3D shear velocity structure of the northwestern South America-Caribbean Subduction Zone from ambient noise and ballistic Rayleigh wave tomography

2021 ◽  
Author(s):  
Wenpei Miao ◽  
John Cornthwaite ◽  
Alan Levander ◽  
Fenglin Niu ◽  
Michael Schmitz ◽  
...  
Keyword(s):  
South America ◽  
Rayleigh Wave ◽  
Ambient Noise ◽  
Crustal Thickness ◽  
P Wave ◽  
Moho Depth ◽  
Good Resolution ◽  
Phase Velocities ◽  
Maracaibo Basin ◽  
Wave Tomography

<p>The Caribbean plate (CAR) collided with and initiated subduction beneath northwestern South America (SA) at about 60-55 Ma. Since the onset of subduction, it has formed the Lara nappes and subsequently the Laramide-style uplifts of the Merida Andes, Sierra de la Perija and Santa Marta ranges, with maximum elevations > 5km. The triangular Maracaibo block, bounded by the Santa Marta-Bucaramanga, Bocono and Oca-Ancon Faults, is currently escaping to the north relative to SA over both the subducting and nonsubducting elements of the CAR plate.</p><p>Although many petroleum related seismic studies have been done in this area, the details of the subduction geometry of the CAR plate beneath the Maracaibo block remain unclear. The few deeper seismic investigations are either very large scale, very local, or only peripheral to this area. Previous geodetic studies have suggested that this region has potential for a great (M~8+) earthquake (Bilham and Mencin, 2013). To investigate this complex region we fielded a 65 element broadband seismic array to complement the 48 existing stations of the Colombian and Venezuelan national seismic networks. The array is collectively referred to as the CARMArray.</p><p>In this study, we jointly inverted ambient noise Rayleigh wave Z/H ratios, phase velocities in the 8-30s band and ballistic Rayleigh wave phase velocities in 30-80s band to construct a 3D S-wave velocity model in the area from 75<sup>o</sup>-65<sup>o</sup> west and 5<sup>o</sup>-12<sup>o</sup> north. Rayleigh wave Z/H ratios are sensitive to the shallow sedimentary structure, while the phase velocity data have good resolution of the crust and upper mantle. The Vs model shows strong low-velocity anomalies beneath the Barinas-Apure and Maracaibo Basins, and the Paraguana Peninsula that are well correlated with surface geology. Sediment thickness beneath the Maracaibo basin reaches up to ~9 km depth, consistent with previous studies (Kellogg & Bonini, 1982). Crustal thickness beneath the Santa Marta uplift is 27-30 km, shallow for its nearly 4km elevation. From the trench to the southeast, Moho depth increases from 25-30 km near the coast to 40-45 km beneath the Maracaibo Basin, with the thickest crust, ~50 km, lying under the Merida Andes beneath the Bocono Fault. Crustal thickness decreases under the Venezeulan interior to ~45 km. From 50km to 150km depth, the CAR plate shows ~2% high Vs anomalies beneath the Santa Marta uplift and the Serrania de Perija range. Our slab image matches local slab seismicity very well (Cornthwaite et al., EGU 2021 GD7.1), and is consistent with and complements images from teleseismic P-wave tomography (Cornthwaite et al, 2021, submitted).</p>

Measurements of Rayleigh-wave phase velocities in Nevada: Implications for explosion sources and the Massachusetts Mountain earthquake

1982 ◽  
Vol 72 (4) ◽  
pp. 1329-1349
Author(s):  
H. J. Patton
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Moment Tensor ◽  
Test Site ◽  
P Wave ◽  
Stress Axis ◽  
Phase Velocities ◽  
Wave Phase ◽  
Single Station ◽  
Source Phase

abstract Single-station measurements of Rayleigh-wave phase velocity are obtained for paths between the Nevada Test Site and the Livermore broadband regional stations. Nuclear underground explosions detonated in Yucca Valley were the sources of the Rayleigh waves. The source phase φs required by the single-station method is calculated for an explosion source by assuming a spherically symmetric point source with step-function time dependence. The phase velocities are used to analyze the Rayleigh waves of the Massachusetts Mountain earthquake of 5 August 1971. Measured values of source phase for this earthquake are consistent with the focal mechanism determined from P-wave first-motion data (Fischer et al., 1972). A moment-tensor inversion of the Rayleigh-wave spectra for a 3-km-deep source gives a horizontal, least-compressive stress axis oriented N63°W and a seismic moment of 5.5 × 1022 dyne-cm. The general agreement between the results of the P-wave study of Fischer et al. (1972) and this study supports the measurements of phase velocities and, in turn, the explosion source model used to calculate φs.

