Using coda waves to resolve the scattering and intrinsic attenuation structure of Southern California

Wei Wang, & Peter M. Shearer

Submitted August 12, 2016, SCEC Contribution #6672, 2016 SCEC Annual Meeting Poster #205

Measuring intrinsic and scattering attenuation is important for a variety of geophysical applications. Charactering scattering and absorbing properties and the power spectrum of crustal heterogeneity is a fundamental problem for informing strong ground motion estimates at high frequencies, where scattering and attenuation effects are critical. We perform a comprehensive study of coda behavior in Southern California to constrain scattering and intrinsic attenuation structure. We stack 31,894 vertical-component envelopes and 29,203 transverse-component envelopes at 2 to 4 Hz from 1224 spatially distributed earthquakes from 1981–2013 at source depths of 10 to 15 km and epicentral distances from 0–250 km with magnitudes larger than 1.8. The stacked envelopes are averaged as a function of distance, depth and frequency. We model these observations using a particle-based Monte Carlo algorithm to simulate regional scattering and intrinsic attenuation. This method has the advantage of including both P- and S-wave scattering and both single and multiple scattering events. The synthetic results show that coda waves for the Southern California region can be reasonably fit with a two-layered model, composed of a shallow crustal layer with strong wide-angle scattering and high intrinsic attenuation and a deeper layer with weaker scattering and lower intrinsic attenuation (top 5.5 km: QP = 250, QS = 125, heterogeneity correlation length a = 50 m, velocity heterogeneity rms e = 0.5; lower crust: QP = 900, QS = 400, a = 2 km, e = 0.05).

Key Words
Coda wave, attenuation, stacking, Monte Carlo Simulation

Citation
Wang, W., & Shearer, P. M. (2016, 08). Using coda waves to resolve the scattering and intrinsic attenuation structure of Southern California. Poster Presentation at 2016 SCEC Annual Meeting.


Related Projects & Working Groups
Seismology