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在清理调整全国倾斜台站的工作中,必须兼顾观测条件、观测信息以及临测能力等几方面的内容。本文提出用模糊综合评判方法对倾斜台站进行等级判定,并用21个台站的资料进行了验证。效果较理想。 相似文献
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《地球物理学进展》2017,(5)
福建台网共建有88个速度型观测台站,利用这些台站记录的50个地震波形资料,用Atkinson方法反演了福建地区的非弹性衰减,其非弹性衰减Q(f)=483.6f~(0.352),这与福建地区构造活动较为稳定,介质的均匀程度相对较高,对频率的依赖较少的理论相符.用Moya方法计算台站的场地响应,大部分台站在1~2附近波动,说明其台基良好;部分台站在高频部分出现放大效应,说明台基存在一定的风化;部分台站则在高频出现衰减,说明台基存在一定的松软沉积层.经过本文的研究,为下一步福建台网产出地震的震源参数建立数据基础,丰富了福建台网的数据服务内容.对震级校正、台站场地选点及评价、地震工程和灾害评估有一定的参考意义. 相似文献
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将Kp指数与国际地磁学与高空物理学协会(International Association of Geomagnetism and Aeronomy,下文简称IAGA)推荐的FMI方法(V1.0)计算的K值对比分析后发现,二者的差值在中国区域内出现"不同台站之间K1~K8两头离散、K值整体高出K_p约0.5个单位、个别日期S_R计算错误、相邻日期S_R频繁出现跨天台阶"现象.针对这些现象,分析了可能产生的原因,并对原FMI算法进行了四处改进.用改进后的FMI算法计算了全球8个台站、中国5个台站在2003-2005年和2009年共4年的K指数数据,并将计算结果分别与Kp指数以及这些台站用其他方法计算的K值进行一致性比较,发现改进后的计算结果与二者更为接近,说明本文对FMI方法的改进是有效的. 相似文献
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本文讨论用P_(11)、S_(11)振幅比资料测定震源参数的可行性问题;文中提出算法原理并以北京、河北地区廿五个台站的不同分布组合构成44种资料采集方式进行人工数据试验。结果表明,在台站甚偏地分布于震中一侧的情况下,本文的方法仍然有效。 相似文献
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利用2010年以来河北省测震台网记录到的654个M_L≥2.5地震波形数据,使用Moya方法联合反演计算震源谱及各台站场地响应。河北省测震台网实时接收168个台站数据,最终反演得到151个测震台站场地响应结果。结果显示,频率1~20Hz内各台站均存在不同程度的场地放大效应,随着频率的变化,各类基岩台的场地响应变化较为复杂。位于第四系沉积类的台站场地响应在低频段1~8Hz内放大效应显著,在高频段8~20Hz内呈现快速衰减趋势。选取2017年以来河北省测震台网记录的M_L≥2.0地震数据,对各台站单台震级与台网平均震级进行对比统计、分析,最终得出代表河北地区的地方性震级M_L新量规函数。针对2020年7月12日河北唐山5.1级地震,利用本文得到的台站场地响应结果对震级偏大且有放大作用的台站进行放大作用消除,再分别用现用地方性震级M_L量规函数和河北地区地方性震级M_L新量规函数对单台震级进行重新计算,结果显示震级偏差均有所减小。 相似文献
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内蒙古地区场地响应区域特征分析 总被引:2,自引:0,他引:2
本文以内蒙古地区台站分布、地质构造和地震活动性为基础,将内蒙古的大部地区划分为三个研究区域分别进行了场地响应研究。对近几年积累的大量ML≥3.0级以上地震,共计39个台站记录到的124次地震事件的785条波形,根据S波的观测振幅谱,采用遗传算法分别反演了三个区域的介质非弹性衰减系数和台站场地响应,并对其进行了讨论。本文得到的介质衰减模型和台站场地响应,将对台网测定ML震级需要考虑的量规函数、台站校正值等提供重要参考。研究结果表明:除个别台站存在场地放大或缩小的响应外,绝大多数台站的场地响应表现出一定的区域性特征;西部区域(除极个别台站外)对高频存在明显衰减;中东部区域对整个频段的反映都比较稳定;东部区域对整个频段存在明显放大,这与该区域覆盖层厚度大相吻合。 相似文献
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Recent inversions of electrical profiles of the upper mantle beneath the oceans permit a variety of conductivity-depth profiles ranging from models with monotonically increasing conductivity to layered models having decreases of conductivity with depth. Laboratory data on possible mantle materials can physically explain high mantle conductivities in terms of a fluid phase (partial melt, hydrous fluid) or a good solid conductor (amorphous or graphitic carbon) and favor a profile having a high conductivity layer (HCL) underlain by a more resistive layer. 相似文献
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Temperature profiles in the earth of importance to deep electrical conductivity models 总被引:3,自引:0,他引:3
Deep in the Earth, the electrical conductivity of geological material is extremely dependent on temperature. The knowledge of temperature is thus essential for any interpretation of magnetotelluric data in projecting lithospheric structural models. The measured values of the terrestrial heat flow, radiogenic heat production and thermal conductivity of rocks allow the extrapolation of surface observations to a greater depth and the calculation of the temperature field within the lithosphere. Various methods of deep temperature calculations are presented and discussed. Characteristic geotherms are proposed for major tectonic provinces of Europe and it is shown that the existing temperatures on the crust-upper mantle boundary may vary in a broad interval of 350–1,000°C. The present work is completed with a survey of the temperature dependence of electrical conductivity for selected crustal and upper mantle rocks within the interval 200–1,000°C. It is shown how the knowledge of the temperature field can be used in the evaluation of the deep electrical conductivity pattern by converting the conductivity-versustemperature data into the conductivity-versus-depth data. 相似文献
