2:15 PM - 2:30 PM
[SSS14-15] Analysis of Noto Earthquake History Based on Radiocarbon Dating of Serpulid Worms
Keywords:2024 Noto Earthquake, Radiocarbon Dating, Serpulid worm
The earthquake that struck the Noto Peninsula on January 1, 2024, was historically significant, causing a more than 4m uplift. Given that large earthquakes have repeatedly occurred in the region, evaluating coastal marine active faults has become increasingly important. However, nearshore faults are difficult to assess, and their deformation rates and histories along the land-sea boundary remain poorly understood. Yet, as the 2024 event shows, offshore faults can induce onshore deformation; detailed coastal geomorphology can therefore help reconstruct uplift and subsidence histories, offering new perspectives for fault evaluation.
In this study, we focused on the calcareous tubes of serpulid worms and used radiocarbon dating to reconstruct past uplift events. Five samples were collected from the inner wall of the Blue Cave in northeastern Suzu City, where uplift from the 2024 earthquake was observed, with one sample taken from the northern wall. Since only one sample was obtained from the northern wall and no high-elevation specimens were available, that sample was excluded from the discussion. The sample NAD-01, thought to have been uplifted by the 2024 earthquake, exhibited a delta 14C value of 25.2. Comparison with 2021 surface seawater data from the Japan Sea coast of Aomori Prefecture confirmed recent uplift, allowing a precise assessment of the uplift amount. Using NAD-01 as the baseline, altitude corrections yielded corrected elevations of 1.117m for NAD-1.5, 1.918m for NAD-02, and 3.022m for NAD-03.
AMS results were calibrated with Marine20 (delta R = 0), yielding radiocarbon ages of 784-548 calBP for NAD-1.5, 938-688 calBP for NAD-02, and 2676-2351 calBP for NAD-03. Notably, NAD-03 (the highest sample) corresponds to the L3 surface. Although the age of the L3 surface was previously undetermined, dating of serpulid worm tubes at similar elevations identified an uplift event around 2600-2300 years ago, suggesting that the L3 surface was formed by an uplift-induced emergence event at that time. Our findings indicate that approximately 3m of uplift occurred over the past 2600 years, yielding an uplift rate of about 1.15m/kyr. This value is similar to the ~1.0m/kyr estimated for northern Noto Peninsula based on MIS 5e elevations, offering insights into the regional long-term crustal deformation.
Analysis of NAD-03, NAD-02, NAD-1.5, and the 2024 earthquake revealed variability in recurrence intervals. The interval between NAD-03 (ca. 2600-2300 years ago) and NAD-02 (ca. 900-700 years ago) was about 1400-1700 years, while that between NAD-02 and NAD-1.5 (ca. 800-500 years ago) was only 150-250 years. The interval between NAD-1.5 and the 2024 event was around 800-500 years. These data suggest that uplift-associated earthquakes generally recur roughly every 1000 years but may occasionally exceed 1400 years or occur as frequently as every 200-300 years. Moreover, despite a 150-250-year gap between NAD-02 and NAD-1.5, the elevation difference was only about 1m, implying that uplift resulted from multiple events rather than a single occurrence. If the 2024 earthquake is one of the latest uplift events, historical patterns suggest an additional event could occur within the next 100-200 years.
In summary, this study provides a precise evaluation of recent uplift, which includes that from the 2024 earthquake, in the Noto Peninsula and, for the first time, determines the age of the previously undated L3 surface. The findings reveal that the recurrence intervals of uplift events vary, generally clustering around 1000 years, and underscore the potential for a major earthquake within the next 100-200 years. These results improve the precision of active fault evaluation methods for coastal marine environments and offer valuable insights into both past and future earthquake risks.
In this study, we focused on the calcareous tubes of serpulid worms and used radiocarbon dating to reconstruct past uplift events. Five samples were collected from the inner wall of the Blue Cave in northeastern Suzu City, where uplift from the 2024 earthquake was observed, with one sample taken from the northern wall. Since only one sample was obtained from the northern wall and no high-elevation specimens were available, that sample was excluded from the discussion. The sample NAD-01, thought to have been uplifted by the 2024 earthquake, exhibited a delta 14C value of 25.2. Comparison with 2021 surface seawater data from the Japan Sea coast of Aomori Prefecture confirmed recent uplift, allowing a precise assessment of the uplift amount. Using NAD-01 as the baseline, altitude corrections yielded corrected elevations of 1.117m for NAD-1.5, 1.918m for NAD-02, and 3.022m for NAD-03.
AMS results were calibrated with Marine20 (delta R = 0), yielding radiocarbon ages of 784-548 calBP for NAD-1.5, 938-688 calBP for NAD-02, and 2676-2351 calBP for NAD-03. Notably, NAD-03 (the highest sample) corresponds to the L3 surface. Although the age of the L3 surface was previously undetermined, dating of serpulid worm tubes at similar elevations identified an uplift event around 2600-2300 years ago, suggesting that the L3 surface was formed by an uplift-induced emergence event at that time. Our findings indicate that approximately 3m of uplift occurred over the past 2600 years, yielding an uplift rate of about 1.15m/kyr. This value is similar to the ~1.0m/kyr estimated for northern Noto Peninsula based on MIS 5e elevations, offering insights into the regional long-term crustal deformation.
Analysis of NAD-03, NAD-02, NAD-1.5, and the 2024 earthquake revealed variability in recurrence intervals. The interval between NAD-03 (ca. 2600-2300 years ago) and NAD-02 (ca. 900-700 years ago) was about 1400-1700 years, while that between NAD-02 and NAD-1.5 (ca. 800-500 years ago) was only 150-250 years. The interval between NAD-1.5 and the 2024 event was around 800-500 years. These data suggest that uplift-associated earthquakes generally recur roughly every 1000 years but may occasionally exceed 1400 years or occur as frequently as every 200-300 years. Moreover, despite a 150-250-year gap between NAD-02 and NAD-1.5, the elevation difference was only about 1m, implying that uplift resulted from multiple events rather than a single occurrence. If the 2024 earthquake is one of the latest uplift events, historical patterns suggest an additional event could occur within the next 100-200 years.
In summary, this study provides a precise evaluation of recent uplift, which includes that from the 2024 earthquake, in the Noto Peninsula and, for the first time, determines the age of the previously undated L3 surface. The findings reveal that the recurrence intervals of uplift events vary, generally clustering around 1000 years, and underscore the potential for a major earthquake within the next 100-200 years. These results improve the precision of active fault evaluation methods for coastal marine environments and offer valuable insights into both past and future earthquake risks.