Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean
Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean
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DOI：
10.1130/g36446.1
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发表时间：
2015-04
期刊：
影响因子：
5.8
通讯作者：
J. Geersen;J. Bull;L. McNeill;T. Henstock;C. Gaedicke;N. Chamot‐Rooke;M. Delescluse
中科院分区：
文献类型：
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作者：
J. Geersen;J. Bull;L. McNeill;T. Henstock;C. Gaedicke;N. Chamot‐Rooke;M. Delescluse
海洋盆地内的大规模板内地震还没有得到很好的了解。2012年4月11日发生的Mw 8.6和Mw 8.2走滑型板内地震，虽然明显发生在赤道印度洋扩散板块边界区，但就是一个很好的例子，对震源机制和断裂断层的性质存在分歧。我们使用测深和地震反射数据从破裂区的地震在北方沃顿盆地，以证明普遍的脆性变形之间的Ninetyeast海岭和巽他俯冲带。除了最近的走滑变形的证据沿着大约南北走向的化石断裂带，我们确定了一种新的类型的变形结构在印度洋：共轭里德尔剪切局限于沉积物部分和倾斜的南北断裂带。里德尔切变发展于中新世，与印度洋中部扩散变形的开始时间相似。然而，现有断裂带的左旋走滑活动开始得更早，在古新世至始新世早期，并划分了沃顿盆地。2012年4月11日板内地震期间的模拟破裂与两个重新激活的、间隔紧密的、近似南北走向的断裂带的位置一致。然而，我们没有发现证据的WNW-ESE走向的断层在地壳浅部，这是在大多数的地震断层模型的差异。
Large-magnitude intraplate earthquakes within the ocean basins are not well understood. The Mw 8.6 and Mw 8.2 strike-slip intraplate earthquakes on 11 April 2012, while clearly occurring in the equatorial Indian Ocean diffuse plate boundary zone, are a case in point, with disagreement on the nature of the focal mechanisms and the faults that ruptured. We use bathymetric and seismic reflection data from the rupture area of the earthquakes in the northern Wharton Basin to demonstrate pervasive brittle deformation between the Ninetyeast Ridge and the Sunda subduction zone. In addition to evidence of recent strike-slip deformation along approximately north-south–trending fossil fracture zones, we identify a new type of deformation structure in the Indian Ocean: conjugate Riedel shears limited to the sediment section and oriented oblique to the north-south fracture zones. The Riedel shears developed in the Miocene, at a similar time to the onset of diffuse deformation in the central Indian Ocean. However, left-lateral strike-slip reactivation of existing fracture zones started earlier, in the Paleocene to early Eocene, and compartmentalizes the Wharton Basin. Modeled rupture during the 11 April 2012 intraplate earthquakes is consistent with the location of two reactivated, closely spaced, approximately north-south–trending fracture zones. However, we find no evidence for WNW-ESE–trending faults in the shallow crust, which is at variance with most of the earthquake fault models.