Bowden, D. C. and Tsai, V. C. and Lin, F. C. (2015) Site amplification, attenuation, and scattering from noise correlation amplitudes across a dense array in Long Beach, CA. Geophysical Research Letters, 42 (5). pp. 1360-1367. ISSN 0094-8276. http://resolver.caltech.edu/CaltechAUTHORS:20150423-094707871
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For accurate seismic hazard evaluation, both the spatial and frequency-dependent variabilities in the amplitudes of earthquake ground motions are needed. While this information is rarely fully available due to the paucity of relevant seismic data, dense arrays like the 5200-geophone array in Long Beach, California provide the opportunity to study this amplitude variability. Here we show that ambient noise correlation amplitudes from the Long Beach array can be used to directly determine frequency-dependent site amplification factors. We analyze Rayleigh-wavefield amplitude gradients from ambient noise correlations that are processed so that relative amplitudes satisfy the wave equation and are therefore meaningful. Ultimately, we construct maps of site amplification across Long Beach at frequencies of 0.67, 1.0, and 2.0 Hz. These maps correlate well with local structure, notably the Newport-Inglewood Fault and also to known velocity structure. Through this process, we also obtain constraints on average attenuation structure and local scattering.
|Additional Information:||© 2015 American Geophysical Union. Received 2 December 2014; accepted 27 January 2015; accepted article online 2 February 2015; published online 6 March 2015. The authors gratefully acknowledge Dan Hollis at NodalSeismic LLC, and Signal Hill Petroleum, Inc., for permitting us to use the Long Beach data. We thank Dunzhu Li for scripts and advice in handling the large quantity of cross correlations, and Rob Clayton and Asaf Inbal for helpful discussion. We are also thankful for the constructive and helpful comments from Jesse Lawrence and an anonymous reviewer. This project is supported by NSF grants EAR-1252191, EAR-1214912, and CyberSEES-1442665. Fan-Chi Lin also acknowledges the financial support from Signal Hill Petroleum for this research. The Editor thanks two anonymous reviewers for their assistance in evaluating this paper.|
|Subject Keywords:||seismology; site amplification; ambient noise; wavefront tracking|
|Official Citation:||Bowden, D. C., Tsai, V. C. and Lin, F. C. (2015), Site amplification, attenuation, and scattering from noise correlation amplitudes across a dense array in Long Beach, CA. Geophys. Res. Lett., 42: 1360–1367. doi: 10.1002/2014GL062662.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||23 Apr 2015 18:04|
|Last Modified:||23 Nov 2016 19:26|
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