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Towards a High-Resolution Velocity Model with a Very Dense Array at Diablo Canyon, California

Nori Nakata, & Gregory C. Beroza

Published August 14, 2017, SCEC Contribution #7565, 2017 SCEC Annual Meeting Poster #022

Correlation-based analyses of ambient seismic wavefields is a powerful tool for retrieving subsurface information such as stiffness, anisotropy, and heterogeneity at a variety of scales. Especially with very dense arrays recently used for seismology (e.g., the Long Beach array), we can avoid aliasing of wavefields in the wavenumber domain and estimate velocity models with very high spatial resolution. At Diablo Canyon, Central California, about 7200 geophones were deployed within a 20x20 km2 area for six weeks in 2011. Here, we apply correlation-based methods to this dataset to extract coherent surface waves in the 0.5--4.0 Hz frequency range and use them for imaging subsurface structure. Note that this frequency range is much higher than previous studies for ambient seismic wavefields. Because of the dense array, we can spatially average seismic data over several sensors to improve the signal-to-noise ratio and extract multiple wave types including P and both fundamental and higher-mode Rayleigh waves. We anticipate that the subsurface velocity model imaged by this array has much higher spatial resolution than that developed from regional arrays with receiver spacing of about 10~20 km. Because small-scale heterogeneities are important for high-frequency motion prediction for earthquakes, the velocity model would be useful for improving the ground-motion prediction.

Nakata, N., & Beroza, G. C. (2017, 08). Towards a High-Resolution Velocity Model with a Very Dense Array at Diablo Canyon, California. Poster Presentation at 2017 SCEC Annual Meeting.

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