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>

Ambient noise Rayleigh wave tomography in western Sichuan and eastern Tibet

2009 ◽  
Vol 282 (1-4) ◽  
pp. 201-211 ◽  
Author(s):  
Hongyi Li ◽  
Wei Su ◽  
Chun-Yong Wang ◽  
Zhongxian Huang
Keyword(s):  
Rayleigh Wave ◽  
Ambient Noise ◽  
Western Sichuan ◽  
Eastern Tibet ◽  
Wave Tomography ◽  
Rayleigh Wave Tomography

Caribbean slab dynamics beneath northwest South America from SKS and Local S splitting

2021 ◽  
Author(s):  
John Cornthwaite ◽  
Fenglin Niu ◽  
Alan Levander ◽  
Michael Schmitz ◽  
Germán Prieto ◽  
...  
Keyword(s):  
South America ◽  
Seismic Anisotropy ◽  
P Wave ◽  
Large Igneous Province ◽  
Mantle Dynamics ◽  
Fast Axis ◽  
Shallow Subduction ◽  
Wave Tomography ◽  
Plate Coupling ◽  
Fast Polarization

<p>     The southernmost edge of the Caribbean (CAR) plate, a buoyant large igneous province, subducts shallowly beneath northwestern South America (NWSA) at a trench that lies northwest of Colombia. Recent finite frequency P-wave tomography results show a segmented CAR subducting at a shallow angle under the Santa Marta Massif to the Serrania de Perijá (SdP) before steepening while a detached segment beneath the Mérida Andes (MA) descends into the mantle transition zone. The dynamics of shallow subduction are poorly understood. Plate coupling between the flat subducting CAR and the overriding NWSA is proposed to have driven the uplift of the MA. In this study we analyze SKS shear wave splitting to investigate the seismic anisotropy beneath the slab segments to relate their geometry to mantle dynamics. We also use local S splitting to investigate the seismic anisotropy between the slab segments and the overriding plate. The data were recorded by a 65-element portable broadband seismograph network deployed in NWSA and 40 broadband stations of the Venezuelan and Colombian national seismograph networks.</p><p>     SKS fast polarization axes are measured generally trench-perpendicular (TP) west of the SdP but transition to trench-parallel (TL) at the SdP where the slab was imaged steepening into the mantle, consistent with previous studies. West of the MA the fast axis is again TP but transitions to TL under the MA. This second transition from TP to TL is likely due to mantle material being deflected around a detached slab under the MA. Local S fast polarization axes are dominantly TP throughout the study area west of the Santa Marta Massif and are consistent with slab-entrained flow. Under the Santa Marta Massif the fast axis is TL for reasons we do not yet understand.</p>

scholarly journals Crust and upper mantle structures of the Makran subduction zone in south-east Iran by seismic ambient noise tomography

2014 ◽  
Vol 6 (1) ◽  
pp. 1-34 ◽  
Author(s):  
M. Abdetedal ◽  
Z. H. Shomali ◽  
M. R. Gheitanchi
Keyword(s):  
Surface Wave ◽  
Rayleigh Wave ◽  
Group Velocity ◽  
Ambient Noise ◽  
Surface Wave Tomography ◽  
Seismic Ambient Noise ◽  
Velocity Anomaly ◽  
Empirical Green’S Functions ◽  
Wave Tomography ◽  
Cross Correlations

Abstract. We applied seismic ambient noise surface wave tomography to estimate Rayleigh wave empirical Green's functions from cross-correlations to study crust and uppermost mantle structure beneath the Makran region in south-east Iran. We analysed 12 months of continuous data from January 2009 through January 2010 recorded at broadband seismic stations. We obtained group velocity of the fundamental mode Rayleigh-wave dispersion curves from empirical Green's functions between 10 and 50 s periods by multiple-filter analysis and inverted for Rayleigh wave group velocity maps. The final results demonstrate significant agreement with known geological and tectonic features. Our tomography maps display low-velocity anomaly with south-western north-eastern trend, comparable with volcanic arc settings of the Makran region, which may be attributable to the geometry of Arabian Plate subducting overriding lithosphere of the Lut block. At short periods (<20 s) there is a pattern of low to high velocity anomaly in northern Makran beneath the Sistan Suture Zone. These results are evidence that surface wave tomography based on cross correlations of long time-series of ambient noise yields higher resolution group speed maps in those area with low level of seismicity or those region with few documented large or moderate earthquake, compare to surface wave tomography based on traditional earthquake-based measurements.

