TY - JOUR

T1 - Scattering attenuation and intrinsic absorption using uniform and depth dependent model-application to full seismogram envelope recorded in Northern Chile

AU - Hoshiba, Mitsuyuki

AU - Rietbrock, Andreas

AU - Scherbaum, Frank

AU - Nakahara, Hisashi

AU - Haberland, Christian

N1 - Funding Information:
The authors thank two reviewers and associate editor, R. Madariaga, for their comments. The investigation using a depth dependent model was motivated by Margerin et al. (1999). A discussion with K. Kato suggested to us the meaning of scattering strength in a 3D velocity structure model. A part of this study was conducted when one of the authors (M.H) was a visiting scientist of Ludwig-Maximilians Uni-versität München through a fund of the Science and Technology Agency, Japan. The operations of the PISCO’94 and CINCA’95 seismic networks were funded by the German Research Association (Deutsche Forschungsgemeinschaft (DFG)) as part of the Son-derforschungsbereich (Collaborative Research Center) SFB167 ‘Deformation Process in the Andes’ and by GFZ Potsdam. Figure 1 was made using GMT(Wessel and Smith, 1995).

PY - 2001

Y1 - 2001

N2 - Two seismic wave attenuation factors, scattering attenuation Qs-1 and intrinsic absorption Qi-1 are measured using the Multiple Lapse Time Window (MLTW) analysis method for three different frequency bands, 1-2, 2-4, and 4-8 Hz. Data from 54 temporally deployed seismic stations located in northern Chile are used. This method compares time integrated seismic wave energies with synthetic coda wave envelopes for a multiple isotropic scattering model. In the present analysis, the wave energy is assumed to decay with distance in proportion to 1/GSF-exp(- (Qs-1+Qi-1)·w r/v), where r, w and v are the propagation distance, angular frequency and S wave velocity, respectively, and GSF is the geometrical spreading factor. When spatial uniformity of Qs-1, Qi-1 and v is assumed, i.e. GSF = 4π r2, the estimates of the reciprocal of the extinction length, Le-1 (= (Qs-1+Qi-1)·w/v), are 0.017, 0.012 and 0.010 km-1, and those of the seismic albedo, Bo (= Qs-1/(Qs-1+Qi-1)), are 0.48, 0.40 and 0.34 for 1-2, 2-4 and 4-8 Hz,respectively, which indicates that scattering attenuation is comparable to or smaller than intrinsic absorption. When we assume a depth dependent velocity structure, we also find that scattering attenuation is comparable to or smaller than intrinsic absorption. However, since the quantitative estimates of scattering attenuation depend on the assumed velocity structure (strength of velocity discontinuity and/or Moho depth), it is important to consider differences in velocity structure models when comparing attenuation estimates.

AB - Two seismic wave attenuation factors, scattering attenuation Qs-1 and intrinsic absorption Qi-1 are measured using the Multiple Lapse Time Window (MLTW) analysis method for three different frequency bands, 1-2, 2-4, and 4-8 Hz. Data from 54 temporally deployed seismic stations located in northern Chile are used. This method compares time integrated seismic wave energies with synthetic coda wave envelopes for a multiple isotropic scattering model. In the present analysis, the wave energy is assumed to decay with distance in proportion to 1/GSF-exp(- (Qs-1+Qi-1)·w r/v), where r, w and v are the propagation distance, angular frequency and S wave velocity, respectively, and GSF is the geometrical spreading factor. When spatial uniformity of Qs-1, Qi-1 and v is assumed, i.e. GSF = 4π r2, the estimates of the reciprocal of the extinction length, Le-1 (= (Qs-1+Qi-1)·w/v), are 0.017, 0.012 and 0.010 km-1, and those of the seismic albedo, Bo (= Qs-1/(Qs-1+Qi-1)), are 0.48, 0.40 and 0.34 for 1-2, 2-4 and 4-8 Hz,respectively, which indicates that scattering attenuation is comparable to or smaller than intrinsic absorption. When we assume a depth dependent velocity structure, we also find that scattering attenuation is comparable to or smaller than intrinsic absorption. However, since the quantitative estimates of scattering attenuation depend on the assumed velocity structure (strength of velocity discontinuity and/or Moho depth), it is important to consider differences in velocity structure models when comparing attenuation estimates.

KW - Absorption

KW - Andes

KW - Chile

KW - Layered media

KW - Lithosphere

KW - Q

KW - Scattering

KW - Seismic coda

KW - Seismic wave propagation

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U2 - 10.1023/A:1011478202750

DO - 10.1023/A:1011478202750

M3 - Article

AN - SCOPUS:0035043652

SN - 1383-4649

VL - 5

SP - 157

EP - 179

JO - Journal of Seismology

JF - Journal of Seismology

IS - 2

ER -