Measurements of intrinsic and scattering seismic attenuation in the crust

1995 ◽  
Vol 85 (5) ◽  
pp. 1373-1380 ◽  
Author(s):  
Edoardo Del Pezzo ◽  
Jesus Ibanez ◽  
José Morales ◽  
Aybige Akinci ◽  
Rosalba Maresca
Keyword(s):  
Seismic Attenuation ◽  
Campi Flegrei ◽  
Etna Volcano ◽  
S Wave ◽  
Coda Q ◽  
Shallow Earthquakes ◽  
Tectonically Active ◽  
Intrinsic And Scattering Attenuation ◽  
Q Values ◽  
Degree Of Heterogeneity

Abstract Intrinsic and scattering attenuation parameters, Qi and QS, have been measured in three different tectonic areas for local and shallow earthquakes located close to the receiver. The approach developed by Wennerberg (1993), which takes into account the numerical correction of the coda-Q parameter for the multiple scattering formulation of Zeng, was used to infer from the estimates of coda Q and direct S-wave Q the intrinsic (Qi) and scattering (QS) Q values. Results for 1 to 12 Hz range show that Qi is comparable to QS for the Etna volcano and for the Campi Flegrei area, while Qi for the tectonically active area of Granada is lower than QS. Coda Q is close to intrinsic Q, suggesting that, at least in the crust, coda Q is a good estimate of the intrinsic Q. Volcanic areas show a reasonable higher degree of heterogeneity, if compared with the nonvolcanic area of Granada.

S-wave attenuation in the crust in northern Greece

1995 ◽  
Vol 85 (5) ◽  
pp. 1381-1387 ◽  
Author(s):  
P. M. Hatzidimitriou
Keyword(s):  
Wave Attenuation ◽  
Amplitude Ratio ◽  
Single Scattering ◽  
Coda Wave ◽  
S Wave ◽  
Coda Q ◽  
Northern Greece ◽  
Single Station ◽  
The University ◽  
Q Values

Abstract The attenuation of shear waves in the crust is estimated, for frequencies between 1.5 and 12.0 Hz, by applying a single-station method based on the rate of decay of the S-wave to coda-wave amplitude ratio with distance. The data used come from local earthquakes that occurred in the Thessaloniki area, northern Greece, during the period 1983 through 1989 and were recorded by the telemetered network of the Geophysical Laboratory of the University of Thessaloniki. The Qs values obtained are 115, 244, 477, and 755 for 1.5, 3.0, 6.0, and 12.0 Hz, respectively. These values are very close to the coda Q values estimated for the same area using the S-to-S single scattering model for lapse times between 30 and 100 sec but they are higher than the coda Q values for lapse times between 10 and 30 sec. The estimated Qs is found to be strongly frequency dependent, proportional to f0.91, which is very close to the frequency dependence of the coda Q.

Coda Q before the 1983 Hawaii (MS = 6.6) earthquake

1988 ◽  
Vol 78 (3) ◽  
pp. 1279-1296
Author(s):  
Zhong-Xian Huang ◽  
Max Wyss
Keyword(s):  
Unit Volume ◽  
Main Shock ◽  
B Value ◽  
Rectangular Region ◽  
S Wave ◽  
Coda Q ◽  
Seismicity Rate ◽  
High Q ◽  
Source Mechanisms ◽  
Q Values

Abstract Coda Q values were derived for more than 300 microearthquakes that occurred in a 6-yr period before the 16 November 1983 Kaoiki, Hawaii, earthquake (MS = 6.6). The sources were located within a 14 × 16 km rectangular region surrounding the main shock epicenter, and most of them occurred at depths between 5 and 10 km. Digital recordings from three stations at epicentral distances ranging from 0 to 18 km were used. Coda Q was calculated from the amplitude decay rate of the S-wave coda in nine frequency bands from 4.5 to 27 Hz. The average Q of the NW part of the studied area is about 15 per cent higher than that of the SE part. These two subregions also showed differences in seismicity, b value, and microearthquake source mechanisms. In the high-Q volume, the b value was 1.0, and the rate of earthquakes per unit volume was about 50 per cent of the rate in the low-Q volume where b = 1.3. One interpretation of these observations is that more extensive faulting in the SE Kaoiki fault zone leads to lower Q, higher b value, and a higher seismicity rate. During the 5 to 6 yr before the mainshock, the 1-yr average Q values were stable. No significant Q change could be identified as a precursor to the main shock.

