Southern California Earthquake Center Full3 D Tomography of

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

Southern California Earthquake Center Central California • High seismic risk – Diablo canyon power plant – Dam safety (Sierra Navada) New Melones Dam 2

Southern California Earthquake Center The initial model • NC : Xu et al. ’s (2013) – 3 full-3 D tomography (F 3 DT) iterations NC model • SC : Lee et al. ’s (2014) – 26 F 3 DT iterations – CVM-S 4. 26 • Background: Lin et al. ’s (2010) state-wide model CVM-S 4. 26

Southern California Earthquake Center 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 Southern California Earthquake Center

ANGF Dataset • ANGFs among various instruments – Broadband stations – Short-period stations • Very good data coverage for our study area 5 th iteration 200 stations Southern California Earthquake Center

Southern California Earthquake Center Waveform Processing • Separate seismic phases • Find waveform pairs • Freq. dependent measurements Lee & Chen, (2013), GJI CWT TW ICWT

Southern California Earthquake Center Measurements • More than 12, 000 windows • More than 59, 000 frequency dependent measurement 8

Results Southern California Earthquake Center • Sum of RWM reduces about 28. 5% 9

Southern California Earthquake Center Results • Variance of dtg reduces about 56% 10

Southern California Earthquake Center 5 th iteration model • Heal the velocity artifacts in the initial model • Increase the velocity gradient across SAF • Enhance basin structures – Great Valley – Cuyama Basin 11

Southern California Earthquake Center ANGF Waveform examples. Initial waveforms Updated waveforms Black: data Red: synthetic Initial waveforms Updated waveforms

Southern Great Valley • Similar basin structures Shallow Harvard’s basin model Deep Shallow Southern California Earthquake Center Deep

Southern California Earthquake Center 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 Southern California Earthquake Center

Southern California Earthquake Center 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 16