| Project/Area Number |
21K20374
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Multi-year Fund |
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| Review Section |
0204:Astronomy, earth and planetary science, and related fields
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Project Period (FY) |
2021-08-30 – 2025-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
Fiscal Year 2022: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2021: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
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| Keywords | Rapid hydration / Reaction zones / Slow Slip Events / 流体フラックス / 岩石流体反応帯 / 地震活動 / 地震モーメント / 地震規模 |
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| Outline of Research at the Start |
地震発生に地殻内の流体が深く関与することが，認識されているが，地殻内で流体がどのように移動するかについては，地熱地帯などの一部の例を除いてはほとんど明らかにされていない．流体流動現象をコントロールする物理パラメータは浸透率である．すなわち，流体-岩石反応帯に保存されている地球化学的証拠を使用して、流体の浸透時間、時間積分された流体フラックスを推定し、それらを地震モーメントとマグニチュードの推定に結び付けることが申請者の手法である.
本研究は，流体の浸透によって引き起こされる地震活動を理解し、そのモデルを提供し，流体駆動による地殻の破砕と地震活動を高い解像度で理解することを目的とする.
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| Outline of Annual Research Achievements |
I conducted an analysis of metamorphic rocks that underwent rapid hydration over a period of tens of hours, estimating hydrological properties such as permeability evolution between the host rock and fluid-rock reaction zones. Employing all calculated parameters, I applied the advective reaction-transport equation to model fluid speciation phase equilibrium, estimating fluid volume based on Si solubility. The estimated fluid volumes correspond closely with the results of injection experiments conducted in geothermal fields. Subsequently, these fluid volumes were utilized to approximate seismic moments and magnitudes of potential seismic events.
I identified similarities in both the duration of fluid infiltration and magnitudes to slow slip events and tremors. These significant findings were published in Geophysical Research Letters in 2023, Volume 50, Issue 5, under the title "Short-lived and Voluminous Fluid-Flow in a Single Fracture Related to Seismic Events in the Middle Crust." Additionally, I presented this work as an oral presentation during the Slow-to-Fast workshop held in Taiwan and participated in fieldwork subsequent to the presentation.
During my involvement in several fieldworks in Japan, I collected potential samples for further analysis. Notably, during a visit to the Kochi core samples center, I discovered a core sample from Nobeoka that can be analyzed using the same methodology to potentially uncover evidence of slow slip events.
This research and its subsequent dissemination contribute significantly to our understanding of fluid dynamics and seismic events.
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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
New samples have been selected to employ the same methodology, but for rocks representing different fluid compositions. Estimating timescales using the previous advective-diffusion profile is not feasible, so I am exploring alternative methods. However, estimating timescales and fluid volumes for samples with varying fluid compositions may offer diverse insights into fluid-rock interactions in the continental crust.
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| Strategy for Future Research Activity |
I will be implementing a different method to estimate timescales based on the advective-diffusion profile in titanite. Additionally, I intend to calculate the time-integrated fluid flux for both scapolite-bearing veins and amphibolite epidote-bearing veins. These fluid fluxes can then be utilized to estimate fluid volumes and approximate the magnitudes of potential seismic events triggered by fluids with varying compositions. This approach may shed light on the impact of CO2-bearing fluids on the generation of seismic activity in the continental crust.
Furthermore, I am planning to enhance the visibility of my research by presenting it at the prominent international conference, EGU (European Geosciences Union). Attending this conference will provide an excellent platform to showcase my research findings and engage with the broader scientific community.
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