scholarly journals Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1001-1010 ◽  
Author(s):  
J. M. Carcione ◽  
F. Poletto ◽  
B. Farina ◽  
A. Craglietto
Keyword(s):  
Seismic Waves ◽  
In Situ Stress ◽  
Seismic Attenuation ◽  
Earth’S Crust ◽  
S Wave ◽  
Fourier Pseudospectral Method ◽  
Stress Criterion ◽  
Brittle Ductile Transition ◽  
Earth's Crust

Abstract. The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P and S wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P−S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle–ductile transition.

scholarly journals P- and S-wave seismic attenuation for deep natural gas exploration and development

2005 ◽  
Author(s):  
Joel Walls ◽  
Richard Uden ◽  
Scott Singleton ◽  
Rone Shu ◽  
Gary Mavko
Keyword(s):  
Natural Gas ◽  
Seismic Attenuation ◽  
S Wave ◽  
Exploration And Development

Comparison of P‐ and S‐wave velocities and Q’S from VSP and sonic log data

Geophysics ◽  
1994 ◽  
Vol 59 (10) ◽  
pp. 1512-1529 ◽  
Author(s):  
Gopa S. De ◽  
Donald F. Winterstein ◽  
Mark A. Meadows
Keyword(s):  
Velocity Dispersion ◽  
P Wave ◽  
S Wave ◽  
S Waves ◽  
Wave Velocities ◽  
Sonic Log ◽  
Transit Times ◽  
Wave Slope ◽  
Northern Alberta ◽  
Q Values

We compared P‐ and S‐wave velocities and quality factors (Q’S) from vertical seismic profiling (VSP) and sonic log measurements in five wells, three from the southwest San Joaquin Basin of California, one from near Laredo, Texas, and one from northern Alberta. Our purpose was to investigate the bias between sonic log and VSP velocities and to examine to what degree this bias might be a consequence of dispersion. VSPs and sonic logs were recorded in the same well in every case. Subsurface formations were predominantly clastic. The bias found was that VSP transit times were greater than sonic log times, consistent with normal dispersion. For the San Joaquin wells, differences in S‐wave transit times averaged 1–2 percent, while differences in P‐wave transit times averaged 6–7 percent. For the Alberta well, the situation was reversed, with differences in S‐wave transit times being about 6 percent, while those for P‐waves were 2.5 percent. For the Texas well, the differences averaged about 4 percent for both P‐ and S‐waves. Drift‐curve slopes for S‐waves tended to be low where the P‐wave slopes were high and vice versa. S‐wave drift‐curve slopes in the shallow California wells were 5–10 μs/ft (16–33 μs/m) and the P‐wave slopes were 15–30 μs/ft (49–98 μs/m). The S‐wave slope in sandstones in the northern Alberta well was up to 50 μs/ft (164 μs/m), while the P‐wave slope was about 5 μs/ft (16 μs/m). In the northern Alberta well the slopes for both P‐ and S‐waves flattened in the carbonate. In the Texas well, both P‐ and S‐wave drifts were comparable. We calculated (Q’s) from a velocity dispersion formula and from spectral ratios. When the two Q’s agreed, we concluded that velocity dispersion resulted solely from absorption. These Q estimation methods were reliable only for Q values smaller than 20. We found that, even with data of generally outstanding quality, Q values determined by standard methods can have large uncertainties, and negative Q’s may be common.

scholarly journals Downhole distributed acoustic seismic profiling at Skytrain Ice Rise, West Antarctica

