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Maoxin Su Teng Xia Yiguo Xue Deqiang Mao Daohong Qiu Jianye Zhu Ying Zhao Peng Wang 《Geophysical Prospecting》2020,68(4):1399-1415
Tunnel forward geological prediction is indispensable to tunnel construction. The transient electromagnetic method is widely used in the field of tunnel forward geological prediction. A small fixed-loop transient electromagnetic method adapted to the limited space of a tunnel face is proposed for tunnel forward geological prediction for the first time. This method makes use of a large number of non-central points inside the loop. The obtained numerical simulation and field data show opposite trends owing to mutual inductance and self-inductance. A correction method for the field value of non-central points is proposed. The influences of different parameters are verified and the correction function is established by a test method. The validity of the correction function is verified through controlled field tests. The small fixed-loop transient electromagnetic has been successfully applied to a tunnel under the Weiwu expressway. This method can effectively improve the detection depth and better detect unfavourable geological bodies, such as karsts in front of the tunnel face. 相似文献
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地下流体的源兆,场兆,远兆及其在地震预报中的意义 总被引：33，自引：8，他引：33
我国地震地下流体监测网中，发现强震前有３种不同的前兆异常，即来自震源的源兆异常、与地震有关的区域活动关联的场兆异常及远距离强震前出现的远兆异常，它们在成因、特征与地震预报实践中的意义不同。从数量上看，场兆是大量的，源兆是少量的，而远兆也是不可忽略的。因此，地震预报实践中，必须正确地区别这３种前兆，全力寻找源兆，积极地开发场兆的预报功能，承认远兆并揭示其科学意义。 相似文献
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Joint filtration of one-second observations on a system of vector and scalar magnetometers is considered. The filtration provides a reduction of errors in estimates for components of geomagnetic field strength vectors. A formulation for the problem of joint data filtration is proposed based on using approximation piecewise linear models, and a higher speed filtration algorithm is developed. The results of joint filtration of one-second observations are presented. Errors in the proposed filtration on the basis of statistical modeling are estimated. 相似文献
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在系统地分析了目前各种测震学地震预报方法科学思路的基础上,认为测震学地震预报方法基本上可以分为两大类。一类是以已经发生的一些地震作为未来可能发生的地震的“因”,即由于已经发生的地震对区域应力场的影响,导致未来发生较强地震。这一类包括的预报方法较多,如空区、条带、ｂ值、地震迁移、相关地震等等及其由此衍生出来的各种方法。另一类是把已经发生的一些地震作为区域应力场增强的“果”,即已经发生的地震是区域应力场增强过程中的一种反映,而未来地震不一定是已经发生的地震所导致的结果。这一类包括“地震窗口”、小震群活动等方法。针对第一类方法,各种预报方法都是力图从地震三要素中提取未来地震的信息,而具体作法又都是利用地震三要素这个多维空间的某个剖面。为了从地震活动诸要素的多维空间提取综合信息,我们对每个地震加入了破裂面方位,构成了地震第四要素,并依据地震４要素建立了地震综合效应场函数。地震综合效应场函数概括了多种测震学地震预报方法的科学思路和预报经验,从而可以形成测震学的综合预报方法。 相似文献
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应用地震综合效应场函数方法，对地震前的空区、条带及大地震的迁移现象，根据强震前地震活动的四要素，进行了计算，其预报效果令人满意。 相似文献
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IntroductionOneofnotablefeaturesofseismicityistherandomoccurrenceofearthquakesinspaceandtime.Oneessentialelementofseismicityisthatearthquakereleasedenergycanbetakenastherandomfunctionsofspatialandtemporalcoordinates.Therandomfunctioncanbecalledseismicityenergystochasticfieldorearthquakeenergyfield.Sincetheseismicityisrelatedinspaceandtime,usingtheconceptofstochasticfield,thetotalfeatureofregionalseismicactivitycanbeconsidered,ratherthanthestatisticsofasingleearthquakeinthepast.Therefore,thefe… 相似文献
