Amplitude ratio tomography for regional phase Q

Phillips, W. S.; Hartse, Hans E.; Rutledge, James

doi:10.1029/2005gl023870

Cited by 27 publications

(34 citation statements)

References 33 publications

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“…Our merged data set is composed of 770 selected earthquakes with local magnitude > 3, each one recorded by at least 2 stations as required by the amplitude ratio tomography methodology of Phillips et al (2005). The waveforms (~16,000) have beenwere recorded by 54 stations (Table 1) The maps of Figure 1 show the dense ray coverage we obtained with this data set.…”

Section: )mentioning

confidence: 92%

“…The early coda would simply smear this region further laterally. For more details on the methodology we address the reader to Phillips et al 2005 and. We solve for each frequency band using sparse matrix methods (LSQR; Paige and Saunders, 1982), applying the first difference regularization to the attenuation terms and assuming constrain the site terms to sum equal to zero.…”

Section: Methodology Overviewmentioning

confidence: 99%

“…__________ RESPONSE: __________ We address this issue by referring the reader to a number of methodology papers by one of the coauthors (Scott Phillips) who developed the methodology and who co-authored a number of studies that used this same empirical coda envelope tomography methodology. (e.g., Phillips et al, 2005;Mayeda et al, 2005).…”

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confidence: 99%

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Improved 2-D attenuation analysis for Northern Italy using a merged dataset from selected regional seismic networks

Morasca

Massa²,

Laprocina³

et al. 2010

J Seismol

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A merged, high-quality waveform data set from different seismic networks has been used to improve our understanding of lateral seismic attenuation for Northern Italy. In a previous study on the same region, Morasca et al. (2008) were able to resolve only a small area due to limited data coverage. For this reason the interpretation of the attenuation anomalies was difficult given the complexity of the region and the poor resolution of the available data. In order to better understand the lateral changes in the crustal structure and thickness of this region, we selected 770 earthquakes recorded by 54 stations for a total of almost 16000 waveforms derived from seismic networks operating totally or partially in Northern Italy. Direct S-wave and coda attenuation images were obtained using an amplitude ratio technique that eliminates source terms from the formulation. Both direct and early-coda amplitudes are used as input for the inversions and the results are compared.Results were obtained for various frequency bands ranging between 0.3-25.0 Hz, and in all cases show significant improvement with respect to the previous study since the resolved area has been extended and more crossing paths have been used to image smaller scale anomalies. Quality-factor estimates are consistent with the regional tectonic structure exhibiting a general trend of low attenuation under the Po Plain basin and higher values for the western Alps and northern Apennines. The interpretation of the results for the Eastern Alps is not simple, possibly because our resolution for this area is still not adequate to resolve small scale structures.Response to Reviewers: Dear Dr. ZahradnikBelow is our response to the two reviewers' comments and we have uploaded both the revision and another copy with highlighted changes. Both reviewers had very good suggestions and we tried to address each item. We feel fortunate to have received such thorough reviews, particularly reviewer #2 who had numerous comments that ultimately made the paper more clear. We emphasize that this current study is an extension of the 2008 Western Alps study by Morasca et al. (BSSA) but incorporating a much larger data set. The inversion methodology and assumptions on using the early coda is described in detail in the previous work. In addition, we cite in the current study other supporting papers that describe in great detail more of the method. Including this once again in this paper would seem redundant. In addition, we have highlighted changes in the revision as well. COMMENTS FOR THE AUTHOR:Reviewer #1: This paper presents a 2-D Attenuation study for Northern Italy. The authors use earthquakes recorded by several stations deployed in the region. This study extends geographically the knowledge of Q distribution especially north eastern of the studied zone. The presented results agree with previously reported. I found this manuscript to be well written and presenting a very complete study. I support its publication in JOSE. I have some minor comments:1.-Abstract shows ...

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Section: )mentioning

confidence: 92%

Section: Methodology Overviewmentioning

confidence: 99%

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Improved 2-D attenuation analysis for Northern Italy using a merged dataset from selected regional seismic networks

Morasca

Massa²,

Laprocina³

et al. 2010

J Seismol

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“…Lg wave data have also been applied to attenuation tomography (e.g., Mitchell et al, 1997;Phillips et al, 2000Phillips et al, , 2001Phillips et al, , 2005aCong et al, 2003;Taylor et al, 2003;Liu et al, 2004a, b). Tomographic inversion for regional imaging of Q has been performed in earlier studies using limited waveform data sets (e.g., Haberland and Rietbrock, 2001;Liu et al, 2004b;Phillips et al, 2005a). These researches show low resolution because of small data set in a large area.…”

