Direction Of Anisotropy Research Articles

Drag of heavy quarks in an anisotropic QCD medium beyond the static limit

Heavy quark dynamics in an anisotropic QCD medium have been analyzed within the Fokker-Planck approach. Heavy quark drag force and the momentum diffusion tensor have been decomposed by employing a general tensor basis for an anisotropic medium. Depending upon the relative orientation of the direction of the momentum anisotropy of the medium and heavy quark motion, two drag and four diffusion coefficients have been estimated in the anisotropic QCD medium. The relative significance of different components of drag and momentum diffusion coefficients has been explored. The dependence of the angle between the anisotropic vector and heavy quark motion to the drag and diffusion coefficients has also been studied. Furthermore, the energy loss of heavy quarks due to the elastic collisional process in an anisotropic medium has been studied. It is seen that the anisotropic contributions to heavy quark transport coefficients and its collisional energy loss have a strong dependence on the direction and strength of momentum anisotropy in the QCD medium.

Wave-like motion and secondary currents in arrays of emergent cylinders induced by large scale eddying motion

Free-surface flows with riparian corridors are known to develop large eddies resulting from the instability associated to the inflectional profile of the longitudinal velocity in the spanwise direction. They periodically generate strong momentum exchanges inside the vegetation corridor, triggering a wave-like motion, detectable as free-surface oscillations and out-of-phase velocity components. We propose a characterization of the flow inside the vegetation corridor, focusing on the wave-like motion and its influence on secondary currents. We conditionally sample the fluid motion to highlight the structure of the phase-averaged coherent structure. Quadrant analysis shows that there is a strong variation of Reynolds stress anisotropy in the spanwise direction, which is one of the key generation mechanisms of secondary currents. Spectrograms of longitudinal and lateral velocity fluctuations reveal that the oscillatory motion is imposed on the whole of the vegetated layer, because of continuity. The analysis of the phase-averaged 2D vertical-longitudinal flow reveals that there is a complex 3D pattern of mass fluxes associated to each large eddy. In particular there is an anti-symmetric net mass imbalance which, by mass conservation, generates a mass flux directed outwards, to the main channel, near the bottom of the channel. The Eulerian expression of this motion is obtained as the spatial average of the flow over the length of the large eddy, resulting in the pattern of the secondary current in the vertical-spanwise plane. It is shown that the secondary motion is a necessary feature of free-surface turbulent flows that develop large-scale inflectional instabilities.

Pore scale study of the permeability anisotropy of sands containing grain-coating and pore-filling hydrates

Gas hydrates are ice-like crystalline solids that form in marine sediments or permafrost layers. The inhomogeneous distribution of the hydrate will form different hydrate patterns such as grain-coating and pore-filling hydrate, which will further cause permeability anisotropy in different directions. In this study, X-ray computed tomography (CT) test and image analysis by AVIZO were used to investigate the permeability anisotropy of hydrate-bearing sands. The image analysis revealed the following results: (1) For both hydrate patterns, the hydrate formation induced the largest permeability decrease in the y direction and the smallest one in the z direction. (2) The degree of anisotropy of pores after the pore-filling hydrate formation is larger than that after the grain-coating hydrate formation. A decrease in the pore anisotropy ratio will induce a significant increase in permeability anisotropy. (3) Although the increase in the pore shape factor ratio after the pore-filling hydrate formation is smaller than that after the grain-coating hydrate formation, the permeability anisotropy increase is much larger. (4) The tortuosity increase is the largest in the y direction and the smallest in the z direction, which is consistent with the permeability variations. Pore-filling hydrate formation induces a larger variation in the tortuosity ratio, which causes a higher permeability anisotropy.

