Seismic reflection character of the Hikurangi subduction interface, New Zealand, in the region of repeated Gisborne slow slip events
Seismic reflection character of the Hikurangi subduction interface, New Zealand, in the region of repeated Gisborne slow slip events
复制标题
DOI：
10.1111/j.1365-246x.2009.04401.x
复制
发表时间：
2010-01-01
影响因子：
2.8
通讯作者：
Beavan, John
中科院分区：
文献类型：
--
作者：
Bell, Rebecca;Sutherland, Rupert;Beavan, John
我们利用地震反射数据绘制了新西兰希库兰吉俯冲边缘Gisborne地区俯冲界面的几何形状和特征，该地区经历了多次浅（< 15 km）慢滑动事件。该地区的反射特征和几何形状变化很大，我们认为这与海山和下冲断层沉积物的俯冲有关。三个高振幅界面反射率区（HRZ-1、2和3）被解释为俯冲海山夹带的富含流体的沉积物的结果。高分辨率区上方的界面比周围地区浅2-4公里，这是因为界面弯曲以适应海山俯冲。这些区域的高振幅反射率和较浅的界面几何形状与2002年至2008年记录的缓慢滑动事件的位置广泛相关。我们假设，在高振幅反射率区域，沿着东北边缘的界面上的有效应力可能较低，这是由于：（1）富含流体的沉积物的下冲作用增强，（2）在界面被弯曲至较浅深度以适应海山俯冲的地方，上覆岩层应力降低，以及（3）沿着这些较浅界面波纹导致超压的潜在流体流动集中效应。从我们的观察，我们建议在有效应力的界面结构救济所造成的局部减少可能是一个潜在的因素，促进浅慢滑事件。
P>We use seismic reflection data to map the geometry and character of the subduction interface in the Gisborne area of the Hikurangi subduction margin, New Zealand, which experiences repeated shallow (< 15 km) slow slip events. The reflection character and geometry in this area is highly variable, which we interpret to be related to the subduction of seamounts and underthrust sediments. Three zones of high-amplitude interface reflectivity (HRZ-1, 2 and 3) are interpreted to be the result of fluid-rich sediments that have been entrained with subducting seamounts. The interface above the HRZ zones is shallower than the surrounding areas by 2-4 km, due to the warping of the interface to accommodate seamount subduction. These zones of high-amplitude reflectivity and shallower interface geometry correlate broadly with locations of recorded slow slip events from 2002 to 2008. We hypothesize that effective stresses on the interface may be lower along the northeast margin in areas of high-amplitude reflectivity due to; (1) the enhanced underthrusting of fluid-rich sediment, (2) reduced overburden stresses where the interface has been warped to shallower depths to accommodate seamount subduction and (3) potential fluid flow concentration effects leading to overpressure along these shallower interface corrugations. From our observations we propose localized reductions in effective stress caused by interface structural relief may be a potential factor in promoting shallow slow slip events.