Imaging the Hikurangi Plate interface region, with improved local-earthquake tomography
Imaging the Hikurangi Plate interface region, with improved local-earthquake tomography
复制标题
使用改进的局部地震断层扫描技术对希库朗吉板块界面区域进行成像
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
M. Reyners
中科院分区：
文献类型：
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作者：
D. Eberhart‐Phillips;M. Reyners
总结
板块界面区域的性质影响大地震期间板块的耦合和破裂行为。板块耦合变化很大沿着Hikurangi俯冲带在新西兰北岛的南半部，和异质材料属性可以检查记录良好的地震活动。在这项研究中，我们使用了修改后的速度反演，将地震差分时间从选定的组分布的地震，提高了空间分辨率的功能在下地壳，并锐化速度梯度。数据来自临时部署和永久GeoNet网络，该网络在过去十年中扩大了。由此产生的三维速度模型表明，上覆板块表现出与地质构造有关的模式。拉卡伊亚板块具有低Vp/Vs和高Vp的特征，在空间上与板块强耦合带有关。地震活动发生在整个上覆板块，并延伸到板块界面，没有下地壳的地震带。Wairarapa-Waewaepa断裂带可能构成未来板块界面地震强耦合的上倾极限。俯冲板块的地壳以丰富的地震活动为特征，并以强烈的速度梯度为边界。在30至50公里深度处显示出板块界面以上的低速区。板块界面附近的地震速度显示出与板块耦合分布的良好相关性，并提供了对控制这种耦合的原因的深入了解。板界面在最强耦合区域具有最高的Vp/Vs（>1.85）和最尖锐的Vp/Vs梯度，这与强耦合与流体不能穿过板界面有关的建议一致。在周期性缓慢滑动的区域，Vp/Vs仍然很高，但在板块界面附近的Vp/Vs的梯度要宽得多，表明流体穿过板块界面的运动。深部慢滑区对应于板块上方最广泛的高Vp/Vs地幔区。
SUMMARY
The properties of the plate interface region influence plate coupling and rupture behaviour during large earthquakes. Plate coupling varies greatly along the Hikurangi subduction zone in the southern half of the North Island, New Zealand, and heterogeneous material properties can be examined with the well-recorded seismicity. For this study, we have used a modified velocity inversion to incorporate earthquake differential times from selected groups of distributed earthquakes, which improves the spatial resolution of features in the lower crust, and sharpens velocity gradients. Data are selected from temporary deployments and the permanent GeoNet network, which has expanded in the last decade. The resulting 3-D velocity model shows that the overlying plate exhibits patterns related to geologic terranes. The Rakaia terrane has low Vp/Vs and high Vp, and is spatially related to the zone of strong plate coupling. Seismicity occurs throughout the overlying plate, and extends to the plate interface without a lower crustal aseismic zone. The Wairarapa–Waewaepa fault zone may form the updip limit of strong coupling in future plate interface earthquakes. The crust of the subducting plate is characterized by abundant seismicity and is bounded by strong velocity gradients. Low-velocity zones above the plate interface are indicated from 30 to 50 km depth. Seismic velocities near the plate interface show an excellent correlation with the distribution of plate coupling, and provide insight into what controls such coupling. The plate interface has the highest Vp/Vs (>1.85) and sharpest Vp/Vs gradient in the region of strongest coupling, consistent with the suggestion that strong coupling is related to the inability of fluid to cross the plate interface. In regions of recurrent slow slip, Vp/Vs is still high, but the gradient of Vp/Vs near the plate interface is much broader, suggesting movement of fluid across the plate interface. The area of deep slow slip corresponds to the most extensive high Vp/Vs mantle region above the slab.