scholarly journals Estimation of shallow subsurface S-wave velocity structure in urban area based on inversion of apparent dispersion curve

2020 ◽  
Vol 17 (6) ◽  
pp. 940-955
Author(s):  
Zhiwei You ◽  
Peifen Xu ◽  
Suqun Ling ◽  
Yanan Du ◽  
Ruohan Zhang ◽  
...  
Keyword(s):  
Spatial Autocorrelation ◽  
Urban Area ◽  
Wave Velocity ◽  
Simulated Annealing Algorithm ◽  
Velocity Structure ◽  
Dispersion Curves ◽  
Survey Method ◽  
S Wave ◽  
Geological Surveys ◽  
Autocorrelation Method

Abstract Due to its efficiency, convenience, non-destructive nature and strong anti-interference capability, the microtremor survey method (MSM) has found wide applications in urban geological surveys. The spatial autocorrelation method is diffusely applied to extract the dispersion curves from microtremor signals, which needs to satisfy the assumption that the energy of the fundamental Rayleigh wave is dominant. However, for layered media containing a layer with a significant low- or high-velocity contrast, this assumption is distinctly incorrect for certain frequency ranges. We present a processing methodology comprising the extraction and inversion of the apparent dispersion curves based on extended spatial autocorrelation method and fast simulated-annealing algorithm. We analyse synthetic microtremor signals for three selected geological models, and then compare the S-wave velocity structures estimated from their inversions with the actual models. Subsequently, a filed data example is given to detect the shallow stratigraphic structures in Guangzhou city, China, in which the new MSM was used. The estimated two-dimensional S-wave velocity model provided an accurate description of the thickness and depth of the strata in the study area, based on a priori information. Moreover, the S-wave velocity structures estimated from the MSM and the results from the drilling match very well, indicating that MSM is a reliable geophysical technique in urban geological surveys. Combined with available borehole information, MSM can be a very robust and effective method for detecting the shallow three-dimensional velocity structures in an urban area.

scholarly journals Estimation of Deep S-wave Velocity Structure in Osaka Plains Urban Area by Using Microtremor Survey Method

2011 ◽  
Vol 52 (5) ◽  
pp. 192-198
Author(s):  
Yuichiro MINAMI ◽  
Tatsurou MATSUOKA ◽  
Tsuyoshi HARAGUCHI ◽  
Kenta MOTOKI
Keyword(s):  
Urban Area ◽  
Wave Velocity ◽  
Velocity Structure ◽  
Survey Method ◽  
S Wave ◽  
Microtremor Survey

Deep S-wave Velocity Structure in Osaka Plains Urban Area Estimated by Microtremor Survey Method

2014 ◽  
Vol 55 (3) ◽  
pp. 110-117 ◽  
Author(s):  
Yuichiro MINAMI ◽  
Yukihiro MIZUOCHI ◽  
Tatsurou MATSUOKA ◽  
Tsuyoshi HARAGUCHI ◽  
Kenta MOTOKI
Keyword(s):  
Urban Area ◽  
Wave Velocity ◽  
Velocity Structure ◽  
Survey Method ◽  
S Wave ◽  
Microtremor Survey

Window-controlled CMP crosscorrelation analysis for surface waves in laterally heterogeneous media

Geophysics ◽  
2013 ◽  
Vol 78 (6) ◽  
pp. EN95-EN105 ◽  
Author(s):  
Tatsunori Ikeda ◽  
Takeshi Tsuji ◽  
Toshifumi Matsuoka
Keyword(s):  
Surface Waves ◽  
Wave Velocity ◽  
Heterogeneous Media ◽  
Velocity Structure ◽  
Weighting Function ◽  
Dispersion Curves ◽  
Lateral Resolution ◽  
Heterogeneous Structure ◽  
S Wave ◽  
Data Set

CMP crosscorrelation (CMPCC) analysis of surface waves enhances lateral resolution of surface wave analyses. We found the technique of window-controlled CMPCC analysis, which applies two kinds of spatial windows to further improve the lateral resolution of CMPCC analysis. First, a spatial weighting function given by the number of crosscorrelation pairs is applied to CMPCC gathers. Because the number of crosscorrelation pairs is concentrated near the CMP, the lateral resolution in extracting dispersion curves on CMPs can be improved. Second, crosscorrelation pairs with longer receiver spacing are excluded to further improve lateral resolution. Although removing crosscorrelation pairs generally decreases the accuracy of phase velocity estimations, the required accuracy to estimate phase velocities is maintained by considering the wavenumber resolution defined for given receiver configurations. When applied to a synthetic data set simulating a laterally heterogeneous structure, window-controlled CMPCC analysis improved the retrieval of the lateral variation in local dispersion curves beneath each CMP. We also applied the method to field seismic data across a major fault. The window-controlled CMPCC analysis improved lateral variations of the inverted S-wave velocity structure without degrading the accuracy of S-wave velocity estimations. We discovered that window-controlled CMPCC analysis is effective in improving lateral resolution of dispersion curve estimations with respect to the original CMPCC analysis.

