Geodynamic processes of the continental deep subduction: constraints from the fine crustal structure beneath the Pamir Plateau

2020 ◽  
Author(s):  
Wei Li ◽  
Yun Chen ◽  
Ping Tan ◽  
Xiaohui Yuan
Keyword(s):  
Spatial Configuration ◽  
Spline Interpolation ◽  
Joint Inversion ◽  
Receiver Functions ◽  
Crustal Material ◽  
Seismic Zone ◽  
S Wave ◽  
Low Velocity ◽  
Crust And Upper Mantle ◽  
Intermediate Depth

<p>The Pamir plateau, located north of the western syntaxis of the India­–Eurasia collision system, is regarded as one of the most possible places of the ongoing continental deep subduction. Based on a N-S trending linear seismic array across the Pamir plateau, we use the methods of harmonic analysis of receiver functions and the cubic spline interpolation of surface wave dispersions to coordinate their resolutions, and perform a joint inversion of these datasets to construct a 2-D S-wave velocity model of the crust and uppermost mantle. A spatial configuration among the intermediate-depth seismicity, Moho topography, and low-velocity zone(LVZ)s within the crust and upper mantle is revealed. The intermediate-depth seismic zone is enclosed in a mantle LVZ which extends upward to the crustal root and connects with a lower crustal LVZ in the northern Pamir. Just above it, another crustal LVZ is collocated with a Moho uplift. These results not only further confirm the deep subduction of the Asian lower continental crust beneath the Pamir plateau, but also indicate the importance of the metamorphic dehydration of the subducting continental crustal material in the genesis of the intermediate-depth seismicity and crustal deformation.</p>

Structure of the crust and upper mantle of the Great Slave Lake shear zone, northwestern Canada, from teleseismic analysis and gravity modelling

2003 ◽  
Vol 40 (9) ◽  
pp. 1203-1218 ◽  
Author(s):  
David W Eaton ◽  
Jacqueline Hope
Keyword(s):  
Shear Zone ◽  
Upper Mantle ◽  
Receiver Function ◽  
Function Analysis ◽  
Crustal Material ◽  
S Wave ◽  
Crust And Upper Mantle ◽  
Fast Axis ◽  
Great Slave Lake ◽  
Basic Features

The Great Slave Lake shear zone (GSLsz) exposes lower crustal rocks analogous to deep-seated segments of modern strike-slip fault zones, such as the San Andreas fault. Extending for 1300 km beneath the Western Canada Sedimentary Basin to the southern margin of the Slave Province, the GSLsz produces one of the most prominent linear magnetic anomalies in Canada. From May to October 1999, 13 three-component portable broadband seismograph stations were deployed in a 150-km profile across a buried segment of the shear zone to investigate its lithospheric structure. Splitting analysis of core-refracted teleseismic shear waves reveals an average fast-polarization direction (N49°E ± 19°) that is approximately parallel to the shear zone. Individual stations near the axis of the shear zone show more northerly splitting directions, which we attribute to interference between regional anisotropy in the upper mantle (fast axis ~N60°E) and crustal anisotropy within the shear zone (fast axis ~N30°E). At the location of our profile, the shear zone is characterized by a 10-mGal axial gravity high with a wavelength of 30 km, superimposed on a longer wavelength 12-mGal low. This gravity signature is consistent with the basic features of the crustal model derived from receiver-function analysis: a Moho that dips inward toward the shear-zone axis and a mid-crustal zone with high S-wave velocity (ΔVs = 0.6 ± 0.2 km/s). The axial gravity high may be related to uplift of deeper crustal material within the shear zone, or protolith-dependent compositional differences between the shear zone and surrounding wall rocks.

Directions of lithosphere interactions in the Pamir – Hindu Kush junction inferred from anisotropic tomography

2020 ◽  
Vol 57 (5) ◽  
pp. 601-616
Author(s):  
Jamshed Aminov ◽  
Ivan Koulakov ◽  
Andrey Jakovlev ◽  
Junmeng Zhao ◽  
Sami El-Khrepy ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Azimuthal Anisotropy ◽  
Tien Shan ◽  
Crustal Material ◽  
Seismic Zone ◽  
The South ◽  
S Wave ◽  
Time Data ◽  
Local Tomography ◽  
Hindu Kush

