Integrating Geologic, Geodetic, and Coastal Tide Gauge Observations with 100-year Vertical Deformation Models of California Earthquake History

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This project investigates earthquake-induced vertical deformation using a synthesis of coastal tide gauge, geodetic, and geologic data of the Pacific-North American plate boundary. While the growing archive of space geodetic data in this region provides precise deformation measurements with a high degree of spatial coverage, these data supply only a 15-year record of crustal motions and therefore only weakly constrain time-dependence of crustal motions. Geologic data provide a 1000-year averaged record of deformation, however these data are often sparsely located and can have large uncertainties. Alternatively, sea level change has been continuously recorded along the California coastline at several tide gauge stations for over the past 50-100 years. These stations provide a temporal record of sea level change, generally attributed to post-glacial rebound and ocean climate phenomena. However, geologic processes, including displacements from large earthquakes, have also been shown to produce sea level variations, as vertical interseismic strain accumulation can contribute uplift and subsidence rates of 1-3 mm/yr. Using coastal tide gauge time series data, this project is exploring the correlation between sea level variations and estimates of vertical displacements produced by a three-dimensional earthquake cycle deformation model that is constrained by geologic slip rates, geodetic velocities, and historical seismic data along the San Andreas fault system. First order vertical deformation estimates derived from geologically and geodetically constrained models are highly compatible with long-term sea level trends, however further analysis is needed to thoroughly explore model parameter space and investigate sources of misfit and unmodeled phonomena. The project will integrate 100-year coastal tide gauge data (Permanent Service for Mean Sea Level), geodetic data (EarthScope Plate Boundary Observatory continuous GPS and InSAR) spanning the last 15 years, and a new geologic database (Southern California Earthquake Center Geologic Vertical Motion Map).This study investigates the long-term role of tectonic deformation on sea level change recorded over the past 100 years along the California coastline. In doing so, these research activities contribute to the objectives of NSF?s EarthScope Initiative by further advancing our understanding of fault system crustal dynamics, earthquake hazards, and data synthesis. The data and model products generated by this investigation will provide an enhanced infrastructure for education and public awareness of both past and present earthquake hazards in California. Furthermore, because a major California earthquake has the potential for massive economic and human loss, quantitative seismic hazard estimates, which rely on an accurate characterization of tectonic motions in California, are critical to the advancement of earthquake science.