scholarly journals Group velocity maps using subspace and Trans-dimensional inversions: ambient noise tomography in the Western part of Java, Indonesia

2019 ◽  
Author(s):  
Shindy Rosalia ◽  
Phil Cummins ◽  
Sri Widiyantoro ◽  
Tedi Yudistira ◽  
Andri Dian Nugraha ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Group Velocity ◽  
Ambient Noise ◽  
Regularization Parameter ◽  
Least Square ◽  
Disaster Mitigation ◽  
Wave Group ◽  
Ambient Noise Tomography ◽  
Waveform Data ◽  
Subspace Optimization

Summary In this paper, we compare two different methods for group velocity inversion: iterative, least-squares subspace optimization, and probabilistic sampling based on the Trans-dimensional Bayesian method with tree-based wavelet parameterization. The wavelet parameterization used a hierarchical prior for wavelet coefficients which could adapt to the data. We applied these inversion methods for ambient noise tomography of the western part of Java, Indonesia. This area is an area prone to multiple geological hazards due to its proximity to the subduction of the Australia Plate beneath Eurasia. It is therefore important to have a better understanding of upper crustal structure to support seismic hazard and disaster mitigation efforts in this area. We utilized a new waveform dataset collected from 85 temporary seismometers deployed during 2016–2018. Cross-correlation of the waveform data was applied to retrieve empirical Rayleigh wave Green's functions between station pairs, and the spatial distribution of group velocity was obtained by inverting dispersion curves. Our results show that, although computationally expensive, the Trans-dimensional Bayesian approach offered important advantages over optimization, including more effective explorative of the model space and more robust characterization of the spatial pattern of Rayleigh wave group velocity. Meanwhile, the iterative, least-square subspace optimization suffered from the subjectivity of choice for reference velocity model and regularization parameter values. Our Rayleigh wave group velocity results show that for short (1–10 s) periods group velocity correlates well with surface geology, and for longer periods (13–25 s) it correlates with centers of volcanic activity.

Crustal and upper mantle velocity structure of the Pannonian Region using Rayleigh wave ambient noise tomography

2021 ◽  
Author(s):  
Máté Timkó ◽  
Lars Wiesenberg ◽  
Amr El-Sharkawy ◽  
Zoltán Wéber ◽  
Thomas Meier ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Pannonian Basin ◽  
Vertical Component ◽  
High Heat ◽  
Moho Depth ◽  
Ambient Noise Tomography ◽  
Period Range ◽  
Waveform Data

<p>The Pannonian Basin is located in Central-Europe surrounded by the Alpine, Carpathian, and Dinarides mountain ranges. This is a back-arc basin characterized by shallow Moho depth, updoming mantle and high heat flow. In this study, we present the results of the Rayleigh wave based ambient noise tomography to investigate the velocity structure of the Carpathian-Pannonian region. </p><p>For the ambient noise measurements, we collected the continuous waveform data from more than 1280 seismological stations from the broader Central-Eastern European region. This dataset embraces all the permanent and the temporary (AlpArray, PASSEQ, CBP, SCP) stations from the 9-degree radius of the Pannonian Basin which were operating between the time period between 2005 and 2018. All the possible vertical component noise cross-correlation functions were calculated and all phase velocity curves were determined in the 5-80 s period range using an automated measuring algorithm. </p><p>The collected dispersion measurements were then used to create tomographic images that are characterized by similar velocity anomalies in amplitude, pattern and location that are consistent with the well-known tectonic and geologic structure of the research area and are comparable to previous tomographic models published in the literature.</p>

scholarly journals Rayleigh wave group velocities at periods of 6–23 s across Brazil from ambient noise tomography

2015 ◽  
Vol 203 (2) ◽  
pp. 869-882 ◽  
Author(s):  
Bruno Goutorbe ◽  
Diogo Luiz de Oliveira Coelho ◽  
Stéphane Drouet
Keyword(s):  
Rayleigh Wave ◽  
Ambient Noise ◽  
Wave Group ◽  
Ambient Noise Tomography ◽  
Group Velocities

scholarly journals Velocity structure of the Whataroa Valley using Ambient Noise Tomography

2021 ◽  
Author(s):  
◽  
Andy McNab
Keyword(s):  
Rayleigh Wave ◽  
Group Velocity ◽  
Shear Wave Velocity ◽  
Correlation Functions ◽  
Ambient Noise ◽  
Cross Correlation ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Velocity Model ◽  
Ambient Noise Tomography

