally generated.; Chapter 8 describes analysis of data from another ocean bottom station. KEBB is located offshore Washington, in deeper water and further offshore than MOBB. Results suggests that in this case the infragravity waves are generated from shorter period ocean waves in the coastal region and not locally at KEBB.; Chapter 9 focuses on the removal of the long-period background as well as signal-generated noise from the MOBB data. Methods used to improve signal-to-noise ratio for the ocean bottom seismic data are presented.