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The Sendai river terraces monitored the co-seismic mega-thrusting.
Soichi Osozawa1,2, Hisatoshi Ito3
1Institute of Geology and Paleontology, Faculty of Science, Tohoku University, Sendai, 980-8578, Japan. kawaoso@icloud.com.
Scientific Reports
|August 28, 2023
Summary
Geological surveys in Sendai reveal river terraces formed by fault activity, indicating potential earthquake risks. These findings highlight the importance of monitoring the Nagamachi-Rifu fault for seismic events.
Area of Science:
- Geology
- Seismology
- Quaternary Science
Background:
- River terraces provide crucial archives of tectonic and environmental changes.
- Understanding fault behavior is essential for seismic hazard assessment in populated areas.
Purpose of the Study:
- To geologically map the Sendai region, focusing on river terraces and the Nagamachi-Rifu fault.
- To determine the timing of terrace formation and its relationship to fault activity.
- To assess the seismic potential of the Nagamachi-Rifu fault.
Main Methods:
- Detailed geological mapping of river terraces and fault lines.
- Zircon U-Pb dating of terrace deposits.
- Sedimentation rate calculations and extrapolation for age determination.
Main Results:
- River terraces were mapped and categorized based on elevation and stratigraphy.
- Terrace formation correlates with periods of significant fault activity, including uplift and subsidence.
- The Nagamachi-Rifu fault and associated structures show evidence of recurrent seismic events.
Conclusions:
- The formation of Sendai's river terraces is directly linked to the co-seismic activity of the Nagamachi-Rifu fault.
- The study provides insights into the fault's long-term behavior and seismic history.
- Continued vigilance is necessary due to the potential for future significant earthquakes.
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