Local dispersion curve estimation from seismic ambient noise using spatial gradients

2016 ◽  
Vol 4 (3) ◽  
pp. SJ17-SJ27 ◽  
Author(s):  
Pascal Edme ◽  
Shihao Yuan
Keyword(s):  
Ambient Noise ◽  
Dispersion Curves ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Local Dispersion ◽  
Time Frequency ◽  
Seismic Ambient Noise ◽  
Spatial Gradients ◽  
Active Source ◽  
Analysis Scheme

A novel acquisition and processing technique is described to derive surface-wave dispersion curves from seismic ambient noise. We have determined that the use of spatial gradients of the wavefield provides new opportunities for high-resolution near-surface characterization with minimal field effort. In contrast to conventional active source data analysis that provides spatially smoothed results from large and dense arrays of receivers, our method provides local phase velocity information from ambient noise using only three closely spaced geophones. A time-frequency domain polarization-based analysis scheme is implemented to (1) detect the useful part of the data satisfying fundamental gradiometry assumptions, (2) estimate the noise source azimuthal distribution, and finally, (3) derive the desired local dispersion curves. The robustness and effectiveness of the developed method is demonstrated using the synthetic and real data, with a comparison to results from active source measurements.

Near-surface Structure of Downtown Jinan, China: Application of Ambient Noise Tomography with a Dense Seismic Array

2019 ◽  
Vol 24 (4) ◽  
pp. 641-652
Author(s):  
Feng Liang ◽  
Zhihui Wang ◽  
Hailong Li ◽  
Kai Liu ◽  
Tao Wang
Keyword(s):  
Surface Wave ◽  
Human Activities ◽  
High Frequency ◽  
Urban Areas ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Ambient Noise Tomography ◽  
Surface Wave Dispersion ◽  
Near Surface

Urban geophysics ups the ante in the world of applied geophysics, which requires innovative thinking and seemingly off-the-wall approaches, if for no other reason than the settings. Ambient-noise-tomography (ANT) can play a pivotal role in yielding subsurfa2ce information in urban areas, which is capable of dealing with challenges related to these scenarios ( e.g., human activities and low signal-to-noise ratio). In this study, the ANT was conducted to investigate the near-surface shear-velocity structure in the surrounding area of the Baotu Spring Park in downtown Jinan, Shandong Province, China. Quiet clear Rayleigh waves have been obtained by the cross-correlation, which indicates that strong human activities, such as moving vehicles and municipal engineering constructions, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surface-wave tomographic method with period-dependent ray-tracing was used to invert all surface-wave dispersion data in the period band 0.2-1.5 s simultaneously for 3D variations of shear-velocity (Vs) structure. Our results show a good correspondence to the geological features with thinner Quaternary sediments, the geological structural characteristic of the limestone surrounded by the igneous which has the highest velocity than that of the limestone in the study area, and several concealed faults of which specific location has been detected at depth. The results demonstrate that it is possible to successfully use ANT with high-frequency signal in an urban environment provided a detailed planning and execution is implemented.

scholarly journals Void Hunting

2021 ◽  
Author(s):  
John B. Paustian
Keyword(s):  
Surface Wave ◽  
Ambient Noise ◽  
Temporal Variations ◽  
Ambient Noise Tomography ◽  
Active Dissolution ◽  
Near Surface ◽  
Karst Environment ◽  
Active Source ◽  
Seismic Methods ◽  
Spatio Temporal

Karst environments are characterized by voids, i.e. sinkholes and conduits of varying size that arise from the active dissolution of carbonate rock by acidic groundwater. These voids, whether air-, water-, or soil-filled, can be difficult to image using near-surface geophysical methods due to the limited investigation depths of most active-source methods. In addition, due to the significant effort it takes to collect active-source data, investigators are often unable to monitor spatio-temporal variations in the subsurface. The ability to detect, image, and monitor subsurface voids improves the understanding of processes that create and transform voids, a vitally important insight across a variety of scientifc disciplines and engineering applications, including hydrogeology, geotechnical engineering, planetary science and even issues of national security. Using a 54-element nodal array (1C and 3C sensors), I image the subsurface of the USF GeoPark with ambient noise surface wave tomography. I also use complementary active-source geophysical datasets (e.g. 2D ERT) collected at the GeoPark to constrain and/or validate the tomography results. I address two research questions with this study: (1) How do ambient seismic methods complement active-source near-surface methods? (2) Can ambient noise tomography resolve voids in the karst environment? In this thesis, I discuss my answers to these questions and present the current state of surface wave methods in the karst environment, including the feasibility for utilizing ambient noise methods to monitor spatio-temporal changes in sinkhole and conduit formation. In addition to the ability to use seismic methods for temporal monitoring, ambient noise provides lower frequencies than what are achievable with active-source seismic methods. Using frequencies from 5-28 Hz, ambient noise tomography is able to image deeper into the subsurface (up to 100 m at 5 Hz) than previous active-source seismic studies at the GeoPark field site. This study yields a more robust and simple method to image voids in covered karst environments and a long-term installation of ambient seismic nodes enables future investigations of spatio-temporal variations in void structures.

