基于微动方法提高浅层横波波速结构反演精度——以海口江东新区为例  

Improving the inversion accuracy of shallow shear wave velocity structure based on microtremor method:A case study of Haikou Jiangdong New District

作　　者：张前 吴小洁 钟宙灿[1,3] 蔡水库 ZHANG Qian;WU Xiaojie;ZHONG Zhoucan;CAI Shuiku(Key Laboratory of Marine Geological Resources and Environment of Hainan Province,Haikou,Hainan 570206,China;Hainan Survey Institute of Mineral Resources,Haikou 571100,Hainan,China;Hainan Geological Survey Institute,Haikou 570206,Hainan,China)

机构地区：[1]海南省海洋地质资源与环境重点实验室,海南海口570206 [2]海南省矿产资源勘查院,海南海口571100 [3]海南省地质调查院,海南海口570206

出　　处：《地质力学学报》2025年第1期109-123,共15页Journal of Geomechanics

基　　金：海南省海洋地质资源与环境重点实验室自主课题(22-HNHYDZZYHJKF023,HNHYDZZYHJZZ003)。

摘　　要：微动方法不受地震源时空分布的限制,已成为探测浅层地下横波速度空间结构的重要方法。在海口江东新区开展微动与钻孔、横波测井的对比试验,试验显示:微动反演结果与测井曲线形态一致,对应深度地层的横波速度基本吻合,取得了一定的应用效果;但在分层上微动和钻孔结果并非完全对应,就波速而言,微动结果未反演出一个波速差异较小界面,钻孔结果未区分出一个波速差异较大界面,对两者在微动反演结果中的影响机制进行研究,有助于提高对微动反演模型的认识,获得更合理的反演结果。基于波速差异较小和较大界面,设计物性分层模型、地质分层模型以及组合模型,从频散曲线形态、软弱夹层、分层变化等方面讨论两类界面影响反演结果的规律。结果显示:物性分层模型反演结果能更好地反映出软弱层位置;改变界面主要影响相邻地层,增加波速差异较小和较大界面,分别使相邻地层波速误差增大和减小;波速差异较大界面对相邻层波速的影响程度要小于差异较小界面,误差大幅变化主要是由波速差异较小界面引起,反演对波速差异较小界面更敏感。微动方法在海口江东新区实际应用研究表明,合并模型中波速差异较小界面或增设波速差异较大的界面,不改变地层局部的变化趋势时,有助于提高波速的反演精度。选取实测数据反演得到二维微动横波速度剖面,结合钻孔提供工程基岩面的埋深及起伏信息,为海口江东新区场地条件评价和地下空间利用规划提供可靠依据。[Objective]The microtremor survey method is not limited by the spatiotemporal distribution of seismic sources and has become an effective method for observing the structure of shallow shear wave velocity.An experiment to compare microtremor,drilling,and shear wave logging was conducted in Jiangdong New District.The experiment showed that the microtremor inversion results were consistent with the logging curve shape,and the shear wave velocities of the strata and the corresponding depths were basically in agreement.Thus,good application results can be achieved.However,it was found that the microtremor inversion strata and the drilled strata did not completely correspond.In terms of wave velocity,the microtremor results could not reveal an interface with a small difference in wave velocity,while the drilling data did not distinguish an interface with a large difference in wave velocity.The study of the influence mechanism of the two factors on the microtremor inversion results is helpful to improve the understanding of the microtremor inversion model and to obtain more reasonable inversion results.[Methods]On the basis of a small or a large wave velocity difference,a physical stratification model,a geological stratification model,and a combined model are designed.The factors and rules affecting the inversion results are discussed by dispersion curves,low-velocity layers,layer variations,and inversion method.[Results]The inversion results of the physical property stratification model can better reflect the location of a weak layer.Changing the interface mainly affects the adjacent layers.Adding interfaces with small and large differences in wave velocity increases and decreases the wave velocity errors of the adjacent layers,respectively.The interface with a large velocity difference has less influence on the velocity of the adjacent layers than an interface with a small velocity difference.A large error change is mainly caused by an interface with a small velocity difference,and the inversion is more sensitive to a

关 键 词：横波速度结构 波速差异界面 反演模型 微动方法 

分 类 号：P315.61[天文地球—地震学]