Frictional Properties of a Novel Artificial Snakeskin for Soft Robotics

Although snake-like robots are only rarely used in real applications, numerous designs have been proposed by different researchers. In addition to the capability of grasping objects by bending their body around them, snakes travel in various environments by using different gaits. To move forward, they need a skin which provides friction anisotropy to the ground. The designs of snake-like robots vary in their actuation mechanism as well as in the design of their artificial skin. In this work, we present a novel design of an artificial snakeskin. The design is related to an application in soft robotics, but is not restricted to this type of robot. Since soft robots are flexible and can stretch, our artificial skin is also able to. It is inspired by the belly of snakes and provides friction anisotropy in forward-reverse direction. To achieve this, we embed scales with a specific angle of attack into a flexible base body. In the experimental investigation of the artificial snakeskin, we determine the friction anisotropy for two base body materials with different stiffness and for three angles of attack. Although the development of the artificial skin is at an early stage, the results of the experimental investigation are promising. The dynamic behavior of the artificial snakeskin indicates that a flexible base material reduces friction in forward direction and increases friction in reverse direction, thus enhancing friction anisotropy. Furthermore, the results obtained give important information for further design improvements in future.Presentation of a modular and stretchable artificial snakeskin Systematic investigation of the frictional properties when changing the angle of attack of the scales and the softness of the base material the scales are embedded in A soft base material increases friction anisotropy and reduces inaccuracies of hand manufacturing Demonstration of a soft robotic actuator which uses the artificial snakeskin for crawling.

Microstructure Characterization of High Explosives by Wavelet Transform

The key macro properties of high explosives including sensitivity to shock, the possibility of initiation, and the subsequent chemical reaction are known to be controlled by processes occurring at their microstructure level. However, there is a lack of an easy, effective, and accurate method to quantify the microstructure, termed as fabric, of high explosives despite an abundance of evidence regarding its importance. This study proposes a rotational Haar wavelet transform (RHWT) method to characterize the fabric of high explosives from two-dimensional images, yielding key fabric parameters including rose diagram, fabric direction, and degree of fabric anisotropy. The fabric tensor commonly used in numerical simulations and constitutive models can also be determined by RHWT. The RHWT was implemented on microscopic images of six high explosives captured by various imaging techniques including scanning electrical microscopy, polarized light microscopy, and micro X-ray computed tomography. Despite these variables, the proposed RHWT successfully identifies fabric in these images, demonstrating robustness and validity of RHWT.

Upper mantle anisotropy in the southeastern margin of the Tibetan plateau and geodynamic implications

Continued northeastward compression owing to the colliding Indian subcontinent has led to pronounced surface uplift and significant crustal and mantle deformation in the Sichuan–Yunnan region along the southeastern margin of the Tibetan Plateau. Seismic anisotropy is an effective physical property for characterising crustal and upper-mantle deformation, as these deformation mechanisms can be investigated by analysing the splitting of compressional-to-shear-wave (P-to-S) converted phases (XKS, which includes the SKS, SKKS, PKS and PKKS phases) at the core–mantle boundary. However, we cannot distinguish any crustal and/or mantle anisotropy variations owing to the relatively low vertical resolution of XKS splitting. Here we compute the P-wave receiver functions from teleseismic events recorded at 90 permanent and 350 mobile broadband seismic stations that were established by the ChinArray project in the Sichuan–Yunnan region and analyse the P-to-S converted phases at the Moho interface (Pms) to measure the crustal anisotropic parameters. The Pms splitting results are then regarded as the crustal anisotropic parameters, and the anisotropic parameters in the upper mantle beneath 347 stations are extracted from the XKS splitting parameters by removing this crustal anisotropy. The results indicate that an approximately E–W anisotropic fast-wave polarisation direction (FPD) exists in the upper mantle beneath the southeastern margin of the Tibetan Plateau, and that the splitting times range from 0.06 to 1.39 s, with an average splitting time of 0.93 s. The approximately E–W anisotropic FPD in the upper mantle is mainly due to asthenospheric flow induced by the eastward subduction of the Indian Plate beneath Myanmar. The small splitting times within the southern Sichuan–Yunnan diamond-shaped block (SYDSB) may be attributed to vertical growth of the lithosphere induced by mantle-plume-related magmatic uplift.