scholarly journals Ambient Vibration Analysis on Large Scale Arrays When Lateral Variations Occur in the Subsurface: A Study Case in Switzerland

2020 ◽  
Vol 177 (9) ◽  
pp. 4247-4269
Author(s):  
Dario Chieppa ◽  
Manuel Hobiger ◽  
Paolo Bergamo ◽  
Donat Fäh
Keyword(s):  
Wave Velocity ◽  
Vibration Analysis ◽  
Velocity Structure ◽  
Velocity Profiles ◽  
Dispersion Curves ◽  
Love Waves ◽  
Ambient Vibration ◽  
S Wave ◽  
Single Station ◽  
Rayleigh And Love Waves

Abstract The ambient vibration analysis is a non-invasive and low-cost technique used in site characterization studies to reconstruct the subsurface velocity structure. Depending on the goal of the research, the investigated depth ranges from tens to hundreds of meters. In this work, we aimed at investigating the deeper contrasts within the crust and in particular down to the sedimentary-rock basement transition located at thousands of meters of depth. To achieve this goal, three seismic arrays with minimum and maximum interstation distances of 7.9 m and 26.8 km were deployed around the village of Schafisheim. Schafisheim is located in the Swiss Molasse Basin, a sedimentary basin stretching from Lake Constance to Lake Geneva with a thickness ranging from 800 to 900 m in the north to 5 km in the south. To compute the multimodal dispersion curves for Rayleigh and Love waves and the Rayleigh wave ellipticity angles, the data were processed using two single-station and three array processing techniques. A preliminary analysis of the inversion results pointed out a good agreement with the fundamental modes of Rayleigh and Love waves used in the inversion and a quite strong disagreement with the higher modes. The impossibility to explain at the same time most of the dispersion curves was interpreted as the co-existence, within the investigated area, of portions of the subsurface with different geophysical properties. The hypothesis was confirmed by the Horizontal-to-Vertical spectral analysis (H/V) which indicated the presence of two distinguished areas. The observation allowed a new interpretation and the identification of the Rayleigh and Love wave fundamental modes and of the S-wave velocity profiles to be reconstructed for each investigated zone. It results in two S-wave velocity profiles with similar velocities down to 15 km deferring only in their shallow portions due to the occurrence of a low velocity zone at a depth of 50–150 m at the centre of the investigated area.

Inversion on S-Wave Velocity Structure of Shallow Soil Layer Site Using Parallel Genetic Algorithm

2011 ◽  
Vol 243-249 ◽  
pp. 319-322
Author(s):  
Lian Cheng Dong ◽  
Guang Ying Li ◽  
Xia Xin Tao ◽  
Da Gang Lu ◽  
Juan Liu ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Wave Velocity ◽  
Simulated Annealing Algorithm ◽  
Velocity Structure ◽  
Soil Layer ◽  
Test System ◽  
Coarse Grained ◽  
Parallel Genetic Algorithm ◽  
S Wave ◽  
Shallow Soil

Microtremors was developed to inverse S-wave velocity structure of sites because it costs little and easy to monitor, can be performed at any place even in a densely populated city with non-destructive measurements, the genetic algorithm is widely used in inversion and there are many disadvantages in using genetic algorithms to solve practical problems, so the authors did a lot of efforts to overcome these disadvantages. In order to solve these disadvantages, a coarse-grained parallel genetic algorithm(PGA) based on personal computer cluster was proposed to inverse S-wave velocity structure of shallow soil layer of actual engineering sites, the simulated annealing algorithm and parallel technique message passing interface(MPI) were adopted to implement the coarse-grained parallel compute. The subpopulations were collaboratively optimized through individual migration strategy and the dynamic populations were adopted to balance the computing load. The shallow S-wave velocity structures of two examples and the actual engineering sites were inversed through a 4-node PC cluster test system, the results showed that the algorithm has a good parallel efficiency and can be used in engineering site.