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P. W. J. Glover J. B. Gomez P. G. Meredith S. A. Boon P. R. Sammonds S. A. F. Murrell 《Surveys in Geophysics》1996,17(3):307-330
Measurement of complex electrical conductivity as a function of frequency is an extremely sensitive probe for changes in pore and crack volume, crack connectivity, and crack surface topography. Such measurements have been made as a function of pore fluid chemistry, hydrostatic confining pressure, as well as uniaxial and triaxial deformation. This paper will; (1) describe the effects of triaxial deformation on the complex electrical conductivity of saturated porous rocks, (2) use the electrical data to model the mechanical stress-strain behaviour, and (3) compare the modelled behaviour with the stress-strain behaviour measured during the deformation. Experimental conductivity data tracks how the rock undergoes compaction with progressive loss of crack volume, followed by dilatation due to new crack formation, growth of existing cracks, crack interlinkage, and finally failure, as axial strain is increased. We have used the complex electrical data to produce a direction-sensitive (anisotropic) crack damage parameter, and used it to calculate the effective Young's modulus by employing the models of Walsh and Bruner. Comparison of the synthetic stress-strain curves so produced, with the experimentally derived stress-strain curves shows good agreement, particularly for undrained tests. This modelling is an improvement on similar curves produced using isotropic crack damage parameters derived from acoustic emission data. The improvement is likely to be due to the directional sensitivity of the electrical conductivity measurement, and its ability to discriminate between the formation of isolated cracks, and those cracks that contribute to the inter-connected crack space i.e. those cracks upon which transport properties of the rock such as electrical conductivity, and mechanical properties depend most critically during triaxial deformation. 相似文献
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YingXing Guo DuoJun Wang YaoLin Shi YongSheng Zhou YongSheng Dong Cai Li 《中国科学:地球科学(英文版)》2014,57(9):2071-2078
The electrical conductivity of Tibetan eclogite was investigated at pressures of 1.5–3.5 GPa and temperatures of 500–803 K using impedance spectroscopy within a frequency range of 10-1–106 Hz. The electrical conductivity of eclogite increases with increasing temperature(which can be approximated by the Arrhenius equation), and is weakly affected by pressure. At each tested pressure, the electrical conductivity is weakly temperature dependent below ~650 K and more strongly temperature dependent above ~650 K. The calculated activation energies and volumes are 44±1 kJ/mol and-0.6±0.1 cm3/mol for low temperatures and 97±3 kJ/mol and-1.2±0.2 cm3/mol for high temperatures, respectively. When applied to the depth range of 45–100 km in Tibet, the laboratory data give conductivities on the order of 10-1.5–10-4.5 S/m, within the range of geophysical conductivity profiles. 相似文献
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Kiyoshi Baba 《Surveys in Geophysics》2005,26(6):701-731
This review paper presents recent research on electrical conductivity structure in various marine tectonic settings. In at
least three areas, marine electromagnetic studies for structural exploration have increasingly progressed: (1) data accumulations,
(2) technical advances both for hardware and software, and (3) interpretations based on multidisciplinary approaches. The
mid-ocean ridge system is the best-studied tectonic setting. Recent works have revealed evidence of conductive zones of hydrothermal
circulation and axial magma chambers in the crust and partial melt zones of the mid-ocean ridge basalt source in the mantle.
