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We investigated the upper mantle anelastic structure beneath the northern Philippine Sea region, including the Izu-Bonin subduction zone and the Shikoku Basin. We used regional waveform data from 69 events in the Pacific and the Philippine Sea slabs, recorded on F-net and J-array network broadband stations in western Japan. Using the S–P phase pair method, we obtained differential attenuation factors, δt*, which represent the relative whole path Q. We conducted a tomographic inversion using 978 δt* values to invert for a fine-scale (50–100 km) three-dimensional anelastic structure.
The results shows two high-Q regions (QP>1000) which are consistent with the locations of the Pacific and the Philippine Sea slabs. Also there is a low-Q (QP110) area extending to the deeper parts (350–400 km) of the model just beneath the old spreading center and the Kinan Seamount Chain in the Shikoku Basin. A small depth dependence of the laterally averaged QP was found, with values of 266 (0–250 km), 301 (250–400 km), and 413 (400–500 km). 相似文献
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地质成因和构造/热应力导致地壳岩石中的孔隙结构（裂隙和粒间孔）的变化.影响岩石黏弹性的因素包括压力、孔隙度、孔隙中包含的流体和孔隙几何形状等.相对于岩石中的硬孔隙,岩石黏弹性（衰减和频散）受软孔隙（裂隙）的影响更大.本文选取三块白云岩样本,进行了不同围压和流体条件下的超声波实验测量.利用CPEM（Cracks and Pores Effective Medium,裂隙和孔隙有效介质）模型获得了岩石高、低频极限的弹性模量,并通过Zener体（标准线性体）模型将CPEM模型拓展到全频带而得到CPEM-Zener模型,用该模型拟合岩石松弛和非松弛状态下的实验数据,本文得到平均裂隙纵横比和裂隙孔隙度以及纵波速度和品质因子随频率的变化关系.结果表明,饱水岩石的平均裂隙纵横比和裂隙孔隙度均高于饱油岩石,随着压差（围压和孔隙压力的差值）的增加,饱油岩石中的裂隙首先闭合.并且压差在70 MPa以内时,随着压差增大,岩石的平均裂隙纵横比和裂隙孔隙度在饱水和饱油时的差值增大,此时流体类型对于岩石裂隙的影响越来越显著,此外,对饱水岩石,平均裂隙纵横比随压差增加而增大,这可能是由于岩石中纵横比较小的裂隙会随压差增大而逐渐趋于闭合.在饱水和饱油岩石中,裂隙孔隙度和裂隙密度都随着压差增加而减小.通过对裂隙密度和压差的关系进行指数拟合,本文获得压差趋于0时的裂隙密度,且裂隙密度随孔隙度增大而增大,增大速率随压差增加而降低.针对饱水和饱油的白云岩样本,CPEM-Zener模型预测的纵波频散随压差增大而减小,此变化趋势和实验测得的逆品质因子随压差的变化关系基本一致,由此进一步验证了模型的实用性.本研究对岩石的孔隙结构和黏弹性分析以及声波测井、地震勘探的现场应用有指导意义. 相似文献
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用反相直接加载的方法研究了微粒对多晶冰滞弹性的影响.结果表明：在较高频率时(1 Hz 和 10-1 Hz),滞弹性应变与应力峰值呈线性关系;在较低频率时(10-2 Hz),其应力/应变偏离线性关系.微粒在高频时(1 Hz)通过阻碍晶界滑移对晶界弛豫产生重要影响,增加了模量和降低了内耗.但微粒对低频时的位错弛豫没有明显的影响.通过滞弹性实验计算了非线性弛豫模型的两个重要参数,计算表明K值约为007 Pa,α值约为054. 相似文献
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N. S. Bagdassarov 《Physics and Chemistry of Minerals》1999,26(6):513-520
The present study deals with the small strain torsion deformation of MACOR glass-ceramic samples at high temperatures (450–850 °C)
and over a range of low frequencies (20 Hz–5 mHz). The samples of MACOR ceramic consist of 55 vol% randomly oriented, sheet-like
fluorophlogopite mica crystals (∼100–20 μm in planar size, 1–2 μm in thickness) and 45 vol% of isotropic alumino-borosilicate
glass matrix. Measurements of the complex shear modulus show that the sample does not possess the relaxed shear viscosity
even at temperatures above the glass transition temperature of the glass matrix. The maximum of the imaginary component G
′′() of the shear modulus is ∼0.15 of the unrelaxed value G
∞, the relaxation strength Δ≈0.9. The activation energy of the peak of G
′′() is ∼245 kJ mol−1. Using this value of E
a
, the data obtained at various frequencies and temperatures have been reduced to a master curve using the dimensionless variable
ωτ, where ∼0 exp(−E
a
/RT). The internal friction Q−1(ωτ) is ∝1/()0.35−0.4 in the low-temperature high-frequency range (1); passes through a maximum at ∼1 and trends asymptotically to a value Q−1∼0.25–0.30 at ≪1. The behaviour of Q
−1(ωτ) differs from that of a Caputo body by the presence of the resolved peak which may be attributed to the slow mechanical
relaxation of mica crystals due to rotation as well as flexing and bending modes of crystal deformation.
