High Resolution 3‐D Shear Wave Velocity Model of Northern Taiwan via Bayesian Joint Inversion of Rayleigh Wave Ellipticity and Phase Velocity with Formosa Array

2021 ◽  
Author(s):  
Cheng‐Nan Liu ◽  
Fan‐Chi Lin ◽  
Hsin‐Hua Huang ◽  
Yu Wang ◽  
Elizabeth M. Berg ◽  
...  
Keyword(s):  
High Resolution ◽  
Phase Velocity ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Joint Inversion ◽  
Velocity Model ◽  
Northern Taiwan

High Resolution 3-D Shear Wave Velocity Model of Northern Taiwan via Bayesian Joint Inversion of Rayleigh Wave Ellipticity and Phase Velocity with Formosa Array

2021 ◽  
Author(s):  
Cheng-Nan Liu ◽  
Fan-Chi Lin ◽  
Hsin-Hua Huang ◽  
Yu Wang ◽  
Elizabeth M. Berg ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Model ◽  
Low Velocity ◽  
Geological Features ◽  
D Model ◽  
Northern Taiwan

<p>Taiwan located at the convergence margin of the Eurasian Plate (EP) and Philippine Sea Plate (PSP) is one of the most active orogenic belts around the world. Under vigorously tectonic activities, the northern Taiwan is composed of complicated geological features including rifting basins, fold-and-thrust systems, volcanoes, and hydrothermal activity. In this study, we apply the technique of Ambient Noise Tomography (ANT) to eight months of continuous waveforms from the Formosa Array and Broadband Array for Seismology in Taiwan (BATS), with 137 broadband stations and ~5km station spacing. We first calculate multi-components cross-correlation functions to extract the information of Rayleigh wave signals. We then invoke Eikonal tomography to calculate the phase velocity map through 3 to 10 second periods and estimate Rayleigh wave ellipticity at each station between 2 to 13 second periods. For each grid point, we jointly invert the two types of Rayleigh wave measurements through a Bayesian-based inversion method to obtain the local 1-D shear wave velocity model. All 1-D models are then combined to construct a comprehensive 3-D model. Our 3-D model reveals upper crustal structures that well correlate with surface geological features. Near the surface, the model delineates the low-velocity Taipei and Ilan basins from the adjacent fast-velocity mountainous areas, with basin geometries consistent with the results of previous geophysical exploration and geological studies. At greater depths, low velocity anomalies are observed associated with the Linkou tableland, Tatun volcano group, and a possible dyke intrusion beneath the southern Ilan basin. The model also provides new geometrical constraints on the major active fault systems in the area, which are important to understand the basin formation and orogeny dynamics. The new 3-D shear wave velocity model allows a comprehensive investigation of shallow geologic structures in northern Taiwan.</p>

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

2019 ◽  
Vol 220 (3) ◽  
pp. 1555-1568 ◽  
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.

scholarly journals 3-D shear wave velocity model of the lithosphere below the Sardinia–Corsica continental block based on Rayleigh-wave phase velocities

2019 ◽  
Vol 220 (3) ◽  
pp. 2119-2130 ◽  
Author(s):  
Fabrizio Magrini ◽  
Giovanni Diaferia ◽  
Islam Fadel ◽  
Fabio Cammarano ◽  
Mark van der Meijde ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Model ◽  
Western Mediterranean ◽  
Crust And Upper Mantle ◽  
Phase Velocities ◽  
Continental Block ◽  
Wide Range

SUMMARY Rayleigh-wave dispersion curves from both ambient noise and teleseismic events allow us to provide the first high-resolution 3-D shear wave velocity (VS) model of the crust and upper mantle below the Sardinia–Corsica microplate, an important continental block for understanding the evolution of the central-western Mediterranean. For a wide range of periods (from 3 to ∼30 s), the phase velocities of the study area are systematically higher than those measured within the Italian peninsula, in agreement with a colder geotherm. Relative and absolute variations in the VS allow us to detect a very heterogeneous upper crust down to 8 km, as opposed to a relatively homogeneous middle and lower crust. The isosurface at 4.1 km s−1 is consistent with a rather flat Moho at a depth of 28.0 ± 1.8 km (2σ). The lithospheric mantle is relatively cold, and we constrain the thermal lithosphere–asthenosphere boundary at ∼100 km. We find our estimate consistent with a continental geotherm based on a surface heat flow of 60 mW m−2. Our results suggest that most of the lithosphere endured the complex history of deformation experienced by the study area and imply, in general, that deep tectonic processes do not easily destabilize the deeper portion of the continental lithosphere, despite leaving a clear surface signature.

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