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1.
关断时间是影响瞬变电磁资料处理和解释质量的一个重要因素 ,也是衡量TEM仪器性能的一个关键参数。提出了一种直接数值校正方案 ,并通过对线性和指数关断电流的校正描述了该方案的实施过程。根据文中提出的方案 ,只要仪器记录了一次场的衰减曲线 ,就可以进行较为精确的校正 ,并不必要假设线性衰减或指数衰减 ,这一结论无论是对TEM的仪器设计还是数据处理都具有重要意义 相似文献
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分形方法在地震序列类型早期判别中的应用 总被引：3，自引：0，他引：3
着重讨论了地震序列的空间分布随时间变化的特性，利用分形方法提取大震后余震的空间分维信息，从而达到早期判别地震序列类型的目的。以１９６６年以来定位精度较好、余震记录较全的１２个７级以上大震和大同６级强震序列为资料，计算了震后１个月内余震随时间变化的空间分维数。结果发现，不同类型的地震序列分维数不同。一般震后５－６天，主震型序列的分维数在１．１－１．２之间，多震型序列的分维数在１．３以上。利用前７天的 相似文献
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Domenico Giardini Adam M. Dziewonski John H. Woodhouse 《Physics of the Earth and Planetary Interiors》1985,40(4):259-272
The Centroid-Moment Tensor technique is applied to 113 large earthquakes of the period 1977–1980, including all the shallow events with magnitude mb, Ms or ML 6.5. We use digital data recorded by the Global Digital Seismograph Network (GDSN) and International Deployment of Accelerometers (IDA) networks. Solutions are determined for three sequences of events close in time by inverting mantle wave data simultaneously for multiple sources. 相似文献
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肃南5.7级地震过程剪切波分裂特征 总被引：3，自引：0，他引：3
剪切波分裂应用于地震预报中的３个主要困难是：（１）如何自动定量识别剪切波快慢波到时；（２）用以认识其基本特征的震例太少；（３）因各次地震的复杂性，对所给剪切波分裂结果难以给出恰当的解释，本文研究了１９８８年１１月２２日甘肃肃南５．７级地震过程剪切波分裂的特征。所用资料为１９８８年８月到１９９０年８月中法合作张掖数字台网的记录。通过对张掖～肃南地区地壳结构模型的研究，确认了所用各次地震的真实出射角基 相似文献
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Various exact methods of inverting the complete waveform of vertical seismic reflection data to produce acoustic impedance profiles have been suggested. These inverse methods generally remain valid for nonvertical, plane-wave data, provided total reflection does not occur. Thus, in principle, the “seismogram” at each ray parameter in a slant stack can be interpreted separately. Rather than invert each plane-wave seismogram separately, they can all be interpreted simultaneously and an “average” model thus obtained. Inversion for both the velocity and the density also becomes possible when two or more plane-wave seismograms are simultaneously inverted. The theory for a noniterative inversion method, based on the time-domain Riccati equation, is discussed. Numerical examples of inversions using this technique on synthetic data demonstrate its numerical stability and the advantage of simultaneous inversion of several seismograms to reduce the effect of noise in the data and increase the stability of the inversion process. 相似文献
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This paper investigates the form of the nonwhiteness found in the reflection coefficients from a wide variety of rock sequences around the world. In all but one case densities are taken as constant due to the paucity of suitable density data. The reflection sequences are pseudo-white only above a corner frequency, below which their power spectrum falls away according to a power law fβ, where β is between 0.5 and 1.5. This spectrum can be adequately modelled in practice very simply with an ARMA (1, 1) process which acts on a white innovation sequence. The corollary of this is that before wavelet estimation methods are applied (all of which-except those based on synthetic seismograms—presuppose white reflection sequences) or deconvolution filters estimated, seismic traces should be filtered with the inverse of this process. Interestingly, the estimated ARMA processes group themselves into two clearly differentiated categories, having very different indices of predictability (or, strictly, indices of linear determinism). The two categories apparently correlate precisely with two kinds of sedimentation: one which consists largely of sequences of rocks with repeating properties, called “repetitive” in this paper but perhaps loosely describable as “cyclic”, and the other which is randomly bedded with no apparent pattern of components. The former has indices of predictability which are two to four times as great as those of the latter. Another, probably related, property is that β for the repetitive sequences tends to be greater than that for non-repetitive rock columns. The observed power spectra are shown to be consistent with a simple model for the logarithm of acoustic impedance consisting of a mixture of processes where the distribution of (time) scale parameters is reciprocal. Detailed effects of block-averaging and sampling the logs are shown to depend on the type of sequence under examination. 相似文献
