scholarly journals Bulk Crustal Properties and Layered Velocity Structure in Fujian, SE China: Constraints From P and S Receiver Functions

2021 ◽  
Vol 9 ◽  
Author(s):  
Ayush Goyal ◽  
Shu-Huei Hung
Keyword(s):  
Velocity Structure ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
Nonlinear Inversion ◽  
Low Velocity ◽  
Metamorphic Belt ◽  
Crustal Layer ◽  
Late Mesozoic ◽  
Geological Features ◽  
Lower Crustal

Multiple tectonic events since the Neoproterozoic era have framed the present-day lithosphere in the Fujian province affiliated with the eastern part of the South China Block. Comprehensive information of the crustal structure and bulk properties can aid to understand the geological features and tectonic processes of still much debate in this region. An attempt is made in this study to explore crustal thickness and internal velocities across Fujian using the teleseismic receiver functions (RFs). The H-V stacking of joint P and S RFs improves to simultaneously estimate crustal thickness, average Vp and Vs, and derived Vp/Vs ratio and bulk sound speed in three backazimuth sectors for each of 17 stations. Furthermore, a Neighborhood Algorithm nonlinear inversion of P RFs is employed to determine the layered structures of Vs and Vp/Vs beneath all the stations. Results indicate the crustal thickness varies from at most ∼35 km in northwest Fujian to 30–35 km in the inland mountains and 27–30 km in the southeastern coasts. The inferred Moho geometry is nonplanar or inclined across the Zhenghe-Dapu (ZD) and Changle-Zhaoan (CZ) fault zones, especially in the southern ZD fault area. The average Vp/Vs suggests that the crust is predominantly felsic in the Wuyi-Yunkai orogen and intermediate-to-mafic in the Cretaceous magmatic and metamorphic zones. A high-velocity upper crust along the coastline is revealed, which attributes to the Pingtan-Dongshan metamorphic belt. At the sites near the ZD fault zone, the intracrustal negative discontinuity occurs at a shallower depth of ∼15 km marking an abrupt Vs decrease into the low-velocity mid-to-lower crustal layer, probably linked to the closed paleo-rift basin remnants. The lower crust across the Fujian is generally characterized by relatively lower Vs and higher Vp/Vs (1.80–1.84) consistent with those of the mafic-ultramafic rocks, which do not support the proposed extensive magmatic underplating in the Late Mesozoic.

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.

scholarly journals Crustal velocity structure of the Apennines (Italy) from P-wave travel time tomography

1996 ◽  
Vol 39 (6) ◽  
Author(s):  
C. Chiarabba ◽  
A. Amato
Keyword(s):  
Velocity Structure ◽  
P Wave ◽  
Depth Interval ◽  
Low Velocity ◽  
Data Set ◽  
Arrival Times ◽  
Velocity Anomaly ◽  
Minimum Number ◽  
Velocity Images ◽  
Lower Crustal

In this paper we provide P-wave velocity images of the crust underneath the Apennines (Italy), focusing on the lower crustal structure and the Moho topography. We inverted P-wave arrival times of earthquakes which occurred from 1986 to 1993 within the Apenninic area. To overcome inversion instabilities due to noisy data (we used bulletin data) we decided to resolve a minimum number of velocity parameters, inverting for only two layers in the crust and one in the uppermost mantle underneath the Moho. A partial inversion of only 55% of the overall dataset yields velocity images similar to those obtained with the whole data set, indicating that the depicted tomograms are stable and fairly insensitive to the number of data used. We find a low-velocity anomaly in the lower crust extending underneath the whole Apenninic belt. This feature is segmented by a relative high-velocity zone in correspondence with the Ortona-Roccamonfina line, that separates the northern from the southern Apenninic arcs. The Moho has a variable depth in the study area, and is deeper (more than 37 km) in the Adriatic side of the Northern Apennines with respect to the Tyrrhenian side, where it is found in the depth interval 22-34 km.

Crustal velocity structure from SAREX, the Southern Alberta Refraction Experiment

2002 ◽  
Vol 39 (3) ◽  
pp. 351-373 ◽  
Author(s):  
Ron M Clowes ◽  
Michael JA Burianyk ◽  
Andrew R Gorman ◽  
Ernest R Kanasewich
Keyword(s):  
Velocity Structure ◽  
Data Interpretation ◽  
Crustal Thickening ◽  
Tectonic Zone ◽  
Crustal Layer ◽  
Crustal Velocity ◽  
Crustal Velocity Structure ◽  
Southern Alberta ◽  
Magmatic Underplating ◽  
Lower Crustal

