Receiver Functions of Seismic Waves in Layered Anisotropic Media: Application to the Estimate of Seismic Anisotropy

2008 ◽  
Vol 98 (6) ◽  
pp. 2990-3006 ◽  
Author(s):  
M. Nagaya ◽  
H. Oda ◽  
H. Akazawa ◽  
M. Ishise
Keyword(s):  
Seismic Waves ◽  
Seismic Anisotropy ◽  
Anisotropic Media ◽  
Receiver Functions

scholarly journals Seismic anisotropy: an original tool to understand the geodynamic evolution of the Italian peninsula

1997 ◽  
Vol 40 (3) ◽  
Author(s):  
L. Margheriti ◽  
C. Nostro ◽  
A. Amato ◽  
M. Cocco
Keyword(s):  
Upper Mantle ◽  
Common Property ◽  
Seismic Waves ◽  
Seismic Anisotropy ◽  
Structural Features ◽  
Relative Strength ◽  
Plate Motion ◽  
Mantle Minerals ◽  
Anisotropic Bodies ◽  
Shallow Crust

Anisotropy is a common property of the Earth's crust and the upper mantle; it is related to the strain field of the medium and therefore to geodynamics. In this paper we describe the different possible origins of anisotropic behavior of the seismic waves and the seismological techniques used to define anisotropic bodies. In general it is found that the fast polarization direction is parallel to the absolute plate motion in cratonic areas, to the spreading direction near rifts or extensional zones, and to the main structural features in transpressive regimes. The delay times between fast and slow waves reflect the relative strength and penetration at depth of the deformation field. The correspondence between surface structural trends and anisotropy in the upper mantle, found in many regions of the world, strongly suggest that orogenic processes involve not only the shallow crust but the entire lithosphere. Recently in Italy both shear wave splitting analysis and Pn inversion were applied to define the trend of seismic anisotropy. Along the Northern Appeninic arc fast directions follow the strike of the arc (i.e., parallel to the strike of the Miocene-Pleistocene compressional features), whereas in the Tyrrhenian zone fast directions are about E-W SW-NE; parallel to the post-Miocene extension that is thought to have reoriented the mantle minerals fabric in the astenosphere.

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

Solid Earth ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 893-905 ◽  
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.

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

2019 ◽  
Vol 220 (3) ◽  
pp. 1585-1603
Author(s):  
Zhenxin Xie ◽  
Vadim Levin ◽  
Qingju Wu
Keyword(s):  
Tibetan Plateau ◽  
Seismic Anisotropy ◽  
Receiver Function ◽  
Flow Direction ◽  
Receiver Functions ◽  
Low Velocity ◽  
Northeastern Tibetan Plateau ◽  
Harmonic Decomposition ◽  
Anisotropic Layers ◽  
Qilian Orogen

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.

scholarly journals A discontinuous Galerkin fast-sweeping eikonal solver for fast and accurate traveltime computation in 3D tilted anisotropic media

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. C107-C118 ◽  
Author(s):  
Philippe Le Bouteiller ◽  
Mondher Benjemaa ◽  
Ludovic Métivier ◽  
Jean Virieux
Keyword(s):  
Discontinuous Galerkin ◽  
Seismic Anisotropy ◽  
Computational Cost ◽  
Anisotropic Media ◽  
Finite Difference Schemes ◽  
Seismic Amplitude ◽  
Fast Sweeping ◽  
Complex Models ◽  
Dg Method ◽  
Sweeping Method

We tackle the challenging problem of efficient and accurate seismic traveltime computation in 3D anisotropic media by applying the fast-sweeping method to a discontinuous Galerkin (DG)-based eikonal solver. Using this method leads to a stable and highly accurate scheme, which is faster than finite-difference schemes for a given precision, and with a low computational cost compared to the standard Runge-Kutta DG formulation. The integral formulation of the DG method also makes it easy to handle seismic anisotropy and complex topographies. Several numerical tests on complex models, such as the 3D SEG advanced modeling model, are given as illustration, highlighting the efficiency and the accuracy of this new approach. In the near future, these results will be used together with accurate solvers for seismic amplitude and take-off angle computation to revisit asymptotic inversion (traveltime/slope tomography) and imaging approaches (quantitative migration involving amplitudes and angles).

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

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

<p>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° and 90°) 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.</p>

Seismic complex ray tracing in 2D/3D viscoelastic anisotropic media by a modified shortest-path method

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. T331-T342
Author(s):  
Xing-Wang Li ◽  
Bing Zhou ◽  
Chao-Ying Bai ◽  
Jian-Lu Wu
Keyword(s):  
Ray Tracing ◽  
Shortest Path ◽  
Anisotropic Medium ◽  
Wave Energy ◽  
Seismic Data ◽  
Seismic Waves ◽  
Effective Means ◽  
Anisotropic Media ◽  
The Real ◽  
Complex Ray

In a viscoelastic anisotropic medium, velocity anisotropy and wave energy attenuation occur and are often observed in seismic data applications. Numerical investigation of seismic wave propagation in complex viscoelastic anisotropic media is very helpful in understanding seismic data and reconstructing subsurface structures. Seismic ray tracing is an effective means to study the propagation characteristics of high-frequency seismic waves. Unfortunately, most seismic ray-tracing methods and traveltime tomographic inversion algorithms only deal with elastic media and ignore the effect of viscoelasticity on the seismic raypath. We have developed a method to find the complex ray velocity that gives the seismic ray speed and attenuation in an arbitrary viscoelastic anisotropic medium, and we incorporate them with the modified shortest-path method to determine the raypath and calculate the real and imaginary traveltime (wave energy attenuation) simultaneously. We determine that the complex ray-tracing method is applicable to arbitrary 2D/3D viscoelastic anisotropic media in a complex geologic model and the computational errors of the real and imaginary traveltime are less than 0.36% and 0.59%, respectively. The numerical examples verify that the new method is an effective and powerful tool for accomplishing seismic complex ray tracing in heterogeneous viscoelastic anisotropic media.

scholarly journals Seismic waves in stratified anisotropic media

1984 ◽  
Vol 78 (3) ◽  
pp. 691-710 ◽  
Author(s):  
G. J. Fryer ◽  
L. N. Frazer
Keyword(s):  
Seismic Waves ◽  
Anisotropic Media

scholarly journals The results of explicit record of velocity anisotropy concerning seismic imaging

2013 ◽  
pp. 42-55
Author(s):  
P. Zagorodnyuk ◽  
G. Lisny
Keyword(s):  
Data Processing ◽  
Seismic Data ◽  
Seismic Waves ◽  
Seismic Anisotropy ◽  
Seismic Imaging ◽  
Seismic Data Processing ◽  
Velocity Anisotropy ◽  
Velocity Modeling ◽  
Midpoint Method ◽  
Depth Scale

The researches shows that the explicit account of the seismic waves velocities anisotropy is preferable comparing to the traditional one, the meaning of which became clear due to the authors’ publications. The main advantages of an explicit account of seismic anisotropy are:  the usage of a depth scale, not the time scale, in seismic data processing and interpretation;  depth-velocity modeling without using the technologies of common midpoint method, thus, preventing from a number of errors, which is highly important for 3-D seismic;  possibility to use technology of seismic images anisotropic decomposition. Dnieper-Donetsk depression seismic data processing results convincingly demonstrate the advantages of the seismic anisotropy explicit account for seismic imaging of anisotropic media.   

Sign in / Sign up

Export Citation Format

Share Document