2023 Fiscal Year Research-status Report
Effects of phyllosilicate minerals on fault slip of sandstone
| Project/Area Number |
22K14122
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| Research Institution | Hiroshima University |
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Principal Investigator |
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | Fault slip behavior / Main Frontal Thrust / Fault friction / Earthquake nucleation / Creep behavior |
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| Outline of Annual Research Achievements |
The objective of present research is to elucidate the weakening mechanism and fault-slip behavior of sandstone, which is a dominant rock type in both continental collisional zones (like the Himalaya) and accretionary complexes (like the Japanese Islands). Deformation experiment using rotary shear apparatus were conducted at 10 MPa effective normal stress and wet conditions on powdered sandstone samples and gouge samples, simulating shallow crustal deformation. Velocity weakening behavior were observed for the powdered sandstone and quartz-rich gouge sample. However, the gouge sample rich in illite show velocity strengthening behavior (or aseismic creep behavior).
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
As per plan, velocity step experiments in wet condition (simulating natural conditions) has already been conducted. The reproducibility of the low velocity experiments were also verified.
A set of single velocity experiment and experiment at seismic velocity has also been completed. The mineralogical characterization using XRD and SEM-EDS has also been achieved.
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| Strategy for Future Research Activity |
At present we completed the mineralogical and microstructural characterization of the recovered samples from the rotary shear deformation experiments. In the final year of the project we plan to do additional set of creep experiments <10 μm/s and compare the frictional behavior and microstructures with the rotary shear experiments. This experiments will provide insights of the frictional behavior of the sandstone and gouge rocks of shallow crust (Nahan Thrust) over a range of slip velocities (creep-to-seismic velocities).
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| Causes of Carryover |
Sampling and consumable costs for the very slow slip experiments were not used, as the final set of sampling and the experiments were re-planned to be conducted in the 2024 fiscal year. Hence, the incurring amount will be used in experimental consumables, and traveling expenses related to conferences and fieldwork.
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