%0 Journal Article %1 Hwang:2009 %A Hwang, Y. K. %A Ritsema, J. %A Goes, S. %C WASHINGTON %D 2009 %I AMER GEOPHYSICAL UNION %J JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH %K ALLEGHANIAN ANELASTIC APPALACHIANS; ATTENUATION; CODA CONTINENTAL FREQUENCY-DEPENDENCE; LG LOW-VELOCITY MELT; OROGENY PARTIAL Q; SEISMIC SOUTHERN SURFACE-WAVE; TOMOGRAPHY; UNITED-STATES; ZONE; %P B06312 %R 10.1029/2008JB006091 %T Spatial variations of P wave attenuation in the mantle beneath North America %V 114 %X We estimate the spatial variation of the seismic parameter t* using teleseismic (epicentral distance = 30 degrees-85 degrees) P wave spectra of about 200 deep (focal depths >200 km) earthquakes recorded by 378 broadband seismometers in the United States and Canada. Relative P wave spectral ratios up to 1 Hz for about 63,000 station pairs with high signal-to-noise ratio and impulsive P waveforms are inverted for t(P)* by least squares inversion. The continental-scale t(P)* pattern correlates to the age of geological terrains and the seismic, heat flow, gravity, and magnetic variations across North America. Predominantly low values of t(P)* are obtained in stable central North America (SNA), and high t(P)* values are obtained for stations in the tectonically active western part of the continent (TNA). This variation is similar to that observed previously in short-period amplitude anomalies, spectral ratio variations, and ScS reverberations. On average, we resolve a contrast in t(P)* between SNA and TNA of about 0.2 s. We resolve regional variations in t(P)*, which correlate with tectonics. Relatively low t(P)* is associated with currently active subduction below Alaska. Relatively high t(P)* is found in SNA below the Appalachians and the Gulf Coast. The consistency between t(P)* and tectonics suggests that the observed variations in t(P)* are, on the scale of around 200-500 km, predominantly due to intrinsic attenuation. The similar patterns in t(P)* and predicted values for a recent global attenuation model confirm this further. The compatibility with the t(P)* computed for attenuation estimated via a thermal interpretation of shear wave velocity anomalies illustrates that variations in seismic velocity are predominantly due to physical effects with a strong attenuation signature, most likely temperature or a combination of temperature and water content.

@article{Hwang:2009, abstract = {We estimate the spatial variation of the seismic parameter t* using teleseismic (epicentral distance = 30 degrees-85 degrees) P wave spectra of about 200 deep (focal depths >200 km) earthquakes recorded by 378 broadband seismometers in the United States and Canada. Relative P wave spectral ratios up to 1 Hz for about 63,000 station pairs with high signal-to-noise ratio and impulsive P waveforms are inverted for t(P)* by least squares inversion. The continental-scale t(P)* pattern correlates to the age of geological terrains and the seismic, heat flow, gravity, and magnetic variations across North America. Predominantly low values of t(P)* are obtained in stable central North America (SNA), and high t(P)* values are obtained for stations in the tectonically active western part of the continent (TNA). This variation is similar to that observed previously in short-period amplitude anomalies, spectral ratio variations, and ScS reverberations. On average, we resolve a contrast in t(P)* between SNA and TNA of about 0.2 s. We resolve regional variations in t(P)*, which correlate with tectonics. Relatively low t(P)* is associated with currently active subduction below Alaska. Relatively high t(P)* is found in SNA below the Appalachians and the Gulf Coast. The consistency between t(P)* and tectonics suggests that the observed variations in t(P)* are, on the scale of around 200-500 km, predominantly due to intrinsic attenuation. The similar patterns in t(P)* and predicted values for a recent global attenuation model confirm this further. The compatibility with the t(P)* computed for attenuation estimated via a thermal interpretation of shear wave velocity anomalies illustrates that variations in seismic velocity are predominantly due to physical effects with a strong attenuation signature, most likely temperature or a combination of temperature and water content.}, added-at = {2010-08-12T23:06:12.000+0200}, address = {WASHINGTON}, af = {Hwang, Yong Keun Ritsema, Jeroen Goes, Saskia}, author = {Hwang, Y. K. and Ritsema, J. and Goes, S.}, author-address = {[Hwang, Yong Keun; Ritsema, Jeroen] Univ Michigan, Dept Geol Sci, Ann Arbor, MI 48109 USA. [Goes, Saskia] Univ London Imperial Coll Sci Technol & Med, Dept Earth Sci & Engn, London SW7 2AZ, England.}, bdsk-file-1 = {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}, bdsk-url-1 = {http://dx.doi.org/10.1029/2008JB006091}, biburl = {https://www.bibsonomy.org/bibtex/250f3924d4dcdec11ba12fce697b1eb55/jkmacc}, cited-reference-count = {71}, date-added = {2010-04-03 14:22:38 -0600}, date-modified = {2010-04-03 14:22:38 -0600}, document-type = {Article}, doi = {10.1029/2008JB006091}, e-mail-address = {ykhwang@umich.edu}, fu = {IRIS/DMC ; GEOSCOPE Data Center ; Geological Survey of Canada ; Southern California Seismic Network (SCSN) ; USGS ; Northern California Earthquake Data Center (NCEDC) ; University of California Berkeley Seismological Laboratory (BSL) ; GMT ; NSF [EAR-0609763]}, fx = {Data have been provided by the IRIS/DMC, the GEOSCOPE Data Center, the Geological Survey of Canada, the Southern California Seismic Network (SCSN) Data Center operated by Caltech and USGS, and the Northern California Earthquake Data Center (NCEDC), a joint project of the University of California Berkeley Seismological Laboratory (BSL) and the USGS. Figures are produced by GMT ( Generic Mapping Tools) software. We thank Colleen Dalton for providing us with her Q model and for giving advice on model interpretation. We thank Jonathan Lees for providing us with the MTM (Multi-Taper Spectral Analysis Methods) software. Constructive comments by two anonymous reviewers and the Associate Editor helped us improve the article. This research has been supported by NSF grant EAR-0609763.}, interhash = {a08d3422db7d586f84b8e7d3518c865e}, intrahash = {50f3924d4dcdec11ba12fce697b1eb55}, isi = {ISI:000267190800002}, isi-document-delivery-number = {460MC}, iso-source-abbreviation = {J. Geophys. Res.-Solid Earth}, issn = {0148-0227}, journal = {JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH}, keywords = {ALLEGHANIAN ANELASTIC APPALACHIANS; ATTENUATION; CODA CONTINENTAL FREQUENCY-DEPENDENCE; LG LOW-VELOCITY MELT; OROGENY PARTIAL Q; SEISMIC SOUTHERN SURFACE-WAVE; TOMOGRAPHY; UNITED-STATES; ZONE;}, language = {English}, month = Jun, page-count = {11}, pages = {B06312}, publication-type = {J}, publisher = {AMER GEOPHYSICAL UNION}, publisher-address = {2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA}, reprint-address = {Hwang, YK, Univ Michigan, Dept Geol Sci, 2534 CC Little Bldg,1100 N Univ Ave, Ann Arbor, MI 48109 USA.}, source = {J GEOPHYS RES-SOLID EARTH}, subject-category = {Geochemistry & Geophysics}, times-cited = {0}, timestamp = {2010-08-12T23:06:14.000+0200}, title = {Spatial variations of P wave attenuation in the mantle beneath North America}, volume = 114, year = 2009 }