COLLABORATIVE RESEARCH: Deformation of the Lower Crust Beneath Strike-Slip Faults: Array Studies of Anistropy and Converted Phases in the Marlborough Fault Zone of New Zealand

该项目拟在新西兰南岛北方端的马尔伯勒地区安装10个便携式地震台阵，每个台阵由11个三分量短周期地震仪组成，以测量地壳和上地幔的地壳厚度和各向异性。 其目的是量化走滑断层下方莫霍面的偏移，并确定剪切是否发生在这些断层附近的下地壳的广阔区域。 这种剪切是位于上地壳块体之下的下地壳中的韧性变形的预测结果，上地壳块体沿着沿着走滑断层和地幔岩石圈彼此相对运动，地幔岩石圈在横向宽的区域上被剪切。 相反，如果断层直接从上地壳进入下地幔，则下地壳中几乎不存在各向异性，并且可能在走滑断层进入地幔的地方发生莫霍面的偏移。 新西兰的马尔伯勒地区是一个很好的位置，因为：它是活跃的，大位移发生在断层上;有丰富的本地中等深度的地震活动，提供高频率体波与陡峭的入射角;和初步结果表明各向异性，虽然不是它的深度范围。

MolnarEAR-9910145This project proposes to install ten portable arrays, each consisting of eleven 3-component, short-period seismographs, in the Marlborough region at the northern end of the South Island of New Zealand to measure both crustal thickness and anisotropy in the crust and uppermost mantle. The goal is to quatify the offset of the Moho below strike-slip faults and to determine whether shear has occurred over broad regions in the lower crust near such faults. Such shear is a predicted consequence of ductile deformation in the lower crust lying beneath blocks of upper crust that move with respect to one another along strike-slip faults and mantle lithosphere that is sheared over a laterally wide zone. Conversely, if faults passed directly from the upper crust into the lower mantle, little or no anisotropy would be present in the lower crust, and possible an offset of the Moho would occur where strike-slip faults pass into the mantle. The Marlborough region of New Zealand is an excellent location because: it is active and large displacements have occurred on the faults; there is abundant local intermediate depth seismicity to provide high-frequency body waves with steep angles of incidence; and preliminary results indicate anisotropy, although not its depth range.