The Pamir and Hindu Kush are examples of a puzzling collision system where a complex junction of colliding lithospheric plates coexists with intermediate depth seismicity at 300 km. In this study, we constructed a new tomography model using travel time data from local events recorded by the TIPAGE (Tien Shan – Pamir Geodynamic program) network. In addition to the P- and S-wave velocities down to 200 km, we derived the azimuthal anisotropy. The velocity anomalies were consistent with the results of previous studies. In the crust, the velocity structure and anisotropy directions were mainly oriented along major suture zones. At depths of 80–120 km, a narrow low-velocity anomaly coinciding with the distribution of deep seismicity was interpreted as a trace of entrained crustal material by the dipping lithosphere. The anisotropy directions at these depths were mainly oriented northwest–southeast and were interpreted as indicating the direction of the motion of colliding plates. The difference in the magnitude of anisotropy south and north of the Pamir seismic zone suggests that the lithosphere coming from the south possesses less anisotropy than that of the Asian plate. The local tomography model was supplemented by previously computed regional tomography that expanded the area both laterally and axially. Beneath the Pamir, both continental plates coming from the north and south form a drop-shaped anomaly that will possibly delaminate in time. Beneath the Hindu Kush, we could clearly trace a continuous almost vertical subduction of the Katawaz block from the south. Thus, the continental collision beneath the Pamir and subduction beneath the Hindu Kush are separate processes with different rates and directions of plate movement.

Lithospheric structure of the Arabian Shield from joint inversion of P- and S-wave receiver functions and dispersion velocities

2015 ◽  
Vol 65 (2) ◽  
pp. 239-255 ◽  
Author(s):  
Abdullah M. Al-Amri
Keyword(s):  
Green's Functions ◽  
Velocity Structure ◽  
Green’S Functions ◽  
Joint Inversion ◽  
Receiver Functions ◽  
Gulf Of Aqaba ◽  
Arabian Shield ◽  
S Wave ◽  
Velocity Models ◽  
Seismic Networks

Abstract New velocity models of lithospheric thickness and velocity structure have been developed for the Arabian Shield by three tasks: 1) Computing P-Wave Receiver Functions (PRFs) and S-Wave Receiver Functions (SRFs) for all the broadband stations within the Saudi seismic networks. The number of receiver function waveforms depends on the recording time window and quality of the broadband station. 2) Computing ambient noise correlation Green’s functions for all available station pairs within the Saudi seismic networks to image the shear velocity in the crust and uppermost mantle beneath the Arabian Peninsula. Together they provided hundreds of additional, unique paths exclusively sampling the region of interest. Both phase and group velocities for all the resulting empirical Green’s functions have been measured and to be used in the joint inversion. 3) Jointly inverted the PRFs and SRFs obtained in task 1 with dispersion velocities measured on the Green’s functions obtained in task 2 and with fundamental-mode, Rayleigh-wave, group and phase velocities borrowed from the tomographic studies to precisely determine 1D crustal velocity structure and upper mantle. The analysis of the PRFs revealed values of 25-45 km for crustal thickness, with the thin crust next to the Red Sea and Gulf of Aqaba and the thicker crust under the platform, and Vp/Vs ratios in the 1.70-1.80 range, suggesting a range of compositions (felsic to mafic) for the shield’s crust. The migrated SRFs suggest lithospheric thicknesses in the 80-100 km range for portions of the shield close to the Red Sea and Gulf of Aqaba and near the Arabian Gulf. Generally, the novelty of the velocity models developed under this paper has consisted in the addition of SRF data to extend the velocity models down to lithospheric and sub-lithospheric depths.

Mapping crustal structure of the Nechako–Chilcotin plateau using teleseismic receiver function analysis,

2014 ◽  
Vol 51 (4) ◽  
pp. 407-417 ◽  
Author(s):  
H.S. Kim ◽  
J.F. Cassidy ◽  
S.E. Dosso ◽  
H. Kao
Keyword(s):  
Wave Velocity ◽  
Crustal Structure ◽  
Velocity Structure ◽  
Receiver Function ◽  
Function Analysis ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
S Wave ◽  
Low Velocity ◽  
Velocity Models

This paper presents results of a passive-source seismic mapping study in the Nechako–Chilcotin plateau of central British Columbia, with the ultimate goal of contributing to assessments of hydrocarbon and mineral potential of the region. For the present study, an array of nine seismic stations was deployed in 2006–2007 to sample a wide area of the Nechako–Chilcotin plateau. The specific goal was to map the thickness of the sediments and volcanic cover, and the overall crustal thickness and structural geometry beneath the study area. This study utilizes recordings of about 40 distant earthquakes from 2006 to 2008 to calculate receiver functions, and constructs S-wave velocity models for each station using the Neighbourhood Algorithm inversion. The surface sediments are found to range in thickness from about 0.8 to 2.7 km, and the underlying volcanic layer from 1.8 to 4.7 km. Both sediments and volcanic cover are thickest in the central portion of the study area. The crustal thickness ranges from 22 to 36 km, with an average crustal thickness of about 30–34 km. A consistent feature observed in this study is a low-velocity zone at the base of the crust. This study complements other recent studies in this area, including active-source seismic studies and magnetotelluric measurements, by providing site-specific images of the crustal structure down to the Moho and detailed constraints on the S-wave velocity structure.