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1966年邢台Ms7.2级地震的前震序列分析 总被引：4，自引：0，他引：4
断层或裂纹在其失稳破裂之前都要经历准静态的加速扩展过程。加速是失稳的一个必要条件。加速释放是成核在脆性层中的大地震的普遍前兆。且可将该加速过程简要地概括为地震释放速率比例于失稳破裂产剩余时间的负幂。 相似文献
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Biot流动和喷射流动是含流体多孔隙介质中流体流动的两种重要力学机制．文中基于同时包含这两种力学机制的非饱和多孔隙BISQ模型,利用小生境遗传算法实现了储层参数(孔隙度、渗透率、含流体饱和度等)的反演．结果表明,本文方法在储层参数的反演过程中目标函数收敛快、且具有较强的抗“噪声”干扰性能,当观测噪声ε≤5%时,储层参数的反演精度很高．最后,通过实测数据的反演应用验证了该方法处理储层参数反演问题的有效性和非饱和BISQ模型的准确性． 相似文献
11.
Stochastic nature of three dimensional bursting events and sediment entrainment in vortex chamber 总被引：1，自引：1，他引：1
Ali Reza Keshavarzi Ali Reza Gheisi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,21(1):75-87
In this study, three dimensional quadrant analysis of bursting process was used to recognize the susceptible regions for sediment entrainment and deposition at the bed of a vortex chamber. From the analysis, it was found that two dimensional quadrant analysis in unable to find the turbulent coherent structure of flow near the bed of the vortex chamber. Therefore, a new method based on three dimensional bursting process is introduced in this study to define the turbulent flow structure. Based on the new methodology in this study, the bursting event is divided into eight different cube zones according to three dimensional velocity fluctuations. It was realized that, four cube zones interactions are toward the central orifice of the vortex chamber and four cube zones interactions are toward the wall of the chamber and they are categorized as classes A and B, respectively. The results from the experiments showed that in class A, the internal sweep events (class IV-A) moves the settled sediment particles toward the central orifice of the chamber, whereas in class B the external sweep events (class IV-B) moves the settled sediment particles toward the external region of the chamber. Also the transition probabilities of the bursting events in 64 particular movements were determined. The result showed that stable organizations of each class of the events had highest transition probabilities whereas cross organizations had lowest transition probabilities. Additionally, an effort was made to find the average inclination angle of the three dimensional bursting events in each cube zone. The results showed that near the bed of the vortex chamber by increasing the tangential velocity toward the center of the chamber, the average inclination angle of the events in the cube zones decreased. Also, at the region where the sediment particles were deposited, the inclination angles had higher values. 相似文献
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本文用三维有限差分法,在计算电导率异常的电磁响应时作了一次网格收敛试验.该收敛解和其它几种数值解法得到的结果作了比较.这些方法是Hohmann的积分方程法、Lee等的混合法和Gupta等的混合法.我们的结果基本上和Hohmann的以及Gupta等的结果一致.试验表明,有限差分法所用的计算机时间比SANGAM混合法的少.为了缩减迭代过程的计算时间,我们使用了一种新的技巧--变区域迭代法,这种方法的收敛速度和一般的（在全区域迭代的）迭代法的收敛速度相同. 相似文献
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A careful examination of the seismic refraction technique details the general assumptions and processes on which it is based. It is apparent that the normal interpretive process of determining velocity by hand fitting time breaks, while necessary to identify the refractors, is subject to imprecision. We describe a digital technique that calculates velocity and its precision from the time break measurements. The technique also facilitates examining for the possibility of systematic errors. Having observed the kind of imprecision that was apparent with velocity we extended our study to layer thicknesses (and thus depth) and found that the imprecision was significantly magnified. The technique and our claims for it are supported by an example of its application to a refraction survey in the Sturt Block, Western Australia. 相似文献
