Q−1 of forsterite single crystals

Guéguen, Yves; Darot, M.; Mazot, P.; Woirgard, J.

doi:10.1016/0031-9201(89)90073-3

Cited by 69 publications

(47 citation statements)

References 12 publications

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“…Studies have invoked frequency dependence to reconcile Q values observed for free oscillations of the Earth and 1-Hz body waves (JEFFREYS, 1967;LIU et al, 1976) to explain shear-wave Q observed for ScS waves at low and high frequencies (SIPKIN and JORDAN, 1979), and to explain variations in Q with frequency for teleseismic P and S waves in the range 0.02-4.0 Hz (DER et al, 1982). Frequency dependence of Q for upper mantle material rock has also been observed in laboratory experiments (e.g., GUEGUEN et al, 1989;JACKSON et al, 2003).…”

Section: Introductionmentioning

confidence: 73%

Frequency-dependent Shear-wave Q Models for the Crust of China and Surrounding Regions

Jemberie

Mitchell

2005

Pure appl. geophys.

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Starting with fundamental-mode Rayleigh-wave attenuation coefficient values (c R ) predicted by previously determined frequency-independent models of shear-wave Q (Q l ), we have obtained frequency-dependent Q l models that explain measured values of c R as well as of Lg coda Q and its frequency dependence at 1 Hz (Q o and g, respectively) for China and some adjacent regions. The process combines trial-and-error selection of a model for the depth distribution of the frequency dependence parameter (f) for Q l with a formal inversion for the depth distribution of Q l at 1 Hz. Fifteen of the derived models have depth distributions of f that are constant, or nearly constant, between the surface and a depth of 30 km. f distributions that vary with depth in the upper 30 km are necessary to explain the remaining seven models. f values for the depth-independent models vary between 0.4 and 0.7 everywhere except in the western portion of the Tibetan Plateau where they range between about 0.1 and 0.3 for three paths. These low f values lie in a region where Q Lg and crustal Q l are very low and suggest that they should also be low for high-frequency propagation. The models in which f varies with depth all show a decrease in that value ranging between 0.55 and 0.8 in the upper 15 km of the crust and (with two exceptions where f ¼ 0.0) between 0.3 and 0.55 in the depth range 15-30 km. The distribution of f values between 0.6 and 0.8 (the higher part of the range) in the upper crust indicates that high-frequency waves will propagate most efficiently, relative to low-frequency waves, in a band that includes, and strikes north-northeastward from the path between event 212/97 and KMI to the path between event 180/95 and station HIA in the north.

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Section: Introductionmentioning

confidence: 73%

Frequency-dependent Shear-wave Q Models for the Crust of China and Surrounding Regions

Jemberie

Mitchell

2005

Pure appl. geophys.

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“…A dislocation mechanism is also favoured by Gueguen et al [1981] and Kampfmann and Berckhemer [1985]. Gueguen et al [1989] present Q values obtained for single forsterite crystals at seismic frequencies. The measurements show that attenuation increases with temperature in a manner similar to that observed in polycrystaline samples.…”

Section: Laboratory Determinations Of Q At High Temperatures In Maficmentioning

confidence: 85%

“…Obtaining measurements that are valid for both the compositional, pressure, and temperature conditions in the Earth and for the frequency, scale, and strain rates of seismic observations is a formidable task [e.g., Jackson, 1986;Christensen and Wepfer, 1989]. A number of measurements have been carried out on mafic and ultramafic samples at elevated temperatures [Woirguard and Gueguen, 1978;Berckhemer et al, 1979;Sacks and Murase, 1983;Kampfmann and Berckhemer, 1985;Sato and Manghnani, 1985;Manghnani et al, 1986;Sato et al, 1988Gueguen et al, 1989;Jackson et al, 1992]. The majority of these works were motivated by a desire to understand the properties of the asthenosphere and are thus primarily devoted to ultramafic samples.…”

