Seismic scattering and absorption parameters in the W-Bohemia/Vogtland region from elastic and acoustic radiative transfer theory

Gaebler, Peter; Eulenfeld, Tom; Wegler, Ulrich

doi:10.1093/gji/ggv393

Cited by 46 publications

(49 citation statements)

References 44 publications

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“…We compare results from three locations dominated by sediments (Landau, Insheim, Unterhaching) and two locations dominated by crystalline rock [Czech-German border region Vogtland, Continental Deep Drilling Programme (KTB)]. Results for the Vogtland area were obtained using the method of this paper (compare Gaebler et al 2015). Results for the KTB were taken from table 2 of Fielitz & Wegler (2015).…”

Section: Discussionmentioning

confidence: 99%

“…Dimensions for E mod , W, R and G are Jm −3 Hz −1 , JHz −1 , 1 and m −3 , respectively. Gaebler et al (2015) compared different methods to calculate the Green's function using anisotropic elastic versus isotropic acoustic radiative transfer theory. For their data set results of the two methods for the transport mean-free path are the same within the inherent precision of the methods.…”

Section: O D E L E D a N D O B S E Rv E D E N E Rg Y D E N S I T I E Smentioning

confidence: 99%

“…In principle, our algorithm which will be described in Section 3 can be used to invert for a vector of multiple scattering parameters and is capable of using Green's functions determined by acoustic or elastic radiative transfer theory. Assured by the described findings of Gaebler et al (2015), we choose the computationally cheap solution to calculate the Green's function for acoustic isotropic scattering in a homogeneous half-space. For simplicity, we use the analytic approximation of the solution for 3-D isotropic radiative transfer (Paasschens 1997).…”

Section: O D E L E D a N D O B S E Rv E D E N E Rg Y D E N S I T I E Smentioning

confidence: 99%

“…The relative error to the exact solution of acoustic isotropic radiative transfer provided by Zeng et al (1991) is below 3 per cent (Ugalde & Carcolé 2009). The assumption of isotropic scattering is not valid for real media, anyway it is beneficial as the scattering coefficient g 0 determined with this wrong assumption can be interpreted as the transport scattering coefficient g * in a more realistic anisotropic scattering scenario: g * = g 0 (Gaebler et al 2015). The modeled envelope E mod will be compared to observed envelopes at seismic stations.…”

Section: O D E L E D a N D O B S E Rv E D E N E Rg Y D E N S I T I E Smentioning

confidence: 99%

“…The restriction to S waves and the consequent usage of the acoustic approximation is justified by the high ratio of S-to-P versus P-to-S scattering conversion. The assumption of isotropic scattering is not correct but is a simple and effective way of describing the transport for the anisotropic case by interpreting the obtained scattering coefficient as transport scattering coefficient (Gaebler et al 2015). The inaccuracy of the used Green's function in the S-wave window is dealt with by averaging in this time window.…”

Section: T Eulenfeld and U Weglermentioning

confidence: 99%

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Measurement of intrinsic and scattering attenuation of shear waves in two sedimentary basins and comparison to crystalline sites in Germany

Eulenfeld¹,

Wegler²

2016

Geophys. J. Int.

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S U M M A R YWe developed an improved method for the separation of intrinsic and scattering attenuation of seismic shear waves by envelope inversion called Qopen. The method optimizes the fit between Green's functions for the acoustic, isotropic radiative transfer theory and observed energy densities of earthquakes. The inversion allows the determination of scattering and intrinsic attenuation, site corrections and spectral source energies for the investigated frequency bands. Source displacement spectrum and the seismic moment of the analysed events can be estimated from the obtained spectral source energies. We report intrinsic and scattering attenuation coefficients of shear waves near three geothermal reservoirs in Germany for frequencies between 1 and 70 Hz. The geothermal reservoirs are located in Insheim, Landau (both Upper Rhine Graben) and Unterhaching (Molasse basin). We compare these three sedimentary sites to two sites located in crystalline rock with respect to scattering and intrinsic attenuation. The inverse quality factor for intrinsic attenuation is constant in sediments for frequencies smaller than 10Hz and decreasing for higher frequencies. For crystalline rock, it is on a lower level and strictly monotonic decreasing with frequency. Intrinsic attenuation dominates scattering except for the Upper Rhine Graben, where scattering is dominant for frequencies below 10Hz. Observed source displacement spectra show a high-frequency fall-off greater than or equal to 3.Key words: Hydrothermal systems; Earthquake source observations; Seismic attenuation; Site effects; Wave scattering and diffraction. I N T RO D U C T I O NThe MAGS2 project (microseismic activity of geothermal systems) aims at the observation, understanding and hazard analysis of induced earthquake activity at deep geothermal systems. In the scope of the project geothermal reservoirs in the sedimentary basins of the Upper Rhine Graben and the Molasse basin are monitored for induced seismic activity. The three geothermal plants in Landau, Insheim (Upper Rhine Graben) and Unterhaching (Molasse basin) already induced earthquakes with magnitudes up to M2.7. One major goal of the project is the calculation of shake maps and its uncertainties for induced earthquakes, leading to the problem of interpolation of peak ground velocity (PGV) measurements. Therefore, it is important to understand high-frequency wave propagation and attenuation properties of the medium between the hypocentres of induced events and the surface. Furthermore, as the three geothermal sites are located in sedimentary basins and the induced earthquakes rupture near the interface between sediments and bedrock, the presented study allows for insights into scattering and absorption properties of shear waves in sediments.Attenuation of seismic waves, besides geometrical spreading, can be classified by the acting mechanism into intrinsic and scattering attenuation. Intrinsic attenuation is due to the absorption of seismic waves. Scattering attenuation is due to the redistribution...

