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Morphostratigraphic Studies in Testing for Characteristic Earthquakes and in Evaluating for Earthquake triggered Ground Movement

特征地震测试和地震引发的地面运动评估中的地层形态研究

基本信息

批准号：
16500643
负责人：
SUGAI Toshihiko
金额：
$ 2.05万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Two typical reverse fault systems, the Yoro and the Fukaya fault system, and their surrounded areas were selected. Sediment coring and intensive 14C dating for the sediments coupled with geomorphological investigation revealed the following results.1. Yoro fault system composed of Yoro, Kuwana and Yokkaichi fault, has produced a large earthquake of Mw=8.0 repetitively during Holocene.2. The earthquake history shows an average recurrence interval of about 1000 years with a standard deviation of around 300 years.3. Timing of the faulting events of Kuwana and Yokkaichi fault are almost the same during the middle to late Holocene and Yoro, Kuwana and Yokkaichi fault displaced at around 1586 A.D.( Tensyo-historical earthquake) and 745 A.D. (Tenpyo-historical earthquake). This indicates that Yoro fault system is a single behavior segment during the Holocene.4. Nobi tectonic basin located in the downthrown side of the Yoro fault system has been subsided and filled with fluvial sediments rapidly during the Holocene with a high ratio of around 2mm/y. The flood sediments may remain the subsidence history. Especially comparison among the relative sea level curves reconstructed from core sediments for each individual coring site has potential to reconstruct the tectonic deformation over the basin.5. Fukaya fault system is composed of Haruna, Takasaki, Fukaya, and Ayasegawa fault. The paleoseismological study revealed Ayasegawa fault is different behavioral segment with much lower activity from the other part of the system.6. Long term activity of the fault shown by the subsurface geology is in agreement with the late Pleistocene faulting history. Ground penetrating radar survey coupled with arrayed coring is strong tool to clear the subsurface geology and its tectonic deformation in urbanized areas.7. Relation between the huge scale sediment transport event and earthquake, whether the event was triggered by earthquakes should be studied.

选取了约罗断裂系统和福宫断裂系统两个典型的逆断裂系统及其周围地区。沉积物取心和高强度~(14)C测年与地貌调查相结合，揭示了以下结果。由yoro、Kuwana和yokkaichi断裂组成的yoro断裂系统，在全新世期间反复发生了8.0级大地震。地震历史表明，地震的平均重现期约为1000年，标准差约为300年。全新世中晚期，Kuwana断裂和Yokkaichi断裂的活动时间基本相同，Yoro断裂、Kuwana断裂和Yokkaichi断裂在公元1586年(Tensyo-历史性地震)和745年(Tenpyo-历史性地震)左右错动。这表明约罗断裂系统在全新世是一个单一的行为段。诺比构造盆地位于约罗断裂系的凹陷一侧，全新世以来快速下沉充填河流沉积，沉积速率高达2 mm/a左右，洪泛沉积可能保留了沉降史。特别是通过对比各取心部位的岩心沉积物重建的相对海平面曲线，有可能重建盆地的构造变形。福谷断裂系统由春纳断裂、高崎断裂、福谷断裂和小谷川断裂组成。古地震学研究表明，阿谷川断裂是不同于系统其他部分的活动性较低的行为段。地下地质显示的断裂长期活动性与晚更新世断裂史相吻合。探地雷达与阵列取心相结合是清除城市化地区地下地质及其构造变形的有力工具。大尺度输沙事件与地震的关系、大尺度输沙事件是否由地震触发等问题有待进一步研究。