Lithoprobe's Southern Alberta Refraction Experiment, SAREX, extends 800 km from east-central Alberta to central Montana. It was designed to investigate crustal velocity structure of the Archean domains underlying the Western Canada Sedimentary Basin. From north to south, SAREX crosses the Loverna domain of the Hearne Province, the Vulcan structure, the Medicine Hat block (previously considered part of the Hearne Province), the Great Falls tectonic zone, and the northern Wyoming Province. Ten shot points along the profile in Canada were recorded on 521 seismographs deployed at 1 km intervals. To extend the line, an additional 140 seismographs were deployed at intervals of 1.25–2.50 km in Montana. Data interpretation used an iterative application of damped least-squares inversion of traveltime picks and forward modeling. Results show different velocity structures for the major blocks (Loverna, Medicine Hat, and Wyoming), indicating that each is distinct. Wavy undulations in the velocity structure of the Loverna block may be associated with internal crustal deformation. The most prominent feature of the model is a thick (10–25 km) lower crustal layer with high velocities (7.5–7.9 km/s) underlying the Medicine Hat and Wyoming blocks. Based on data from lower crustal xenoliths in the region, this layer is interpreted to be the result of Paleoproterozoic magmatic underplating. Crustal thickness varies from 40 km in the north to almost 60 km in the south, where the high-velocity layer is thickest. Uppermost mantle velocities range from 8.05 to 8.2 km/s, with the higher values below the thicker crust. Results from SAREX and other recent studies are synthesized to develop a schematic representation of Archean to Paleoproterozoic tectonic development for the region encompassing the profile. Tectonic processes associated with this development include collisions of continental blocks, subduction, crustal thickening, and magmatic underplating.

Imaging the Moho and Main Himalayan Thrust beneath the Kumaon Himalaya: constraints from receiver function analysis

2020 ◽  
Vol 224 (2) ◽  
pp. 858-870
Author(s):  
Devajit Hazarika ◽  
Somak Hajra ◽  
Abhishek Kundu ◽  
Meena Bankhwal ◽  
Naresh Kumar ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Receiver Function ◽  
Function Analysis ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
P Wave ◽  
Poisson's Ratio ◽  
Kumaon Himalaya ◽  
Receiver Function Analysis ◽  
Lower Crustal

SUMMARY We analyse P-wave receiver functions across the Kumaon Himalaya and adjoining area to constrain crustal thickness, intracrustal structures and seismic velocity characteristics to address the role of the underlying structure on seismogenesis and geodynamic evolution of the region. The three-component waveforms of teleseismic earthquakes recorded by a seismological network consisting of 18 broad-band seismological stations have been used for receiver function analysis. The common conversion point (CCP) depth migrated receiver function image and shear wave velocity models obtained through inversion show a variation of crustal thickness from ∼38 km in the Indo-Gangetic Plain to ∼42 km near the Vaikrita Thrust. A ramp (∼20°) structure on the Main Himalayan Thrust (MHT) is revealed beneath the Chiplakot Crystalline Belt (CCB) that facilitates the exhumation of the CCB. The geometry of the MHT observed from the receiver function image is consistent with the geometry revealed by a geological balanced cross-section. A cluster of seismicity at shallow to mid-crustal depths is detected near the MHT ramp. The spatial and depth distribution of seismicity pattern beneath the CCB and presence of steep dipping imbricate faults inferred from focal mechanism solutions suggest a Lesser Himalayan Duplex structure in the CCB above the MHT ramp. The study reveals a low-velocity zone (LVZ) with a high Poisson's ratio (σ ∼0.28–0.30) at lower crustal depth beneath the CCB. The high value of Poisson's ratio in the lower crust suggests the presence of fluid/partial melt. The shear heating in the ductile regime and/or decompression and cooling associated with the exhumation of the CCB plausibly created favorable conditions for partial melting in the lower crustal LVZ.

scholarly journals Crustal structure from a seismic refraction profile across southern British Columbia

1979 ◽  
Vol 16 (5) ◽  
pp. 1024-1040 ◽  
Author(s):  
W. B. Cumming ◽  
R. M. Clowes ◽  
R. M. Ellis
Keyword(s):  
British Columbia ◽  
Seismic Refraction ◽  
Rocky Mountain ◽  
Seismic Structure ◽  
Metamorphic Belt ◽  
Crustal Layer ◽  
Arrival Times ◽  
Short Period ◽  
Mine Blasts ◽  
Lower Crustal