<p>This thesis applies ambient noise tomography to investigate the shallow structure of the Whataroa Valley. Ambient noise techniques are applied to continuous seismic recordings acquired on 158 geophones deployed during the Whataroa Active Source Seismic Experiment. Despite only having four days of data, a robust shear-wave velocity model is calculated using a phase-weighted stacking approach to improve the cross-correlation functions' signal-to-noise ratios, allowing for robust velocity measurements to be obtained between periods of 0.3 and 1.8\,s. This yields a database of 12,500 vertical component cross correlation functions and the corresponding Rayleigh wave phase and group velocity dispersion curves. Linearised straight-ray tomography is applied to phase and group velocity dispersion measurements at periods ranging from periods of 0.3 to 1.8\,s. The tomography reveals a velocity that decreases from the vicinity of the DFDP-2B borehole to the centre of the valley. This is interpreted to be the geologic basement deepening towards the centre of the valley. A Monte-Carlo inversion technique is used to jointly invert Rayleigh-wave phase and group velocity dispersion curves constructed from phase and group velocity tomography maps of successively higher periods. Linear interpolation of the resulting 1D shear-wave velocity profiles produces a pseudo-3D velocity model of the uppermost 1,000\,m of the Whataroa Valley. Using sharp increases in velocity to represent lithological change, we interpret two velocity contours at 1,150 and 1,250\,m/s as potential sediment-basement contacts. Depth isocontours of these velocities reveal that the basement deepens towards the centre of the valley, reaching a maximum depth of 400 or 600\,m for the 1,150 and 1,250\,m/s velocity contours respectively. These depths indicate strong glacial over-deepening and have implications for future drilling projects in the Whataroa Valley. A sharp velocity increase of 200\,m/s also occurs at 100\,m depth at the DFDP-2B borehole. We interpret this to be a change in sedimentary rock lithology from fluvial gravels to lacustrine silty sands, related to a change in sedimentary depositional environment.</p>

scholarly journals Delineation of Upper Crustal Structure Beneath the Island of Lombok, Indonesia, Using Ambient Seismic Noise Tomography

2021 ◽  
Vol 9 ◽  
Author(s):  
Achmad F. N. Sarjan ◽  
Zulfakriza Zulfakriza ◽  
Andri D. Nugraha ◽  
Shindy Rosalia ◽  
Shengji Wei ◽  
...  
Keyword(s):  
Group Velocity ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Inversion Method ◽  
Good Resolution ◽  
Ambient Noise Tomography ◽  
Fast Marching ◽  
Waveform Data ◽  
Short Period

We have successfully conducted the first ambient noise tomography on the island of Lombok, Indonesia using local waveform data observed at 20 temporary stations. Ambient noise tomography was used to delineate the seismic velocity structure in the upper crust. The waveform data were recorded from August 3rd to September 9th, 2018, using short-period and broadband sensors. There are 185 Rayleigh waves retrieved from cross-correlating the vertical components of the seismograms. We used frequency-time analysis (FTAN) to acquire the interstation group velocity from the dispersion curves. Group velocity was obtained for the period range of 1 s to 6 s. The group velocity maps were generated using the subspace inversion method and Fast Marching Method (FMM) to trace ray-paths of the surface waves through a heterogeneous medium. To extract the shear wave velocity (Vs) from the Rayleigh wave group velocity maps, we utilize the Neighborhood Algorithm (NA) method. The 2-D tomographic maps provide good resolution in the center and eastern parts of Lombok. The tomograms show prominent features with a low shear velocity that appears up to 4 km depth beneath Rinjani Volcano, Northern Lombok, and Eastern Lombok. We suggest these low velocity anomalies are associated with Quaternary volcanic products, including the Holocene pyroclastic deposits of Samalas Volcano (the ancient Rinjani Volcano) which erupted in 1257. The northeast of Rinjani Volcano is characterized by higher Vs, and we suggest this may be due to the presence of igneous intrusive rock at depth.

scholarly journals Velocity structure of the Whataroa Valley using Ambient Noise Tomography

2021 ◽  
Author(s):  
◽  
Andy McNab
Keyword(s):  
Rayleigh Wave ◽  
Group Velocity ◽  
Shear Wave Velocity ◽  
Correlation Functions ◽  
Ambient Noise ◽  
Cross Correlation ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Velocity Model ◽  
Ambient Noise Tomography

