南印度洋地区双T波现象及形成机制解释

The double T wave in south Indian Ocean and its generation mechanism

T波是由地震激发而在海洋低速层中传播的声波.海洋T波的产生过程相当复杂,对其激发机制的解释,目前存在两种较为流行的模型,倾斜海底反射和海底散射.本文从地震台站(COCO)记录到的印尼苏门答腊半岛的地震信号中,提取出了清晰的T波信号.进一步研究发现,在第一个T波波峰出现后一段时间,又出现了一个明显的T波波峰,即在南印度洋区域存在双T波现象.为解释这一现象,本文通过分析T波信号时域和频域特征,并计算T波理论到时,与实际T波双峰到时比较,推知发生这一独特现象的主要原因可能是狭长海岛的反射作用.

T waves are seismically generated acoustic waves that propagate in low velocity zone of the oceanic sound channel. The mechanism of the T wave generation is extremely complex. At present, there are two popular models to explain the process of the T wave generation： the reflection and scattering theory. In this research, we extract clear double T waves recorded in station （COCO） from the earthquakes occurred at Sumatra Island. In order to explain this strange phenomenon, we firstly calculate the synthetic travel time of the T wave converted from seismic P and S wave, and also the T wave signal both in time and frequency domain. From the comparison between the synthetic and real data, we find out the reflection of the island is the probable reason for the generation of the double T waves.