scholarly journals High-resolution 3D shallow crustal structure in Long Beach, California: Application of ambient noise tomography on a dense seismic array

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. Q45-Q56 ◽  
Author(s):  
Fan-Chi Lin ◽  
Dunzhu Li ◽  
Robert W. Clayton ◽  
Dan Hollis
Keyword(s):  
Phase Velocity ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Seismic Array ◽  
Clear Correlation ◽  
Long Beach ◽  
Ambient Noise Tomography ◽  
Station Pair ◽  
Dense Seismic Array

Ambient noise tomography has proven to be effective in resolving shallow earth structure. We applied ambient noise tomography on a dense seismic array in Long Beach, California. The array was composed of more than 5200 stations with an average spacing close to 100 m. Three weeks of passive ambient noise were crosscorrelated between each station pair, which resulted in more than 13.5 million crosscorrelations within the area. Clear fundamental-mode Rayleigh waves were observed between 0.5 and 4 Hz, which were most sensitive to structure above 1-km depth. For each station pair, we applied frequency-time analysis to determine the phase traveltime dispersion, and, for each frequency, we applied eikonal tomography to determine the Rayleigh wave phase velocity map. The eikonal tomography accounted for ray bending by tracking the wavefront and allowed uncertainties to be estimated through statistical analysis. The compilation of phase velocity maps was then used to invert for 3D shear velocity structure. The inverted model showed clear correlation with the known geologic features such as the shallow south–north velocity dichotomy and a deeper fast anomaly associated with the Newport-Inglewood fault zone. Our results can potentially be used to complement traditional active source studies.

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.

A pilot project of ambient noise tomography on a dense seismic array in Ji’nan urban area

2018 ◽  
Vol 31 (5-6) ◽  
pp. 262-271
Author(s):  
Feng Liang ◽  
◽  
Lei Gao ◽  
Zhihui Wang ◽  
Tao Wang ◽  
...  
Keyword(s):  
Urban Area ◽  
Ambient Noise ◽  
Pilot Project ◽  
Seismic Array ◽  
Ambient Noise Tomography ◽  
Dense Seismic Array

Ambient noise tomography across Mount St. Helens using a dense seismic array

2017 ◽  
Vol 122 (6) ◽  
pp. 4492-4508 ◽  
Author(s):  
Yadong Wang ◽  
Fan-Chi Lin ◽  
Brandon Schmandt ◽  
Jamie Farrell
Keyword(s):  
Ambient Noise ◽  
Seismic Array ◽  
Ambient Noise Tomography ◽  
Dense Seismic Array ◽  
Mount St Helens

Topography effect on ambient noise tomography using a dense seismic array

2018 ◽  
Vol 31 (5-6) ◽  
pp. 291-300
Author(s):  
Shuang Wang ◽  
◽  
Xinlei Sun ◽  
Keyword(s):  
Ambient Noise ◽  
Seismic Array ◽  
Ambient Noise Tomography ◽  
Topography Effect ◽  
Dense Seismic Array

Azimuthally anisotropic ambient-noise tomography using the AlpArray seismic network

2020 ◽  
Author(s):  
Emanuel Kästle ◽  
Irene Molinari ◽  
Lapo Boschi ◽  
AlpArray Working Group
Keyword(s):  
Phase Velocity ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Sedimentary Basins ◽  
Shear Velocity ◽  
Velocity Model ◽  
Azimuthal Anisotropy ◽  
Seismic Network ◽  
Fast Axis ◽  
Noise Field

<p>We make use of the AlpArray Seismic Network to study the properties of the ambient-noise field and create a new 3D shear-velocity model of the Alpine crust. The latter will be used to improve our understanding of the tectonic processes that formed the Alps.</p><p>From two years of data, more than 150,000 station-station cross-correlations are extracted and used to evaluate strength and directivity of the noise field and its seasonal variations. Phase-velocity measurements for both Love and Rayleigh waves are obtained and the anisotropic phase-velocity structure is imaged. At mid-crustal levels, the strongest azimuthal anisotropy is found underneath the northern Italian Po plain and in the northern Dinarides, with strengths of 10-20% and a fast axis direction pointing NNE in Italy and NE in the Dinarides. In the western and central Alps we find an approximately NE direction and a strength of 5%; the eastern Alpine fast axis point toward the north with strengths of 2-5%.</p><p>We apply a probabilistic inversion to resolve the 3D shear-velocity structure of the crust. The homogeneous and dense station setup results in a shear-velocity model of unprecedented resolution for the uppermost 60 km of the crust underneath the entire orogen. By using data in the period range between 2 and 100s, we are able to better constrain shallow structures, such as the sedimentary basins, and to link surface-geological features to velocity variations observed at depth.</p>

Lithospheric structure of the Pannonian Basin using Rayleigh wave ambient noise tomography – preliminary results

2020 ◽  
Author(s):  
Máté Timkó ◽  
Lars Wiesenberg ◽  
Amr El-Sharkawy ◽  
Zoltán Wéber ◽  
Thomas Meier ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Pannonian Basin ◽  
Vertical Component ◽  
Ambient Noise Tomography ◽  
Crust And Upper Mantle ◽  
Mountain Chain ◽  
One Year

<p>We used Rayleigh wave ambient noise tomography to investigate the crust and uppermost mantle structure of the Pannonian Basin. The Pannonian Basin and the surrounding orogens are located within the arcuate Alpine–Carpathian mountain chain in Central Europe. It is a back-arc basin characterized by a thinned lower crust and an updoming mantle. Benath the basin both the crust and the lithosphere have smaller thickness than the continental average. Imaging the velocity structure of the crust and upper mantle may help us to better understand the structure and formation of the Carpathian–Pannonian region.</p><p>We used data from the permanent seismological stations of the broader Central European region together with the AlpArray Seismic Network (AASN) and analysed one-year seismic data from 2017. More than 18 thousand vertical component noise cross-correlation functions were calculated and Rayleigh wave inter-station phase velocity curves were determined using an automated measuring algorithm. Anisotropic phase velocity tomographic imaging were carried out for the whole Pannonian Basin between 2 and 40s periods (~5-60 km).</p><p>The locations of the retrieved phase-velocity anomalies consistent with the well-known geologic and tectonic structure of the area (deep basins and orogenic belts) and are comparable to recent tomographic models published in the literature.</p>

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