Detection of urban hidden faults using group-velocity ambient noise tomography beneath Zhenjiang area, China

AbstractThe Mufushan-Jiaoshan fault (MJF) is a hidden active fault located on the north side of the Ningzhen Mountain Range and developed along the Yangtze River in Zhenjiang area, China. In this paper, the structure of MJF is detected and studied using group-velocity ambient noise tomography. In the study area (18 km × 25 km), 47 short-period seismic stations were deployed with the average station spacing of about 3 km and 24 days (from 27 February to 22 March 2019) of continuous ambient-noise recordings were collected. And 510 group velocity dispersion curves in the period band 0.5–5 s were extracted using the vertical component data. And then the three-dimensional shear-wave velocity structure was inverted using group dispersion data by the direct surface-wave tomographic method. Our results are consistent with the geological background of the study area, showing that in the depth range of 0.6–1.5 km, the north side of MJF presents a relatively high velocity, and the south side presents a distribution pattern of high and low velocity. While in the depth range of 1.5–2.0 km, the shear-wave velocity (Vs) model is relatively simple with relatively low velocity on the north side and relatively high velocity on the south side. And the gradient zone of Vs may be the location of the main fracture surface of MJF. The good correspondence between the Vs model and the fault structure indicates that the ambient noise tomography method can be used as an effective method for detecting hidden faults in urban environments.

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First step towards an integrated geophysical-geological model of the W-Alps: A new Vs model from transdimensional ambient-noise tomography

10.5194/egusphere-egu21-3197 ◽

2021 ◽

Author(s):

Ahmed Nouibat ◽

Laurent Stehly ◽

Anne Paul ◽

Romain Brossier ◽

Thomas Bodin ◽

...

Keyword(s):

Group Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Receiver Functions ◽

Time Inversion ◽

Geological Model ◽

Ambient Noise Tomography ◽

Low Velocity

We have successfully derived a new 3-D high resolution shear wave velocity model of the crust and uppermost mantle of a large part of W-Europe from transdimensional ambient-noise tomography. This model is intended to contribute to the development of the first 3-D crustal-scale integrated geophysical-geological model of the W-Alps to deepen understanding of orogenesis and its relationship to mantle dynamics. We used an exceptional dataset of 4 years of vertical-component, daily seismic noise records (2015 - 2019) of more than 950 permanent broadband seismic stations located in and around the Greater Alpine region, complemented by 490 temporary stations from the AlpArray sea-land seismic network and 110 stations from Cifalps dense deployments.We firstly performed a 2-D data-driven transdimensional travel time inversion for group velocity maps from 4 to 150 s (Bodin & Sambridge, 2009). The data noise level was treated as a parameter of the inversion problem, and determined within a Hierarchical Bayes method. We used Fast Marching Eikonal solver (Rawlinson & Sambridge, 2005) jointly with the reversible jump algorithm to update raypath geometry during inversion. In the inversion of group velocity maps for shear-wave velocity, we set up a new formulation of the approach proposed by Lu et al (2018) by including group velocity uncertainties. Posterior probability distributions on Vs and interfaces were estimated by exploring a set of 130 millions synthetic 4-layer 1-D Vs models that allow for low-velocity zones. The obtained probabilistic model was refined using a linearized inversion. For the ocean-bottom seismometers of the Ligurian-Provencal basin, we applied a specific processing to clean daily noise signals from instrumental and oceanic noises (Crawford & Webb, 2000) and adapted the inversion for Vs to include the water column.Our Vs model evidences strong variations of the crustal structure along strike, particulary in the subduction complex. The European crust includes lower crustal low-velocity zones and a Moho jump of ~8-12 km beneath the W-boundary of the external crystalline massifs. We observe a deep LVZ structure (50 - 80 km) in the prolongation of the European continental subduction beneath the Ivrea body. The striking fit between the receiver functions ccp migrated section across the Cifalps profile and this new Vs model validate its reliability.

