Implications of Local Wave Propagation Effects on the Performance of P/S Source Discriminants Using High-Frequency Simulations of a Chemical Explosion and Small Earthquake
Description:
Analysis of seismic records of local earthquakes and a series of underground chemical explosions conducted during the Source Physics Experiment (SPE) at the Nevada National Security Site have shown that at local distances (<200 km) the effectiveness of the single-station P/S ratio source discriminant is inconsistent, and with high spatial variability. The main factors that are known to affect the spatial variations of P and S waves amplitude at local distances are the source radiation pattern and wave propagation effects. We used high-frequency (0-10Hz) simulations of recorded earthquakes and the SPE-5 underground chemical explosion to investigate the effects of source radiation pattern and propagation of seismic waves on the performance of the P/S source discriminant at local distances. In our simulations we used a local velocity model that was generated by combining the regional Geological Framework Model with small-scale correlated stochastic perturbations.
Through waveform matching, we found that the deterministic high-frequency modeling requires velocity models that also include small-scale complexities of the shallow crust. The inclusion of correlated depth-dependent stochastic velocity perturbations in our model, greatly improved the quality of simulated source radiation and local waveforms, which resulted in better reproduction of the observed spatial variations of the P/S discriminant. We found that the performance of the P/S discriminant declines in areas where the shallow wave scattering effects deform the radiation pattern of source generated P and S waves. The overall variability in local P/S ratios at different locations was reduced when network averaging of P/S ratios was applied.
Session: Exploiting Explosion Sources: Advancements in Seismic Source Physics
Type: Oral
Date: 4/19/2023
Presentation Time: 02:45 PM (local time)
Presenting Author: Arben Pitarka
Student Presenter: No
Invited Presentation:
Authors
Arben Pitarka Presenting Author Corresponding Author pitarka1@llnl.gov Lawrence Livermore National Laboratory |
William Walter walter5@llnl.gov Lawrence Livermore National Laboratory |
Moira Pyle pyle4@llnl.gov Lawrence Livermore National Laboratory |
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Implications of Local Wave Propagation Effects on the Performance of P/S Source Discriminants Using High-Frequency Simulations of a Chemical Explosion and Small Earthquake
Category
Exploiting Explosion Sources: Advancements in Seismic Source Physics