Synchronized gravitational slope deformation and active faulting: A case study on and around the Neodani fault, central Japan
Synchronized gravitational slope deformation and active faulting: A case study on and around the Neodani fault, central Japan
复制标题
同步重力斜坡变形和活动断层：日本中部 Neodani 断层及其周围的案例研究
DOI：
10.1016/j.geomorph.2020.107214
复制
发表时间：
2020
期刊：
影响因子：
3.9
通讯作者：
Nishio Tomohiro
中科院分区：
文献类型：
--
作者：
Komura Keitaro;Kaneda Heitaro;Tanaka Tomoki;Kojima Satoru;Inoue Tsutomu;Nishio Tomohiro
地震被认为是地震活动区深部重力斜坡变形（DGSD）的重要触发因素，如果是这样的话，DGSD特征可能是断层外古地震学研究的候选者。在一个非断层DGSD场地的基坑开挖和沉积物岩心以及附近场地横跨活动Neodani断层的沟槽开挖的基础上，我们研究了DGSD和Neodani断层的地表破裂古地震记录。最近4次DGSD事件的日期为240 cal BP、1710-340 cal BP、4730-3970 cal BP和5570-5340 cal BP之后。最近的四次地表破裂地震分别发生在公元1891年（Nobi地震）、2010-1220 cal BP、7180-2110 cal BP和9540 cal BP之前。我们的结论是，四次DGSD事件的年龄与邻近Neodani断层上的地表破裂地震一致。我们推断，静态地壳应变重复孕震断层起着重要的作用，在DGSD事件的发生，至少在活动断层附近，虽然同震严重震动至少会有一定的影响。我们的案例研究表明，离断层DGSD可以用来重建或改善附近的活动断层的古地震历史。我们建议，一个理想的DGSD为此目的将位于附近的终端，弯曲，或跨越目标故障的应变集中的区域。
Earthquakes are considered to be important triggers of deep-seated gravitational slope deformation (DGSD) in seismically active regions, and if that is the case, DGSD features could be candidates for off-fault paleoseismology investigations. On the basis of pit excavations and sediment cores at an off-fault DGSD site and a trench excavation across the active Neodani fault at a nearby site, we examined the records of DGSD and surface-rupturing paleoearthquakes of the Neodani fault. The four most recent DGSD events were dated at after 240 cal BP, 1710–340 cal BP, 4730–3970 cal BP, and 5570–5340 cal BP. The four most recent surface-rupturing earthquakes were dated at 1891 CE (the Nobi earthquake), 2010–1220 cal BP, 7180–2110 cal BP, and before 9540 cal BP. We conclude that the ages of the four DGSD events are consistent with surface-rupturing earthquakes on the adjacent Neodani fault. We infer that static crustal strain from repeated seismogenic faulting plays an important role in the occurrence of DGSD events, at least in the immediate vicinity of active faults, although coseismic severe shaking would have at least some effect on them. Our case study suggests that off-fault DGSDs can be used to reconstruct or refine the paleoseismic history of a nearby active fault. We propose that an ideal DGSD for that purpose would be located in an area of concentrated strain near a termination, bend, or stepover of the target fault.