Detecting lithospheric discontinuities beneath the Mississippi Embayment using S-wave receiver functions

2021 ◽  
Vol 228 (2) ◽  
pp. 744-754
Author(s):  
Arushi Saxena ◽  
Charles Adam Langston
Keyword(s):  
Careful Analysis ◽  
Receiver Functions ◽  
S Wave ◽  
Low Velocity ◽  
Mississippi Embayment ◽  
Velocity Anomaly ◽  
Common Depth Point ◽  
Study Support ◽  
Upper Mantle Discontinuities ◽  
Temperature Water

SUMMARY Identifying upper-mantle discontinuities in the Central and Eastern US is crucial for verifying models of lithospheric thinning and a low-velocity anomaly structure beneath the Mississippi Embayment. In this study, S-wave receiver functions (SRFs) were used to detect lithospheric boundaries in the embayment region. The viability of SRFs in detecting seismic boundaries was tested before computing them using the earthquake data. A careful analysis using a stochastic noise and coda model on the synthetics revealed that a negative velocity contrast could be detected with certainty at low to moderate noise levels after stacking. A total of 31 518 SRFs from 688 earthquakes recorded at 174 seismic stations including the Northern Embayment Lithospheric Experiment, EarthScope Transportable Array and other permanent networks were used in this study. Common depth point stacks of the SRFs in 1° × 1° bins indicated a continuous and broad S-to-P converted phase (Sp) arrival corresponding to a negative velocity contrast at depths between 50 and 100 km. The observed negative Sp phase is interpreted as a mid-lithospheric discontinuity (MLD), and several possible origins of the velocity drop corresponding to the MLD are explored. After quantitative analysis, a combination of temperature, water content and melt content variations are attributed to explain the observed MLD in this study. The observations and interpretations in this study support the previous claims of an MLD in the Central and Eastern US and provide a possible mechanism for its origin.

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>

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.

The case for a shallow-crustal anomalous zone (magma body?) near the south end of Hilton Creek fault, California, including new evidence from an interpretation of pre-S arrivals

1989 ◽  
Vol 79 (3) ◽  
pp. 805-812
Author(s):  
William A. Peppin ◽  
William Honjas ◽  
Thomas W. Delaplain ◽  
Ute R. Vetter
Keyword(s):  
Seismic Gap ◽  
The South ◽  
S Wave ◽  
Low Velocity ◽  
Magma Body ◽  
Velocity Anomaly ◽  
Anomalous Zone ◽  
Double Couple ◽  
A Site ◽  
New Evidence

Abstract Seven independent lines of evidence can be cited for the existence of a shallow-crustal anomalous zone at a site near the south end of Hilton Creek fault, near Mammoth Lakes, California. They are: (1) the presence of a persistent seismic gap since detailed observations began in 1979; (2) S-wave shadowing for travel paths crossing the site; (3) a low-velocity anomaly associated with the south end of Hilton Creek fault discovered by seismic tomography; (4) the observation of two non-double-couple mechanisms for large earthquakes a few km east and west of the site; (5) a concentration of pre-S-arrivals indicative of a possible reflection in the vicinity of this site; (6) a geometric symmetry of source-receiver paths showing pre-S arrivals about this site; and (7) [new evidence presented herein] travel-time fits of strong pre-S arrivals recorded at epicenter of the 1978 Wheeler Crest event (ML 5.7).

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.

scholarly journals Lithosphere–asthenosphere Boundary Beneath the Sea of Japan From Transdimensional Inversion of S Receiver Functions

2021 ◽  
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

Abstract The 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.

scholarly journals Adjoint traveltime tomography unravels a scenario of horizontal mantle flow beneath the North China craton

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xingpeng Dong ◽  
Dinghui Yang ◽  
Fenglin Niu ◽  
Shaolin Liu ◽  
Ping Tong
Keyword(s):  
North China Craton ◽  
Lithospheric Mantle ◽  
North China ◽  
Three Dimensional ◽  
Mantle Flow ◽  
S Wave ◽  
Low Velocity ◽  
Traveltime Tomography ◽  
Velocity Anomaly ◽  
The North

