测线方位对微动线形台阵探测效果影响研究

Influence of line orientation on the detection effect of a microtremor linear array

微动探测技术是一种经济环保、可靠实用并广泛应用于资源勘探及工程地质领域的新型物探技术。为了探讨测线方位对线形台阵探测结果的影响,研究利用武汉中心地震台实测的小尺度密集台阵数据,对比分析了多时段双重圆形、T形和不同方向线形台阵微动探测结果。研究发现不同方向的线形台阵探测结果具有明显差异,测线方位从北向东变化时实测相速度逐渐增加,且在NE45°角左右时与双重圆形结果最接近。数值模拟结果也显示当测线与主噪声源中心线夹角在30°~55°范围内时,线形台阵探测效果较好,且随着夹角增加实测相速度逐渐增加。在测区周边存在主噪声源时,实测和模拟结果均表明有限地增长观测时间难以弥补线形台阵方位分布的不足。因此,在微动探测实践前应考虑测区周边可能存在的噪声源分布,选择合适的台阵形式进行探测。

As a recent geophysical prospecting technique,microtremor survey technology is economical,environmentally friendly,practical,and widely used in resource exploration and engineering geology.To study the influence of line orientation on the results of a linear array,the microtremor survey results of a multisession double-circular linear array,T-shaped linear array,and linear arrays in different directions were compared and analyzed using the small-scale dense array data measured by the Wuhan Central Seismic Station.The results show that the results of linear arrays in different directions are remarkably different:The measured phase velocity increases gradually with a change in line orientation from north to east,and the results are closest to those of the double-circular linear array at approximately NE45°.The numerical simulation results also show that the results of the linear array are good when the angle between the survey line and the centerline of the main noise source is within a range of 30°-55°,and the measured phase velocity increases gradually with an increase in this angle.When a main noise source is present near the survey area,the measured and simulated results show that an increase in observation time cannot overcome the deficiency of the orientation distribution of the linear array.Therefore,the possible noise source distribution near the survey area should be considered before a microtremor survey.