Received: 26 June 1998 / Revised, accepted: 13 January 1999 相似文献
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Anelasticity and microcreep in polycrystalline MgO at high temperature: an exploratory study 总被引：1，自引：0，他引：1
The frequency dependence of the shear modulus and dissipation in polycrystalline MgO has been determined at high temperature
using both microcreep (ɛ = 10−4) and seismic frequency forced-oscillation (ɛ = 10−5) measurements. The frequency-dependent and time-dependent data have been described in terms of the elastic, anelastic and
viscous components of deformation using the Andrade model. The forced-oscillation measurements show that for temperatures
above 700 °C the shear modulus begins to decrease dramatically and the modulus becomes frequency-dependent with increasing
temperature. This is accompanied by an increase in dissipation, which also becomes frequency-dependent. The microcreep measurements
resolve this frequency-dependent behaviour into an anelastic regime from 700–1050 °C, and a viscoelastic regime from 1100–1300
°C. At 1300 °C, the seismic frequency shear wave speed is ∼60% of the extrapolated low-temperature frequency-independent value,
and the dissipation has risen to Q
−1 = 10−1 from 10−3 at temperatures below 600 °C. The mechanism by which this frequency-dependent rheology occurs appears to be diffusional creep,
which produces viscous slip on the grain boundaries. It is proposed that the anelastic behaviour is due to viscous slip occurring
on segments of grain boundaries, with the viscous deformation being accommodated by elastic distortion of adjacent unslipped
regions of the grain boundary. At higher temperatures, slippage occurs across the entire grain boundary and viscoelastic behaviour
begins to occur.
Received: 11 April 2002 / Accepted: 9 January 2003
Acknowledgements Samples were precision-ground by Andrew Wilson, and polished sections prepared by Harri Kokkonen, who also did the SEM work.
Uli Faul calculated the volume fraction of grain sizes. The density measurements were done by Lara Weston. 相似文献
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非弹性的表面波大尺度波形反演的理论方法以如下三方面提出的。（１）计算本征值和本征函数可获得第一阶的频散参数，并把体波的复数形式和波能的吸收引入非弹性中，（２）根据弗拉尔和斯奈德的理论方法，计算了非弹性表面波的激发和合成地震图，球阶非弹性用频散的计算按Ｂｉｓｗａｓ－Ｋｎｏｐｐｏｆ公式被变换成平滑的弹性形式，（３）使用自伴微工子导出关于模型参数的波形Ｆｒｅｃｈｅｔ导数，然后应用非线性反演拟合波形。 相似文献
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Seismic acquisition can be costly and inefficient when using spiked geophones. In most cases, such as the desert, the most practical solution is the use of flat bases, where geophone‐ground coupling is based on an optimal choice of the mass and area of contact between the receiver and the ground. This optimization is necessary since areas covered by sand are loose sediments and poor coupling occurs. Other cases include ground coupling in stiff pavements, for instance urban areas and ocean‐bottom nodes. We consider three different approaches to analyse coupling and model the geophone with a flat base (plate) resting on an elastic half‐space. Two existing models, based on the full‐wave theory, which we refer to as the Wolf and Hoover‐O'Brien models, predict a different behaviour with respect to the novel method introduced in this work. This method is based on the transmission coefficient of upgoing waves impinging in the geophone‐ground contact, where the ground is described as an anelastic half‐space. The boundary conditions at the contact have already been used to model fractures and are shown here to provide the equation of the damped oscillator. This fracture‐contact model depends on the stiffness characteristic of the contact between the geophone base plate and the ground. The transmission coefficient from the ground to the plate increases for increasing weight and decreasing base plate area. The new model predicts that the resonant frequency is independent of the geophone weight and plate radius, while the recorded energy increases with increasing weight and decreasing base plate area (as shown from our own experiments and measurements by Krohn) which is contrary to the theories developed by Wolf and Hoover‐O'Brien. The transient response is obtained by an inverse Fourier transform. Optimal geophone‐ground coupling and energy transmission are required, the first concept meaning that the geophone is following the motion of the ground and the second one that the signal is detectable. As a final example, we simulate seismic acquisition based on the novel theory, showing the differences between optimal and poor ground‐to‐geophone energy transmission. 相似文献
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