scholarly journals IDENTIFIKASI ORIENTASI REKAHAN MIKRO AREA PANAS BUMI MONTE AMIATA BERDASARKAN ANALISIS STUDI SHEAR WAVE SPLITTING

2020 ◽  
Vol 3 (2) ◽  
pp. 72
Author(s):  
Irfan - Hanif ◽  
Ahmad Zaenudin ◽  
Nandi Haerudin ◽  
Rahmat C Wibowo
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Shear Wave Splitting ◽  
Earthquake Source ◽  
Polarization Direction ◽  
Fracture Orientation ◽  
High Anisotropy ◽  
Wave Splitting ◽  
Fracture Intensity ◽  
Fracture Distribution

Shear Wave Splitting is an application of seismic wave to analyse the anisotropy level of a certain medium. Generally, shear wave propagation through a rock formation will be polarized (φ) into two parts especially when the medium structures are different, such as fracture. The polarized shear wave which is perpendicular to fracture will propagate slower than the wave that propagates parallel to the fracture. The delay time (δt) of both wave is proportional with the fracture intensity along the wave propagation from the source to the station. The description regarding fracture orientation can be obtained by analysing both Shear Wave Splitting parameters (φ and δt), and this information is adequately important in geothermal exploration or exploitation phase at Mt. Amiata. Based on the result of this research, the micro earthquake source is focused on the east to the south area and spread along 3 earthquake stations. The existence of micro earthquake source is mainly focused at the depth of 1 to 4 km. In addition, the polarization direction of each earthquake station at the geological map shows a dominant fracture orientation consistently at NW-SE. All of the three stations also show that the polarization direction is integrated to the local fault existence in the subsurface. Furthermore, the research shows that the high intensity fracture distribution occurred at MCIV station area in the southern part of research location. Meanwhile, the low intensity fracture distribution occurred at ARCI and SACS station area in the western and the eastern part of research location. The high value of fracture intensity accompanied by the high amount of structure intensity, strengthen the prediction of the high anisotropy existence which potentially tends to the high permeability presence at the area.Keywords: shear wave splitting, anisotropy, fracture, geothermal, polarization direction, fracture intensity.

A physical model study of shear wave splitting and fracture intensity

1987 ◽  
Author(s):  
Robert H. Tatham ◽  
Martin D. Matthews ◽  
K. K. Sekharan ◽  
Christopher J. Wade ◽  
Louis M. Liro
Keyword(s):  
Physical Model ◽  
Shear Wave ◽  
Shear Wave Splitting ◽  
Model Study ◽  
Wave Splitting ◽  
Fracture Intensity

A physical model study of shear‐wave splitting and fracture intensity

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 647-652 ◽  
Author(s):  
Robert H. Tatham ◽  
Martin D. Matthews ◽  
K. K. Sekharan ◽  
Christopher J. Wade ◽  
Louis M. Liro
Keyword(s):  
Physical Model ◽  
Shear Wave ◽  
Shear Wave Splitting ◽  
Constant Thickness ◽  
Petroleum Reservoir ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Wave Splitting ◽  
Fracture Intensity ◽  
Degree Of Anisotropy

In a series of physical model experiments, fractured media are simulated by stacks of thin Plexiglas sheets clamped together tightly to form blocks. The plates are assembled underwater, and a very thin water layer between the sheets prevents formation of an effectively welded interface between them. Thus, the stacked material is not a series of welded plates but rather a truly fractured medium simulating a potential petroleum reservoir with only fracture porosity and permeability. Sheets of constant thickness are used, but the intensity of fracturing between the different models is simulated by using different thicknesses of Plexiglas for each model. Observation of direct shear‐wave arrivals through the stack, with propagation parallel to the sheets and polarization of particle motion allowed to be parallel to, normal to, or in any arbitrary angle to the sheets, definitively demonstrate the existence of shear‐wave splitting and hence anisotropy. For Plexiglas sheets 1/16 in thick (0.16 cm) representing a fracture intensity of about 16 fractures per wavelength, shear‐wave splitting and hence anisotropy are clearly observed. For greater fracture intensities (i.e., thinner plates) the degree of anisotropy is greater, and for less intense fracturing (i.e., thicker plates), the degree of anisotropy is less. These experimental data suggest that for fracture intensities of greater than about 10 fractures per wavelength there is a simple relation between fracture intensity and degree of anisotropy in two different polarizations of shear waves. For fracture intensities less than a threshold of about 10 per wavelength, there is no simple observed relation between them. Further, the faster of the split shear‐wave velocities is near the solid material velocity, and the observed variation in velocity for various fracture intensities is in the slower of the split shear‐wave velocities.

Application of seismic interferometry to extract P- and S-wave propagation and observation of shear-wave splitting from noise data at Cold Lake, Alberta, Canada

Geophysics ◽  
2008 ◽  
Vol 73 (4) ◽  
pp. D35-D40 ◽  
Author(s):  
Masatoshi Miyazawa ◽  
Roel Snieder ◽  
Anupama Venkataraman
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Structural Parameters ◽  
Shear Wave Splitting ◽  
Seismic Interferometry ◽  
Stress Axis ◽  
S Wave ◽  
S Waves ◽  
Wave Splitting ◽  
Cold Lake

