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Yield and Depth of an Explosion From Regional Seismograms With Source Complexity - Illustration of the Effectiveness Using Synthetic Seismograms

Description: 

A method for inverting waveforms to estimate yield and depth of an explosion when accompanied a double couple (DC) and a strong compensated linear vector dipole (CLVD) source contribution will be presented. This paper points out an amplitude correction for the generalized CLVD source green’s functions (GFs) represented as a combination of contributions from three orthogonal force dipoles without torque. For a vertically symmetric CLVD GFs, they are a factor of 2 smaller than the 45^o dipping dip-slip fault observed at 45^o azimuth (often referred to as ZDD or RDD GFs for the DC mechanism) which are routinely used in waveform inversions. This amplitude discrepancy is also evident in the radiation coefficients of force dipole (FDP) vs DC sources (Saikia et al., 2008) which is also noted in waveforms simulated using three-dimensional SW4 and F-K codes using 1D velocity models. Using this correction, a set of regional waveforms were constructed including a source complexity and effects of regional wave propagation. The explosion sources were represented by the yield and depth dependent time-domain source function (TDSF) and non-isotropic sources just by the impulse source functions. These waveforms were used to set up an inversion scheme which requires partials of the simulated explosion waveforms with respect to yield and depth including the partials of green functions at each depth. We modified the TDSFs (Saikia, 2017, https://doi.org/10.1093/gji/ggx072) and the F-K code (FKPROG, Saikia and Burdick, 1991,https://doi.org/10.1029/91JB00921) to formulate analytic expressions for the partials of the GFs with respect to the yield and depth using only the source layered matrix. The newly derived partials of explosion sources are independent of the elastic radius of the explosion source which we validated using against the numerical partials. Using numerically simulated waveforms, results from this new set of codes will be presented to illustrate the method effectiveness

Session: Numerical Modeling in Seismology: Theory, Algorithms and Applications [Poster]

Type: Poster

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Chandan

Student Presenter: No

Invited Presentation: 

Poster Number: 127

Authors