Tsunamis caused by offshore active faults and their deposits
Tsunamis caused by offshore active faults and their deposits
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近海活动断层及其沉积物引发的海啸
DOI：
10.1016/j.earscirev.2020.103380
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发表时间：
2020
影响因子：
12.1
通讯作者：
Urabe Atsushi
中科院分区：
文献类型：
--
作者：
Takashimizu Yasuhiro;Kawakami Gentaro;Urabe Atsushi
本文根据地震和海啸的历史记录和现代观测资料，评述了日本海东缘（EMJS）沿着活动断裂引起的海岸海啸的变化特征。海啸沉积物发现沿着EMJS海岸也介绍和分类，根据其沉积环境。沿着东、中、西海岸活动断裂带密集分布，是晚渐新世至中新世日本海弧后盆地张开的产物，并产生海啸。在EMJS引起大海啸的地震震级低于8.0级。断层面的大小（约等于海啸震源区）约为10 × 100，长度为数十公里。反转型断层的滑动距离小于20米。海啸沉积的沉积特征和沉积过程中获得的沉积在不同的环境，如沿海低地，海洋阶地，沿海泻湖，和内陆池塘。审查了用于识别海啸沉积物的某些独特方法，如插入无机土壤的砾石层，全新世海洋阶地，甲藻孢囊和有孔虫衬里，这些可能来自海洋，以及化学特征（例如，Ca 2 +/Mg 2+比值）作为海水流入沿海泻湖的指标。根据以往的古海啸研究，发现EMJS中地震和海啸的空间分布和复发。近海活动断裂海啸沉积与大地震海啸沉积的差异只表现在水平和垂直方向上，而不表现在沉积环境和构造上。所得资料可作为未来近海活动断层模型之评估及海啸灾后重建之验证。
This paper reviews the variable features of coastal tsunamis caused by offshore active faults along the eastern margin of the Japan Sea (EMJS) based on the historical records and modern observations of earthquakes and tsunamis. Tsunami deposits discovered along the EMJS coast were also introduced and categorized depending on their sedimentary environments. The offshore active faults, which are densely distributed along the EMJS and generate tsunamis, are originated from the opening of the Japan Sea back-arc basin during the late Oligocene to Miocene period. The magnitudes of the earthquakes that caused large tsunamis in the EMJS were under 8.0. The size of the fault plane (approximately equal to the tsunami source area) was approximately 10 × 100 and several tens of kilometers in length. The slip distance of the reverse-type faults was less than 20 m.The sedimentary characteristics and depositional processes of tsunami deposits were obtained from deposits in various environments, such as coastal lowlands, marine terraces, coastal lagoons, and inland ponds. Certain unique approaches used to identify tsunami deposits were reviewed, such as gravel layers that intercalate inorganic soils, and a Holocene marine terrace, dinoflagellate cysts, and foraminiferal linings, which are potentially derived from the sea, and chemical features (e.g., the Ca2+/Mg2+ratio) as indicators of seawater inflow into a coastal lagoon. The spatial distribution and recurrence of earthquakes and tsunamis in the EMJS were found based on previous paleo-tsunami studies. The difference between tsunami deposits caused by offshore active faults and those by megathrust earthquakes only manifests itself in the horizontal and vertical directions, but not in the sedimentary environments and structures. The data thus inferred can be used for the estimation of offshore active fault models and validation of previous tsunami disaster reconstructions in the future.