甲烷气爆震源性能研究及其在粤港澳大湾区化龙断层探测中的应用

针对近年兴起的甲烷气爆主动震源，设计了不同尺寸震源装置，分别在不同激发环境下，通过比较激发信号能量及频带分布进行了震源性能研究，实现了震源参数优化.同点甲烷气爆和炸药震源成像结果研究表明，甲烷气爆震源引起的地表振动速度更小，更符合安全环保的需求.将优化后的甲烷气爆震源用于粤港澳大湾区的化龙断裂浅部结构勘查，单炮记录结果可见高信噪比初至信号.对10炮激发记录进行初至走时拾取后进行走时层析成像发现，化龙断裂推测位置附近纵波速度在第四系下方200~400 m深度范围明显错断.基于横波/纵波波谱比分析结果（HVSR），根据经验关系推断了该地区沉积层厚度分布，发现与走时层析成像结果中的第四系沉积底界面位置吻合良好.以上成像结果与该地区已有钻孔及早期反射地震结果高度吻合，证明了此次采用的甲烷气爆主动震源作为炸药震源的替代品，在未来城市地下结构浅勘工作中有广泛的应用前景.

Performance study of methane gas explosion source and its application in exploring of Hualong fault in Guangdong-Hong Kong-Macao Greater Bay Area

This work was concerned with a recently developed active source based on methane gas. We compared the explosion performance by designing the container with different dimensional sizes, inflating it with different pressures, and stimulating the source at different depths. Consequently, we found the optimal parameter combination which is suitable for shallow underground structure imaging. The imaging results from both methane gas and traditional explosion at the same location show that the ground motion caused by methane gas explosion is smaller and more environment-friendly. We applied the methane gas explosion to imaging the shallow underground structure in the Hualong fault area, where first arrivals were found obviously from each shot. The tomography results based on P-wave arrivals show that there is an obvious velocity contrast underground near the Hualong fault with depths 200 m to 400 m. We also analyzed the horizontal-to-vertical spectral ratios and concluded the sedimentary depths using the empirical formula in the local area, and found that they agree well with the resultant depths form tomography imaging. The imaging results in this study are highly consistent with that from the well boring and reflection seismology based on traditional explosions in previous work, which shows that the methane gas explosion source has a bright future in imaging shallow underground structure of urban areas as a substitute to the traditional explosion source.