The effect of frequency bandwidth on DSI anisotropy evaluation

Anisotropy evaluation in carbonate rocks plays a pivotal role in their reservoir characterization and modeling. This study demonstrates the benefits of advanced interpretation using the Dipole Shear Sonic Imager (DSI) log data for anisotropy evaluations of porous media. Splitting the shear wave into fast and slow components, with different polarizations and velocities, provides useful indications of formation anisotropy. Fast shear waves travel faster in directions parallel to layering and fracturing while slow shear waves travel more slowly perpendicular to layering and fracture networks. Quantifying the difference between fast and slow shear velocities provides a measure of acoustic anisotropy in the medium penetrated.The purpose of the research is to evaluate the effects of frequency bandwidth on the depth of the wave propagation rates and slowness values for anisotropy analysis, thus four bandwidth frequencies: 1–2 kHz, 2–4 kHz, 4–6 kHz, and 1–5 kHz are selected and examined in a vertical drilled well in the gas reservoirs of Upper Dalan Member, and Kangan Formations in the South Pars Gas-Condensate Field.The frequency filtering, semblance analysis, and slowness picking are done on waveforms for frequency-slowness dispersion analysis and slowness correction. The dispersion correction for bandwidth 4–6 kHz isn't performed completely in good hole condition intervals, because high- frequencies around 6 kHz are absorption due to the intrinsic attenuation of the rocks. Therefore, the considered bandwidth is decreased to 4–5.5 kHz. In the following, Alford rotation, align waveforms, and calculation and evaluation of derived fast and slow components are done for deriving the azimuth of the fast shear wave for each bandwidth of waveforms. The dominant trend of the azimuth of anisotropy is that aligned with the azimuth of the fast shear wave.The azimuth of the fast shear wave as azimuth of anisotropy and its corresponding intervals are compared with the results of image log data for the same well interval. This made it possible to reject or confirm the findings of the DSI acoustic anisotropy analysis for each bandwidth considered.In the low bandwidth frequency (1–2 kHz), the differences in slowness, energy, travel time, and penetration depth are more extreme than those recorded by the other bandwidths considered. The azimuth of anisotropy is NW-SE with a slight E-W trend. However, the azimuth of anisotropy was found to be contrary to the image log interpretation where the dominant trend is NE-SW.The dominant trend of the azimuth of anisotropy for bandwidth 2–4 kHz is NE-SW with a slight E-W trend. The anisotropy directions and zones are consistent with those identified from the wellbore image log results. Moreover, the penetration depth is meaningful and far away from the borehole drilling and mud effects. These results suggest that the bandwidth (2–4 kHz) is best suited for acoustic anisotropy analysis of wellbore sections using Dipole Shear Sonic Imager (DSI) recorded data in this well.The trends of the azimuth of anisotropy for bandwidth 4–5.5 kHz are NE-SW, and NW-SE, with expanded tolerance azimuth of anisotropy. The results that have been achieved in a small penetration depth and close to the borehole wall are affected by signal absorption and attenuation in flushed and transition areas. This leads to some errors and inconsistencies with the image log interpretation.The trends of the azimuth of anisotropy for bandwidth 1–5 kHz are NE-SW, NW-SE, and E-W. The outcomes are the consequence of the variety of directions and zones associated with this wider bandwidth, together with the penetration depths of the waveforms in the diverse zones considered. However, the azimuth of anisotropy is inconsistent with the image log interpretation.

