Numerical estimation of maximum possible sizes of paleo-earthquakes and tsunamis from storm-derived boulders
Numerical estimation of maximum possible sizes of paleo-earthquakes and tsunamis from storm-derived boulders
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风暴产生的巨石对古地震和海啸最大可能规模的数值估计
DOI：
10.1016/j.epsl.2021.117354
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发表时间：
2022
影响因子：
5.3
通讯作者：
Kan Hironobu
中科院分区：
文献类型：
--
作者：
Minamidate Kenta;Goto Kazuhisa;Kan Hironobu
估计潜在的大地震和相关的海啸灾害的震级沿着俯冲带是重要的风险评估。海岸卵石沉积物可以作为具有高波速的潮间带的有价值的地质指标，即使较细的沉积物通常被冲走。本报告提出了一种新的方法来限制最大可能的规模的古地震和海啸使用巨石风暴波的起源作为一个约束条件，在数值模拟。基本的假设是，目前观察到的风暴衍生的巨石没有移动了很大的距离，由过去的海啸波。本研究以琉球海沟对面的冲绳县久高岛为例，探讨风暴波漂砾的大小与空间分布。总共假设了47个不同位置和断层参数的海啸情景。结果表明，最高水位为2.2 m，最大流速为1.5 m/s的海啸波在久高岛的海滩没有袭击该岛。在此条件下，如果遵循俯冲地震的经验标度律，则在琉球海沟中部不可能发生Mw≥ 8.3的地震;如果断层尺寸固定为100 km× 50 km，则在海沟附近不可能发生最大可能滑动≥ 2 m的地震。如果假设库达卡岛的珊瑚礁和风暴巨石的就位始于3500多年前，那么这些海啸和地震的规模就不可能在这一时期产生。这一发现意味着，琉球海沟的孕震机制和发生大地震的危险性与日本海沟和智利海沟等其他海沟不同，这些海沟过去曾多次发生Mw≥ 9.0的大地震。所提出的方法将使研究人员能够估计任何地区古地震和海啸波的最大可能规模，即使是在过去事件历史模糊或未知的地区，因为缺乏桑迪沉积物或地震记录。
Estimating the magnitudes of potential large earthquakes and associated tsunami hazards along a subduction zone is important for risk evaluation. Coastal boulder deposits can serve as valuable geological indicators in intertidal zones with high wave velocity, even though finer sediments are generally washed away. This report presents a new method to constrain the maximum possible sizes of paleo-earthquakes and tsunamis using boulders of storm wave origin as a constraint in numerical simulations. The fundamental assumption is that presently observed storm-derived boulders have not moved a great distance by past tsunami waves. This illustrative case study uses the sizes and spatial distributions of storm wave boulders on the reef at Kudaka Island, Okinawa Prefecture, which faces the Ryukyu Trench. In all, 47 tsunami scenarios with different locations and fault parameters were assumed. Results show that tsunami waves with a maximum water level of 2.2 m and maximum flow speed of 1.5 m/s at a beach of Kudaka Island did not strike the island. Under this condition, earthquakes of Mw≥ 8.3 are unlikely to have occurred in the central Ryukyu Trench if one obeys an empirical scaling law for subduction earthquakes or≥ 2 m of maximum possible slip near the trench if the fault size is fixed as 100 km× 50 km. Those tsunami and earthquake sizes could not have been generated during this period if one assumes that the reef of Kudaka Island and emplacement of storm boulders began more than 3500 years ago. This finding implies that the seismogenic mechanism of the Ryukyu Trench and the risk of a giant earthquake differ from those of other trenches such as the Japan Trench and the Chilean Trench, where giant earthquakes of Mw≥ 9.0 have occurred repeatedly during the past. The proposed method would enable researchers to estimate the maximum possible sizes of the paleo-earthquakes and tsunami waves in any region, even in regions with a vague or unknown history of past events because of a lack of sandy tsunami deposits or seismic records.
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影响因子：
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作者：
N. Nandasena;R. Paris;N. Tanaka
通讯作者：
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影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
Imamura, Fumihiko
根据块状珊瑚礁的现有位置对记录在案的风暴中士进行的估计是在礁石上进行的。
DOI：
10.2208/proce1989.36.65
发表时间：
1989
期刊：
--
影响因子：
--
作者：
E. Nakaza
通讯作者：
E. Nakaza
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DOI：
10.4157/grj1984a.72.11_746
发表时间：
1999
期刊：
Geographical Review of Japa,. Ser. A, Chirigaku Hyoron
影响因子：
--
作者：
M. Onda
通讯作者：
M. Onda