2021 ◽  
Author(s):  
Alex Brisbourne ◽  
Mike Kendall ◽  
Sofia Kufner ◽  
Thomas Hudson ◽  
Andrew Smith
Keyword(s):  
Wave Energy ◽  
Drilling Fluid ◽  
Ice Sheet ◽  
Seismic Profile ◽  
Seismic Attenuation ◽  
Weddell Sea ◽  
P Wave ◽  
West Antarctica ◽  
S Wave ◽  
Ice Flow

<p>Antarctic ice sheet history is imprinted in the structure and fabric of the ice column. At ice rises, the signature of ice flow history is preserved due to the low strain rates inherent at these independent ice flow centres. We present results from a distributed acoustic sensing (DAS) experiment at Skytrain Ice Rise in the Weddell Sea Sector of West Antarctica, aimed at delineating the englacial fabric to improve our understanding of ice sheet history in the region. This pilot experiment demonstrates the feasibility of an innovative technique to delineate ice rise structure. Both direct and reflected P- and S-wave energy, as well as surface wave energy, are observed using a range of source offsets, i.e., a walkaway vertical seismic profile (VSP), recorded using fibre optic cable. Significant noise, which results from the cable hanging untethered in the borehole, is modelled and suppressed at the processing stage. At greater depth, where the cable is suspended in drilling fluid, seismic interval velocities and attenuation are measured. Vertical P-wave velocities are high (V<sub>INT</sub> = 4029 ± 244 m s<sup>-1</sup>) and consistent with a strong vertical cluster fabric. Seismic attenuation is high (Q<sub>INT </sub>= 75 ± 12) and contrary to observations in ice sheets over this temperature range. The signal level is too low, and the noise level too high, to undertake analysis of englacial fabric variability. However, modelling of P- and S-wave traveltimes and amplitudes with a range of fabric geometries, combined with these measurements, demonstrates the capacity of the DAS method to discriminate englacial fabric distribution. From this pilot study we make a number of recommendations for future experiments aimed at quantifying englacial fabric to improve our understanding of recent ice sheet history.</p><p> </p>

scholarly journals Seismic Attenuation Anisotropy in the Southernmost Part of the Taupo Volcanic Zone, North Island, New Zealand

2022 ◽  
Author(s):  
◽  
Syuhada, Syuhada
Keyword(s):  
Frequency Dependence ◽  
Seismic Attenuation ◽  
Taupo Volcanic Zone ◽  
S Wave ◽  
Volcanic Zone ◽  
S Waves ◽  
Distance Range ◽  
Uncertainty Estimates ◽  
Q Model ◽  
Attenuation Anisotropy

<p>We investigate the mechanisms of seismic anisotropy and attenuation (1/Q) beneath the southernmost part of the Taupo Volcanic Zone (TVZ) by computing variations in S-wave attenuation factors with the direction of wave polarization. We rotate pairs of horizontal components in steps of 22.5◦ from 0◦ to 67.5◦ and into the radial and transverse directions to search for the optimal separation of the attenuation curves and thereby determine an anisotropy symmetry system. The frequency dependence of Q for the rotated S-waves is estimated by means of the non-parametric generalized inversion technique (GIT) of Castro et al. (1990) using shallow earthquakes (< 40 km depth) recorded by GeoNet within 100 km of Mt. Ruapehu. To analyze the effects on computed attenuation properties of source locations, we divide our dataset into two groups: a “TVZ” group containing earthquakes within the TVZ in a distance range of 5–55 km and a “non-TVZ” group containing earthquakes outside the TVZ in a distance range of 5–50 km. To measure Q, we compute the spectral amplitude decay with distance in terms of empirical functions at 20 separate frequencies in the frequency bands 2–10 Hz and 2– 12 Hz for the TVZ and non-TVZ datasets respectively. We construct homogeneous and two-layer Q models for the TVZ dataset based on characteristic features of the attenuation function, while for outside TVZ we only analyse a homogeneous Q model. The homogeneous Q models obtained for the two datasets indicate that S-waves are more attenuated within the TVZ than outside. The homogeneous Q model for the TVZ dataset reveals that the S-wave is anisotropic at high frequencies ( f > 6 Hz) along N–S/E– W directions with the relation QSE ( f ) = (6.15±1.22) f (1.73±0.12) and QSN ( f ) = (4.14± 1.26) f (2.06±0.14), while the non-TVZ dataset shows a weak frequency dependence of attenuation anisotropy at low frequencies in NE–SW/SE–NW directions giving the power law function QSNE ( f ) = (50.93±1.18) f (0.20±0.10) and QSSE ( f ) = (22.60±1.10) f (0.53±0.06). Here, the uncertainty estimates are 95% confidence intervals. To investigate the variation of attenuation anisotropy with depth within the TVZ, we first calculate Q along propagation paths (< 25 km, which corresponds to a maximum turning point depth of 9 km ) and then using paths of 25–55 km length. Small attenuation anisotropy with low attenuation in the N–S direction for the upper crust of TVZ may be related to heterogenous structure as reported by previous studies. Attenuation anisotropy in the northwest direction yielding lower attenuation inferred for the deeper crust suggests the presence of connected melt aligned with the extension direction of TVZ .</p>

