Permeability and seismic velocity and their anisotropy across the Alpine Fault, New Zealand: An insight from laboratory measurements on core from the Deep Fault Drilling Project phase 1 (DFDP-1)
Permeability and seismic velocity and their anisotropy across the Alpine Fault, New Zealand: An insight from laboratory measurements on core from the Deep Fault Drilling Project phase 1 (DFDP-1)
复制标题
DOI：
10.1002/2017jb014355
复制
发表时间：
2017-08-01
影响因子：
3.9
通讯作者：
Boulton, C.
中科院分区：
文献类型：
--
作者：
Allen, M. J.;Tatham, D.;Boulton, C.
阿尔卑斯断层是澳大利亚板块和太平洋板块之间的一个挤压板块边界，已知它准周期性地破裂，伴随着大地震（M-W类似于8）。断层带的水力和弹性特性被认为在地震周期中变化，影响地震破裂的性质和类型以及相关过程。我们提出了一套实验室渗透率和P（V-P）和S（V-S）波速度测量的断层岩性恢复在第一阶段的深断层钻探项目（DFDP-1），采样主滑动带（PSZ）断层泥，碎裂岩，和破碎的超糜棱岩，与所有恢复的岩性叠加丰富的次生矿化，记录增强的流体-岩石相互作用。芯材在三个正交方向上进行测试，相对于芯轴和叶理（如果存在）进行定向。在5-105 MPa的有效压力（P-eff）范围内，孔隙压力（H2O）保持在5 MPa下进行测量。渗透率和地震波速度随着接近PSZ而降低，在超糜棱岩/碎裂岩中，渗透率范围为10（-17）至10（-21）m（2），V-p和V-s范围为4400至5900 m/s，在PSZ处为3900至4200 m/s。与完整的围岩原岩相比，高度可变的碎裂构造和次生层状硅酸盐和碳酸盐导致渗透率和地震波速度的整体降低，以及断层核内各向异性的降低。这些结果与其他成熟构造断层在其震间期的类似研究一致。
The Alpine Fault, a transpressional plate boundary between the Australian and Pacific plates, is known to rupture quasiperiodically with large magnitude earthquakes (M-w similar to 8). The hydraulic and elastic properties of fault zones are thought to vary over the seismic cycle, influencing the nature and style of earthquake rupture and associated processes. We present a suite of laboratory permeability and P (V-p) and S (V-s) wave velocity measurements performed on fault lithologies recovered during the first phase of the Deep Fault Drilling Project (DFDP-1), which sampled principal slip zone (PSZ) gouges, cataclasites, and fractured ultramylonites, with all recovered lithologies overprinted by abundant secondary mineralization, recording enhanced fluid-rock interaction. Core material was tested in three orthogonal directions, orientated relative to the down-core axis and, when present, foliation. Measurements were conducted with pore pressure (H2O) held at 5 MPa over an effective pressure (P-eff) range of 5-105 MPa. Permeabilities and seismic velocities decrease with proximity to the PSZ with permeabilities ranging from 10(-17) to 10(-21)m(2) and V-p and V-s ranging from 4400 to 5900 m/s in the ultramylonites/cataclasites and 3900 to 4200 m/s at the PSZ. In comparison with intact country rock protoliths, the highly variable cataclastic structures and secondary phyllosilicates and carbonates have resulted in an overall reduction in permeability and seismic wave velocity, as well as a reduction in anisotropy within the fault core. These results concur with other similar studies on other mature, tectonic faults in their interseismic period.