Relationship between the mechanical properties and structure of a suspension plasma-sprayed thermal barrier coating with columnar microstructure

To investigate the mechanical properties of a suspension plasma-sprayed (SPS) thermal barrier coating (TBC) with a unique cauliflower-like columnar structure, shear and cantilever bending tests were conducted on its single submillimeter-sized columns. In the shear test, the fracture of the single columns occurred at the porous layer near the top-coating/bond-coating interface. Compared with conventional atmospheric plasma-sprayed (APS) TBCs having a lamellar microstructure, the cantilever bending test revealed a significantly low Young's modulus along the out-of-plane direction and strong anisotropy in the elastic modulus of the SPS TBC. The shear strength and out-of-plane Young's modulus of the single columns increased due to the sintering resulting from thermal aging; however, the increasing ratio of the shear strength was higher than that of the Young's modulus. Both experimental and finite element analysis results indicated that the mechanical properties of the SPS TBC, as well as their variation with thermal aging, are dominated by those of the porous layer within the single column undergoing sintering. Moreover, the experimental results suggested that SPS TBCs having a cauliflower-like columnar microstructure have superior durability to thermal cycles compared with APS TBCs.

Possible applications of Mo2C in the orthorhombic and hexagonal phases explored via ab-initio investigations of elastic, bonding, optoelectronic and thermophysical properties

Binary carbides demonstrate an attractive set of physical properties that are suitable for numerous and diverse applications. In the present study, we have explored the structural properties, electronic structures, elastic constants, acoustic behaviors, phonon dispersions, optical properties, and various thermophysical properties of binary orthorhombic and hexagonal Mo2C (O-MC and H-MC, respectively) compounds in detail via first-principles calculations using the density functional theory (DFT). The calculated ground state lattice parameters in both the symmetries are in excellent agreement with available experimental results. The calculated electronic band structure, density of states, and optical properties of Mo2C in both structures reveal metallic features. The orthorhombic crystal shows a higher level of mechanical and thermal anisotropy compared to that in the hexagonal phase. The elastic constants and phonon dispersion calculations show that, in both structures, Mo2C is mechanically and dynamically stable. A comprehensive mechanical and thermophysical study shows that both phases possess high structural stability, reasonably good machinability, ductile nature, high hardness, low compressibility, high Debye temperature and high melting temperature. Moreover, the electronic energy density of states, electron density distribution, elastic properties, and Mulliken bond population analyses indicate that the structures under consideration consist of mixed bonding characteristics with ionic and covalent contributions. Investigation of the optical properties reveals that the reflectivity spectra are anisotropic with respect to the polarization directions of the electric field in the visible to mid‑ultraviolet regions. High reflectivity over a wide spectral range makes the compound suitable as reflecting coating. Both the structures are efficient absorbers of ultraviolet radiation. The refractive indices are quite high in the infrared to the visible range. Both structures show directional optical anisotropy. Though, H-MC exhibits stronger optical anisotropy than the O-MC.

Process-Aid Solid Engineering Triggers Delicately Modulation of Y-Series Non-Fullerene Acceptor for Efficient Organic Solar Cells.

Volatile solids with symmetricπ-backbone are intensively implemented on manipulating the nanomorphology for improving the operability and stability of organic solar cells. However, due to the isotropic stacking, the announced solids with symmetric geometry cannot modify the microscopic phase separation and component distribution collaboratively, which will constrain the promotion of exciton splitting and charge collection efficiency. Inspired by the superiorities of asymmetric configuration, a novel process-aid solid (PAS) engineering is proposed. By coupling with BTP core unit in Y-series molecule, an asymmetric, volatile 1,3-dibromo-5-chlorobenzene solid can induce the anisotropic dipole direction, elevated dipole moment, and interlaminar interaction spontaneously. Due to the synergetic effects on the favorable phase separation and desired component distribution, the PAS-treated devices feature the evident improvement of exciton splitting, charge transport, and collection, accompanied by the suppressed trap-assisted recombination. Consequently, an impressive fill factor of 80.2% with maximum power conversion efficiency (PCE) of 18.5% in the PAS-treated device is achieved. More strikingly, the PAS-treated devices demonstrate a promising thickness-tolerance character, where a record PCE of 17.0% is yielded in PAS devices with a 300nm thickness photoactive layer, which represents the highest PCE for thick-film organic solar cells.