Lithosphere velocity structure of the Khibiny and Lovozero plutons (Eastern part of the Baltic shield) from receiver functions

2021 ◽  
Author(s):  
Andrey Goev
Keyword(s):  
Baltic Shield ◽  
Upper Mantle ◽  
Velocity Structure ◽  
Deep Structure ◽  
Joint Inversion ◽  
Receiver Functions ◽  
Function Technique ◽  
High Porosity ◽  
Low Velocity ◽  
The Baltic

<p>The Kola region of the Russian Arctic is located in the northeast of the Baltic Shield and is widely known for its unique geology in regards to the presence of massive Paleozoic intrusions. Multidisciplinary researches have been carried out to provide a comprehensive reconstruction of Khibiny and Lovozero plutons’ formation and their structure models The main source of geochronological data comes from isotope analysis of the arrays’ rocks. The amount of research focuses on the deep structure beneath the Khibiny pluton is scarce. To investigate velocity structure of the investigated region we used receiver function technique. Essence of the method is to analyze P-S (PRF) and S-P (SRF) converted waves form seismic boundaries along with their multiples. For the given research we used seismograms of the teleseismic events recorded by the Apatity (APA) and Lovozero (LVZ) broadband seismic stations since 2000. We selected 220 and 232 individual PRF;147 and 122 individual SRF for LVZ and APA station respectively. As both LVZ and APA are located relatively close to each other, we combined all 452 PRF to get a robust estimation of delay times of P410s and P660s phases. Our estimations of P410s and P660s phases are 43.6 and 67.6 sec respectively. Delay time between these phases is 24 sec that is close to “standard” according to the IASP91 model. The individual times of each phase are slightly less than predicted by IASP91 (by 0.4 sec) and could indicate an increase of velocities in the upper mantle, but it is not unusual for cratonic regions. Joint inversion of PRF and SRF was used to restore velocity sections for the depth up to 300 km. All models have shown a gradient increase in velocities in the earth's crust and sharp crust-mantle boundary at depth of 40 ± 1 km with a velocity jump from 3.9 to 4.4 km/s. The most prominent feature of the upper mantle structure is the presence of the low-velocity zone at a depth from 90 to 140 km. One of the possible explanation of this discontinuity could be the presence of deep fluids and the high porosity of this zone. This study was partially supported by the RFBR grant 18-05-70082 and the SRW theme No. АААА-А19-119022090015-6.</p>

ScanArray - Seismological study of the connection between topographic change and deep structure in Fennoscandia

2021 ◽  
Author(s):  
Hans Thybo ◽  
Nevra Bulut ◽  
Michael Grund ◽  
Alexandra Mauerberger ◽  
Anna Makushkina ◽  
...  
Keyword(s):  
Baltic Shield ◽  
Upper Mantle ◽  
Deep Structure ◽  
Broad Band ◽  
Receiver Functions ◽  
High Mountain ◽  
Mountain Range ◽  
S Wave ◽  
Crust And Upper Mantle ◽  
The Baltic

<p>The Baltic Shield is located in northern Europe. It was formed by amalgamation of a series of terranes and microcontinents during the Archean to the Paleoproterozoic, followed by significant modification in Neoproterozoic to Paleozoic time. The Baltic Shield includes a high mountain range, the Scandes, along its western North Atlantic coast, despite being a stable craton located far from any active plate boundary.</p> <p>The ScanArray international collaborative program has acquired broad band seismological data at 192 locations in the Baltic Shield during the period between 2012 and 2017. The main objective of the program is to provide seismological constraints on the structure of the lithospheric crust and mantle as well as the sublithospheric upper mantle. The new information will be applied to studies of how the lithospheric and deep structure affects observed fast topographic change and geological-tectonic evolution of the region. The recordings are of very high quality and are used for analysis by suite of methods, including P- and S-wave receiver functions for the crust and upper mantle, surface wave and ambient noise inversion for seismic velocity, body wave P- and S- wave tomography for upper mantle velocity structure, and shear-wave splitting measurements for obtaining bulk anisotropy of the upper and lower mantle. Here we provide a short overview of the data acquisition and initial analysis of the new data with focus on parameters that constrain the fast topographic change in the Scandes.</p> <p> </p>

scholarly journals Crustal structure of Sri Lanka derived from joint inversion of surface wave dispersion and receiver functions using a Bayesian approach

