Crustal anisotropy beneath northeastern Tibetan Plateau from the harmonic decomposition of receiver functions

SUMMARY A uniformly spaced linear transect through the northeastern Tibetan Plateau was constructed using 54 stations from ChinaArray Phase II. We used a set of colocated earthquakes to form receiver function beams that were then used to construct a 2-D image of main converting boundaries in our region and to investigate lateral changes in main impedance contrasts along the transect. The image revealed obvious mid-crustal low-velocity zones beneath the Qilian Orogen and the Alxa Block. We developed a new procedure that uses harmonically decomposed receiver functions to characterize seismic anisotropy, and that can determine both the orientations of symmetry axes and their type (fast or slow). We tested our technique on a number of synthetic models, and subsequently applied it to the data from the transect. We found that: (1) within the upper crust the orientations of slow symmetry axes are nearly orthogonal to the strike directions of faults, and thus anisotropy is likely caused by the shape preferred orientation of fluid-saturated cracks or fractures and (2) together with the low-velocity zones revealed from receiver functions stacks, anisotropic layers in the middle-to-lower crust could be explained by the crustal channel flow that was proposed for this region by previous studies. The shear within the boundary layers of crustal flow forms anisotropy with symmetry axes parallel to the flow direction.

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Distribution of the crustal low velocity zones beneath the central and northeastern Tibetan Plateau: Insights from joint analysis of receiver functions and surface wave dispersion observations

Physics of The Earth and Planetary Interiors ◽

10.1016/j.pepi.2018.12.003 ◽

2019 ◽

Vol 286 ◽

pp. 179-189 ◽

Cited By ~ 4

Author(s):

Mengkui Li ◽

Tengfei Wu ◽

Xu Lin ◽

Yujin Hua

Keyword(s):

Surface Wave ◽

Tibetan Plateau ◽

Wave Dispersion ◽

Receiver Functions ◽

Joint Analysis ◽

Low Velocity ◽

Surface Wave Dispersion ◽

Northeastern Tibetan Plateau

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Crust-Mantle Kinematics in and around the Hellenic Arc Elucidated by Local Shear Wave Splitting and Receiver Function Analyses

10.5194/egusphere-egu21-11501 ◽

2021 ◽

Author(s):

Derya Keleş ◽

Tuna Eken ◽

Judith M. Confal ◽

Tuncay Taymaz

Keyword(s):

Seismic Anisotropy ◽

Receiver Function ◽

Receiver Functions ◽

Data Sets ◽

S Wave ◽

Uppermost Mantle ◽

Hellenic Arc ◽

Wave Splitting ◽

Harmonic Decomposition ◽

Local Shear

The fundamental knowledge on seismic anisotropy inferred from various data sets can enhance our understanding of its vertical resolution that is critical for a better interpretation of past and current dynamics and resultant crustal and mantle kinematics in the Hellenic Trench and its hinterland. To investigate the nature of deformation zones, we perform both local S-wave splitting (SWS) measurements and receiver functions (RFs) analysis. Our preliminary findings from the harmonic decomposition technique performed on radial and tangential RFs suggest relatively more substantial anisotropic signals in the lower crust and uppermost mantle with respect to upper and middle crustal structure in the region. Apparent anisotropic orientations obtained from RFs harmonic decomposition process show several consistencies with those discovered from local SWS measurements at selected stations. The actual anisotropic orientation for the structures, however, requires further modelling of the receiver functions obtained.

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

Geophysics ◽

10.1190/geo2016-0471.1 ◽

2017 ◽

Vol 82 (4) ◽

pp. KS41-KS55 ◽

Cited By ~ 9

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.

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Lithospheric and sublithospheric deformation under the Borborema Province of northeastern Brazil from receiver function harmonic stripping

Solid Earth ◽

10.5194/se-10-893-2019 ◽

2019 ◽

Vol 10 (3) ◽

pp. 893-905 ◽

Cited By ~ 3

Author(s):

Gaelle Lamarque ◽

Jordi Julià

Keyword(s):

Lithospheric Mantle ◽

Seismic Anisotropy ◽

Receiver Function ◽

Seismic Station ◽

Atlantic Coast ◽

Shear Zones ◽

Receiver Functions ◽

Azimuthal Anisotropy ◽

Northeastern Brazil ◽

Borborema Province

Abstract. The depth-dependent anisotropic structure of the lithosphere under the Borborema Province in northeast Brazil has been investigated via harmonic stripping of receiver functions developed at 39 stations in the region. This method retrieves the first (k=1) and second (k=2) degree harmonics of a receiver function dataset, which characterize seismic anisotropy beneath a seismic station. Anisotropic fabrics are in turn directly related to the deformation of the lithosphere from past and current tectonic processes. Our results reveal the presence of anisotropy within the crust and the lithospheric mantle throughout the entire province. Most stations in the continental interior report consistent anisotropic orientations in the crust and lithospheric mantle, suggesting a dominant northeast–southwest pervasive deformation along lithospheric-scale shear zones developed during the Brasiliano–Pan-African orogeny. Several stations aligned along a northeast–southwest trend located above the (now aborted) Mesozoic Cariri–Potiguar rift display large uncertainties for the fast-axis direction. This non-azimuthal anisotropy may be related to a complex anisotropic fabric resulting from a combination of deformation along the ancient collision between Precambrian blocks, Mesozoic extension and thermomechanical erosion dragging by sublithospheric flow. Finally, several stations along the Atlantic coast reveal depth-dependent anisotropic orientations roughly (sub)perpendicular to the margin. These results suggest a more recent overprint, probably related to the presence of frozen anisotropy in the lithosphere due to stretching and rifting during the opening of the South Atlantic.

