Prototype Investigations into Integrated GPS/Seismic Networks for Improved Finite Fault Slip Modeling and Earthquake Characterization

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Recent great earthquakes and ensuing tsunamis in Sumatra, Chile and Japan have demonstrated the need for accurate ground displacements that fully characterize the great amplitudes and broad dynamic range associated with these vast, complex ruptures. Our ability to model these events, whether in real-time or after the fact, is limited by the weaknesses of both seismic and geodetic networks. Geodetic instruments provide the static component as well as coarse dynamic motions but are much less precise than seismic instruments, especially in the vertical direction. Seismic instruments, in turn, provide exceptionally-sensitive dynamic motions but typically have difficulty recovering unbiased near-field static offsets and low-frequency motions because of contamination, for example, from instrument tilt. This three-year project is demonstrating a new paradigm for studying the processes of large earthquakes and the hazards they pose. Accurate three-dimensional seismogeodetic waveforms (broadband displacements and velocities) that span the full spectrum of seismic motion will be achieved through integration of geodetic and seismic measurements instrumentation developed at Scripps Institution of Oceanography. The main science objectives are to improve finite-fault slip inversions through the optimal combination of geodetic and seismic data at the observational level and to investigate appropriate methodologies to perform full waveform inversions using the resulting data. With UNAVCO engineers, a test bed of integrated GPS/seismic stations is being established at existing real-time Plate Boundary Observatory stations along the southern San Andreas fault system as a prototype for further expansion along the Western North America plate margin. The stations are being upgraded with low-cost MEMS accelerometers and a Geodetic Module that will synchronize the GPS and accelerometer data and estimate seismogeodetic displacements and velocities.The project is installing and testing seismic upgrades to existing GPS monitoring stations for improved response to and modeling and understanding of large earthquakes and ensuing tsunamis, such as recent ones in Sumatra, Chile and Japan. The broader impacts of this project are significant in terms of scientific value, engineering infrastructure, civilian use, and economic impact, and are related for the most part to the real-time nature and capabilities of enhanced GPS/seismic monitoring. The new observations contribute directly to natural hazards research and early warning systems for earthquakes, volcanoes and tsunamis, to atmospheric research including short-term weather forecasting and related flooding hazards, and to earthquake engineering research for large structures (e.g., bridges, buildings, dams). The ultimate goal is to save lives and minimize damage to essential infrastructure. The new observations also contribute to civilian applications requiring precise real-time positioning (e.g., surveying, geographic information systems, agriculture) and hence to economic stimulus. Finally, the project supports collaborative and interdisciplinary research, education of technologically sophisticated graduate students, strengthening of diversity in support of workforce development, and enhancement of curricula at a variety of levels through engagement new types of data sets that have direct societal impact.