Section: Laboratory Determinations Of Q At High Temperatures In Maficmentioning

confidence: 99%

The seismic attenuation structure of the East Pacific Rise

Wilcock¹

1992

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Studies of seismic propagation through oceanic crust have contributed enormously to our understanding of the generation and evolution of oceanic crust. However, such work has largely been confined to the seismic velocity structure. In this thesis we present results from a study of seismic attenuation using a data set collected for three-dimensional tomographic imaging of a fast-spreading ridge. The experiment location at 9 0 30'N on the East Pacific Rise is the site of a strong mid-crustal seismic reflector which has been inferred to be the roof of a small axial magma chamber at about 1.6 km depth.A spectral method is used to estimate t*, a measure of the integrated attenuation along a wave path. Such a method assumes that the dominant frequency-dependent component of propagation is intrinsic attenuation. A logarithmic parameterization is then used to invert t* measurements for Q-I structure assuming that the velocity structure is given from earlier studies. To evaluate the method of Q tomography a full-waveform finitedifference technique which does not include attenuation is used to calculate solutions for seismic propagation through a two-dimensional velocity model. The results show a complex pattern of seismic propagation in the vicinity of the axial magma chamber. The first arrival always passes above the magma chamber. However, for paths of significant length that cross the rise axis the amplitude of this arrival is very small, and the first phase with significant amplitude is a diffraction below the magma chamber. High-amplitude Moho turning and PP arrivals may also be important secondary arrivals. Synthetic inversions show the importance of selecting time windows for power spectral estimation which are dominated by a single phase and of using wave paths which closely corresponds to that of the selected phase.A comparison of the finite difference solutions and the predictions of the a twodimensional, exact ray-tracing algorithm with record sections obtained during the tomography experiment significantly improves our understanding of seismic propagation across the East Pacific Rise. The results enable an objective choice of the position and length of the time window for t* estimation. Moreover, additional constraints are incorporated into an approximate three-dimensional ray-tracing algorithm used in the inversion so that the wave paths more closely correspond to those of the desired phase. The full data set to be inverted comprises about 3500 t* estimates and includes crustal paths which do not cross the rise axis, diffractions above and below the axial magma chamber, and Moho-turning phases. Wave paths for the Moho-turning phases cross the rise axis at a wide range of lower crustal depths.The Q-1 models resulting from two-dimensional and three-dimensional tomographic inversions show that the attenuation of seismic waves on the East Pacific Rise is dominated by two regions of low Q; one in the upper 1 km of crust, and one at depths greater than about 2 km below the rise axis. While the data do not ...

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“…They model the attenuation as a thermally activated process with a power-law frequency dependence (BERCKHEMER et al, 1982), and their experimentally determined parameter of h=0.25 for = 0.003 -30 Hz. GUEGUEN et al (1989), in experiments with forsterite single crystals, found Q −1 −0.2 at high temperature and seismic frequencies, while SATO et al (1989), in a study at high temperature and pressure but ultrasonic frequencies, found a weaker frequency dependence of hB −0.2. JACKSON and PATERSON (1993) made measurements at 1000°C and 300 MPa over the frequency range 0.03 to 1 Hz, and found yet a weaker dependence with h= 0.19 to 0.15.…”

Section: Comparison With Mineral Physics Experimentsmentioning

confidence: 99%

Attenuation of Broadband P and S Waves in Tonga: Observations of Frequency Dependent Q

Flanagan¹,

Wiens²

1998

Pure and Applied Geophysics

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Teleseismic broadband recordings of intermediate and deep focus earthquakes are used to quantify both compression (Q h ) and shear (Q i ) wave attenuation within the Lau backarc basin. A spectral-ratio method is employed to measure differential attenuation (lt*) between the depth phases sS, pP, and sP and the direct S and P phases over the frequency band 0.05 and 0.5 Hz. We use a stacking algorithm to combine the spectra of several phase pairs from a single event, having similar azimuth and range, to obtain more robust lt* measurements; these estimates are then used to compute the average Q above the focal depth. Q i and Q h are measured directly from the sS-S and pP-P phase pairs respectively, however, the interpretation of lt* measured from sP-P requires assumptions about the ratio Q h /Q i . We find an empirical ratio of Q h /Q i =1.93 for this region and use it to compute Q h and Q i from the Q sP observations.We observe lateral and depth variations in both Q i and Q h beneath the tectonically active Lau Basin and the geologically older, inactive Lau Ridge and Fiji Plateau. The upper 200 km beneath the Central and Northern Lau Basin show a Q i of 45 -57 and a Q h of 102 -121, and Q appears to increase rapidly with depth. The upper 600 km beneath the Lau backarc basin has a Q i of 118 -138, while over the same depth interval we observe a higher Q i of 139 -161 beneath the Lau Ridge and Fiji Plateau. We also find Q h of 235-303 beneath the northern Lau Basin and a higher Q h of 292 -316 beneath the Fiji Plateau and the Lau Ridge measured directly from pP-P phase pairs. These geographic trends in the broadband Q measurements correlate with our previous long-period estimates of Q i in this region, however, the broadband measurements themselves are higher by about a factor of two. These observations suggest substantial frequency dependence of Q in the upper mantle, beginning at frequencies less than 1.0 Hz and consistent with the power-law form: Q8 h with h between −0.1 and −0.3.

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Q−1 of forsterite single crystals

Cited by 69 publications

References 12 publications

Frequency-dependent Shear-wave Q Models for the Crust of China and Surrounding Regions

Frequency-dependent Shear-wave Q Models for the Crust of China and Surrounding Regions

The seismic attenuation structure of the East Pacific Rise

Attenuation of Broadband P and S Waves in Tonga: Observations of Frequency Dependent Q

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