SCEC Project Details
| SCEC Award Number | 24125 | View PDF | |||||
| Proposal Category | Individual Research Project (Single Investigator / Institution) | ||||||
| Proposal Title | Investigating the effects of velocity contrasts on rupture propagation along branching faults: Implications for the junction between the Mission Creek, Banning and the Southern San Andreas fault | ||||||
| Investigator(s) |
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| SCEC Milestones | C2-1, C3-1, D3-2 | SCEC Groups | FARM, Seismology, Geology | ||||
| Report Due Date | 03/15/2025 | Date Report Submitted | 03/21/2025 | ||||
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Project Abstract |
Crustal faults often separate material with differing elastic properties. Dissimilar media around faults has been shown to cause effects on the rupture process along vertical strike-slip faults, where asymmetry in wave propagation across a bimaterial interface introduces normal stress changes on the fault near the rupture front that can lead to asymmetric bilateral or unilateral propagation. Considering the effects caused by bimaterial interface on rupture propagation, it is worth understanding whether these effects can impact throughgoing rupture across a geometric complexity. In this work we use dynamic rupture simulations to investigate the effects of a bimaterial interface on rupture propagation along a main fault that bifurcates into a Y branch geometry (S1 and S2) where each branching at an angle of 15°. We vary the material contrast where we assign a zone of stiffer material to one side of the branch system, such that each branch segment is in separate dissimilar media. For the case when branch S1 in the stiffer region, the results show that when rupture nucleates on the main fault, it propagates slower as the material contrast increases. Furthermore, for lower material contrast models, upon reaching the branch intersection the rupture continues solely on the extensional S1 secondary fault but increasing the material contrast model will cause the rupture to propagate onto both the extensional S1 segment and the compressional S2 segment. Velocity contrast appear to have a strong hazard implication since it facilitate rupture onto the unfavorable branch faults. |
| Intellectual Merit | This study indicate bimaterial interface can significantly influence throughgoing rupture across geometric discontinuities. Our work will advance the science of fault dynamics in regions of geometrical complexity, especially fault branches. The results obtained in this project can be applicable to the branch fault systems in southern California where bimaterial interface has been observed such as the San Andreas and Garlock faults, the San Andreas and San Jacinto faults and the San Andreas, Mission Creek and Banning fault segments. |
| Broader Impacts | This work has broader impacts on the assessment of seismic hazard along branch fault systems at locations with strong velocity contrast. Understanding how material contrast can prevent or facilitate throughgoing rupture across branch faults is vital to the estimation of potential earthquake size in Southern California for example. |
| Project Participants |
1) Evan Marschall (Graduate Student), University of California, Riverside 2) Roby Douilly (PI), University of California, Riverside 3) Nobuki Kame (Partner), Earthquake Research Institute, University of Tokyo |
| Exemplary Figure | Figure 3: Snapshots of slip rate evolution and final slip for the right lateral case 1 geometry with varying material contrast. For models with 0%, 10% and 15% the rupture is constrained solely to the extensional S1 fault but for the 20% model both secondary faults rupture. Figure credits: Evan Marschall. |
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Linked Publications
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