scholarly journals Simulation of seismic waves at the Earth crust (brittle-ductile transition) based on the Burgers model

2014 ◽  
Vol 6 (1) ◽  
pp. 1371-1400 ◽  
Author(s):  
J. M. Carcione ◽  
F. Poletto ◽  
B. Farina ◽  
A. Craglietto
Keyword(s):  
Seismic Waves ◽  
Grid Method ◽  
In Situ Stress ◽  
Seismic Attenuation ◽  
S Wave ◽  
Fourier Pseudospectral Method ◽  
Stress Criterion ◽  
Brittle Ductile Transition ◽  
The Earth

Abstract. The Earth crust presents two dissimilar rheological behaviours depending on the in-situ stress-temperature conditions. The upper, cooler, part is brittle while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behaviour is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in-situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P- and S-wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P-S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle-ductile transition.

scholarly journals Seismic Attenuation Tomography From 2018 Lombok Earthquakes, Indonesia

2021 ◽  
Vol 9 ◽  
Author(s):  
Awali Priyono ◽  
Andri Dian Nugraha ◽  
Muzli Muzli ◽  
Ardianto Ardianto ◽  
Atin Nur Aulia ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Source Region ◽  
Bouguer Anomaly ◽  
High Ratio ◽  
Seismic Attenuation ◽  
P Wave ◽  
S Wave ◽  
Fluid Content ◽  
P Wave Velocity ◽  
Lombok Island

Local earthquake data was used to determine a three-dimensional (3D) seismic attenuation structure around the aftershock source region of the 2018 Lombok earthquake in Indonesia. The aftershocks were recorded by 13 seismic stations from August 4 to September 9, 2018. The selected data consist of 6,281 P-wave t∗ values from 914 events, which had good t∗ quality in at least four stations. Our results show that the two aftershock clusters northwest and northeast of Lombok Island have different attenuation characteristics. A low P-wave quality factor (low-Qp), low P-wave velocity (Vp), and high ratio of P-wave velocity and S-wave velocity (Vp/Vs), which coincide with a shallower earthquake (&lt;20 km) northwest of Lombok Island, might be associated with a brittle area of basal and imbricated faults influenced by high fluid content. At the same time, the high-Qp, low Vp, and low Vp/Vs, which coincide with a deeper earthquake (&gt;20 km) northeast of Lombok Island, might be associated with an area that lacks fluid content. The difference in fluid content between the northwest and northeast regions might be the cause of the early generation of aftershocks in the northwest area. The significant earthquake that happened on August 5, 2018, took place in a region with moderate Qp, close to the contrast of high and low-Qp and high Vp, which suggests that the earthquake started in a strong material before triggering the shallower aftershocks occurring in an area affected by fluid content. We also identified an old intrusive body on the northeast flank of the Rinjani volcano, which was characterized by a high-Qp, high-velocity, and a high Bouguer anomaly.

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