AbstractThe North China craton (NCC) was dominated by tectonic extension from late Cretaceous to Cenozoic, yet seismic studies on the relationship between crust extension and lithospheric mantle deformation are scarce. Here we present a three dimensional radially anisotropic model of NCC derived from adjoint traveltime tomography to address this issue. We find a prominent low S-wave velocity anomaly at lithospheric mantle depths beneath the Taihang Mountains, which extends eastward with a gradually decreasing amplitude. The horizontally elongated low-velocity anomaly is also featured by a distinctive positive radial anisotropy (VSH > VSV). Combining geodetic and other seismic measurements, we speculate the presence of a horizontal mantle flow beneath central and eastern NCC, which led to the extension of the overlying crust. We suggest that the rollback of Western Pacific slab likely played a pivotal role in generating the horizontal mantle flow at lithospheric depth beneath the central and eastern NCC.

scholarly journals Lithospheric dynamics in the vicinity of the Tengchong volcanic field (southeastern margin of Tibet): an investigation using P receiver functions

2020 ◽  
Vol 224 (2) ◽  
pp. 1326-1343
Author(s):  
Hengchu Peng ◽  
José Badal ◽  
Jiafu Hu ◽  
Haiyan Yang ◽  
Benyu Liu
Keyword(s):  
Upper Mantle ◽  
Lower Crust ◽  
Volcanic Field ◽  
Receiver Functions ◽  
Indian Plate ◽  
Fast Wave ◽  
Low Velocity ◽  
Crust And Upper Mantle ◽  
Velocity Anomaly ◽  
Lateral Extrusion

SUMMARY Tengchong volcanic field (TVF) in the northern Indochina block lies in a critical area for understanding complex regional dynamics associated with continent–continent convergence between the Indian and Eurasian plates, including northeastward compression generated by subduction of the Indian Plate beneath the Burma Arc, and southeastward lateral extrusion of the crust from below central Tibet. We gathered 3408 pairs of P receiver functions with different frequencies and calculated the splitting parameters of the Moho-converted Pms phase. An anisotropic H-κ stacking algorithm was used to determine crustal thickness and Vp/Vs ratios. We also inverted for the detailed S-velocity structure of the crust and upper mantle using a two-step inversion technique. Finally, we mapped the topography of the lithosphere–asthenosphere boundary. Results show fast-wave polarization directions with a dominant NE–SW orientation and delay times varying between 0.19 and 1.22 s, with a mean of 0.48 ± 0.07 s. The crustal Vp/Vs ratio varies from 1.68 to 1.90 and shows a maximum value below the central part of the TVF, where there is relatively thin crust (∼35–39 km) and a pronounced low-velocity anomaly in the middle–lower crust. The depth of the lithosphere–asthenosphere boundary ranges from 53 to 85 km: it is relatively deep (∼70–85 km) in the vicinity of the TVF and relatively shallow in the south of the study area. In the absence of low shear wave velocity in the upper mantle below the TVF, we propose that the low-velocity anomaly in the lower crust beneath the TVF derives from the upper mantle below the neighbouring Baoshan block.

Sedimentary basin exploration with receiver functions: Seismic structure and anisotropy of the Dublin Basin (Ireland)

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. KS41-KS55 ◽  
Author(s):  
Andrea Licciardi ◽  
Nicola Piana Agostinetti
Keyword(s):  
Seismic Anisotropy ◽  
Sedimentary Basin ◽  
Structural Data ◽  
Receiver Functions ◽  
Seismic Structure ◽  
S Wave ◽  
Low Velocity ◽  
Velocity Models ◽  
Sonic Log ◽  
Anisotropic Layers

