Due to various strong electromagnetic mechanical interference and traffic barriers, many geophysical exploration techniques are ineffective in urban geophysical exploration.Based on transient surface waves,microtremor arrays,and microtremor spectral ratios,this study synthetically extracted two kinds of characteristic curves for joint inversion from the multi-source frequency-domain seismic data obtained by multi-point three-component low-frequency sensors.Consequently,this study achieved multi-source frequency-domain seismic exploration that integrated three techniques and developed the two-source synthetic dispersive spectrum extraction technique,the two-source characteristic curve joint inversion technique,and the equivalent homogeneous medium forward modeling technique based on inhomogeneous media.Engineering practice results demonstrate the improvements in the exploration accuracy and efficiency.
Technical flow of multi-source frequency domain seismic wave exploration
Schematic of data acquisition for linear observation device
Schematic of data acquisition for nonlinear observation device a—embedded triangle type;b—concentric type;c—cross-bonding type;d—L-type;e—irregular type
Comparison of dispersion spectrum of multi-source data before and after merging a—transient surface wave source dispersion spectrum;b—frequency dispersion spectrum of micro motion array source;c—mixed source dispersion spectrum
Image of microtremor spectral ratio curve
Schematic of equivalent dynamic weighting method
Spectral ratio curves of different measuring points
C7 comprehensive spectral ratio curve
The section plan of shear wave velocity after inversion a—shear wave velocity profile based on inhomogeneous medium inversion;b—shear wave velocity profile based on horizontal water layered medium inversion
Comparison of the results of different data sources a—transient surface wave;b—transient surface wave + micro motion array;c—transient surface wave + micro motion array + micro motion spectral ratio
Typical spectral ratio characteristic curve in exploration line
Schematic of comparison between inversion results of multi-source frequency domain seismic wave exploration and boreholes
Inversion and interpretation results
[1]
Haskell N A. The dispersion of surface waves on multilayered media[J]. Bulletin of the Seismological Society of America, 1953, 43(1):17-34.
[2]
Aki K, Richards P G. Quantitative seismology:Theory and methods[M]. San Francisco: Freeman,1980.
[3]
Knopoff L. A matrix method for elastic wave problems[J]. Bulletin of the Seismological Society of America, 1964, 54(1):431-438.
[4]
Abo-Zena A. Dispersion function computations for unlimited frequency values[J]. Geophysical Journal International, 1979, 58(1):91-105.
[5]
Chen X F. A systematic and efficient method of computing normal modes for multilayered half-space[J]. Geophysical Journal International, 1993, 115(2):391-409.
Fan Y H, Liu J Q, Xiao B X. Fast vector-transfer algorithm for computation of Rayleigh wave dispersion curves[J]. Journal of Hunan University:Natural Sciences Edition, 2002, 29(5):25-30.
[7]
Toksöz M N, Lacoss R T. Microseisms:Mode structure and sources[J]. Science, 1968, 159(3817):872-873.
[8]
Aki K. Space and time spectra of stationary stochastic waves,with special reference to microtremors[J]. Bulletin of Earthquake Research Institution, 1957,35:415-456.
Xu P F, Du Y N, Ling S Q, et al. Microtremor survey method based on inversion of the SPAC coefficient of multi-mode Rayleigh waves and its application[J]. Chinese Journal of Geophysics, 2020, 63(10):3857-3867.
Xu P F, Li C J, Ling S Q, et al. Mapping collapsed columns in coal mines utilizing Microtremor Survey Methods[J]. Chinese Journal of Geophysics, 2009, 52(7):1923-1930.
Du Y N, Gong X, Xu P F, et al. Study on the influence of the inhomogeneity of noise field distribution on circular and linear array in microtremor exploration[J]. Progress in Geophysics, 2022, 37(3):1007-1012.
Zhang M H, Wu Z B, Ma L X, et al. Research progress of passive source detection technology based on short-period dense seismic array[J]. Progress in Geophysics, 2020, 35(2):495-511.
Nogoshi, Igarashi. A Study on the characteristics of microseismic amplitude[J] .Journal of Seismology(Japanese), 1971,24:26-40.
[14]
Nakamura Y. Clear identification of fundamental idea of nakamura's technique and its applications[C]// Auckland:Proceedings of the 12nd World Conference on Earthquake Engineering, 2000.
[15]
Arai H. S-wave velocity profiling by inversion of microtremor H/V spectrum[J]. Bulletin of the Seismological Society of America, 2004, 94(1):53-63.
Zhang R H, Xu P F, Ling S Q, et al. Detection of the soil-rock interface based on microtremor H/Vspectral ratio method:A case study of the Jinan urban area[J]. Chinese Journal of Geophysics, 2020, 63(1):339-350.
Wang W J, Liu L B, Chen Q F, et al. Applications of microtremor H/V spectral ratio and array techniques in assessing the site effect and near surface velocity structure[J]. Chinese Journal of Geophysics, 2009, 52(6):1515-1525.
Liu T H, Liu T, Zhang B, et al. Inhomogeneous media-based forward modeling technique of spectrum ratio curves and its application[J]. Geophysical and Geochemical Exploration, 2022, 46(5):1276-1282.
[19]
王振东. 双源面波勘探构想[J]. 中国地质, 1998, 25(4):47-48.
[19]
Wang Z D. Conception of surface wave exploration in Shuang Yuan[J]. Chinese Geology, 1998, 25(4):47-48.
[20]
Park C B, Miller R D, Ryden N, et al. Combined use of active and passive surface waves[J]. Journal of Environmental & Engineering Geophysics, 2005, 10(3):323-334.
Liu T H. Research and application of geological exploration methods in urban drilling blind area[J]. Chinese Journal of Engineering Geophysics, 2019, 16(5):572-579.
Liu T H. Analysis and application of geological exploration methods in urban drilling blind area[J]. Journal of Railway Engineering Society, 2019, 36(10):88-93.
