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Effects of Multi-Scale Structure on Shear Wave Generation and Propagation Using Source Physics Experiment Data

Session: Explosion Seismology Applications and Advances II

Type: Oral

Date: 4/19/2021

Presentation Time: 02:30 PM Pacific

Description: 

We study the generation and propagation of shear waves from chemical explosion sources by focusing a multidisciplinary effort on the Source Physics Experiment (SPE) Phase I, located in a granite outcrop, and Phase II, located at a dry alluvium geology site (DAG). Using data recorded by dense networks of seismic stations and fiber optic cables, we have conducted first arrival analysis, Rg propagation analysis, and horizontal-to-vertical spectral ratio analysis to constrain the geological structure. Our results differentiate between alluvium, volcanic tuff, and Paleozoic basement units, depending on site, and identify clear 3-D variations at different scales. Body wave analyses (first arrival) and Rg phase propagation studies focus on reconciling models produced using different data types. To understand the generation of shear energy within the 3D subsurface from DAG explosions, we have undertaken full waveform modeling using the spectral element code SPECFEM3D, varying the velocity of each geological unit in the model to account for uncertainties assessed by an in-situ mapping campaign and material characterization of borehole samples. We quantify the shear energy in the modeled wavefield by measuring the amplitude of the transverse component and P/S ratio for about 900 stations. Our results show that the P/S ratio is strongly affected by the subsurface properties. We will compare the P/S ratio modeling results to observations and will refine the model by changing attenuation properties and by studying the effects of random heterogeneities and anisotropy.

Presenting Author: Ting Chen

Student Presenter: No

Authors