<p>This thesis applies ambient noise tomography to investigate the shallow structure of the Whataroa Valley. Ambient noise techniques are applied to continuous seismic recordings acquired on 158 geophones deployed during the Whataroa Active Source Seismic Experiment. Despite only having four days of data, a robust shear-wave velocity model is calculated using a phase-weighted stacking approach to improve the cross-correlation functions' signal-to-noise ratios, allowing for robust velocity measurements to be obtained between periods of 0.3 and 1.8\,s. This yields a database of 12,500 vertical component cross correlation functions and the corresponding Rayleigh wave phase and group velocity dispersion curves. Linearised straight-ray tomography is applied to phase and group velocity dispersion measurements at periods ranging from periods of 0.3 to 1.8\,s. The tomography reveals a velocity that decreases from the vicinity of the DFDP-2B borehole to the centre of the valley. This is interpreted to be the geologic basement deepening towards the centre of the valley. A Monte-Carlo inversion technique is used to jointly invert Rayleigh-wave phase and group velocity dispersion curves constructed from phase and group velocity tomography maps of successively higher periods. Linear interpolation of the resulting 1D shear-wave velocity profiles produces a pseudo-3D velocity model of the uppermost 1,000\,m of the Whataroa Valley. Using sharp increases in velocity to represent lithological change, we interpret two velocity contours at 1,150 and 1,250\,m/s as potential sediment-basement contacts. Depth isocontours of these velocities reveal that the basement deepens towards the centre of the valley, reaching a maximum depth of 400 or 600\,m for the 1,150 and 1,250\,m/s velocity contours respectively. These depths indicate strong glacial over-deepening and have implications for future drilling projects in the Whataroa Valley. A sharp velocity increase of 200\,m/s also occurs at 100\,m depth at the DFDP-2B borehole. We interpret this to be a change in sedimentary rock lithology from fluvial gravels to lacustrine silty sands, related to a change in sedimentary depositional environment.</p>

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

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.

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

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.

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

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

&lt;p&gt;&lt;span&gt;We have successfully derived a new &lt;/span&gt;&lt;span&gt;3-D&lt;/span&gt;&lt;span&gt; high resolution shear wave velocity model of the crust and uppermost mantle of a large part of W-Europe from transdimensional&lt;/span&gt;&lt;span&gt;&lt;strong&gt; &lt;/strong&gt;&lt;/span&gt;&lt;span&gt;ambient-noise tomography. This model is intended to contribute to the development of the first &lt;/span&gt;&lt;span&gt;3-D&lt;/span&gt;&lt;span&gt; crustal-scale integrated geophysical-geological model of the W-Alps to deepen understanding of orogenesis and its relationship to mantle dynamics. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;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.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;We firstly performed a &lt;/span&gt;&lt;span&gt;2-D&lt;/span&gt;&lt;span&gt; data-driven transdimensional travel time inversion for group velocity maps from 4 to 150 s (Bodin &amp; 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 &amp; 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&lt;/span&gt;&lt;span&gt; approach proposed by Lu et al (2018) by including group velocity uncertainties. Posterior probability distributions on &lt;/span&gt;&lt;span&gt;Vs&lt;/span&gt;&lt;span&gt; and interfaces were estimated by exploring a set of 130 millions synthetic &lt;/span&gt;&lt;span&gt;4-&lt;/span&gt;&lt;span&gt;layer &lt;/span&gt;&lt;span&gt;1-D Vs&lt;/span&gt;&lt;span&gt; models that allow for &lt;/span&gt;&lt;span&gt;low-velocity zones&lt;/span&gt;&lt;span&gt;&lt;em&gt;.&lt;/em&gt;&lt;/span&gt;&lt;span&gt; The obtained probabilistic model was refined using a linearized inversion&lt;/span&gt;&lt;span&gt;&lt;em&gt;. &lt;/em&gt;&lt;/span&gt;&lt;span&gt;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 &lt;/span&gt;&lt;span&gt;&amp;&lt;/span&gt;&lt;span&gt; Webb, 2000) and adapted the inversion for Vs to include the water column.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;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&lt;em&gt; &lt;/em&gt;structure (50 - 80 km) in the prolongation&lt;em&gt; &lt;/em&gt;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.&lt;/p&gt;

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