Section: Introductionmentioning

confidence: 99%

“…Surface waves are often inverted for attenuation (e.g., Romanowicz, 1995;Li et al, 2000;Hong et al, 2003;Gung and Romanowicz, 2004;Jemberie and Mitchell, 2004). Lg wave data have also been applied to attenuation tomography (e.g., Mitchell et al, 1997;Phillips et al, 2000Phillips et al, , 2001Phillips et al, , 2005aCong et al, 2003;Taylor et al, 2003;Liu et al, 2004a, b). Tomographic inversion for regional imaging of Q has been performed in earlier studies using limited waveform data sets (e.g., Haberland and Rietbrock, 2001;Liu et al, 2004b;Phillips et al, 2005a).…”

Section: Introductionmentioning

confidence: 99%

The updated crustal attenuation in North China using ML amplitude tomography

Pei

Chen

2010

Earthq Sci

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We have updated the lateral variations of the quality factor Q 0 (Q at 1 Hz) beneath the crust of North China using M L amplitude tomography with near three times data. The data were selected from the Annual Bulletin of Chinese Earthquakes (ABCE) in 1985−2009, including 26 283 M L amplitude readings from 4 204 events recorded by 38 stations. The result is similar with previous research but has higher resolution. Estimated Q 0 values are consistent with tectonic and topographic structure in North China. Q 0 is low in the active tectonic regions having many faults, such as Bohai bay, North China basin, the Shanxi and Yinchuan grabens, while it is high in the stable Ordos craton. Q 0 values are low in several topographically low-lying areas, such as the North China, Taikang-Hefei, and Subei-Huanghai Sea basins, whereas it is high in mountainous and uplift regions exhibiting surface expressions of crystalline basement rocks: the Yinshan, Yanshan, Taihang, Qinling and Dabie mountains, Luxi and Jiaoliao uplifts. Quality factor estimates are also consistent with Pn and Sn velocity patterns. High velocity values in general correspond with high Q 0 and vice versa. This coincides with a common temperature influence in the crust and uppermost mantle.

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Can We Improve Estimates of Seismological Q Using a New “Geometrical Spreading” Model?

Xie

2010

Pure Appl. Geophys.

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Abstract-Precise measurements of seismological Q are difficult because we lack detailed knowledge on how the Earth's fine velocity structure affects the amplitude data. In a number of recent papers, Morozov (Geophys J Int 175:239-252, 2008; Seism Res Lett 80:5-7, 2009; Pure Appl Geophys, this volume, 2010) proposes a new procedure intended to improve Q determinations. The procedure relies on quantifying the structural effects using a new form of geometrical spreading (GS) model that has an exponentially decaying component with time, e -ct Ác is a free parameter and is measured together with Q. Morozov has refit many previously published sets of amplitude attenuation data. In general, the new Q estimates are much higher than previous estimates, and all of the previously estimated frequency-dependence values for Q disappear in the new estimates. In this paper I show that (1) the traditional modeling of seismic amplitudes is physically based, whereas the new model lacks a physical basis; (2) the method of measuring Q using the new model is effectively just a curve fitting procedure using a first-order Taylor series expansion; (3) previous highfrequency data that were fit by a power-law frequency dependence for Q are expected to be also fit by the first-order expansion in the limited frequency bands involved, because of the long tails of power-law functions; (4) recent laboratory measurements of intrinsic Q of mantle materials at seismic frequencies provide independent evidence that intrinsic Q is often frequency-dependent, which should lead to frequency-dependent total Q; (5) published long-period surface wave data that were used to derive several recent Q models inherently contradict the new GS model; and (6) previous modeling has already included a special case that is mathematically identical to the new GS model, but with physical assumptions and measured Q values that differ from those with the new GS model. Therefore, while individually the previous Q measurements have limited precision, they cannot be improved by using the new GS model. The large number of Q measurements by seismologists are sufficient to show that Q values in the Earth are highly laterally variable and are often frequency dependent.

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Amplitude ratio tomography for regional phase Q

Cited by 27 publications

References 33 publications

Improved 2-D attenuation analysis for Northern Italy using a merged dataset from selected regional seismic networks

Improved 2-D attenuation analysis for Northern Italy using a merged dataset from selected regional seismic networks

The updated crustal attenuation in North China using ML amplitude tomography

Can We Improve Estimates of Seismological Q Using a New “Geometrical Spreading” Model?

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