编码震源提高地震探测能力的野外实验研究

A field experiment study of improving the seismic detectability with coded source

地球深部结构研究是地震预报和地球动力学研究的基础,传统人工地震受到探测深度、分辨率或震源能量的环保限制,探索利用小能量震源进行深部高分辨率探测技术具有重要意义.本文借鉴雷达探测中的编码原理,开展了震源编码探测实验,利用人工震源向地下发送具有独特特征的随机编码序列脉冲,作为一次等效激发,利用准确记录的编码震源的源函数与地震连续观测的互相关进行“解码”分析,获取地下信息,形成编码地震探测技术.实验表明编码地震能够大幅度提高地震探测能力,利用小能量震源获得远距离的探测和高分辨率,是一种具有重要发展前景的人工探测技术.

The deep earth structure is the basis of earthquake prediction and geedynamics. Detecting with natural seismic source, i.e., earthquakes, can reach large depth but with lower resolution. Traditional active exploration can attain to high resolution but at shallow depths, as the charge of explosion is limited by environmental factors. It is desired to develop a new technique to detect the deep structure using a low-energy seismic source. In this paper, we present a new approach to detect the low signal-to-noise ratio （SNR） seismic signal using the coding theory that is well used in radar detecting. A field experiment was carried out. We encode the seismic pulses in time domain randomly as an equivalent excitation and detect the signal by cross- correlating source signal with a seismic record at distance. The experiment shows that this approach can largely improve the detectability of seismic signal, can give high-precision seismic time delay and have great noise resistivity. Further theoretical analysis and more experiments are needed for the advancement of coding seismology.