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Electrokinetic phenomena in a water-porous medium with a fractal structure above percolation threshold are theoretically investigated. Fracture zone with space-variable porosity is considered as a model of an earthquake hypocenter zone in which the electrokinetic current results from fluid filtration in a fractal pore network. A critical exponent of the streaming potential coefficient is found to depend on both the transport critical exponent and correlation length critical exponent. In this model, logarithmic dependence of electric field amplitude E on the earthquake magnitude M is derived which is compatible with the one observed by the VAN group. Without fractal properties, this form of dependence contradicts the empirical data. The electromagnetic field far from the hypocenter is calculated, which leads to the prediction of weak magnetic field variations. To explain the observed amplitude of VAN's Seismic Electric Signals (SES), the electric source must be at a distance of about 10 km from the registration point if the medium is homogeneous. Therefore, some conductive channel(s) are needed to explain the long distance selective SES transmission. 相似文献
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基于统计学习理论与地理信息系统(GIS)技术的地震滑坡灾害空间预测是一个重要的研究方向,其可以对相似地震条件下地震滑坡的发生区域进行预测.2010年4月14日07时49分(北京时间),青海省玉树县发生了Mw6.9级大地震,作者基于高分辨率遥感影像解译与现场调查验证的方法,圈定了2036处本次地震诱发滑坡,这些滑坡大概分布在一个面积为1455.3 km2的矩形区域内.本文以该矩形区域为研究区,以GIS与支持向量机(SVM)模型为基础,开展基于不同核函数的地震滑坡空间预测模型研究.应用GIS技术建立玉树地震滑坡灾害及相关滑坡影响因子空间数据库,选择高程、坡度、坡向、斜坡曲率、坡位、水系、地层岩性、断裂、公路、归一化植被指数(NDVI)、同震地表破裂、地震动峰值加速度(PGA)共12个因子作为地震滑坡预测因子.以SVM模型为基础,基于线性核函数、多项式核函数、径向基核函数、S形核函数等4类核函数开展地震滑坡空间预测研究,分别建立了玉树地震滑坡危险性指数图、危险性分级图、预测结果图.4类核函数对应的模型正确率分别为79.87%,83.45%,84.16%,64.62%.基于不同的训练样本开展模型训练与讨论工作,表明径向基核函数是最适用于该地区的地震滑坡空间预测模型.本文为地震滑坡空间预测模型中核函数的科学选择提供了依据,也为地震区的滑坡防灾减灾工作提供了参考. 相似文献
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Jürgen Pilz Gunter Spöck 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(5):621-632
The spatial prediction methodology that has become known under the heading of kriging is largely based on the assumptions
that the underlying random field is Gaussian and the covariance function is exactly known. In practical applications, however,
these assumptions will not hold. Beyond Gaussianity of the random field, lognormal kriging, disjunctive kriging, (generalized
linear) model-based kriging and trans-Gaussian kriging have been proposed in the literature. The latter approach makes use
of the Box–Cox-transform of the data. Still, all the alternatives mentioned do not take into account the uncertainty with
respect to the distribution (or transformation) and the estimated covariance function of the data. The Bayesian trans-Gaussian
kriging methodology proposed in the present paper is in the spirit of the “Bayesian bootstrap” idea advocated by Rubin (Ann
Stat 9:130–134, 1981) and avoids the unusual specification of noninformative priors often made in the literature and is entirely based on the
sample distribution of the estimators of the covariance function and of the Box–Cox parameter. After some notes on Bayesian
spatial prediction, noninformative priors and developing our new methodology finally we will present an example illustrating
our pragmatic approach to Bayesian prediction by means of a simulated data set. 相似文献
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Singular value decomposition (SVD) is a useful method for random noise suppression in seismic data processing. A structure-oriented SVD (SOSVD) approach which incorporates structure prediction to the SVD filter is effcient in attenuating noise except distorting seismic events at faults and crossing points. A modified SOSVD approach using a weighted stack, called structure-oriented weighted SVD (SOWSVD), is proposed. In this approach, the SVD filter is used to attenuate noise for prediction traces of a primitive trace which are produced via the plane-wave prediction. A weighting function related to local similarity and distance between each prediction trace and the primitive trace is applied to the denoised prediction traces stacking. Both synthetic and field data examples suggest the SOWSVD performs better than the SOSVD in both suppressing random noise and preserving the information of the discontinuities for seismic data with crossing events and faults.
相似文献12.
