LgCoda Q in Australia and its Relation to Crustal Structure and Evolution
LgCoda Q in Australia and its Relation to Crustal Structure and Evolution
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DOI：
10.1007/s000240050211
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发表时间：
1998-12
影响因子：
2
通讯作者：
B. Mitchell;S. Baqer;A. Akinci;L. Cong
中科院分区：
文献类型：
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作者：
B. Mitchell;S. Baqer;A. Akinci;L. Cong
我们已经确定了LgCodaQLgc）从地面运动记录在七个宽带站在澳大利亚，使用叠加谱比方法。尽管相对较少的事件和不到最佳的站点覆盖范围，我们能够使用这些数据来获得一个层析mapQLgcand它的频率依赖性，在1赫兹几乎整个岛屿continents.QLgcat 1赫兹在澳大利亚之间变化约330和600。澳大利亚东部的塔斯曼褶皱带具有最低值（330-400）的特征;这可能与泥盆纪和石炭纪期间发生的造山活动或侏罗纪和三叠纪时期发生的沉积作用产生的流体有关。澳大利亚中部和西部的QLgc相对于最大值的较小降低可能与晚前寒武纪和石炭纪之间较长时间间隔内发生的沉积或与中澳大利亚移动的带发生的变形有关。澳大利亚大部分地区的QLgc比大多数其他稳定大陆地区低30%至60%。假设thatQLgc变化在相同的比例作为QLg，地面运动计算的一维模型的澳大利亚地壳和上地幔表明，高达20%的减少QLgc可以产生，如果速度梯度，而不是一个尖锐的边界，驻留在壳幔过渡。QLg消减的其余部分可能是由横向变化的厚度，深度和严重程度的速度梯度，导致额外的Lg能量泄漏到地幔。
We have determinedLgCodaQLgc) from ground motion recorded at seven broadband stations in Australia, using a stacked spectral ratio method. In spite of the relatively small number of events and less than optimum station coverage, we were able to use those data to obtain a tomographic mapQLgcand its frequency dependence, at 1 Hz for almost the entire island continent.QLgcat 1 Hz in Australia varies between about 330 and 600. The lowest values (330–400) characterize the Tasman Fold Belt in eastern Australia; these may be associated with fluids produced by orogenic activity that occurred during the Devonian and Carboniferous periods or by sedimentation that occurred in Jurassic and Triassic times. Smaller reductions ofQLgc, relative to maximum values, in central and western Australia, may be associated with sedimentation that occurred over a long-time interval between late Precambrian time and the Carboniferous period or with deformation that occurred in the Central Australian Mobile Belts during the Carboniferous.QLgcthroughout most of Australia is 30 to 60% lower than it is in most other stable continental regions. Assuming thatQLgcvaries in the same proportion asQLg, ground motion computations for one-dimensional models of the Australian crust and upper mantle indicate that up to 20% reductions inQLgccan be produced if a velocity gradient, rather than a sharp boundary, resides at the crust-mantle transition. The remaining portion of theQLgcreduction may be caused by lateral variability in the thickness, depth, and severity of the velocity gradient which causes additional Lg energy to leak into the mantle.