scholarly journals Crustal Anisotropy Beneath the Trans-North China Orogen and its Adjacent Areas From Receiver Functions

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaoming Xu ◽  
Zhifeng Ding ◽  
Li Li ◽  
Fenglin Niu
Keyword(s):  
Crustal Deformation ◽  
North China ◽  
Receiver Function ◽  
Bouguer Anomaly ◽  
Receiver Functions ◽  
Seismic Hazards ◽  
Moho Depth ◽  
Tectonic Deformation ◽  
Bohai Bay ◽  
Crustal Anisotropy

As an important segment of the North China Craton, the Trans-North China Orogen (TNCO) has experienced strong tectonic deformation and magmatic activities since the Cenozoic and is characterized by significant seismicity. To understand the mechanism of the crustal deformation and seismic hazards, we determined the crustal thickness (H), Vp/Vs ratio (κ) and crustal anisotropy (the fast polarization direction φ and splitting time τ) beneath the TNCO and its adjacent areas by analyzing receiver function data recorded by a dense seismic array. The (H, κ) and (φ, τ) at a total of 309 stations were measured, respectively. The Moho depth varies from ∼30 km beneath the western margin of the Bohai bay basin to the maximum value of ∼48 km beneath the northern Lüliang Mountain, which shows the positive and negative correlations with the elevation and the Bouguer anomaly. The average φ is roughly parallel to the strikes of the faults, grabens and Mountains in this study area, whereas a rotating distribution is shown around the Datong-Hannuoba volcanic regions. Based on the φ measured from the Moho Ps and SKS/SKKS phases, we propose that the crustal deformation and seismic hazards beneath the TNCO could be due to the counterclockwise rotation of the Ordos block driven by the far-field effects of the India-Eurasian collision.

Crustal Anisotropy beneath Northern Iran calculated by harmonic decomposition of Receiver Functions.

2020 ◽  
Author(s):  
Mohsen Azqandi ◽  
Mohammad Reza Abbassi ◽  
Meysam Mahmoodabadi ◽  
Ahmad Sadidkhouy
Keyword(s):  
Receiver Function ◽  
Receiver Functions ◽  
Upper Crust ◽  
Northern Iran ◽  
Crustal Anisotropy ◽  
Principal Stress Direction ◽  
South Central ◽  
Stress Direction ◽  
Harmonic Decomposition ◽  
Time Variations

<p>This study concerns crustal anisotropy at 16 permanent seismic stations to investigate preferentially aligned cracks or structures and their relation to the stress-state in the South Central Alborz (northern Iran). We consider plunging anisotropy and dipping interfaces of multiple layers using harmonic functions to correct the arrival time variations of <em>Ps</em> phases from different back-azimuths.</p><p>The dominant fast orientation of integrated crustal anisotropy strikes NE, almost parallel to the stress direction in the upper crust. The magnitude of crustal anisotropy is found to be in range of 0.1 s to 0.5 s. In some stations, intracrustal interface is observed, for which we analyzed harmonic decomposition of receiver functions to consider anisotropy in the upper crust. Upper crustal anisotropy strikes NE, close to the principal stress direction, indicating that stress in the upper crust plays a major role in producing anisotropy and deformation. In a few stations, crustal anisotropy display different directions rather than NE, which maybe controlled by cracks and fractures of dominant faults.</p><p>Keywords: Anisotropy, Receiver function, harmonic decomposition, Northern Iran.</p>

The Tibet lithosphere is not all hot

2020 ◽  
Author(s):  
Bing Xia ◽  
Irina Artemieva ◽  
Hans Thybo
Keyword(s):  
Heat Flow ◽  
Large Scale ◽  
North China ◽  
Receiver Function ◽  
Thermal Structure ◽  
Surface Heat ◽  
Moho Depth ◽  
Good Match ◽  
Isostatic Compensation ◽  
Surface Heat Flow

