Stress State in the Kumano Basin and in Slope Sediment Determined From Anelastic Strain Recovery: Results From IODP Expedition 338 to the Nankai Trough
Stress State in the Kumano Basin and in Slope Sediment Determined From Anelastic Strain Recovery: Results From IODP Expedition 338 to the Nankai Trough
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通过滞弹性应变恢复确定熊野盆地和斜坡沉积物的应力状态：南海海槽 IODP 338 探险队的结果
DOI：
10.1002/2017gc007137
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Yamamoto Yuhji
中科院分区：
文献类型：
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作者：
Oohashi Kiyokazu;Lin Weiren;Wu Hung-Yu;Yamaguchi Asuka;Yamamoto Yuhji
利用岩心样品的滞弹性应变恢复（ASR），确定了日本西南部南海海槽熊野盆地和斜坡沉积物（IODP站点C 0002和C 0022）的三维原地应力。从位于熊野盆地底部的C 0002 J孔采集的两个样品表明，最大主应力σ1为垂直应力。中间主应力σ2的方向为ENE-WSW，平行于海沟轴线。这些应力方向与以前勘探中使用ASR和钻孔崩落法获得的应力方向相似。相比之下，斜坡沉积物下部（孔C 0022 B）的样品位于巨型断层下方，其特征是σ 1适度倾伏至ESE，σ 3接近水平，走向NNE-SSW。从ASR（WNW-ESE）获得的最大水平应力方向与从相邻孔的钻孔崩落（NW-SE）推断的方向相似。海沟正向压缩和近垂直的σ 2也可以从南海增生棱柱体内极低频地震的震源机制和巨型断层上盘的钻孔崩落中推断出来。这些观察结果表明，水平挤压机制延伸到比之前认为的更浅的水平，这可能是由于大型断层的浅层部分响应板块会聚而积累了构造应力。
Three‐dimensional, in situ stresses in the Kumano Basin and slope sediment (IODP Sites C0002 and C0022) in the Nankai Trough, southwest Japan, have been determined using the anelastic strain recovery (ASR) of core samples. Two samples taken from Hole C0002J, located in the bottom of the Kumano Basin, indicate that the maximum principal stress,σ1, is vertical. The intermediate principal stress,σ2, is oriented ENE–WSW, parallel to the trench axis. These stress orientations are similar to those obtained using ASR and borehole breakout methods in previous expeditions. In contrast, a sample from the lower section of the slope sediment (Hole C0022B), located beneath the megasplay fault, is characterized byσ1plunging moderately to the ESE andσ3oriented near‐horizontally, trending NNE–SSW. The direction of maximum horizontal stress obtained from ASR (WNW–ESE) is similar to that inferred from borehole breakouts in an adjacent hole (NW–SE). Trench‐normal compression and a near‐verticalσ2are also inferred from focal mechanisms of very‐low‐frequency earthquakes within the Nankai accretionary prism, and from borehole breakouts in the hanging wall of the megasplay fault. These observations suggest that the horizontal compressional regime extends to a shallower level than previously thought, likely due to the shallow portion of the megasplay fault accumulating tectonic stress in response to plate convergence.