Seismogram Envelope Inversion Using a Multiple Isotropic Scattering Model: Application to Aftershocks of the 2001 Bhuj Earthquake

Padhy, Simanchal; Wegler, Ulrich; Korn, M.

doi:10.1785/0120060035

Cited by 18 publications

(20 citation statements)

References 49 publications

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“…Other authors only use one time window with stronger smoothing containing coda and onset in a similar method (Padhy et al 2007;Fielitz & Wegler 2015). This makes the method less complex, because the discrimination between direct S-wave window and coda window is omitted.…”

Section: N V E R S I O N F O R At T E N Uat I O N Pa R a M E T E R mentioning

confidence: 99%

“…A Green's function based on anisotropic scattering theory is expected to better fit the observations near the S onset. The approach of Padhy et al (2007) and Fielitz & Wegler (2015) would be adequate for this kind of Green's function. The simple and effective solution to the mismatch of observed and isotropically modeled envelopes is to just use the averages in the S-wave time window as suggested by SensSchönfelder & Wegler (2006).…”

Section: N V E R S I O N F O R At T E N Uat I O N Pa R a M E T E R mentioning

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: N V E R S I O N F O R At T E N Uat I O N Pa R a M E T E R mentioning

confidence: 99%

Section: N V E R S I O N F O R At T E N Uat I O N Pa R a M E T E R mentioning

confidence: 99%

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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“…The detailed introduction to RTT in seismology is described in Margerin (2005). RTT was solved numerically by considering both the vector (Margerin et al, 2000;Przybilla et al, 2006) and scalar (Margerin et al, 1998(Margerin et al, , 1999Lacombe et al, 2003;Padhy et al, 2007) nature of the underlying wave motion. Wu (1985) separated the effect of scattering and intrinsic attenuation using RTT.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the studies on attenuation in India (Table 1) focus on estimating Q 1 for coda wave (for Garhwal Himalaya, see Gupta et al [1995], Mandal et al [2001], and Mukhopadhyay et al [2008]; for Koyna, see Mandal and Rastogi [1998]; for Kumaon Himalaya, see Paul et al [2003]; for northwestern Himalaya, see Kumar et al [2005] and Mukhopadhyay et al [2006]), S wave (for Garhwal Himalaya, see Nath et al [2002] and Joshi [2006]; for Bhuj, see Padhy et al [2007]), and Lg wave (for Himayan arc, see Singh et al [2002]; for Indian shield, see Singh et al [2004]). Two such studies Padhy et al, 2007) separated the Q 1 i and Q 1 s using different approaches for Garhwal Himalaya and Bhuj, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Inversion of Seismogram Envelopes Using a Multiple Isotropic Scattering Model in Garhwal Himalaya

Padhy¹

2009

Bulletin of the Seismological Society of America

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We estimated intrinsic attenuation Q 1 i , scattering attenuation Q 1 s , site amplification Z, and source energy S from inversion of three-component coda envelopes of the 1999 Chamoli earthquake of India for central frequencies 1.5, 3, 6, 12, and 24 Hz. The multiple isotropic scattering of S waves was numerically simulated by using a Monte Carlo method based on the radiative transfer theory. Isotropic sources and acoustic scattering in a full space were assumed. Adapting a grid search for scattering coefficient g and least-squares inversion for intrinsic attenuation parameter b, and source energy S, we inverted the observed envelopes of ten aftershocks (M L ≥ 3:5) in 1-24 Hz.Our results reveal that both Q 1 s and Q 1 i are weakly frequency dependent with the power-law forms of 0:006 0:004f 0:890:33 and 0:003 0:0005f 0:840:08 , respectively. High scattering loss can be interpreted to be due to the presence of large lateral velocity heterogeneities in the crust. The total attenuation Q 1 decreases with frequency, taking the power-law form of 0:009 0:003f 0:870:19 . The mean free path ranges from 30 to 300 km, with an average value of 100 km, and the intrinsic attenuation parameter b ranges from 0.01 to 0:05 sec 1 , with an average value of 0:03 sec 1 . Our estimates of source energy are in good agreement with the values obtained assuming an ω 2 -source model. Site effects estimated using the fixed values of S k , b, and g exhibit less scatter, ranging from 0.73 to 2.54 with no significant frequency dependence consistent with the rock sites.

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High-frequency Seismology

Padhy

2020

Encyclopedia of Solid Earth Geophysics

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Seismogram Envelope Inversion Using a Multiple Isotropic Scattering Model: Application to Aftershocks of the 2001 Bhuj Earthquake

Cited by 18 publications

References 49 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

Inversion of Seismogram Envelopes Using a Multiple Isotropic Scattering Model in Garhwal Himalaya

High-frequency Seismology

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