Estimation of slip rate and fault displacement during shallow earthquake rupture in the Nankai subduction zone
Estimation of slip rate and fault displacement during shallow earthquake rupture in the Nankai subduction zone
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DOI：
10.1186/s40623-015-0208-0
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发表时间：
2015-03-13
影响因子：
3
通讯作者：
Kimura, Gaku
中科院分区：
文献类型：
--
作者：
Hamada, Yohei;Sakaguchi, Arito;Kimura, Gaku
巨大的地震反复发生在俯冲带，沿着巨型逆冲断层的滑动，特别是那些传播到前弧楔脚趾的滑动，产生了毁灭性的海啸。定量评价该断层浅部海啸成因部分过去滑动事件的滑动参数（即滑动速度、上升时间和滑动距离）对于表征此类地震至关重要。在这里，我们试图量化这些滑移的参数，这些滑移可能发生在日本西南部南开海槽的浅层大储层断层和板块边界滑脱上。本文应用动力学模型对海洋综合钻探计划（IODP）获得的两个断层岩石样品的镜质组反射率剖面进行了模拟。该方法包括热生成和镜质组反射率数据的数值剖面拟合两个计算过程。为了获得最优滑移参数，采用残差计算来估计拟合精度。结果表明，镜质组反射率的实测分布与大气层和前缘滑脱层的产热速率(Q) /点和滑移持续时间（t(r)）分别为16600 J/s/m(2)和6250 s和23200 J/s/m(2)和2350 s，较好地拟合。然后将估计的滑移参数与之前的报告进行比较。南开大储层断裂的最高温度Tmax与前人提出的温度约束一致。这些断裂带具有滑移速度慢、上升时间长、位移大的特点（均为大型储层和前缘滑脱）。这些参数比典型同震滑动更长、更慢，但与快速余震相当一致。
Enormous earthquakes repeatedly occur in subduction zones, and the slips along megathrusts, in particular those propagating to the toe of the forearc wedge, generate ruinous tsunamis. Quantitative evaluation of slip parameters (i.e., slip velocity, rise time and slip distance) of past slip events at shallow, tsunamigenic part of the fault is critical to characterize such earthquakes. Here, we attempt to quantify these parameters of slips that may have occurred along the shallow megasplay fault and the plate boundary decollement in the Nankai Trough, off southwest Japan. We apply a kinetic modeling to vitrinite reflectance profiles on the two fault rock samples obtained from Integrated Ocean Drilling Program (IODP). This approach constitutes two calculation procedures: heat generation and numerical profile fitting of vitrinite reflectance data. For the purpose of obtaining optimal slip parameters, residue calculation is implemented to estimate fitting accuracy. As the result, the measured distribution of vitrinite reflectance is reasonably fitted with heat generation rate (Q) over dot and slip duration (t(r)) of 16,600 J/s/m(2) and 6,250 s, respectively, for the megasplay and 23,200 J/s/m(2) and 2,350 s, respectively, for the frontal decollement, implying slow and long-term slips. The estimated slip parameters are then compared with previous reports. The maximum temperature, Tmax, for the Nankai megasplay fault is consistent with the temperature constraint suggested by a previous work. Slow slip velocity, long-term rise time, and large displacement are recognized in these fault zones (both of the megasplay, the frontal decollement). These parameters are longer and slower than typical coseismic slip, but are rather consistent with rapid afterslip.