A partially reversed seismic refraction profile utilizing mine blasts as sources was recorded across southern British Columbia from Sparwood to the Highland Valley. The westwardly directed profile consisted of 32 short period seismograms covering 440 km, while the reversed line extended 330 km with 41 seismograms. From a starting model based on first arrival times and previous geological and geophysical data, a seismic structural section is developed using both synthetic seismograms and a program for ray tracing through inhomogeneous media.The refraction data indicate that the M-discontinuity dips to the east from an approximate depth of 30 km east of the Highland Valley to in excess of 40 km beneath the Purcell Anticlinorium. Undulations of about 165 km wavelength and several kilometres amplitude characterize the crust–mantle boundary. The Pn velocity is 7.8 km/s. Above the M-discontinuity, secondary arrivals are interpreted to be from a lower crustal layer of thickness near 12 km and velocity 6.9 km/s. The upper boundary of this layer also dips gently to the east.The seismic structure of the upper crust correlates closely with the regional geology as evidenced by traveltime and amplitude anomalies where the profile crosses the Rocky Mountain Trench and the Interior Plateau – Eastern Metamorphic Belt boundaries. The crustal P and S phases in the Interior Plateau yield a relatively low value of Poisson's ratio of 0.23. The detailed data close to the Highland Valley indicate significant velocity heterogeneity. For the Guichon Creek batholith, the inner Bethlehem phase is found to have a higher velocity than the surrounding Highland Valley phase.

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>

2D crust-upper mantle velocity structure along a seismic section in Nanling, South China

2020 ◽  
Author(s):  
Jia-ji xi ◽  
Guo-ming jiang ◽  
Gui-bin zhang ◽  
Xiao-long he
Keyword(s):  
Upper Mantle ◽  
Velocity Structure ◽  
Ore Deposits ◽  
Low Velocity ◽  
Seismic Section ◽  
Late Mesozoic ◽  
Velocity Anomaly ◽  
Metallogenic Belt ◽  
Velocity Anomalies ◽  
Mantle Velocity

<p>    There exists an important polymetallic ore belt in Nanling of the southeastern China. Previous studies suggest that the mineralization of Nanling is probably related to the bottom intrusion of magmatic rocks in the late Mesozoic. In this study, a natural seismic section was installed by using 81 portable stations with an interval of 5 km from July 2017 to August 2019, which runs across the Nanling belt in the south of Fujian and Jiangxi provinces. As a result, we have picked up 3,818 relative residual data from 215 teleseismic events with magnitude greater than 5.5. And we have applied the teleseismic full-waveform tomography and the teleseismic travel-time tomography to study the crust and the mantle velocity structure beneath the Nanling metallogenic belt, respectively. Our preliminary results show that: (1) a clear low-velocity anomaly exists in the crust beneath the Zhenghe-Dapu fault and its east side, which might be related to the rich ore deposits in Nanling; (2) some high-velocity anomalies in the uppermost mantle beneath the Wuyi metallogenic belt may be relevant to the igneous rock cooling and the lithospheric thickening; (3) there are obvious low-velocity anomalies at the upper mantle beneath the Wuyi and Nanling metallogenic belts, which are speculated to be hot materials from asthenosphere upwelling into the bottom of the lithosphere. Our results provide a new insight for investigating the deep structures and deep dynamic processes of Nanling tectonic belt.</p>

A comparison of the receiver structure beneath stations of the Canadian National Seismograph Network

1995 ◽  
Vol 32 (7) ◽  
pp. 938-951 ◽  
Author(s):  
John F. Cassidy
Keyword(s):  
Northwest Territories ◽  
Upper Mantle ◽  
Velocity Structure ◽  
Receiver Functions ◽  
Canadian Shield ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Appalachian Orogen ◽  
Seismograph Network ◽  
Velocity Zone

Three-component broadband data from the recently deployed Canadian National Seismograph Network provide a new opportunity to examine the structure of the crust and upper mantle beneath the Canadian landmass. Receiver function analysis is an ideal method to use with this data set, as it can provide constraints on the S-velocity structure beneath each station of this seismograph network. This analysis method is particularly useful in that it provides site-specific information (i.e., within 5–15 km of the station), low-velocity layers can be identified, and it is possible to examine structure to upper mantle depths. In this study, receiver functions were computed for each of the 19 stations that made up the seismograph network in June 1994. Five stations, sampling a variety of tectonic environments, including the Appalachian Orogen, the Canadian Shield, the Western Canadian Sedimentary Basin, and the Cascadia subduction zone, were chosen for detailed modelling. The results presented here are the first estimates of the S-velocity structure beneath these five stations. For those stations where comparisons can be made with seismic reflection and refraction results, there is excellent agreement. In eastern Canada, simple receiver functions and clear Moho Ps conversions at most stations indicate a relatively transparent crust and a Moho depth of 40–45 km. In northwestern Canada, Moho Ps phases indicate a crustal thickness of 33–38 km. Beneath Inuvik, Northwest Territories, the Moho is interpreted as two velocity steps separated in depth by 5 km, and an upper mantle low-velocity zone is near 47 km depth. In western Canada, the data indicate a mid-crustal low-velocity zone beneath Edmonton. The Moho of the subducting Juan de Fuca plate is interpreted at 52 km depth beneath southern Vancouver Island. Several stations exhibiting complex receiver functions warrant further study. They include stations at Schefferville, Quebec, in the Canadian Shield; Deer Lake, Newfoundland, on the boundary of the Grenville Province and the Appalachian Orogen; and Yellowknife, Northwest Territories, at the intersection of the Churchill and Slave provinces and the Western Plains.