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介绍了矿山地震与瓦斯突出等煤矿灾害及成因， 并通过若干煤矿瓦斯突出和矿山地震的同震现象，论述了这些灾害在动力过程中的内在关系.这些震例表明，在高瓦斯煤矿， 矿山地震与瓦斯突出存在密切的相关.认为较大矿震伴随瓦斯的低值延时响应可能是瓦斯突出的预警信号.从矿震定位、震源机制、矿震成因、瓦斯突出条件等分析了矿震与瓦斯突出相关的机理. 进一步介绍了瓦斯流体对矿震的触发作用，尤其超临界流体的特殊性质在矿震发生中的重要作用.依据矿震与构造地震在机制方面的相似性， 讨论了上述结果在震源物理研究中的意义. 相似文献
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本文使用中国ＣＤＳＮ长周期数字资料，采用理论地震图试错法，确定了１９８８年云南澜沧７．６级强震的震源机制参数，改进Ｋｉｋｕｃｈｉ方法，计算出震源破裂时间过程函数，讨论了该地区发展地质构造。 相似文献
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In this article two new approaches are presented for time domain identification of base isolated buildings from recorded response during earthquakes: (1) a least squares technique with time segments is developed to identify the piece-wise linear system properties; and (2) an observer is used to estimate the unmeasured states and initial conditions of different time segments. In base isolated buildings changes in dynamic properties occur during earthquake response due to nonlinear behavior. Hence, a multi-input and multi-output technique using time segments is developed for piece-wise linear system identification. The primary advantage of the developed time segmented technique is that it can be applied to windows of time history instead of the entire duration of earthquake response. The developed technique (1) starts with identification using the entire duration of the earthquake response; (2) evaluation of time segments during which the identified response differs significantly from the recorded response to establish windows of time history during which refined identification is necessary; and (3) identification of the change in dynamic properties in the established windows using the observer based time segmented least squares approach. Only partial state measurements are usually available for identification. Hence, an observer is used to estimate the unmeasured states and initial conditions needed for different time segments. By comparing identified response with recorded response, of an actual base isolated building which experienced Northridge earthquake, it is shown that the change in dynamic system parameters, such as periods and damping ratios, due to nonlinear response, are reliably estimated using the presented technique. 相似文献
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应用遗传算法建立地震预报的分类体系初探 总被引：6，自引：0，他引：6
本文对模拟自然界生物进化过程的遗传算法和用它所建立的分类体系进行了简要介绍，并将它们应用于地震预报探索研究，建立了初步的地震预报分类体系，结果表明：采用具有自动学习和自相适应的方法，结合现有的研究成果，可以将地震活动性的时空参数结合起来综合考虑，获得较为优化的地震预报规则集。 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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This work is a certain stage in investigations devoted to the recognition and examination of the seismic process dynamics in order to assess prospects and elaborate recommendations for the prediction of very strong earthquakes. The work is based on the use of the second-order differential equation, the so-called equation of the dynamics of self-developing processes, as an approximation model. Nine seismic catalogs including information about more than 1.5 million earthquakes were analyzed. The time behavior of three parameters characterizing the seismic process development, namely, the number of seismic events, accumulated conventional strain, and total energy of the events, was examined in terms of the model approximation. More than 17 000 well-defined seismic sequences of activation and attenuation were revealed using these parameters. The sequences account for about 38.5% of the total number of earthquakes from the catalogs studied. The remaining earthquakes belong to sequences of stationary development (in the form of background seismicity and earthquake swarms) and ill-defined sequences of activation and attenuation. The presence of stable regular patterns in the nonlinear development of the seismic process in time makes this process basically predictable. However, additional investigations are required for direct practical use of the regular features revealed in this work. 相似文献