2020 ◽  
Author(s):  
Jennifer Dreiling ◽  
Frederik Tilmann ◽  
Xiaohui Yuan ◽  
Christian Haberland ◽  
S.W. Mahinda Seneviratne
Keyword(s):  
Sri Lanka ◽  
Bayesian Approach ◽  
Crustal Structure ◽  
Joint Inversion ◽  
Receiver Functions ◽  
Silica Content ◽  
Low Velocity ◽  
Surface Wave Dispersion ◽  
Central Highland ◽  
Moho Depths

<p>We study the crustal structure of Sri Lanka by analyzing data from a temporary seismic network deployed in 2016-2017 to shed light on the amalgamation process from the geophysical perspective. Rayleigh wave phase dispersion from ambient noise cross-correlation and receiver functions were jointly inverted using a transdimensional Bayesian approach.</p><p>The Moho depths range between 30 and 40 km, with the thickest crust (38-40 km) beneath the central Highland Complex (HC). The thinnest crust (30-35 km) is found along the west coast, which experienced crustal thinning associated with the formation of the Mannar Basin. Vp/Vs ratios lie within a range of 1.60-1.82 and predominantly favor a felsic composition with intermediate-to-high silica content of the rocks.</p><p>A major intra-crustal (18-27 km), slightly westward dipping (~4.3°) interface with high Vs (~4 km/s) underneath is prominent in the central HC, continuing in the eastern Vijayan Complex (VC). The dipping discontinuity and a low velocity zone in the central Highlands can be related to the HC/VC contact zone and is in agreement with a well-established amalgamation hypothesis of a stepwise collision of the arc fragments, including deep crustal thrusting processes and a transpressional regime along the suture between the HC and VC.</p>

scholarly journals Lithosphere–asthenosphere boundary beneath the Sea of Japan from transdimensional inversion of S-receiver functions

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Takeshi Akuhara ◽  
Kazuo Nakahigashi ◽  
Masanao Shinohara ◽  
Tomoaki Yamada ◽  
Hajime Shiobara ◽  
...  
Keyword(s):  
Sea Of Japan ◽  
Receiver Functions ◽  
The Sea Of Japan ◽  
Detailed Knowledge ◽  
Ocean Bottom ◽  
S Wave ◽  
Low Velocity ◽  
Lithospheric Thickness ◽  
Velocity Models ◽  
Back Arc

AbstractThe evolution history of the Sea of Japan back-arc basin remains under debate, involving the opening of sub-basins such as the Japan and Yamato Basins. Detailed knowledge of the lithospheric structure will provide the key to understanding tectonic history. This study identifies the lithosphere–asthenosphere boundary (LAB) beneath the Sea of Japan back-arc basin using S-receiver functions (S-RFs). The study area, including the Japan and Yamato Basins, has been instrumented with broadband ocean-bottom seismometers (OBSs). S-RFs from these OBSs show negative Sp phases preceding the direct S arrivals, suggesting the LAB. The S-RFs also show abnormally reduced amplitudes. For further qualitative interpretation of these findings, we conduct transdimensional Bayesian inversion for S-wave velocity models. This less-subjective Bayesian approach clarifies that the low-velocity seafloor sediments and damped deconvolution contribute to the amplitude reduction, illuminating the necessity of such considerations for similar receiver function works. Inverted velocity structures show a sharp velocity decrease at the mantle depths, which we consider the LAB. The obtained LAB depths vary among sites: ~ 45 km beneath the Japan and Yamato Basins and ~ 70 km beneath the Yamato Rise, a bathymetric high between the two basins. The thick lithosphere beneath the Yamato Rise most likely reflects its continental origin. However, the thickness is still thin compared to that of eastern Asia, suggesting lithosphere extension by rifting. Notably, the Japan and Yamato Basins show a comparable lithospheric thickness, although the crustal thickness beneath the Yamato Basin is known to be anomalously thick. This consistency in the lithospheric thickness implies that both basins undergo similar back-arc opening processes.

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