Crustal thickness under the Gulf of St. Lawrence, northern Appalachians, from gravity and deep seismic data

1989 ◽  
Vol 26 (8) ◽  
pp. 1517-1532 ◽  
Author(s):  
F. Marillier ◽  
J. Verhoef
Keyword(s):  
Seismic Data ◽  
Bouguer Anomaly ◽  
Crustal Thickness ◽  
Moho Depth ◽  
Crustal Layer ◽  
Reflection Seismic ◽  
Middle Paleozoic ◽  
Lateral Extent ◽  
Well Data ◽  
Lower Crustal

We have determined crustal thickness in the Gulf of St. Lawrence, an area that corresponds to an offset of the main northern Appalachians units. A "complete" Bouguer anomaly was calculated from recent depth-to-basement compilations and sediment densities from well data. The Moho surface was obtained by inverting the Bouguer anomaly, assuming a single density contrast at depth, and using an average depth provided by deep reflection seismic data. The resulting crustal model shows a Moho depth of 42–44 km beneath the Grenville Craton, north of the Appalachian deformation front. South of this front, the depth to Moho displays a pronounced thinning of the crust beneath the Carboniferous Magdalen Basin. This is in striking contrast to the deep seismic data, which give a Moho depth of about 43 km. The modelling of the Bouguer anomaly in the Magdalen Basin, taking into account the seismic reflection and refraction data, reconciles these different results and suggests that a 43 km deep Moho beneath the basin is associated with a lower crustal layer about 13 km thick, with high velocity (7.35 km/s) and density (3.05 g/cm3). The Bouguer anomaly suggests that the lateral extent of this high-density layer is confined roughly to the Magdalen Basin. We suggest that this layer is due to mantle underplating of the crust as a result of the Carboniferous-age formation of the Magdalen Basin, and that it is not a feature related to the early to middle Paleozoic development of the Appalachian Orogen.

scholarly journals Shear Wave Velocity Structure Construction Using Ambient Seismic Noise Tomography (ANT) In Palu, Central Sulawesi

2020 ◽  
Vol 17 (2) ◽  
pp. 1
Author(s):  
F Ikhsan ◽  
Tedi Yudistira
Keyword(s):  
Seismic Noise ◽  
Velocity Structure ◽  
Ambient Seismic Noise ◽  
Surface Wave Tomography ◽  
Low Velocity ◽  
Velocity Anomaly ◽  
Geological Features ◽  
Wave Tomography ◽  
Central Sulawesi ◽  
Shear Wave Velocity Structure

Palu is located in Central Sulawesi, Indonesia, characterized by a complex geological setting due to the intersection of Indo-Australia Plate, Philippine Plate, and Eurasia Plate. These plates intersection causes one of the most active fault systems in Indonesia with 42 mm/year relative block motion, the Palu-Koro Fault. Palu-Koro Fault system is a left-lateral fault causing the 7.5 Mw Palu-Donggala Earthquake on 28 September 2018. Moreover, the thickness of the sediment layer in Palu ampli_ed the groud motion. So, it is critical to understand more about the Palu-Koro Fault and its geological system that can be very important for hazard study. In this study, Ambient Seismic Noise Tomography (ANT) was applied to understand the Palu-Koro Fault and its geological system. ANT uses the recorded ambient seismic noise events to obtain experimental Greens function by cross-correlating two seismic record data from two seismic station. Technically, ANT is similar to surface wave tomography which produces two dimensional velocity maps. To produce the two dimensional velocity maps, processing sequence consists of the preparation of single station data, stacking, cross-correlation, Frequency-Time Analysis (FTAN), and surface wave tomography. In this study, the vertical component seismic data was processed from 22 stations in Palu to extract the Rayleigh wave dispersion. The entire data was processed at 0,5 - 5 s period range. In addition, depth inversion step was also applied to get the geological features for the further interpretation. The results of this study are the interstation dispersion curves which indicate the group velocity varies between 0.2 and 2 Km/s, the group velocity maps and the shear wave velocity structure at 0,5 5 Km depth. These results show us the existence of the low-velocity anomaly in the northern part of Palu associated with the coastal sediment, the high-velocity anomaly in the west alongside the N-S direction fault, the low-velocity anomaly in the southern eastern part, and three main geological features in Palu based on the East West cross-section. These results lead to an insight that the heavy damage of the Palu-Donggala Earthquake in 2018 was caused by the thickness of the sediment in Palu.

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