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Rayleigh wave group velocity and shear wave velocity structure in the San Francisco Bay region from ambient noise tomography

Geophysical Journal International ◽

10.1093/gji/ggy095 ◽

2018 ◽

Vol 213 (3) ◽

pp. 1599-1607

Author(s):

Peng Li ◽

Clifford Thurber

Keyword(s):

Rayleigh Wave ◽

Group Velocity ◽

Shear Wave ◽

San Francisco ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Velocity Structure ◽

Wave Group ◽

Ambient Noise Tomography ◽

Shear Wave Velocity Structure

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Upper Crustal Shear-wave Velocity Structure Beneath Western Java, Indonesia from Seismic Ambient Noise Tomography

10.21203/rs.3.rs-591913/v1 ◽

2021 ◽

Author(s):

shindy rosalia ◽

Sri Widiyantoro ◽

Phil R. Cummins ◽

Tedi Yudistira ◽

Andri Dian Nugraha ◽

...

Keyword(s):

Rayleigh Wave ◽

Group Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Depth Range ◽

Wave Group ◽

Volcanic Arc ◽

Seismic Ambient Noise

Abstract This paper presents the depth inversion of Rayleigh wave group velocity to obtain an S-wave velocity model from seismic ambient noise cross-correlation in the western part of Java, Indonesia. This study utilizes the vertical component data of a temporary seismograph network deployed in 2016, which was used in a previous study to estimate fundamental mode Rayleigh wave group velocity maps. In this study, the Neighbourhood Algorithm was applied to invert the Rayleigh wave group velocities into 1D shear-wave velocity (Vs) profiles, which were then interpolated to produce a high-resolution, pseudo-3D Vs model. These tomographic images of Vs extend to ~20 km depth and show a pronounced NE-SW contrast of low and high Vs in the depth range 1-5 km that correlates well with the Bouguer anomaly map. We interpret the low Vs in the northeastern part of the study area as associated with alluvial and volcanic products from the Sunda Shelf and modern volcanic arc, whereas the high Vs in the southwestern part is associated with volcanic arc products from earlier episodes of subduction. We also obtained the depth of the northern Java basin, which is in the range of 5-7 km, and the Garut Basin, which extends to 5 km depth. For greater depths, Vs gradually increases throughout western Java, which reflects the crystalline basement.

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Upper crustal shear-wave velocity structure Beneath Western Java, Indonesia from seismic ambient noise tomography

Geoscience Letters ◽

10.1186/s40562-021-00208-5 ◽

2022 ◽

Vol 9 (1) ◽

Author(s):

Shindy Rosalia ◽

Sri Widiyantoro ◽

Phil R. Cummins ◽

Tedi Yudistira ◽

Andri Dian Nugraha ◽

...

Keyword(s):

Rayleigh Wave ◽

Group Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Depth Range ◽

Wave Group ◽

Volcanic Arc ◽

Seismic Ambient Noise

AbstractThis paper presents the depth inversion of Rayleigh wave group velocity to obtain an S-wave velocity model from seismic ambient noise cross-correlation in western Java, Indonesia. This study utilizes the vertical component data of a temporary seismograph network deployed in 2016, which was used in a previous study to estimate fundamental mode Rayleigh wave group velocity maps. In this study, the Neighborhood Algorithm was applied to invert the Rayleigh wave group velocities into 1D shear-wave velocity (Vs) profiles, which were then interpolated to produce a high-resolution, pseudo-3D Vs model. These tomographic images of Vs extend to ~ 20 km depth and show a pronounced NE-SW contrast of low and high Vs in the depth range 1–5 km that correlates well with the Bouguer anomaly map. We interpret the low Vs in the northeastern part of the study area as associated with alluvial and volcanic products from the Sunda Shelf and modern volcanic arc, whereas the high Vs in the southwestern part is associated with volcanic arc products from earlier episodes of subduction. We also obtained the depth of the northern Java Basin, which is in the range of 5–6 km, and the Garut Basin, which extends to 5 km depth. For greater depths, Vs gradually increases throughout western Java, which reflects the crystalline basement. This study provides estimates of the shallow crustal Vs structure underneath West Java with higher resolution than previous tomographic studies, which could be useful for supporting future earthquake studies in the region.

