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Title: Regional Body-Wave Attenuation Using a Coda Source Normalization Method: Application to MEDNET Records of Earthquakes in Italy

Abstract

We develop a new methodology to determine apparent attenuation for the regional seismic phases Pn, Pg, Sn, and Lg using coda-derived source spectra. The local-to-regional coda methodology (Mayeda, 1993; Mayeda and Walter, 1996; Mayeda et al., 2003) is a very stable way to obtain source spectra from sparse networks using as few as one station, even if direct waves are clipped. We develop a two-step process to isolate the frequency-dependent Q. First, we correct the observed direct wave amplitudes for an assumed geometrical spreading. Next, an apparent Q, combining path and site attenuation, is determined from the difference between the spreading-corrected amplitude and the independently determined source spectra derived from the coda methodology. We apply the technique to 50 earthquakes with magnitudes greater than 4.0 in central Italy as recorded by MEDNET broadband stations around the Mediterranean at local-to-regional distances. This is an ideal test region due to its high attenuation, complex propagation, and availability of many moderate sized earthquakes. We find that a power law attenuation of the form Q(f) = Q{sub 0}f{sup Y} fit all the phases quite well over the 0.5 to 8 Hz band. At most stations, the measured apparent Q values are quite repeatable frommore » event to event. Finding the attenuation function in this manner guarantees a close match between inferred source spectra from direct waves and coda techniques. This is important if coda and direct wave amplitudes are to produce consistent seismic results.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
913548
Report Number(s):
UCRL-JRNL-227999
Journal ID: ISSN 0094-8276; GPRLAJ; TRN: US200802%%867
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 34; Journal ID: ISSN 0094-8276
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; AMPLITUDES; ATTENUATION; AVAILABILITY; EARTHQUAKES; ITALY; SPECTRA

Citation Formats

Walter, W R, Mayeda, K, Malagnini, L, and Scognamiglio, L. Regional Body-Wave Attenuation Using a Coda Source Normalization Method: Application to MEDNET Records of Earthquakes in Italy. United States: N. p., 2007. Web. doi:10.1029/2007GL029990.
Walter, W R, Mayeda, K, Malagnini, L, & Scognamiglio, L. Regional Body-Wave Attenuation Using a Coda Source Normalization Method: Application to MEDNET Records of Earthquakes in Italy. United States. https://doi.org/10.1029/2007GL029990
Walter, W R, Mayeda, K, Malagnini, L, and Scognamiglio, L. 2007. "Regional Body-Wave Attenuation Using a Coda Source Normalization Method: Application to MEDNET Records of Earthquakes in Italy". United States. https://doi.org/10.1029/2007GL029990. https://www.osti.gov/servlets/purl/913548.
@article{osti_913548,
title = {Regional Body-Wave Attenuation Using a Coda Source Normalization Method: Application to MEDNET Records of Earthquakes in Italy},
author = {Walter, W R and Mayeda, K and Malagnini, L and Scognamiglio, L},
abstractNote = {We develop a new methodology to determine apparent attenuation for the regional seismic phases Pn, Pg, Sn, and Lg using coda-derived source spectra. The local-to-regional coda methodology (Mayeda, 1993; Mayeda and Walter, 1996; Mayeda et al., 2003) is a very stable way to obtain source spectra from sparse networks using as few as one station, even if direct waves are clipped. We develop a two-step process to isolate the frequency-dependent Q. First, we correct the observed direct wave amplitudes for an assumed geometrical spreading. Next, an apparent Q, combining path and site attenuation, is determined from the difference between the spreading-corrected amplitude and the independently determined source spectra derived from the coda methodology. We apply the technique to 50 earthquakes with magnitudes greater than 4.0 in central Italy as recorded by MEDNET broadband stations around the Mediterranean at local-to-regional distances. This is an ideal test region due to its high attenuation, complex propagation, and availability of many moderate sized earthquakes. We find that a power law attenuation of the form Q(f) = Q{sub 0}f{sup Y} fit all the phases quite well over the 0.5 to 8 Hz band. At most stations, the measured apparent Q values are quite repeatable from event to event. Finding the attenuation function in this manner guarantees a close match between inferred source spectra from direct waves and coda techniques. This is important if coda and direct wave amplitudes are to produce consistent seismic results.},
doi = {10.1029/2007GL029990},
url = {https://www.osti.gov/biblio/913548}, journal = {Geophysical Research Letters},
issn = {0094-8276},
number = ,
volume = 34,
place = {United States},
year = {2007},
month = {2}
}

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