Repeatability of multimode Rayleigh‐wave dispersion studies

Geophysics ◽  
2003 ◽  
Vol 68 (3) ◽  
pp. 782-790 ◽  
Author(s):  
Kristen S. Beaty ◽  
Douglas R. Schmitt
Keyword(s):  
Rayleigh Wave ◽  
Velocity Structure ◽  
Wave Dispersion ◽  
Dispersion Curves ◽  
P Wave ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Density Values ◽  
Early Fall ◽  
Rayleigh Wave Dispersion

Rayleigh‐wave dispersion is used to study the near‐surface elastic properties of a thick, lacustrine clay to approximately 10 m depth. Ten repeated sets of Rayleigh dispersion curves were obtained through late spring to early fall. A variety of methodologies were used to extract the dispersion curves, but a modified frequency–ray parameter (f − p) method most successfully yields dispersion curves for the first three Rayleigh modes. The Rayleigh‐wave velocities varied from 100 to ∼350 m/s with frequency over the band from 75 to 10 Hz. Over this band, these velocities did not measurably vary during the study period. The observed phase velocity curves were inverted with P‐wave and density values obtained from shallow coring to obtain the shear‐wave velocity structure at the site down to > 14 m. This case study highlights the robust, repeatable, nature of surface wave dispersion methods when care is taken in the acquisition of field data.

scholarly journals Delineation of Sedimentary Basin Structure beneath the Banyumas Basin, Central Java, Indonesia, Using Ambient Seismic Noise Tomography

2021 ◽  
Author(s):  
Ahmad Setiawan ◽  
Zulfakriza Zulfakriza ◽  
Andri Dian Nugraha ◽  
Shindy Rosalia ◽  
Awali Priyono ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Sedimentary Basin ◽  
Sedimentary Rocks ◽  
Vertical Component ◽  
Dispersion Curves ◽  
Seismic Exploration ◽  
Time Frequency ◽  
Central Java ◽  
Cross Correlations ◽  
Grid Points

Abstract Subsurface images of an area with a thick volcanic layer generally can not be well-imaged with conventional seismic exploration (seismic reflection) due to seismic wave scattering. Another method is needed to obtain an accurate subsurface image in a thick volcanic layer area. In this study, we applied Ambient Noise Tomography (ANT) to image the shear-wave velocity (Vs) structure in the Banyumas Basin, Central Java, Indonesia, which has relatively thick volcanic layers. We aimed to delineate the sediment deposits and the sedimentary thickness in this area. Although this method has limited application for subsurface imaging with a thick volcanic layer area, the application of cross-correlations from ambient noise has been widely applied in numerous locations to obtain greater understanding of subsurface structures. In this study, more than 1,000 pairs of vertical component cross-correlations were used to estimate the Green's Function of the Rayleigh wave. The Multiple Filter Technique (MFT) was used as a Time-Frequency Analysis and 1,291 dispersion curves were obtained. The Neighbourhood Algorithm (NA) was utilized to inverse the dispersion curves at 121 grid points which were used to obtain a vertical depth profile of 1D Vs. The Vs map results show that the low Vs tend to trend in a northwest-southeast direction associated with two areas: the Majenang low, and the Citanduy low. The presence of low Vs values corresponds with Middle Miocene–Pliocene sedimentary rocks. Meanwhile, the high Vs value in this area might correspond with Oligocene–Early Miocene volcanic products and Eocene sediment. Our study was also able to reveal the thickness of sedimentary rocks in the the Banyumas sedimentary basin, which is believed to have hydrocarbon potential.

scholarly journals Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements

2007 ◽  
Vol 169 (3) ◽  
pp. 1239-1260 ◽  
Author(s):  
G. D. Bensen ◽  
M. H. Ritzwoller ◽  
M. P. Barmin ◽  
A. L. Levshin ◽  
F. Lin ◽  
...  
Keyword(s):  
Surface Wave ◽  
Ambient Noise ◽  
Broad Band ◽  
Wave Dispersion ◽  
Surface Wave Dispersion ◽  
Seismic Ambient Noise ◽  
Noise Data
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