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Diversity in the Indian lithosphere revealed from ambient noise and earthquake tomography

10.5194/egusphere-egu2020-1102 ◽

2020 ◽

Author(s):

Gokul Kumar Saha ◽

Shyam S. Rai

Keyword(s):

Group Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Lithospheric Mantle ◽

Ambient Noise ◽

Deccan Volcanic Province ◽

Volcanic Province ◽

Dispersion Data ◽

Indian Lithosphere

We present evidence of significant diversity in the Indian cratonic lithosphere mantle based on the analysis of 3-D shear wave velocity maps. These images are obtained through the inversion of 21600 fundamental mode Rayleigh wave group velocity dispersion data retrieved from ambient noise and from earthquake waveforms. The velocity model is constructed using two step approach-firstly generating group velocity maps at 1&#176; square grid at time periods from 10s to 100s; and subsequently inversion of dispersion data at each grid node to a depth of 200 km in terms of velocity-depth model. Analysis of velocity images suggest a bipolar characteristics of lithospheric mantle. We observe a two layer-lithospheric mantle correlated with the Eastern Peninsular India comprising of Archean cratons like east Dharwar, Bastar, Singhbhum, Chotanagpur, Bundelkhand and Proterozoic Vindhyan Basin. The intra lithospheric mantle boundary is at a depth of ~90 km where Vs increases from 4.5 km/s to over 4.7 km/s. The positive velocity gradient continues to a depth of 140-180 km beyond which it reverses the trend and mapped as layer with lower velocity Vs of 4.3-4.4 km/s, as which could be possibly defined as the lithosphere-asthenosphere boundary. Geologically, the region correlates with the kimberlite fields with the xenoliths showing presence of eclogite in them. The other group of Precambrian terrains like 3.36 Ga western Dharwar, eastern Deccan Volcanics, southern Granulite terrane and the Marwar block in western India are characterized by an almost uniform mantle with shear wave velocity of 4.4-4.5 km/s, also supported by other seismological studies. We do not observe any low-velocity layer underlying these terrains. Presence of such a uniform lower than expected mantle velocity could be due to its fertilization through an early geodynamic process. The velocity imprint of Deccan volcanism is best preserved in term of the thinned lithosphere (100-120 km) restricted to the westernmost part of Deccan Volcanic Province (DVP). This suggests that the plume-Indian lithosphere interaction was primarily confined to the western most Deccan volcanic province and possibly extending into the Indian ocean.

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3-D crustal structure of the Iran plateau using phase velocity ambient noise tomography

Geophysical Journal International ◽

10.1093/gji/ggz537 ◽

2019 ◽

Vol 220 (3) ◽

pp. 1555-1568 ◽

Cited By ~ 2

Author(s):

R Movaghari ◽

G Javan Doloei

Keyword(s):

Phase Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Crustal Structure ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Velocity Model ◽

Central Iran ◽

Ambient Noise Tomography ◽

Iran Plateau

SUMMARY More accurate crustal structure models will help us to better understand the tectonic convergence between Arabian and Eurasian plates in the Iran plateau. In this study, the crustal and uppermost mantle velocity structure of the Iran plateau is investigated using ambient noise tomography. Three years of continuous data are correlated to retrieve Rayleigh wave empirical Green's functions, and phase velocity dispersion curves are extracted using the spectral method. High-resolution Rayleigh wave phase velocity maps are presented at periods of 8–60 s. The tomographic maps show a clear consistency with geological structures such as sedimentary basins and seismotectonic zones, especially at short periods. A quasi-3-D shear wave velocity model is determined from the surface down to 100 km beneath the Iran plateau. A transect of the shear wave velocity model has been considered along with a profile extending across the southern Zagros, the Sanandaj-Sirjan Zone (SSZ), the Urumieh-Dokhtar Magmatic Arc (UDMA) and Central Iran and Kopeh-Dagh (KD). Obvious crustal thinning and thickening are observable along the transect of the shear wave velocity model beneath Central Iran and the SSZ, respectively. The observed shear wave velocities beneath the Iran plateau, specifically Central Iran, support the slab break-off idea in which low density asthenospheric materials drive towards the upper layers, replacing materials in the subcrustal lithosphere.

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