The Oblique Seismic Experiment on DSDP Leg 52
The Oblique Seismic Experiment on DSDP Leg 52
复制标题
DSDP 52腿斜向地震实验
DOI：
10.1111/j.1365-246x.1980.tb04294.x
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发表时间：
1980
影响因子：
2.8
通讯作者：
D. Matthews
中科院分区：
文献类型：
--
作者：
R. Stephen;K. Louden;D. Matthews
摘要提出了斜向地震实验（OSE），以提高IPOD地壳钻孔作为调查大洋地壳第2层的一种手段的有用性。具体目标是：确定钻孔覆盖的结构的横向范围，分析裂缝在第2层速度结构中的作用，寻找可能由具有优先取向的大裂缝引起的各向异性，最后测量海洋地壳中的衰减。1977年3月，在波多黎各以北400英里的一个洞里，首次成功地进行了海洋地壳的斜向地震实验。对横向速度变化的充分研究是不可能的，因为钻孔不够深，钻孔记录不充分，并且不知道小规模的基底地形。在一般情况下，P-和S-波的速度分布表明，在层2中的裂纹密度随深度而减小。层2底部的速度与玄武岩的基质速度相同，这意味着在此深度处裂纹密度可以忽略不计。从走时分析中没有发现第2层或第3层存在各向异性的令人信服的证据。该孔不够深，无法测量垂直入射炮的衰减，振幅也不够一致，无法测量远距离炮的衰减。1 OSE的目标
Summary. The Oblique Seismic Experiment (OSE) has been proposed to increase the usefulness of the IPOD crustal borehole as a means of investigating layer 2 of oceanic crust. Specific objectives are: to determine the lateral extent of the structure intersected by the borehole, to analyse the role of cracks in the velocity structure of layer 2, to look for anisotropy which may be caused by large cracks with a preferred orientation and, finally, to measure attenuation in oceanic crust. The first successful Oblique Seismic Experiment in oceanic crust was carried out in 1977 March in a hole 400 miles north of Puerto Rico. An adequate study of lateral velocity variations was impossible because the hole was not deep enough, the hole was inadequately logged, and the small scale basement topography was not known. In general both P- and S-wave velocity profiles suggest that the crack density decreases with depth in layer 2. Velocities at the bottom of layer 2 are the same as matrix velocities for basalt, implying that crack density may be negligible at this depth. No convincing evidence for anisotropy in either layer 2 or 3 is found from travel time analysis. The hole was not deep enough to measure attenuation from normal incidence shots and amplitudes were not consistent enough to obtain a measure of attenuation from long range shots. 1 Objectives of the OSE