Near-surface velocity structure study using surface waves and first breaks in the middle segment of the Bangong-Nujiang suture zone, Tibetan Plateau

2020 ◽  
Author(s):  
Hui Zhang ◽  
Rizheng He ◽  
Zhiwei Liu
Keyword(s):  
Surface Waves ◽  
Wave Velocity ◽  
Velocity Structure ◽  
Dispersion Curves ◽  
Suture Zone ◽  
Surface Velocity ◽  
S Wave ◽  
Middle Segment ◽  
Near Surface ◽  
Order Dispersion

<p>The Bangong-Nujiang suture zone, located in the central Tibet, is one of several important geological boundaries in Qinghai-Tibet plateau. Abundant researches have been performed and most of them focused on deep tectonic structure and its dynamic mechanism through recent geophysical projects such as INDEPTH-III, Hi-CLIMB, ANTILOPE, SinoProbe, etc. (Zhao Wenjin et al., 2008; N´abelek et al. 2009; Gao Rui, et al., 2013;Zhao Junmeng et al. 2014; He Rizheng et al., 2014; Xu Qiang et al., 2017; Shang Xuefeng et al., 2017; Davlatkhudzha et al.,2018). Near-surface velocity study can not only obtain the physical parameters such as Vp and Vs in the area, but also improve seismic image quality of deep structure (Zhao Lingzhi et al., 2018). However, the velocity information obtained from passive seismic stations using either receiver function or ambient noise tomography is not enough to elaborate the near surface velocity structure of the Bangong-Nujiang suture zone. Besides, the active-source seismic reflection data usually doesn’t have sufficient offset density at near surface which poses a challenge to conventional near-surface velocity analysis methods.</p><p>This study makes full use of surface waves and first breaks to obtain near-surface P- and S-wave velocities based on a 2D deep seismic reflection survey data which was acquired by SinoProbe project in 2009 . We adopt the method of superposition of surface waves in common receiver domain to generate high quality F-K spectrum which enables us to obtain fundamental-order and high-order dispersion curves. First, a 2D layered model with an irregular topography was built and the 2D elastic finite difference modeling was executed to generate 161 synthetic seismic shot gathers which mimicking the actual acquisition geometry. These gathers contain surface waves, refractions, reflections and multiples energy, and the maximum offset is about 18 km. It is shown that the F-K spectrum quality has been improved for each receiver station using superposition of surface waves in the F-K domain by adding more shots. The S-wave velocity inverted from dispersion curves showed good agreement with the synthetic model. Second, high quality F-K spectrum generated from the above method enabled us to pick both fundamental and 1<sup>st</sup> order dispersion curves from the SinoProbe field data. The S-wave velocity was generated using three methods: 1) empirical equations based on dispersion curves; 2) fundamental order dispersion curves inversion; and 3) both fundamental and 1<sup>st </sup>order dispersion curves inversion. Results show that using higher order dispersion curves can generate a more reliable near-surface model. Third, first breaks were picked up to 18 km offset and diving wave tomography was applied to derive near-surface P-wave velocity from abundant first break information. It is shown that there is an excellent correlation between P- and S-wave velocities, the bottom of basin is clearly revealed, and over-thrusts are identified accordingly which is consistent with field geological survey in the middle segment of Bangong-Nujiang suture zone.</p><p>This study was financially supported by the CAGS Research Fund (grant YWF201907), and the National Natural Science Foundation of China (grant 41761134094). Data sources: SinoProbe-02 Project.</p>

scholarly journals Rapid assessment of S-wave profiles from the inversion of multichannel

1998 ◽  
Vol 41 (1) ◽  
Author(s):  
G. A. Tselentis ◽  
G. Delis
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Structure ◽  
Rapid Assessment ◽  
Detailed Knowledge ◽  
S Wave ◽  
Surface Wave Dispersion ◽  
Wave Profiles ◽  
Shear Wave Velocity Structure

The importance of detailed knowledge of the shear-wave velocity structure of the upper geological layers was recently stressed in strong motion studies. In this work we describe an algorithm which we have developed to infer the 1D shear wave velocity structure from the inversion of multichannel surface wave dispersion data (ground-roll). Phase velocities are derived from wavenumber-frequency stacks while the inversion process is speeded up by the use of Householder transformations. Using synthetic and experimental data, we examined the applicability of the technique in deducing S-wave profiles. The comparison of the obtained results with those derived from cross-hole measurements and synthesized wave fields proved the reliability of the technique for the rapid assessment of shear wave profiles during microzonation investigations.

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