Field-dependent shape and magnetic spectrum of magnetic bimeron

Magnetic bimeron composed of a meron and an antimeron can be considered as a magnetic skyrmion in the in-plane magnet and have great potential for spintronic devices. Here, we explored the effect of static magnetic fields on the shape of bimeron. It is found that the size of the bimeron can be adjusted by magnetic fields in an anisotropic direction. Then we study the field-tuned spin excitation spectrum of magnetic bimeron. Unlike the common breathing mode and the two rotation modes, novel resonance modes, which can be considered as a combination of the breathing and rocking-rotation modes, are observed. The results presented in this study can help to open novel research into the spintronics of magnetic bimeron.

The effect of near‐surface azimuthal anisotropy on a joint interpretation of seismic and electrical resistivity data

ABSTRACTIn this paper, we study the anisotropic near surface with seismic refraction surveying and electrical resistivity tomography. We present a field data processing case study and show a significant dependence of the determined P‐ wave velocity and electrical resistivity on the acquisition line direction. We show that the anisotropy influences not only the determined velocities themselves, but also the estimated depths of the determined boundaries and can cause misinterpretation of the arrival time curves and lead to hidden layer issues. We justify our field data‐processing results with ray modelling and synthetic data processing. As a result of our case study, we suggest a consistent direction of anisotropy for electrical resistivity and seismic surveying for the particular site in the Novosibirsk region.

Grain boundary elimination by twinning and dislocation nucleation in front of intergranular crack tips in BCC iron

Grain boundary structures with high resistance to intergranular fracture are the target of grain boundary design. In this work, grain boundary elimination in front of crack tip is observed in two special bcc iron bicrystals through molecular dynamics simulations under mode I loading. Grain boundary elimination depends on crack advance direction and enhances resistance to intergranular fracture. Direction-dependent elimination leads to directional anisotropy of intergranular crack propagation. By analytical analysis and molecular dynamics simulation, grain boundary elimination is found to be attributed to the activities of twinning and dislocation. All twinning bands are formed by atomic slip along ordinary twinning direction, but all dislocations are nucleated by atomic slip along anti-twinning direction. Mechanisms of twinning formation and dislocation nucleation are revealed by calculating energy barriers of atomic slip and shear stress field. According to the mechanism of grain boundary elimination, conditions for grain boundary elimination are proposed to find all special grain boundaries. Results show that twist grain boundaries cannot be eliminated under mode I loading, while tilt grain boundaries with axes of 〈110〉 can. This work provides a good reference for grain boundary design.

Lithospheric Conductors Shed Light on the Non‐Uniform Destruction of North China Craton

AbstractLow resistivity in the continental lower crust and uppermost mantle has been commonly observed in both Phanerozoic and Precambrian areas. Given different tectonic history, these conductors could be attributed to different conductive mechanisms. The North China Craton (NCC) is one of typical craton that have suffered from extensive destruction, part of which was modified by Phanerozoic tectonic‐thermal events and the others remain stable cratonic lithosphere. We here present a high‐resolution 3‐D electrical resistivity model from the inversion of magnetotelluric data collected in 183 sites of NCC. Beneath the stable craton in the north part of Ordos Block, an E‐W trending conductor extends from lower crust to uppermost mantle, which can be attributed to the concentration of sulfides/graphite emplaced through oceanic subduction during the Paleoproterozoic assembly of Columbia. The conductors beneath the Taihang Mountains and the south part of Ordos Block also reflect ancient sutures. In contrast, the conductor in mantle beneath the south part of North China Plain (SNCP) reflects an on‐going process of craton destruction relating to the subduction of the Pacific Plate in Cenozoic. The MT data, combined with seismic radial anisotropy model suggest the lower crust and uppermost mantle beneath SNCP is anisotropic. And a significant electrical anisotropic layer with the most conductive direction along N70°W and the anisotropy factor of 6.3 is revealed in the 20–70 km depth by 2‐D anisotropic inversion. We attribute the enhanced conductivity along anisotropy direction to the accumulation of melts in sills, resulting from the upwelling of asthenosphere in Cenozoic.