<p>We calculated the thermal lithosphere structure of Tibet and adjacent regions based on the new thermal isostasy method. Moho depth is constrained by the published receiver function results. The calculated surface heat flow in the surrounded Tarim, North China, and Yangtze cratons have a good match with the real measurements of surface heat flow. We recognize the northern Tibet anomaly where has a relatively thin lithosphere with a thermal thickness of <80 km and surface heat flow of >80 - 100 mW/m 2 may cause by the removal of lithospheric mantle and upwelling of asthenosphere. In Lhasa Block, the cold and thick lithosphere (>200 km) with a surface heat flow of 40 - 50 mW/m 2. In the east Tibet, the heterogeneous thermal lithosphere does not follow the widely spread large scale strike-slip faults and suggested that the faults do not cut down to the lithosphere. The surrounding cratons have different thermal lithosphere features. The Tarim and Yangtze cratons show typical cold and thick lithosphere with a lithosphere of >200km and surface heat flow of <50 mW/m2. The western North China Craton has an intermated lithosphere with a thickness of 120-200km and surface heat flow of 45-60 mW/m2. Our result suggested that high and flat Tibet has different isostatic compensation in different blocks. The heterogeneous lithosphere thermal structure of the Tibet suggested that the uplife force drive are difference in Tibet.</p><div> <div> </div> </div>

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.

scholarly journals Variations of crustal thickness and average Vp/Vs ratio beneath the Shanxi Rift, North China, from receiver functions

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Yifang Chen ◽  
Jiuhui Chen ◽  
ShunCheng Li ◽  
Zhanyang Yu ◽  
Xuzhou Liu ◽  
...  
Keyword(s):  
North China ◽  
Tectonic Setting ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
Indian Plate ◽  
Moho Depth ◽  
Significant Heterogeneity ◽  
Earthquake Activity ◽  
Strong Earthquakes ◽  
Shanxi Rift

AbstractThe Shanxi Rift located in the central part of the North China Craton (NCC) as a boundary between the Ordos block and the Huabei basin. The Shanxi graben system is a Cenozoic rift and originated from back-arc spreading related to westward subduction of the western Pacific and far field effects caused by northward subduction of the Indian plate. It has also had strong earthquake activity in China since the Quaternary. To investigate the tectonic evolution and tectonic setting of strong earthquakes in the Shanxi Rift, we apply the receiver function $$H$$ H -$$\kappa$$ κ stacking method to determine the crustal thickness and average Vp/Vs ratio in the area. The results show that the thickness of the crust increases from approximately 30 km in the Huabei basin to approximately 47 km in the Yinshan Mountains with a close correlation between the Moho depth and topography. The Yuncheng, Linfen and Taiyuan grabens have varying degrees of crustal thinning. The crustal average Vp/Vs ratio in the Shanxi Rift has significant heterogeneity; the high Vp/Vs ratio (~ 1.85) are found in the Datong and Yuncheng grabens, and Vp/Vs ratio of the Taiyuan and Linfen grabens is approximately 1.75 which close to the global average value ~ 1.782. Combining the observations in this study with previous research, we suggest that the grabens in the Shanxi Rift experienced extensional deformation from south to north and that the possibility of strong earthquakes in the central part of the Shanxi seismic belt is greater than that on the northern and southern sides.

Moho Depth Variations From Receiver Function Imaging in the Northeastern North China Craton and Its Tectonic Implications

2019 ◽  
Vol 124 (2) ◽  
pp. 1852-1870 ◽  
Author(s):  
Ping Zhang ◽  
Huajian Yao ◽  
Ling Chen ◽  
Lihua Fang ◽  
Yan Wu ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Receiver Function ◽  
Moho Depth ◽  
Tectonic Implications

Distribution of crustal azimuthalanisotropy beneath the North China Craton: Insights from analysis of receiver functions

2020 ◽  
Author(s):  
Tuo Zheng ◽  
S. Stephen Gao ◽  
Zhifeng Ding ◽  
Xiaoping Fan
Keyword(s):  
Fault Zone ◽  
North China Craton ◽  
North China ◽  
Receiver Functions ◽  
Azimuthal Anisotropy ◽  
Crustal Anisotropy ◽  
Near Surface ◽  
The North ◽  
Upper Mantle Anisotropy ◽  
Lithospheric Extension

