Three‐dimensional seismic structure beneath the Australasian region from refracted wave observations
Three‐dimensional seismic structure beneath the Australasian region from refracted wave observations
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DOI：
10.1046/j.1365-246x.2000.00087.x
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发表时间：
2000-09
影响因子：
2.8
通讯作者：
Y. Kaiho;Y. Kaiho;B. Kennett
中科院分区：
文献类型：
--
作者：
Y. Kaiho;Y. Kaiho;B. Kennett
在1993-1996年Skippy试验期间部署的65个便携式宽带台站记录的地震活动带从印度尼西亚、新几内亚、瓦努阿图和斐济延伸到汤加-Kermadec俯冲带，提供了澳大利亚大陆、珊瑚海和塔斯曼海下岩石圈和地幔的良好覆盖。地幔上部结构变化的特征是利用清晰的P波和S波至，从叠加记录剖面中确定一套一维结构，为10°方位带内的所有传播路径做好准备。这些波段的方位角旋转20°步长，每个方位角有四个平行走廊。这给出了26个独立的方位角走廊，其中15个独立的一维地震速度结构已被导出，这表明在P和S结构的显着变化。利用转折点近似法沿射线路径沿着投影速度值，并将其叠加成三维单元（5° × 50公里深），从而将一组一维结构组合起来，形成三维表示。尽管这一过程往往会低估波速扰动，但岩石圈中的S速度与ak 135参考模型的偏差超过6%。在上地幔的结果显示复杂的功能和非常高的S波速度下的前寒武纪盾与一个显着的低速带。高速度也被发现向基地的过渡带，高S-波速度在大陆和高P-波速度在海洋下面。的波速模式同意与独立的表面波研究和延迟时间层析成像研究在共同覆盖的区域。
The earthquakes in the seismicity belt extending through Indonesia, New Guinea, Vanuatu and Fiji to the Tonga–Kermadec subduction zone recorded at the 65 portable broad-band stations deployed during the Skippy experiment from 1993–1996 provide good coverage of the lithosphere and mantle under the Australian continent, Coral Sea and Tasman Sea. The variation in structure in the upper part of the mantle is characterized by deter-mining a suite of 1-D structures from stacked record sections utilizing clear P and S arrivals, prepared for all propagation paths lying within a 10° azimuth band. The azimuth of these bands is rotated by 20° steps with four parallel corridors for each azimuth. This gives 26 separate azimuthal corridors for which 15 independent 1-D seismic velocity structures have been derived, which show significant variation in P and S structure. The set of 1-D structures is combined to produce a 3-D representation by projecting the velocity values along the ray path using a turning point approximation and stacking into 3-D cells (5° by 50 km in depth). Even though this procedure will tend to underestimate wave-speed perturbations, S-velocity deviations from the ak135 reference model exceed 6 per cent in the lithosphere. In the uppermost mantle the results display complex features and very high S-wave speeds beneath the Precambrian shields with a significant low-velocity zone beneath. High velocities are also found towards the base of the transition zone, with highS-wave speeds beneath the continent and high P-wave speeds beneath the ocean. The wave-speed patterns agree well with independent surface wave studies and delay time tomography studies in the zones of common coverage.