Teleseismic receiver functions (RFs) were used to investigate the seismic structure of the southern margin of the Dublin Basin, a potential geothermal site. Through an inversion-based approach, the elastic properties and seismic anisotropy of sedimentary basin units were examined, using data from a linear array of closely spaced seismic stations. Our results were compared with sonic logs and lithostratigraphies from two nearby boreholes, NGE1 and NGE2 and colocated active seismic data. Including a high-frequency RF (up to 8 Hz) allowed us to compute S-wave velocity models with a vertical resolution [Formula: see text]. The results indicated the presence of a subvertical lateral discontinuity in [Formula: see text], in correspondence with the main basin-bounding fault (Blackrock-Newcastle Fault [BNF]). North of this discontinuity, a shallow low-velocity layer thickens (from 0.7 to 1.0 km thick) toward the inner basin, in agreement with the geometry of the shallowest reflector found by active seismics. A good correlation was also found between the sonic log at NGE1 and our velocity model. Station DB02 showed an increase in [Formula: see text] at a depth of approximately 0.7 km and a decrease in [Formula: see text] at approximately 1.4 km in depth. Two velocity jumps with matching polarities were also observed in the NGE1 sonic log at the contact between the Upper and Lower Calp formations (positive jump, 688 m deep), and between a calcarenite and a sandstone layers (negative jump, 1337 m deep). Moreover, the main velocity contrasts in our model agree with the major lithostratigraphic boundaries inferred from borehole-drilled samples. Two juxtaposed anisotropic layers are identified close to the BNF. Directions of the slow axis of anisotropy are consistent with the borehole structural data. From these observations, the presence of aligned open cracks within the sandstones, possibly fluid-filled, was inferred up to a depth of 2.3 km in the vicinity of the BNF.

scholarly journals Early Results of Eastern Indonesia P-wave Tomography Study Using Regional Events

2021 ◽  
Vol 873 (1) ◽  
pp. 012068
Author(s):  
M I Sulaiman ◽  
P A Subakti ◽  
Haolia ◽  
D Y Fatimah ◽  
I Madrinovella ◽  
...  
Keyword(s):  
P Wave ◽  
S Wave ◽  
Low Velocity ◽  
Seismicity Pattern ◽  
Velocity Anomaly ◽  
Eastern Indonesia ◽  
The North ◽  
Early Results ◽  
Slab Tear ◽  
Tectonic System

Abstract The tectonic system of Eastern Indonesia is controlled by several major and minor plates, such as Indo-Australian, Australian plate, and Pacific plates. This area is known for its complexity, and high seismic activity. This study tries to image the complex structures beneath this region by employing regional events data and seismic tomography methods. We used five years of regional events catalog provided by the Indonesian Agency of Meteorology, Climatology, and Geophysics. We have sorted 7336 events recorded between 120° – 136° longitude and 0° – 13°(-) latitude consisting of 46446 P and 15467 S wave arrival data. Relocated hypocenter map shows a better constrain location on seismicity along outer Bandar Arc. A dipping pattern of seismicity is seen that is going deeper to the Banda Sea. The seismicity map also images a steep angle pattern of seismicity that could be related to the subduction slab roll-back model at North of Wetar island. Interestingly, we spotted a seismicity gap in West Seram that could be linked with slab tear zone. The checker-board test suggests a proper resolution is still reliable to a depth of 200 km with a less interpretable model at a depth of 300 km. P-wave tomographic models image the high velocity dipping down going slab. The Banda slab is seen to subduct from south Timor Island to the north, from east Tanimbar and Aru Island to west part, and from north Seram Island to south. We observed the down-going slab meet from all directions at about 300 km beneath the Banda sea. P wave tomogram also shows the Timor Island slab has a steeper dip that agrees with the seismicity pattern. Near the Seram island, we identify a low-velocity anomaly zone infiltrate the Banda slab beneath the shallow part of West Seram, which was previously interpreted as slab tear zone. This study also noticed a higher velocity tomogram model at North of Wetar island that might indicate a back-arc thrust. Lastly, a low-velocity band is also exposed at a shallow depth close to the volcano chain along that Banda volcanic arc.

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