<p>To characterize crustal anisotropy beneath the North China Craton (NCC), we apply a recently developed deconvolution approach to effectively remove near-surface reverberations in the receiver functions recorded at 200 broadband seismic stations and subsequently determine the fast orientation and the magnitude of crustal azimuthal anisotropy by fitting the sinusoidal moveout of the P to S converted phases from the Moho and intracrustal discontinuities. The magnitude of crustal anisotropy is found to range from 0.06 s to 0.54 s, with an average of 0.25 ± 0.08 s. Fault-parallel anisotropy in the seismically active Zhangjiakou-Penglai Fault Zone is significant and could be related to fluid-filled fractures. Historical strong earthquakes mainly occurred in the fault zone segments with significant crustal anisotropy, suggesting that the measured crustal anisotropy is closely related to the degree of crustal deformation. The observed spatial distribution of crustal anisotropy suggests that the northwestern terminus of the fault zone probably ends at about 114°E. Also observed is a sharp contrast in the fast orientations between the western and eastern Yanshan Uplifts separated by the North-South Gravity Lineament. The NW-SE trending anisotropy in the western Yanshan Uplift is attributable to “fossil” crustal anisotropy due to lithospheric extension of the NCC, while extensional fluid-saturated microcracks induced by regional compressive stress are responsible for the observed ENE-WSW trending anisotropy in the eastern Yanshan Uplift. Comparison of crustal anisotropy measurements and previously determined upper mantle anisotropy implies that the degree of crust-mantle coupling in the NCC varies spatially.</p>

The mantle flow below the Alps from isolated mantle anisotropy based on differential Ps – XKS Splitting

2020 ◽  
Author(s):  
Frederik Link ◽  
Georg Rümpker
Keyword(s):  
Receiver Function ◽  
Function Analysis ◽  
Receiver Functions ◽  
Model Parameters ◽  
Mantle Flow ◽  
European Alps ◽  
Crustal Anisotropy ◽  
Axis Orientation ◽  
The Alps ◽  
Mantle Anisotropy

<p>SKS-splitting measurements in the European Alps show an anisotropic fast axes parallel/subparallel relative to the mountain-belt. This indicates a mantle flow with a rotational component according to the orogeny under the assumption that the fast axes directly reflect the flow direction. This might be misleading due to a possible crustal contribution of anisotropy. Therefore, we isolate the crustal anisotropy using an improved receiver function method that accounts for anisotropic and structural properties.</p><p>The analysis for the crustal anisotropy is based on the stacking method proposed by Kaviani & Rümpker (2015). We modify their approach by introducing a time-selective splitting analysis of the crustal Ps- and PpPs-phases. The stacking is performed to the phases after correction of the anisotropic effect according to the model parameters H, the crustal thickness,  κ, the P-to S-wave velocity ratio, a, the percentage of anisotropy and φ, the fast axis orientation.</p><p>The Alps show a considerable Moho-topography due to its mountain root and its complex tectonic history. This can significantly deflect the crustal phases introducing a dominating appearance in the receiver functions. We therefore analyse for a dipping interface (not accounting for anisotropy) and then use an improved model in our analysis to infer the anisotropic properties of the crust.</p><p>Knowing the crustal anisotropic contribution we correct for this effect on the XKS-waveforms to isolate the anisotropy of the mantle. The remaining splitting shows an improved approximation of the flow patterns in the asthenosphere, while complexities might still imply an effect of the lithospheric mantle.</p><p>We apply our approach to stations of the AlpArray network resulting in a detailed distribution of the crustal anisotropy in the European Alps and show first results for the isolated mantle anisotropy from the corrected XKS-waveforms and the crustal anisotropy from the receiver-function analysis.</p>

scholarly journals Determination of Moho depth and dip beneath MEDNET station AQU by analysis of broadband receiver functions

