UC San Diego

This dissertation presents several studies focusing on the three phases of the crustal deformation cycle. Using an optimal combination of seismic and space geodetic techniques, we investigate the coseismic phase of an earthquake that includes both shaking and permanent displacements, the postseismic phase where additional slip may occur around the affected region, and the interseismic phase over which stress builds-up at the interface between tectonic plates. Studying the crustal deformation cycle has important implications for understanding tectonic fault zone processes such as slip partitioning and strain accumulation, and to improve real-time systems for tsunami and earthquake early warnings.We first apply a physics-based approach to identify the transition from coseismic to postseismic deformation, and show how early postseismic is significant just minutes to hours after an earthquake. Our results show that the widely used estimates of daily coseismic offsets can lead to an overprediction of earthquake coseismic displacements. We compare the commonly used daily offsets and our rapid coseismic window methodology over several earthquakes and demonstrate that without consideration of the early postseismic stages, both coseismic and postseismic fault slip models can be biased by several meters. We then use the coseismic time window analysis and rely on earthquake source theory to develop a rapid earthquake magnitude determination method. To test our approach, we simulate a real-time environment by replaying historical earthquakes around the Pacific basin. Our results show that we can reliably estimate earthquake magnitude over the 7.2 < Mw < 9.1 range, minutes after rupture initiation. Incorporating long-period information from Global Navigation Satellite System (GNSS) displacements solves the problem of magnitude saturation, making these estimates useful for local tsunami warnings. We later turn to the interseismic phase of the crustal deformation cycle by exploring more than seven years of long-term deformation along the Dead Sea Fault. For several reasons that are mostly political, GNSS station coverage in this area is not ideal with most stations on one side of the fault. For that reason we utilize the combination of GNSS station velocities and Interferometric Synthetic Aperture Radar (InSAR) imagery for a better spatial and temporal resolution representation. We detect left-lateral deformation that is in agreement with other GNSS studies and geological observations. By dividing our study area into sections, we resolve geodetic slip rates and locking depths and reveal that some segments are freely creeping in the shallow subsurface compared to others that are fully locked. These studies present several approaches for the combination of different geophysical datasets to take advantage of their strengths while minimizing their weaknesses, to carefully study each phase of the crustal deformation cycle.