Rayleigh Wave Tomography from Ambient Noise in Central and Eastern Chinese Mainland

2012 ◽  
Vol 55 (5) ◽  
pp. 587-597
Author(s):  
Xian ZHENG ◽  
Cui-Ping ZHAO ◽  
Lian-Qing ZHOU ◽  
Si-Hua ZHENG
Keyword(s):  
Rayleigh Wave ◽  
Ambient Noise ◽  
Chinese Mainland ◽  
Wave Tomography ◽  
Rayleigh Wave Tomography

3D-ambient noise Rayleigh wave tomography of Snæfellsjökull volcano, Iceland

2016 ◽  
Vol 317 ◽  
pp. 42-52 ◽  
Author(s):  
Anne Obermann ◽  
Matteo Lupi ◽  
Aurélien Mordret ◽  
Steinunn S. Jakobsdóttir ◽  
Stephen A. Miller
Keyword(s):  
Rayleigh Wave ◽  
Ambient Noise ◽  
Wave Tomography ◽  
Rayleigh Wave Tomography

scholarly journals Joint ambient noise autocorrelation and receiver function analysis of the Moho

2021 ◽  
Vol 225 (3) ◽  
pp. 1920-1934
Author(s):  
Stefan Mroczek ◽  
Frederik Tilmann
Keyword(s):  
Prior Knowledge ◽  
Ambient Noise ◽  
Wave Reflection ◽  
Receiver Function ◽  
Receiver Functions ◽  
P Wave ◽  
Moho Depth ◽  
Phase Identification ◽  
Zero Offset ◽  
Autocorrelation Method

SUMMARY In the field of seismic interferometry, cross-correlations are used to extract Green’s function from ambient noise data. By applying a single station variation of the method, using autocorrelations, we are in principle able to retrieve zero-offset reflections in a stratified Earth. These reflections are valuable as they do not require an active seismic source and, being zero-offset, are better constrained in space than passive earthquake based measurements. However, studies that target Moho signals with ambient noise autocorrelations often give ambiguous results with unclear Moho reflections. Using a modified processing scheme and phase-weighted stacking, we determine the Moho P-wave reflection time from vertical autocorrelation traces for a test station with a known simple crustal structure (HYB in Hyderabad, India). However, in spite of the simplicity of the structure, the autocorrelation traces show several phases not related to direct reflections. Although we are able to match some of these additional phases in a qualitative way with synthetic modelling, their presence makes it hard to identify the reflection phases without prior knowledge. This prior knowledge can be provided by receiver functions. Receiver functions (arising from mode conversions) are sensitive to the same boundaries as autocorrelations, so should have a high degree of comparability and opportunity for combined analysis but in themselves are not able to independently resolve VP, VS and Moho depth. Using the timing suggested by the receiver functions as a guide, we observe the Moho S-wave reflection on the horizontal autocorrelation of the north component but not on the east component. The timing of the S reflection is consistent with the timing of the PpSs–PsPs receiver function multiple, which also depends only on the S velocity and Moho depth. Finally, we combine P receiver functions and autocorrelations from HYB in a depth–velocity stacking scheme that gives us independent estimates for VP, VS and Moho depth. These are found to be in good agreement with several studies that also supplement receiver functions to obtain unique crustal parameters. By applying the autocorrelation method to a portion of the EASI transect crossing the Bohemian Massif in central Europe, we find approximate consistency with Moho depths determined from receiver functions and spatial coherence between stations, thereby demonstrating that the method is also applicable for temporary deployments. Although application of the autocorrelation method requires great care in phase identification, it has the potential to resolve both average crustal P and S velocities alongside Moho depth in conjunction with receiver functions.

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