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Section: Discussionmentioning

confidence: 99%

Section: O D E L E D a N D O B S E Rv E D E N E Rg Y D E N S I T I E Smentioning

confidence: 99%

Section: O D E L E D a N D O B S E Rv E D E N E Rg Y D E N S I T I E Smentioning

confidence: 99%

Section: O D E L E D a N D O B S E Rv E D E N E Rg Y D E N S I T I E Smentioning

confidence: 99%

Section: T Eulenfeld and U Weglermentioning

confidence: 99%

See 3 more Smart Citations

Measurement of intrinsic and scattering attenuation of shear waves in two sedimentary basins and comparison to crystalline sites in Germany

Eulenfeld¹,

Wegler²

2016

Geophys. J. Int.

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Crustal intrinsic and scattering attenuation of high‐frequency shear waves in the contiguous United States

Eulenfeld

Wegler

2017

JGR Solid Earth

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We use 10 years of data of the USArray project to estimate the areal distribution of crustal intrinsic and scattering attenuation of shear waves for frequencies between 1 Hz and 20 Hz in the contiguous United States. Additionally, we report energy site amplification factors and estimate moment magnitudes for small earthquakes (M 1.5 to M 3.5). The Qopen method is used to invert for intrinsic and scattering attenuation for each event and nearby stations. Observations are collected for around 25,000 events, averaged at each station and interpolated between station locations. In a second inversion, energy site amplifications and moment magnitudes are corrected by assuming that site amplifications for one station and frequency are the same for different earthquakes. We observe a west‐east decline of intrinsic attenuation for high frequencies which reflects the west‐east transition from young, hot to old and cold crust. Scattering attenuation for high frequencies is stronger in the east with an extraordinary high attenuation around the southern part of the Appalachian Highlands and the Interior Low Plateaus. Results at low frequencies do not show clear trends. A large site amplification is observed at high frequencies in parts of the eastern United States. Estimated moment magnitudes show a good agreement to moment magnitudes independently derived from moment tensor inversion. Moment magnitudes in the west are higher than in the east for the same Richter magnitudes.

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Anomalous attenuation of high-frequency seismic waves in Taiwan: observation, model and interpretation

Calvet

Margerin

Hung

2022

Preprint

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High resolution maps of seismic attenuation parameters in Taiwan have been obtained by using a modified "Multiple Lapse Time Window Analysis' (MLTWA). At most of the stations in porous sedimentary and highly faulted areas in Taiwan, the conventional modeling of MLTWA based on the scalar theory of radiative transfer in a half-space with isotropic scattering fails to explain the spatio-temporal distribution of the whole S wavetrain. Using Monte Carlo simulations of wave transport, we demonstrate that this anomalous energy distribution in the coda may be modelled by multiple anisotropic scattering of seismic waves. In addition to the scattering quality factor Qsc, we introduce a parameter g (independant of Qsc) which determines the angular redistribution of energy upon scattering (scattering anisotropy). We determine the attenuation parameters Qsc -1 , Q i -1 and g in three frequency bands (1-2, 2-4 and 4-8Hz). Overall, Taiwan is more attenuating than most orogens with a mean effective scattering loss (Qsc * ) -1 =Qsc -1 (1-g) about 0.025 and a mean intrinsic absorption Q i -1 about 0.009 at 1.5Hz.Scattering loss (Qsc * ) -1 varies over more than one order of magnitude across Taiwan while absorption fluctuations are about 30%. The more attenuating zones are the Coastal Range and the Coastal Plain where scattering dominates over absorption at low frequency, and inversely at high frequency. These regions are also characterized by strong backscattering (g<-0.85) at 1.5Hz and rather high V P /V S ratio. We speculate that the observed strong back-scattering at low frequency is related to strong impedance fluctuations in the crust induced by the presence of fluids.

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Seismic scattering and absorption parameters in the W-Bohemia/Vogtland region from elastic and acoustic radiative transfer theory

Cited by 46 publications

References 44 publications

Measurement of intrinsic and scattering attenuation of shear waves in two sedimentary basins and comparison to crystalline sites in Germany

Measurement of intrinsic and scattering attenuation of shear waves in two sedimentary basins and comparison to crystalline sites in Germany

Crustal intrinsic and scattering attenuation of high‐frequency shear waves in the contiguous United States

Anomalous attenuation of high-frequency seismic waves in Taiwan: observation, model and interpretation

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