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Comparison of Fundamental Fault Green’s Functions (Gfs) Computed Using Frequency-Wavenumber and Finite-Difference (SW4) Techniques for 1D Velocity Models

Description: 

It has been noted that use of the green’s functions (GFs) computed using the three-dimensional (3D) codes such as SW4 and SPECFEM3D produce more reliable moment-tensor solutions compared to those when the GFs of the one-dimensional (1D) models are used. However, none of the studies explored if the GFs computed by the 3D and 1D are similar when they are computed for the same 1D velocity models. In this study, we have used the Dirac and Gaussian source time function in SW4 to compute regional seismograms up to 6Hz for one 1D model. We used three 1D codes, namely the Filon_AS-03, FK_PROG, and zengSAIKIA to compute high-frequency seismograms, ensuring that the wavenumber domain discretization is small enough to reduce the spatial aliasing in the synthetics. The 1D codes uses the delta function as the source time function. To establish the source time equivalence, f_o (the frequency parameter) needed to be set quite high (say about 20Hz) especially when the Gaussian source function is implemented. In this study, we will illustrate the equivalence high-frequency SW4 seismograms with those computed using the 1D code for the fundamental faults except for those computed for the 45^o dipping dip-slip (DD) fault. For seismograms to be similar in amplitude for this fault, the corresponding moment-tensor elements have to be 2 time larger than those that are required by the 1D codes. This also involves the Mxy component, but the contribution from this component is many order lower than other moment-tensor elements, especially for the surface receivers.

Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Chandan

Student Presenter: No

Invited Presentation: 

Authors