Frequency dependence of Q in the mantle underlying the shield areas of Eurasia, Part III: The Q model

Der, Zoltan A.; Lees, Alison C.; Cormier, Vernon F.

doi:10.1111/j.1365-246x.1986.tb01985.x

Cited by 61 publications

(42 citation statements)

References 23 publications

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“…The bands vary with depth (ANDERSON and GIVEN, 1982) and correlate with tectonic structures McELFRESH, 1976, 1980;DER et al, 1986). Across a broad range of surface-and body-wave frequencies from *0.01 to *100 Hz (e.g., DER et al, 1982DER et al, , 1986LEES et al, 1986;ABERCROMBIE, 1998), Q values consistently increase with frequency in a vast majority of observations. However, attenuation is also always measured indirectly and in the background of strong amplitude variations, and the difficulty of differentiating its apparent attributes from the true in situ properties is well known (DER and LEES, 1985;WHITE, 1992).…”

Section: Introductionmentioning

confidence: 81%

“…Most Q models today represent the Earth as a combination of absorption bands with Q(f) = Q 0 f g transitions across their flanks (ANDERSON et al, 1977). The bands vary with depth (ANDERSON and GIVEN, 1982) and correlate with tectonic structures McELFRESH, 1976, 1980;DER et al, 1986). Across a broad range of surface-and body-wave frequencies from *0.01 to *100 Hz (e.g., DER et al, 1982DER et al, , 1986LEES et al, 1986;ABERCROMBIE, 1998), Q values consistently increase with frequency in a vast majority of observations.…”

Section: Introductionmentioning

confidence: 99%

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On the Causes of Frequency-Dependent Apparent Seismological Q

Morozov

2010

Pure Appl. Geophys.

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Variability of the Earth's structure makes a firstorder impact on attenuation measurements which often does not receive adequate attention. Geometrical spreading (GS) can be used as a simple measure of the effects of such structure. The traditional simplified GS compensation is insufficiently accurate for attenuation measurements, and the residual GS appears as biases in both Q 0 and g parameters in the frequency-dependent attenuation law Q(f) = Q 0 f g . A new interpretation approach bypassing Q(f) and using the attenuation coefficient v(f) = c ? pf/Q e (f) resolves this problem by directly measuring the residual GS, denoted c, and effective attenuation, Q e . The approach is illustrated by re-interpreting several published datasets, including nuclear-explosion and local-earthquake codas, Pn, and synthetic 50-300-s surface waves. Some of these examples were key to establishing the Q(f) concept.In all examples considered, v(f) shows a linear dependence on the frequency, c = 0, and Q e can be considered frequency-independent. Short-period crustal body waves are characterized by positive c SP values of (0.6-2.0) 9 10 -2 s -1 interpreted as related to the downward upper-crustal reflectivity. Long-period surface waves show negative c LP & -1.9 9 10 -5 s -1 , which could be caused by insufficient modeling accuracy at long periods. The above c values also provide a simple explanation for the absorption band observed within the Earth. The band is interpreted as apparent and formed by levels of Q e & 1,100 within the crust decreasing to Q e & 120 within the uppermost mantle, with frequencies of its flanks corresponding to c LP and c SP . Therefore, the observed absorption band could be purely geometrical in nature, and relaxation or scattering models may not be necessary for explaining the observed apparent Q(f). Linearity of the attenuation coefficient suggests that at all periods, the attenuation of both Rayleigh and Love waves should be principally accumulated at the sub-crustal depths (*38-100 km).

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Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

On the Causes of Frequency-Dependent Apparent Seismological Q

Morozov

2010

Pure Appl. Geophys.