We extract downward-propagating P- and S-waves from industrial noise generated by human and/or machine activity at the surface propagating down a borehole at Cold Lake, Alberta, Canada, and measure shear-wave splitting from these data. The continuous seismic data are recorded at eight sensors along a downhole well during steam injection into a 420–470-m-deep oil reservoir. We crosscorrelate the waveforms observed at the top sensor and other sensors to extract estimates of the direct P- and S-wave components of the Green’s function that account for wave propagation between sensors. Fast high-frequency and slow low-frequency signals propagating vertically from the surface to the bottom are found for the vertical and horizontal components of the wave motion, which are identified with P- and S-waves, respectively. The fastest S-wave polarized in the east-northeast–west-southwest direction is about 1.9% faster than the slowest S-wave polarized in the northwest-southeast direction. The direction of polarization of the fast S-wave is rotated clockwise by [Formula: see text] from the maximum principal stress axis as estimated from the regional stress field. This study demonstrates the useful application of seismic interferometry to field data to determine structural parameters, which are P- and S-wave velocities and a shear-wave-splitting coefficient, with high accuracy.

Study on Mechanical Automation with a New Method for Defining the Calculation Window of Shear Wave Splitting

2013 ◽  
Vol 473 ◽  
pp. 7-12
Author(s):  
Song Zheng ◽  
Hong Fu Fan ◽  
Yan Hui Zhang
Keyword(s):  
Shear Wave ◽  
Decisive Role ◽  
Shear Wave Splitting ◽  
New Method ◽  
Automated Method ◽  
Accuracy And Precision ◽  
Wave Splitting ◽  
Fracture Intensity

Shear wave splitting technology plays important role in detecting fractures. Picking up the calculation window is necessary in the shear wave splitting technology and plays a decisive role in the accuracy and precision detecting the orientation of fractures and fracture intensity. Conventionally, the calculation window for shear wave splitting is manually set, which is both laborious and subjective. Thus providing an mechanical automated method of picking up the calculation window is very meaningful.

A Physical Model Study of Shear-Wave Splitting and Fracture Intensity

1988 ◽  
Vol 19 (1-2) ◽  
pp. 175-178 ◽  
Author(s):  
Robert H. Tatham ◽  
Martin D. Matthews ◽  
K. K. Sekharan
Keyword(s):  
Physical Model ◽  
Shear Wave ◽  
Shear Wave Splitting ◽  
Model Study ◽  
Wave Splitting ◽  
Fracture Intensity

scholarly journals Shear Wave Splitting Analysis to Estimate Fracture Orientation and Frequency Dependent Anisotropy

2016 ◽  
Vol 64 (1) ◽  
pp. 76-100 ◽  
Author(s):  
Raoof Gholami ◽  
Ali Moradzadeh ◽  
Vamegh Rasouli ◽  
Javid Hanachi
Keyword(s):  
Shear Wave ◽  
Shear Wave Splitting ◽  
Frequency Dependent ◽  
Fracture Orientation ◽  
Wave Splitting

Sensitivity of SK(K)S and ScS phases to heterogeneous anisotropy in the lowermost mantle from global wavefield simulations

2021 ◽  
Vol 228 (1) ◽  
pp. 366-386
Author(s):  
Jonathan Wolf ◽  
Maureen D Long ◽  
Kuangdai Leng ◽  
Tarje Nissen-Meyer
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Shear Wave Splitting ◽  
Forward Modelling ◽  
Finite Frequency ◽  
Specific Flow ◽  
Frequency Wave ◽  
Wave Splitting ◽  
Mantle Anisotropy ◽  
Lowermost Mantle

SUMMARY Observations of seismic anisotropy at the base of the mantle are abundant. Given recent progress in understanding how deformation relates to anisotropy in lowermost mantle minerals at the relevant pressure and temperature conditions, these observations can be used to test specific geodynamic scenarios, and have the potential to reveal patterns of flow at the base of the mantle. For example, several recent studies have sought to reproduce measurements of shear wave splitting due to D″ anisotropy using models that invoke specific flow and texture development geometries. A major limitation in such studies, however, is that the forward modelling is nearly always carried out using a ray theoretical framework, and finite-frequency wave propagation effects are not considered. Here we present a series of numerical wave propagation simulation experiments that explore the finite-frequency sensitivity of SKS, SKKS and ScS phases to laterally varying anisotropy at the base of the mantle. We build on previous work that developed forward modelling capabilities for anisotropic lowermost mantle models using the AxiSEM3D spectral element solver, which can handle arbitrary anisotropic geometries. This approach enables us to compute seismograms for relatively short periods (∼4 s) for models that include fully 3-D anisotropy at moderate computational cost. We generate synthetic waveforms for a suite of anisotropic models with increasing complexity. We first test a variety of candidate elastic tensors in laterally homogeneous models to understand how different lowermost mantle elasticity scenarios express themselves in shear wave splitting measurements. We then consider a series of laterally heterogeneous models of increasing complexity, exploring how splitting behaviour varies across the edges of anisotropic blocks and investigating the minimum sizes of anisotropic heterogeneities that can be reliably detected using SKS, SKKS and ScS splitting. Finally, we apply our modelling strategy to a previously published observational study of anisotropy at the base of the mantle beneath Iceland. Our results show that while ray theory is often a suitable approximation for predicting splitting, particularly for SK(K)S phases, full-wave effects on splitting due to lowermost mantle anisotropy can be considerable in some circumstances. Our simulations illuminate some of the challenges inherent in reliably detecting deep mantle anisotropy using body wave phases, and point to new strategies for interpreting SKS, SKKS and ScS waveforms that take full advantage of newly available computational techniques in seismology.

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