The role of water or dissolved hydrogen and its redistribution at mid-ocean ridges is emphasized for the conductivity pattern
of the oceanic lithosphere and asthenosphere. Regions of mantle upwelling (hotspot or plume) and downwelling (subducting slab)
are attracting attention. Evidence of heterogeneity exists not only in the crust and the upper mantle, but also in the mantle
transition zone. Electrical conductive zones frequently overlap seismic low-velocity zones, but discrepancies are also apparent.
Some studies have compared conductivity models with the results of seismic and other studies to investigate the physical properties
or processes. A new laboratory-based conductivity model for matured oceanic lithosphere and asthenosphere is proposed. It
takes account of both the water distribution in the mantle as well as the thermal structure. It explains observed conductivity
patterns in the depth range of 60–200 km. 相似文献
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在1.0 Pa、室温到880℃分别采用超声波透射法和阻抗谱法测量了斜长岩的纵波速度和电导率,并对实验产物进行了鉴定分析.结果表明,在680℃,由于斜长岩中的含水矿物绢云母和黝帘石发生脱水反应,岩石的纵波速度开始大幅度下降.在410℃~750℃、12~105 Hz的频率范围内,斜长岩只出现颗粒内部传导.由于脱水产生的自由水主要分布于矿物的三联点或颗粒拐角处,没有形成连通的高导性网络,因此,脱水作用不会导致斜长岩电导率显著增加,也不会改变其电传导机制.地球内部低速层和高导层的形成与演化可能具有非同步性,通过含水矿物脱水可以形成地球内部的低速层,但不一定同时形成高导层. 相似文献
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Great strides have been made in understanding the upper part of the crust by in-situ logging in, and laboratory experiments on core recovered from super-deep bore-holes such as the KTB. These boreholes do not extend into the lower crust, and can contribute little to the elucidation of mechanisms that produce the high electrical conductivities that are commonly observed therein by magneto-telluric (MT) methods. Laboratory studies at simulated lower crustal conditions of temperature, pressure and saturation, on electrolyte saturated rocks thought to have been derived from the lower crust, have not been possible up until now due to their experimental difficulty. It is necessary to subject electrolyte-saturated rock samples to independently controlled confining and pore-fluid pressure, which implies that the rock be sleeved in some impermeable but deformable material, that can withstand the very high temperatures required. Metals are the only materials capable of being used, but these cause great difficulties for cell sealing and conductivity measurement. In this paper we describe recent breakthroughs in experimental work, specifically the development of two new types of sophisticated metal/ceramic seal, and a conductivity measurement technique that enables the measurement of saturated rock conductivity in the presence of a highly conducting metallic sleeve. The advances in experimental technique have enabled us to obtain data on the electrical conductivity of brine saturated basic, acidic and graphite-bearing rocks at lower crustal temperatures and raised pressures. These data have facilitated the comparison of MT derived crustal electrical conductivity profiles with profiles obtained from laboratory experiments for the first time. Initial modelling shows a good agreement between laboratory derived and MT derived profiles only if the mid-crust is composed of amphibolite pervaded by aqueous fluids, and the lower crust is composed of granulite that is saturated with aqueous fluids and/or contains interconnected grain surface films of graphite. The experimental data are consistent with a three layer crust consisting of an aqueous fluid saturated acidic uppermost layer, above an aqueous fluid saturated amphibolite mid-crust, and a granulite lowermost crust, which may or may not be saturated with aqueous fluids, but if not, requires the presence of an additional conduction mechanism such as conduction through thin graphite films. 相似文献
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This paper deals with the electrical double layer and the related properties of porous media. In particular, the electrical conductivity, the streaming potential, and the membrane potential are described in a self-consistent set of equations. All these properties are shown to be governed by fluid-matrix interface properties, as well as four geometrical parameters. 相似文献