Separation of intrinsic and scattering attenuation in southern California using TERRAscope data

Journal Article · Sat Sep 10 04:00:00 EDT 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JB01468· OSTI ID:70551

Jin, Anshu; Adams, D; Aki, Keiiti ^[1]; Mayeda, K ^[2]

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1. Univ. of Southern California, Los Angeles, CA (United States)
2. Lawrence Livermore National Lab., CA (United States)

A multiple lapse time window analysis was applied to three-component broadband seismograms recorded at five TERRAscope stations in southern California to separate scattering and intrinsic attenuation. Seismic energies were integrated over three consecutive lapse time intervals: 0-15, 15-30, and 30-45 s (measured from the S arrival for approximately 30 earthquakes with hypocentral distances of less than 70 km from each station). Using the fundamental separability of source, site, and path effects for coda waves, the integrated energies for different magnitude earthquakes were normalized to a common source size at each station, and the effect of near-site amplification is removed. Subsequently, the authors constructed a group of geometric spreading-corrected normalized energy-distance curves for each station region over frequency bands 0.5-1, 1-2, 2-4, and 4-8 Hz for all five stations. Two more frequency bands, 8-16 and 16-32 Hz, were added at stations PAS and SVD, for which higher sample rate data were available. A theoretical model of body wave energy propagation in a randomly heterogeneous elastic medium was employed to interpret the observation. Two parameters describe the medium in this model. These are the scattering attenuation coefficients {eta}{sub s} and the intrinsic attenuation coefficient {eta}{sub i}. By assuming that scattering is isotropic and including all orders of multiple scattering, this model predicts the spatial and temporal distribution of seismic energy. A two-step least squares fitting procedure was used to find the best fitting model parameters. The results show the following: (1) the seismic albedo, B{sub 0} = {eta}{sub s}/({eta}{sub i} + {eta}{sub s}), increases with decreasing frequency for all station regions. (2) Significant differences exist for the scattering attenuation coefficient {eta}{sub s} and seismic albedo B{sub 0} among stations at lower frequencies. 21 refs., 12 figs., 1 tab.

• DOE Contract Number: FG03-87ER13807
• OSTI ID: 70551
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: B9 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ATTENUATION
CALIFORNIA
EARTHQUAKES
FREQUENCY DEPENDENCE
MONITORING
SEISMIC WAVES