Fabric effect on the angle of repose in granular materials

In the present study, we perform a series of physical model experiments and numerical simulations to examine the effect of fabric orientation on angle of repose. The results show that with the deposition plane orientation angle θ varying from 0° to 90°, the angle of repose α reduces firstly and then rebounds, and the minimum values emerge at θ = 30° ~ 45°. Numerical analyses indicate that the microstructure reorganization becomes more intense as θ varies from 0° to 90°, making the anisotropy magnitude decrease and the principal anisotropy direction transit to a specific direction. With the analysis based on a conceptual model, we make a clarification on the fundamentals underlying the effect of fabric orientation on the angle of repose α. By introducing a θ-dependent coefficient, we propose an expression of α as a function of principal anisotropy directions (ϕn and ϕp) of the contact and particle orientations.

Observation of magnetic domain patterns with tilted uniaxial anisotropy using a single-spin magnetometer

Ferromagnets with uniaxial magnetocrystalline anisotropy have been a significant platform to explore applications in magnetic devices. Although it is commonly recognized that the magnetic anisotropy is crucial for the formation of noncollinear domain patterns, the effects of the anisotropy direction are usually neglected in recent studies. Here, we imaged stray fields generated by a polycrystalline MnNiGa sample with a nitrogen-vacancy color center in diamond and found that various stripe domains and magnetic bubbles exist in different regions. These domain patterns could be explained by the difference in anisotropy directions among crystallites via micromagnetic simulation. It can be inferred that the magnetic anisotropy direction plays a key role in energetically favorable domain structures based on our results. The magnetic anisotropy direction may be exploited as an ingredient to modulate domains and develop devices.

Unveiling a Chemisorbed Crystallographically Heterogeneous Graphene/L10-FePd Interface with a Robust and Perpendicular Orbital Moment.

A crystallographically heterogeneous interface was fabricated by growing hexagonal graphene (Gr) using chemical vapor deposition (CVD) on a tetragonal FePd epitaxial film grown by magnetron sputtering. FePd was alternately arranged with Fe and Pd in the vertical direction, and the outermost surface atom was identified primarily as Fe rather than Pd. This means that FePd has a high degree of L10-ordering, and the outermost Fe bonds to the carbon of Gr at the interface. When Gr is grown by CVD, the crystal orientation of hexagonal Gr toward tetragonal L10-FePd selects an energetically stable structure based on the van der Waals (vdW) force. The atomic relationship of Gr/L10-FePd, which is an energetically stable interface, was unveiled theoretically and experimentally. The Gr armchair axis was parallel to FePd [100]L10, where Gr was under a small strain by chemical bonding. Focusing on the interatomic distance between the Gr and FePd layers, the distance was theoretically and experimentally determined to be approximately 0.2 nm. This shorter distance (≈0.2 nm) can be explained by the chemisorption-type vdW force of strong orbital hybridization, rather than the longer distance (≈0.38 nm) of the physisorption-type vdW force. Notably, depth-resolved X-ray magnetic circular dichroism analyses revealed that the orbital magnetic moment (Ml) of Fe in FePd emerged at the Gr/FePd interface (@inner FePd: Ml = 0.16 μB → @Gr/FePd interface: Ml = 0.32 μB). This interfacially enhanced Ml showed obvious anisotropy in the perpendicular direction, which contributed to interfacial perpendicular magnetic anisotropy (IPMA). Moreover, the interfacially enhanced Ml and interfacially enhanced electron density exhibited robustness. It is considered that the shortening of the interatomic distance produces a robust high electron density at the interface, resulting in a chemisorption-type vdW force and orbital hybridization. Eventually, the robust interfacial anisotropic Ml emerged at the crystallographically heterogeneous Gr/L10-FePd interface. From a practical viewpoint, IPMA is useful because it can be incorporated into the large bulk perpendicular magnetic anisotropy (PMA) of L10-FePd. A micromagnetic simulation assuming both PMA and IPMA predicted that perpendicularly magnetized magnetic tunnel junctions (p-MTJs) using Gr/L10-FePd could realize 10-year data retention in a small recording layer with a circular diameter and thickness of 10 and 2 nm, respectively. We unveiled the energetically stable atomic structure in the crystallographically heterogeneous interface, discovered the emergence of the robust IPMA, and predicted that the Gr/L10-FePd p-MTJ is significant for high-density X nm generation magnetic random-access memory (MRAM) applications.

