On the mechanism of conversion of seismic waves to and from T waves in the vicinity of island shores
On the mechanism of conversion of seismic waves to and from T waves in the vicinity of island shores
复制标题
岛岸附近地震波与T波转换机制研究
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
E. Okal
中科院分区：
文献类型：
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作者：
J. Talandier;E. Okal
波利尼西亚地震台网的高频地震记录用于详细研究岛岸声波（T 波）能量与地震波的转换过程。在震源方面，我们根据位于珊瑚盘上的波利尼西亚台站记录的夏威夷事件的 T 相来研究地震到声学的转换；在接收器方面，我们根据波利尼西亚群岛记录的海洋源 T 相研究声波到地震的转换。在这两种情况下，我们的结果都强调了陡坡（通常为 50°）对于实现岛屿结构中的 P 波和水柱中的 T 波之间的有效转换的重要性。这些斜坡可能是珊瑚礁，也可能是年轻的、可能是松散的玄武岩流的顶端。在此几何条件下，基于射线追踪的建模表明，T 相的地震记录由距离转换点大于 9 km 的 P 波组成；距离较短时，会产生 S 波和表面波。在没有陡坡的情况下，仅存在表面波。这些模型可用于计算精确且可预测的走时台校正，从而允许使用位于内陆的地震仪来利用 T 波的卓越检测和定位能力。
High-frequency seismic records from the Polynesian Seismic Network are used to investigate in detail the processes of conversion of acoustic (T-wave) energy from and to seismic waves at island shores. On the source side, we study the seismic-to-acoustic conversion based on T phases from Hawaiian events recorded at Polynesian stations located on the coral platter; on the receiver side, we study the acoustic-to-seismic conversion based on T phases from marine sources recorded across the Polynesian islands. In both instances, our results underline the importance of steep slopes (typically 50°) in allowing an efficient conversion between P waves in the island structure and T waves in the water column. These slopes can be coral reefs or the heads of young, presumably unconsolidated, basalt flows. Under this geometry, modeling based on raytracing indicates that the seismic record of the T phase consists of a P wave at distances from the conversion point greater than 9 km; at shorter distances, S waves and surface waves are generated. In the absence of a steep slope, only surface waves are present. These models can be used to compute precise and predictable travel-time station corrections, allowing the use of seismometers located inland to exploit the superb detection and location capabilities of T waves.