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Seismic anisotropy of the Northeastern Tibetan Plateau from shear wave splitting analysis

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2011.01.026 ◽

2011 ◽

Vol 304 (1-2) ◽

pp. 147-157 ◽

Cited By ~ 49

Author(s):

Yonghua Li ◽

Qingju Wu ◽

Fengxue Zhang ◽

Qiangqiang Feng ◽

Ruiqing Zhang

Keyword(s):

Tibetan Plateau ◽

Shear Wave ◽

Seismic Anisotropy ◽

Shear Wave Splitting ◽

Northeastern Tibetan Plateau ◽

Wave Splitting

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Crustal and upper mantle structure beneath the northeastern Tibetan Plateau from joint analysis of receiver functions and Rayleigh wave dispersions

Geophysical Journal International ◽

10.1093/gji/ggv469 ◽

2015 ◽

Vol 204 (1) ◽

pp. 583-590 ◽

Cited By ~ 14

Author(s):

Dan Zheng ◽

Hongyi Li ◽

Yang Shen ◽

Jing Tan ◽

Longbin Ouyang ◽

...

Keyword(s):

Tibetan Plateau ◽

Rayleigh Wave ◽

Upper Mantle ◽

Receiver Functions ◽

Joint Analysis ◽

Mantle Structure ◽

Northeastern Tibetan Plateau ◽

Upper Mantle Structure

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Crustal seismic anisotropy of the Northeastern Tibetan Plateau and the adjacent areas from shear-wave splitting measurements

Geophysical Journal International ◽

10.1093/gji/ggz489 ◽

2019 ◽

Vol 220 (3) ◽

pp. 1491-1503 ◽

Cited By ~ 2

Author(s):

Nan Hu ◽

Yonghua Li ◽

Liangxin Xu

Keyword(s):

Tibetan Plateau ◽

Shear Wave ◽

Seismic Anisotropy ◽

Active Faults ◽

Shear Wave Splitting ◽

Crustal Anisotropy ◽

Western Qinling ◽

Northeastern Tibetan Plateau ◽

Wave Splitting ◽

Mantle Anisotropy

SUMMARY The Northeastern Tibetan Plateau has thickened crust and is still undergoing strong active crustal shortening and deformation. Crustal anisotropy can provide clues to how the crust is currently deforming and evolving. We use an automatic method to analyse the upper-crustal anisotropy of the NE Tibetan Plateau and the adjacent region using local earthquakes recorded at 39 permanent seismic stations during the period 2009–2018. The majority of the dominant fast directions are consistent with the maximum horizontal stress orientation, suggesting that the upper-crustal anisotropy is mainly controlled by the regional or local stress field. Several fault-parallel measurements are observed for stations on or near to the main faults. These fault-parallel fast directions indicate that the main mechanism of upper-crustal anisotropy is associated with shear fabric caused by deformation. Fast directions neither fault-parallel nor stress-parallel are observed at stations lying several kilometres away from fault zones, likely reflecting the combined influence of stress-aligned microcracks and active faults. A comparison between our upper-crustal anisotropy parameters and those inferred from previous anisotropy studies that used receiver function and teleseismic shear wave splitting measurements suggests that the crust has the same deformation mechanisms as mantle anisotropy in the southern part of the Western Qinling Fault, whereas the upper-crustal anisotropic mechanism is different from those of lower crust and mantle anisotropy in the northern part of the Western Qinling Fault. These observations imply that the Western Qinling Fault may be an important boundary fault.

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Crustal and Upper Mantle Deformation Beneath Northwestern part of North Anatolian Fault Zone from Harmonic Decomposition of Receiver Functions

10.5194/egusphere-egu2020-527 ◽

2020 ◽

Author(s):

Derya Keleş ◽

Tuna Eken ◽

Andrea Licciardi ◽

Tuncay Taymaz

Keyword(s):

Fault Zone ◽

Seismic Anisotropy ◽

Receiver Functions ◽

North Anatolian Fault ◽

Northwestern Part ◽

North Anatolian Fault Zone ◽

The North ◽

Harmonic Decomposition ◽

Harmonic Components ◽

Depth Ranges

A proper understanding of crustal seismic anisotropy beneath the tectonically complex northwestern part of the North Anatolian Fault Zone (NAFZ) will shed light into the depth extent of deformation zones. To investigate the seismic anisotropy in the crustal part of the NAFZ, we applied the harmonic decomposition technique on receiver functions from teleseismic earthquakes (with epicentral distances between 30&#176; and 90&#176;) recorded at the Dense Array for North Anatolia (DANA) seismic network. Harmonic coefficients, k=0, k=1, and k=2 were obtained by applying the harmonic decomposition method to the depth migrated receiver functions. Results from k=0 harmonics suggest south to north (e.g. from Sakarya Zone to Istanbul Zone) increase in crustal thickness. The depth variations of energy associated with k=1 and k=2 harmonic components imply significant lateral variation. For instance, the energy calculated for k=1 harmonics in the north (Istanbul Zone) indicates that seismic anisotropy is likely concentrated in the upper crust (within the first 15 km). However, further south, the signature of anisotropy in Armutlu-Almacik and Sakarya Zones becomes more significant in close proximity to the fault zone and dominates at greater (15-30 km and 30-60 km). Furthermore, k=2 harmonic energy maps exhibit relatively high intensities nearby the fault for all depth ranges.

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

10.5194/egusphere-egu2020-962 ◽

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

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 Ps phases from different back-azimuths.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.Keywords: Anisotropy, Receiver function, harmonic decomposition, Northern Iran.

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