Effects of carbon implantation on the low temperature magnetism behavior in amorphous Fe93Zr7 films

We present a detailed investigation on the effects of C-implantation on low temperature magnetic behavior in Fe93Zr7 amorphous films using spin wave theory, law of approach to saturation, and Alben and Becker's theory. Significant increase in Curie temperature with a decrease in coercivity were observed upon C-implantation. Bloch's law was used to analyze the temperature dependence of magnetization, and several important parameters were extracted such as the stiffness constant of the spin wave, and the exchange constant. The local random anisotropy constant decreases from 0.35 to 0.19 MJ/m3 with increasing carbon concentration from 0 to 11%. The ferromagnetic correlation length for which the anisotropy directions are assumed to be arbitrarily oriented increases significantly with increasing carbon content. By the use of the theory of Alben and Becker, we also extracted the local anisotropy from coercivity, and reasonable agreement was found with random magnetic anisotropy approach.

Structural control on the 2019 Ridgecrest earthquake from local seismic tomography

We apply local seismic tomography to 159,754 P-wave and 101,751 S-wave arrival times of 5287 local earthquakes to determine 3-D images of P- and S-wave velocity (Vp, Vs), Poisson's ratio (ν) and Vp azimuthal anisotropy in the source zone of the 2019 Ridgecrest earthquake in Southern California. Its big foreshock (M6.4) and mainshock (M7.1) took place in a high-velocity (high-V) and low-velocity (low-V) transition belt. The source zone exhibits significant low-Vs and high-ν anomalies in the lower crust and uppermost mantle, probably reflecting crustal fluids associated with upwelling mantle flow. A high consistency between the seismogenic fault of the 2019 Ridgecrest earthquake and a low-Vs and high-ν anomaly suggests that the fluids in the fault zone affected the rupture process. Fast-velocity directions (FVDs) of Vp azimuthal anisotropy in the upper crust reflect effects of faults and cracks, whereas mineral alignments affect the FVDs in the low-V parts of the lower crust. Dominant NW–SE and E–W FVDs are revealed in the study area, indicating that the Pacific-North American plate relative motion causes the crustal deformation of the study area.

Seismic anisotropy beneath the Kumaun–Garhwal Himalaya using core-refracted shear wave phases

SUMMARY We investigate the nature of seismic anisotropy in the Kumaun–Garhwal Himalaya by analysing the core-refracted shear wave splitting phases (SK(K)S, PKS) recorded at 42 broad-band seismic stations. The mean fast anisotropy directions are mostly in ∼E–W and a few in the ∼NE–SW directions. The mean delay time decreases progressively from ∼1.0 s beneath the Sub Himalaya to ∼0.5 s at the Higher Himalaya. The observed seismic anisotropy suggests that the ongoing deformation beneath the Kumaun–Garhwal Himalaya has a large contribution by the relative rotation of the asthenospheric flow by the compression along the Indian Plate motion direction in this collision zone. Also, the southward transportation of the mid-crustal flow is probably responsible for the reduction in the delay times in the Main Central Thrust zone and further north than in the Sub-to-Lower Himalaya. The splitting parameters indicate a complex pattern of deformation beneath the Kumaun–Garhwal Himalaya with contribution from crust, lithospheric mantle and asthenospheric mantle.