一种高频拓展的改进地震干涉算法研究

Study on an improved seismic interference algorithm with high frequency extension

地震干涉法是一种求解两道检波器之间频散曲线的微动勘探算法,然而频率域中传统的地震干涉法在求解频散曲线时,相干系数拟合使用的是第一个单调递减段贝塞尔函数,计算的有效频散点较少,高频段缺失,在进行微动探测时,浅层结构分辨率低,出现深度近似1倍台站距离的勘探盲区。本文提出一种改进的地震干涉法,使用实测信号的信噪比模型来修正两道信号的相干系数,通过第一类零阶贝塞尔函数的单调性把相干系数划分为不同区间段,分段拟合贝塞尔函数来求解面波相速度。工程实践表明,该方法探测效果良好,拓展了高频段,提高了浅层分辨率,有效地解决浅部勘探盲区问题。

The seismic interferometry is a microtremor survey algorithm for achieving the dispersion curve between two geophones. To obtain the dispersion curve, the traditional seismic interferometry in the frequency domain uses monotonically decreasing Bessel functions to fit the coherence coefficients. The effective dispersion points of calculation are less, and high frequencies are missing. To perform microtremor detection, the resolution of shallow structure is low, and there are exploration blind areas with a depth similar to the station distance. An improved seismic interferometry method is proposed, which uses the signal-to-noise ratio model of the measured signal to correct the coherence coefficients of two signals. The coherence coefficients are divided into different intervals by the monotonicity of the first type of zero-order Bessel curve. Piecewise fitting Bessel function is utilized to solve the surface wave phase velocity. The engineering practice shows that this method has a good detection effectiveness. The high frequency band is expanded, and the detection accuracy is improved. The problem of shallow exploration blind areas is effectively addressed.