1994 ◽  
Vol 37 (5) ◽  
Author(s):  
A. Megna ◽  
A. Morelli
Keyword(s):  
Receiver Function ◽  
Receiver Functions ◽  
P Wave ◽  
Function Technique ◽  
Moho Depth ◽  
The North ◽  
Refraction Seismics ◽  
Deep Crustal Structure ◽  
First Motion ◽  
Converted Phases

We applied the receiver function technique to retrieve Moho depth and dip beneath the MEDNET very-broadband seismographic station at l'Aquila, in the Central Apennines. Broadband data available for teleseismic events recorded in two years of operation were sufficient to delineate a rather simple structure consisting of a 32-34 km thick crust, in agreement with previous studies based on refraction seismics. In addition, the data show relatively large variation in the amplitude of the converted P-to-S phase generated at the crust-mantle interface as a function of azimuth. These variations are consistent with synthetic receiver functions generated for an incident P wave interacting with an interface dipping ~ 8° to the north. Observations of amplitude ratios of converted phases, polarity of first-motion in the SH directíon, and relative travel time delay are all consistent with a model assuming a Moho discontinuity about 33 km deep gently dipping towards north. The receiver function technique has shown to be an efficient tool for investigating deep crustal structure, giving localized but reliable information.

Crustal structure of La Palma and Tenerife (Canary Islands) from receiver function analysis.

2021 ◽  
Author(s):  
Víctor Ortega ◽  
Luca D'Auria ◽  
Iván Cabrera-Pérez ◽  
José Barrancos ◽  
Germán D. Padilla ◽  
...  
Keyword(s):  
Canary Islands ◽  
Crustal Structure ◽  
Arrival Time ◽  
Receiver Function ◽  
Function Analysis ◽  
Receiver Functions ◽  
Moho Depth ◽  
La Palma ◽  
Receiver Function Analysis ◽  
Volcanic Islands

<p>The receiver function analysis (RF) is a commonly used and well-established method to investigate crustal and mantle structures, removing the source, ray-path and instrument signatures. RF gives the unique signature of sharp seismic discontinuities and information about P and S wave velocities beneath a seismic station. In particular, using the direct P wave as a reference arrival time, and the relative arrival time of P-to-S (Ps) conversions and multiple reflections allow constraining the principal crustal structures and studying the effects of dipping interfaces and crustal layering.</p><p>We have applied RF analysis to the active volcanic islands of Tenerife and La Palma (Canary Islands). In recent years, both islands have increased their seismic activity and showed variation in geochemical parameters attributed to a magmatic-hydrothermal activity. Previous studies evidenced in La Palma and Tenerife a seismic Moho depth at 14 km and 12 and 15 km, respectively, but it is not clear because there are some others discontinuities under the stations (Lodge et al., 2012). Other RF studies indicated a depth of seismic Moho discontinuity between 16 and 30 km beneath the eastern islands to 11-15 km under the western isles, observing a thinning of the crust towards the west (Martinez-Arévalo et al., 2013). </p><p>We processed 313 teleseisms recorded by 17 stations for Tenerife and 252 teleseisms recorded by six stations for La Palma. Since the receiver functions display a significant complexity, as expected in oceanic volcanic islands, we applied a transdimensional inversion approach to image the 1D velocity structure beneath each station. We observe at least three discontinuities related with the oceanic crust and the overlying volcanic rocks layer. We compare the retrieved crustal structure with the seismicity recorded in recent years, showing how earthquakes have a radically different origin on these two islands. While in Tenerife they seem to be related to the dynamics of a shallow hydrothermal system, in La Palma they are related to magmatic intrusions in the upper mantle beneath the island.</p><p><strong>References</strong></p><p>Lodge, A., Nippress, S. E. J., Rietbrock, A., García-Yeguas, A., & Ibáñez, J. M. (2012). Evidence for magmatic underplating and partial melt beneath the Canary Islands derived using teleseismic receiver functions. Physics of the Earth and Planetary Interiors, 212, 44-54.</p><p>Martinez-Arevalo, C., de Lis Mancilla, F., Helffrich, G., & Garcia, A. (2013). Seismic evidence of a regional sublithospheric low velocity layer beneath the Canary Islands. Tectonophysics, 608, 586-599.</p>

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