Full-3D Tomography of Crustal Structure in Central California 1En-Jui Lee, 1Thomas H. Jordan, 2Po Chen, 1Philip J. Maechling, 3Pierre Boué, 4Marine Denolle, 3Gregory C. Beroza, 1William K. Eymold 1 Southern California Earthquake Center, University of Southern California 2Department of Geology and Geophysics, University of Wyoming 3 Department of Geophysics, Stanford University 4 Scripps Institute of Oceanography, University California San Diego

Central California New Melones Dam High seismic risk Diablo canyon power plant Dam safety (Sierra Navada) New Melones Dam

The initial model NC : Xu et al.’s (2013) NC model 3 full-3D tomography (F3DT) iterations SC : Lee et al.’s (2014) 26 F3DT iterations CVM-S4.26 Background: Lin et al.’s (2010) state-wide model NC model CVM-S4.26

Waveform Data Ambient-noise Green’s functions (ANGFs) Improve data coverage Source and receiver locations are known Different frequencies have sensitivity for different depths Ma et al., (2008), BSSA

ANGFs waveform examples From a station at Parkfield to other stations Bandpass 0.11~0.18 Hz Bandpass 0.03~0.10 Hz Cross the Great Valley Ambient noise Green’s function data from Dr. Beroza’s group

ANGF Dataset 5th iteration 200 stations ANGFs among various instruments Broadband stations Short-period stations Very good data coverage for our study area

Waveform Processing CWT Separate seismic phases Find wave- form pairs Freq. dependent measure-ments TW ICWT Lee & Chen, (2013), GJI

Measurements More than 12,000 windows More than 59,000 frequency dependent measurement

Results Sum of RWM reduces about 28.5%

Results Variance of dtg reduces about 56%

5th iteration model Heal the velocity artifacts in the initial model Increase the velocity gradient across SAF Enhance basin structures Great Valley Cuyama Basin

ANGF Waveform examples Initial waveforms Updated waveforms Black: data Red: synthetic Initial waveforms Updated waveforms

Southern Great Valley Similar basin structures Shallow Deep Harvard’s basin model Deep

Future work Merge Harvard’s basin model for near surface velocity Earthquake source inversion based on updated velocity model Including earthquake waveforms for more iteration Physics-Based Seismic Hazard Model for Central California

Earthquake Source Inversion More accuracy velocity model  Earthquake source inversions & seismic hazard analysis

Summary Use of ANGF data to improve data coverage Heal the velocity artifacts in the initial model Reveal basin & fault structures Improve waveform fittings Future Work Earthquake source inversion Physics-Based Seismic Hazard Model