Source Parameter Determination of Bimaterial Faults through Long-Period Seismic Waves

Yichen Geng, & Miaki Ishii

Published September 8, 2024, SCEC Contribution #13585, 2024 SCEC Annual Meeting Poster #011

The conventional seismic source theory assumes that slips occur on buried faults within homogeneous media. However, there are well-known examples of bimaterial faults, i.e., faults with different materials on two sides (e.g., the San Andreas fault). Displacements of long-period seismic waves are affected by such material contrast and the direction of the slip, which implies that the fault and auxiliary planes are no longer interchangeable. The dependence on the material contrast also suggests that the material properties of the fault may be constrained through waveform modeling. Furthermore, the incorporation of the bimaterial effect could improve the moment tensor determination, especially for a shallow source. Due to the traction-free boundary condition at the surface and dependence on the strains at the source location, seismic displacements produced by a homogeneous fault are insensitive to the vertical dip-slip components of the source mechanism at a shallow depth. On the other hand, those associated with fault bimateriality depend upon the displacements rather than the strains at the source, and hence the vertical dip-slip components of the moment tensor can be deduced. Using a vertical strike-slip bimaterial fault as an example, we show potential ways of how these source parameters, in particular, the fault orientation and material contrast, can be extracted.

Key Words
source parameters, bimaterial faults, long-period seismic waves

Citation
Geng, Y., & Ishii, M. (2024, 09). Source Parameter Determination of Bimaterial Faults through Long-Period Seismic Waves. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology