Amgen Scholars: Announcements of Opportunity
Below are Announcements of Opportunity posted by Caltech faculty for the Amgen Scholars program.
Announcements of Opportunity are posted as they are received. Please check back regularly for new AO submissions! Remember: This is just one way that you can go about identifying a suitable project and/or mentor. For additional tips on identifying a mentor click here.
Please remember:
- Students pursuing Amgen must be U.S. citizens, U.S. permanent residents, or students with DACA status.
- Students pursuing Amgen must complete the 10-week program from June 18 - August 23, 2024. Students must commit to these dates. No exceptions will be made.
- Accepted students must live in provided Caltech housing.
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| Project: | Mathematical and computational explorations of the induced earthquake nucleation process | ||||||||||||
| Disciplines: | Applied and Computational Mathematics, Engineering, Geophysics, Physics | ||||||||||||
| Mentor: | Nadia Lapusta, Professor , (EAS), lapusta@caltech.edu | ||||||||||||
| AO Contact: | Maryam Alghannam, maryamgh@caltech.edu | ||||||||||||
| Background: |
Induced seismicity is a central issue in the development of subsurface energy technologies in the United States and around the world. It is the earthquakes caused by human activities that involve extracting or injecting fluids into the subsurface and modifying subsurface stresses around pre-existing faults. Examples include geologic carbon sequestration, geothermal energy extraction, subsurface water injection, and reservoir impoundment in the vicinity of large dams. While most of the induced earthquakes are fortunately too small to be felt, some can go up to magnitude 5 — large enough to be felt and to cause damage to buildings. Understanding the physical mechanisms behind induced seismicity is essential to successful management and mitigation of the seismic risk associated with subsurface energy technologies and sustainable energy usage. The basic mechanism for induced fault slip is widely understood in terms of the Coulomb failure criterion. When fluid is injected into or withdrawn out of a reservoir, the associated pore pressure perturbations and poroelastic stress changes increase the ratio of shear to effective normal stress on a fault and cause it to slip. This criterion, however, does not address the evolution of the rupture, and whether a fault slips seismically or aseismically. A different criterion, derived from theoretical analyses of frictional slip between two elastic media, differentiates from seismic and aseismic slip. It states that fault slips seismically if the spatial scale for the slipping zone is larger than a critical nucleation length inversely proportional to the effective normal stress, and slips aseismically otherwise. This nucleation criterion, however, assumes spatially and temporally uniform effective normal stress and does take into account the dependence of friction on fluid presence. |
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| Description: |
The goal of this project is to identify the factors that control the nucleation of two dimensional in-plane or antiplane slip-weakening instabilities, and to evaluate the nucleation length that is relevant to fault instabilities and induced earthquake rupture. We consider fault rupture in an infinite, homogeneous space subjected to a nonuniform frictional resistance (effective normal stress * coefficient of friction). The stress is assumed to gradually increase due to fluid injection and locally peak around the injection site. The coefficient of friction is assumed to vary spatially based on the presence or absence of fluids along the fault surface. The size of the slipping region on the fault grows under increased loading stress until finally a critical nucleation length is reached at which no further quasi-static solution exists. That marks the onset of a dynamically controlled instability or an earthquake. The student is expected to: (1) review the derivation for the nucleation length under nonuniform shear loading by Uenishi & Rice (2003), (2) reproduce the solution for nonuniform fluid pore pressure by Garagash & Germanovich (2012), and (3) solve an eigenvalue problem associated with the nucleation length under variable friction either analytically or numerically. |
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| References: |
http://lapusta.caltech.edu Ellsworth, W.L.: Injection-induced earthquakes. Science (6142), 1225942 (2013) Garagash, D.I., Germanovich, L.N.: Nucleation and arrest of dynamic slip on a pressurized fault. Journal of Geophysical Research: Solid Earth (B10) (2012) Uenishi, K., Rice, J.R.: Universal nucleation length for slip-weakening rupture instability under nonuniform fault loading. Journal of Geophysical Research: Solid Earth (B1) (2003) |
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| Student Requirements: | The project may be more relevant for students involved in Mathematics and Computational Science, however it may be of interest to students in Physics, Mechanical Engineering and Geophysics with a strong background in mathematics (level of ACM 95/100 or greater) and computational skills (e.g., Matlab). | ||||||||||||
| Programs: |
This AO can be done under the following programs:
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