In most practical situations, the upper part of a geological section consists of loose sediments, in which heat transfer cannot be described as a purely conductive process. To investigate such situations a one-dimensional numerical model of terrestrial temperature field formation under the combined influence of vertical groundwater filtration and ground surface temperature changes has been developed. The model allows one to consider the perturbation of heat flow interval values resulting from short- and long-period temperature waves propagating into permeable rocks under conditions of advective heat transfer, caused by vertical groundwater filtration. The results show that temperature profiles and interval heat flow values are sensitive to both the paleoclimatic history and the rate of groundwater filtration. The latter plays the prevailing role in the variations of geothermal field parameters, especially within the uppermost part of the loose sediments in unconfined aquifers. The problem was solved for a permeable layer, underlaid by an impermeable layer. This schematisation of water exchange is the typically accepted for hydrogeological analysis. Even at very low rates of filtration the intensity of this effect is enhanced substantially for long-period variations. In the extreme case (for periods of temperature variations of the order of 100,000 years) at typical rates of filtration within the permeable layer, an almost gradient-free zone can be formed down to depths of a few hundred metres. For the case of upward filtration, on the contrary, the influence of climatic variations on the terrestrial temperature field becomes substantially attenuated. 相似文献
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ＲｅｄｉｓｃｕｓｓｉｏｎｏｎｔｈｅｓｅｉｓｍｉｃｒｅｇｉｍｅｎｅｔｗｏｒｋＺｅ－ＧａｏＷＡＮＧ（王泽皋）；Ｐｅｉ－ＱｉｎｇＳＵＮ（孙佩卿）；Ｊｉｎｇ－ＣｈｕｎＧＡＯ（高景春）；Ｓｈｕ－ＬｉａｎＬＩ（李淑莲）；ＸｕｅＺＨＡＮＧ（张雪）ａｎｄＹａｎＧＵＯ... 相似文献
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在唐山地震前两个月至主震后约半年的时段内,西集、宝坻、塘沽等三个地电观测台自然电场断续出现特定周期的变化:其周期为半月、一月及半年;其双振幅每公里达数十乃至一、二百毫伏(超过平时观测标准误差6—20倍);电场呈线性极化,其方向大致平行台址附近断裂带的走向。若把这种变化同复杂的干扰区分开并与理论重力值对比,似与日、月起潮力有所联系。其中半月周期变化的极值点,还与震中周围两口废油井间歇自喷现象同时出现,表明电场的这种变化可能与断裂带內地下液体运动状态的变化有关,故认为是一种过滤速度受起潮力调制的过滤电场.微小的起潮力只在主震前后一段时间内才引起这种过滤电势的变化。 相似文献
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华东地区前兆场时空演化特征的模糊识别 总被引：2，自引：0，他引：2
利用模糊数学中异常从属函数方法对１９９０～１９９７年华东地区１６种前兆观测方法,近５万组数据的综合前兆场进行了时空演化特征研究。结果表明,异常从属函数ｕ对发生在华东地区的Ｍs≤５．０地震有较好的映震能力,可作为中期、中短期预报的综合指标,对地震三要素可作出较为准确的判定。 相似文献
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利用qc,D50评价砂土地震液化势研究 总被引：1，自引：0，他引：1
本文根据国内外地震液化调查资料，建立了利用双桥静力触探锥头阻力ｑｃ和平均粒径Ｄ５０判别地震液化势的半经验性方法。这种方法对评价地震液化势是颇为有效的。 相似文献
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在地震预报的实践过程中，我们深深的体会到地震前兆场源关系的深入了解是十分必要的。虽然地震预报是世界性的难题，但是，只要我们在实践的基础上，能从理论上对这一演化物理问题有逐渐深入的认识，在一定的条件下，对某些地震做出中期和短临预报是很有可能的。本文以共和地震为例，对地震前兆场源关系的复杂性进行了初步的分析研究。其结果认为，正确的认识场源关系，以场求源，以源推场，场源结合，跟踪短临异常是实现短临地震预报的前提和基础。 相似文献
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破坏性地震强度预测可用于工程领域抗震设防以及地震危险性分析评估,是防震减灾中一项很重要的基础工作.为了再现九寨沟地震的地震动强度,评估缺失强震记录的九寨章扎台站的地震动强度,本文用经验格林函数法对九寨沟地震进行了数值模拟.选取了震源周边地震动峰值加速度超过10 Gal的10个强震台站进行模拟.因未得到九寨沟地震的余震,初次尝试将汶川地震和定西地震的余震作为格林函数模拟九寨沟地震.模拟结果整体上可以反映各台站地震动的强度特征,尤其是地震动高频成份拟合较好.模拟值的地震动峰值加速度、时程数据、反应谱等与观测值拟合较好.预测结果显示漳扎镇的地震动峰值加速度值约为180~200 Gal.预测结果也表明在缺少大震的余震记录时,经验格林函数法使用其他大震的余震同样可以再现目标地震的强度特征.本研究也为经验格林函数方法在缺乏小震记录地区的使用积累了经验.最后总结了格林函数的选取标准,为经验格林函数方法来预测未来强震动特征积累了经验. 相似文献