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“…The frequency-independent P-wave Q models from these studies have values from about 100 to 250 for depths between 50 and 150 km. Der et al (1986) construct a P-wave Q model for the Eurasian Shield using a large set of teleseismic body waves. Their model has values between about 350 and 900 for frequencies between 0.3 and 10 Hz at depths between 100 and 200 km.…”

Section: Application To Observed Datamentioning

confidence: 99%

Geometric Spreading of Pn and Sn in a Spherical Earth Model

Yang¹,

Lay²,

Xie³

et al. 2007

Bulletin of the Seismological Society of America

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Geometric spreading of P n and S n waves in a spherical Earth model is different than that of classical headwaves and is frequency dependent. The behavior cannot be fully represented by a frequency-independent power-law model, as is commonly assumed. The lack of an accurate representation of P n and S n geometric spreading in a spherical Earth model impedes our ability to characterize Earth properties including anelasticity. We conduct numerical simulations to quantify P n and S n geometric spreading in a spherical Earth model with constant mantle-lid velocities. Based on our simulation results, we present new empirical P n and S n geometricspreading models in the form Gr; f 10 n 3 f =r 0 r 0 =r n 1 f logr 0 =rn 2 f and n i f n i1 logf=f 0 2 n i2 logf=f 0 n i3 , where i 1, 2, or 3; r is epicentral distance; f is frequency; r 0 1 km; and f 0 1 Hz. We derive values of coefficients n ij by fitting the model to computed P n and S n amplitudes for a spherical Earth model having a 40-km-thick crust, generic values of P and S velocities, and a constant-velocity uppermost mantle. We apply the new spreading model to observed data in Eurasia to estimate average P n attenuation, obtaining more reasonable results compared to using a standard power-law model. Our new P n and S n geometric-spreading models provide generally applicable reference behavior for spherical Earth models with constant uppermost-mantle velocities.

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“…Q(f) typically increases with the frequency (> 0), and large values of ~ 0.5 -1 are not uncommon in Lg Q and Lg coda Q studies (e.g., Nuttli, 1973;Hasegawa, 1985;Der et al, 1986;Campillo, 1987Campillo, , 1990Steensma and Biswas, 1988;Benz et al, 1997;Mandal and Rastogi, 1998;Frankel et al, 1990;McNamara et al, 1996;Mitchell and Cong, 1998;Mitchell et al, 1997Mitchell et al, , 1998McNamara, 2000;and Erickson et al, 2004). Such an increase is somewhat counter-intuitive, considering that the observed abundance of heterogeneities is usually greater at shorter scale-lengths.…”

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confidence: 99%

Frequency Dependence of Coda Q, Part I: Numerical Modeling and Examples from Peaceful Nuclear Explosions

Morozov¹,

Zhang²,

Duenow³

et al. 2008

Bulletin of the Seismological Society of America

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Frequency-dependent coda attenuation values are often reported; however such measurements usually depend on the types of the Q(f) models employed. We use numerical modeling of Peaceful Nuclear Explosion (PNE) codas at far regional to teleseismic distances to compare two of such models, namely the conventional frequency-dependent Q coda (f) = Q 0 f  and frequency-independent coda attenuation (Q c ) with geometrical attenuation (). The results favor strongly the (, Q c ) model and illustrate the mechanisms leading to apparent Q coda (f) dependencies. Tests for variations of the crustal velocity structures show that the values of  are stable and related to lithospheric structural types, and the inverted Q c values can be systematically mapped into the true S-wave attenuation factors within the crust. Modeling also shows that  could increase in areas where relatively thin attenuating layers are present within the crust; such areas could likely be related to younger and active tectonics. By contrast, when interpreted by using the traditional (Q 0 ,) approach, the synthetic coda shows a strong and spurious frequency dependence with   0.5, which is also similar to the observations. Observed Lg codas from two Peaceful Nuclear Explosions located in different areas in Russia show similar values of   0.75·10 -2 s -1 , which are also remarkably close to the independent numerical predictions. At the same time, coda Q c values vary strongly, from 850 in the East European Platform to 2500 within the Siberian Craton. This suggests that parameters  and Q c could provide stable and transportable discriminants for differentiating between the lithospheric tectonic types and ages, and also for seismic coda regionalization in nuclear test monitoring research.

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Frequency dependence of Q in the mantle underlying the shield areas of Eurasia, Part III: The Q model

Cited by 61 publications

References 23 publications

On the Causes of Frequency-Dependent Apparent Seismological Q

On the Causes of Frequency-Dependent Apparent Seismological Q

Geometric Spreading of Pn and Sn in a Spherical Earth Model

Frequency Dependence of Coda Q, Part I: Numerical Modeling and Examples from Peaceful Nuclear Explosions

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