“…The higher terraces emerged at approximately 0.395 and 0.272 Ma, the middle terraces at 0.108 Ma, and the lower terraces at approximately 0.045, 0.026, and 0.010 Ma (Table 3 ). It is important to note that the date of 0.108 Ma for the Dainohara middle terrace corresponds to Marine Isotope Stage (MIS) 5c as assigned by Toyoshima et al 27 , rather than MIS 5e. The fact that the Aobayama higher terrace occupies consistently higher elevations than the Dainohara middle terrace, and the middle terrace consistently higher elevations than the lower terraces, provides evidence of intermittent rock uplift occurring at the aforementioned dates.…”
Section: Rapid Emergence and Intermittent Uplift Of Terracesmentioning
confidence: 97%
“…4 C,D, 5 A). The uppermost reddish-colored pyroclastics constitute the Aoso-Tsubonuma Pumice 1 (TbP1 26 ), known for its characteristic reddish color 27 . Figure 5 Illustrated columns showing distinct scales for the terrace (including the hill) and the plain (along with the volcano).…”
Section: Quaternary Volcanoes and Related Tephras (Fig
3
...mentioning
We conducted a detailed geological survey of the Sendai region, covering an area of 100 × 50 km. Our survey focused on accurately mapping river terraces, identifying the source volcanoes responsible for intercalated tephras, and locating the Nagamachi-Rifu fault and associated faults. The river terraces were observed and categorized based on their elevation relative to the present river channels. These terraces are predominantly found on the hanging wall of major reverse faults. Each terrace comprises fluvial gravels at the lower levels and eolian loam intercalated with local and regional tephras at higher levels, with the contact age corresponding to the time of emergence. To determine the ages of the terrace gravels, we employed a combination of zircon U–Pb dating, sedimentation rate calculations, and extrapolation techniques. This allowed us to establish the abandonment or emergent dates of the terraces. The formation of these terraces coincided with periods of fault activity, including hanging wall uplift, footwall subsidence, and fault vertical displacement, effectively monitoring the co-seismicity of the Nagamachi-Rifu fault. While we cannot predict the exact timing of future events, it is crucial to remain vigilant regarding the potential occurrence of a significant earthquake triggered by these fault activities.
“…The higher terraces emerged at approximately 0.395 and 0.272 Ma, the middle terraces at 0.108 Ma, and the lower terraces at approximately 0.045, 0.026, and 0.010 Ma (Table 3 ). It is important to note that the date of 0.108 Ma for the Dainohara middle terrace corresponds to Marine Isotope Stage (MIS) 5c as assigned by Toyoshima et al 27 , rather than MIS 5e. The fact that the Aobayama higher terrace occupies consistently higher elevations than the Dainohara middle terrace, and the middle terrace consistently higher elevations than the lower terraces, provides evidence of intermittent rock uplift occurring at the aforementioned dates.…”
Section: Rapid Emergence and Intermittent Uplift Of Terracesmentioning
confidence: 97%
“…4 C,D, 5 A). The uppermost reddish-colored pyroclastics constitute the Aoso-Tsubonuma Pumice 1 (TbP1 26 ), known for its characteristic reddish color 27 . Figure 5 Illustrated columns showing distinct scales for the terrace (including the hill) and the plain (along with the volcano).…”
Section: Quaternary Volcanoes and Related Tephras (Fig
3
...mentioning
We conducted a detailed geological survey of the Sendai region, covering an area of 100 × 50 km. Our survey focused on accurately mapping river terraces, identifying the source volcanoes responsible for intercalated tephras, and locating the Nagamachi-Rifu fault and associated faults. The river terraces were observed and categorized based on their elevation relative to the present river channels. These terraces are predominantly found on the hanging wall of major reverse faults. Each terrace comprises fluvial gravels at the lower levels and eolian loam intercalated with local and regional tephras at higher levels, with the contact age corresponding to the time of emergence. To determine the ages of the terrace gravels, we employed a combination of zircon U–Pb dating, sedimentation rate calculations, and extrapolation techniques. This allowed us to establish the abandonment or emergent dates of the terraces. The formation of these terraces coincided with periods of fault activity, including hanging wall uplift, footwall subsidence, and fault vertical displacement, effectively monitoring the co-seismicity of the Nagamachi-Rifu fault. While we cannot predict the exact timing of future events, it is crucial to remain vigilant regarding the potential occurrence of a significant earthquake triggered by these fault activities.
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