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在研究大地电磁响应函数频散关系的基础上,构制了一套滤波系数算法,以用于由一套视电阻率资料估算相应的阻抗相位.理论模型和实际大地电磁观测资料的数字试验表明,该法是行之有效的.由频散关系估算的相位值与观测的相位资料的比较,可用于检验观测资料是否满足频散关系.利用经频散关系校正的阻抗相位值,进行大地电磁阻抗的联合反演则可望获得更为可靠的结果.研究了观测频带相互衔接的电偶源频率电磁测深和大地电磁测深视电阻率的一维联合反演问题.对两个实测点两种电磁法的观测资料进行了联合反演试验,与钻井资料对比表明,所获得的电性分层参数是较为可信的.在补充了由频散关系获取的电偶源频率电磁相位资料后,对于两种电磁法的视电阻率————阻抗相位、阻抗实部视电阻率-阻抗虚部视电阻率进行了拟大地电磁反演,获得了相近的反演结果. 相似文献
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针对匹配追踪计算量大、大地电磁数据处理效率低的问题,提出基于匹配追踪和遗传算法的大地电磁噪声压制方法.首先,利用Gabor原子构建过完备原子库,并对过完备原子库集合进行划分.然后,借助遗传算法的自适应性,快速搜寻最优匹配原子及所在位置.最后,运用最优匹配原子对待处理信号进行稀疏分解,重构有用信号.通过对计算机模拟的典型强干扰和矿集区实测大地电磁数据进行分析处理,实验结果表明,相对于匹配追踪和正交匹配追踪,文中所提方法能从过完备原子库中快速、自适应地选取最优匹配原子与不同噪声干扰类型高精度的匹配,极大地提升了计算效率;大地电磁时间域序列中的大尺度强干扰被有效剔除,视电阻率曲线更为光滑、连续,低频段的数据质量得到明显改善. 相似文献
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地球曲率对长周期大地电磁测深法的影响 总被引：1，自引：1，他引：0
基于电磁理论,导出了层状球体大地条件下长周期大地电磁响应的计算公式,编制了计算机程序,并对相应理论模型进行正演计算。根据计算结果,分析了地球曲率对长周期大地电磁测深法视电阻率和阻抗相位的影响。理论模型的计算结果显示,随着探测周期的增大,地球曲率对长周期大地电磁响应的影响逐渐增大,视电阻率曲线会明显下降,阻抗相位曲线逐渐趋于90°;在一维情况下,对于目前的仪器测量范围可以忽略地球曲率带来的影响,但随着仪器技术的进一步发展,地球曲率对长周期大地电磁测深法的影响不可忽视。 相似文献
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《地球物理学进展》2016,(3)
大地电磁测深采集的是天然电磁场,具有振幅微弱、频带宽的特点.在人文活动密集地区,电磁噪声干扰日趋严重,导致大地电磁测深曲线具有明显的近场源效应.本文利用电偶极子理论模型分析了电磁相关噪声对大地电磁测深数据的影响特征,并对湖南衡阳某矿区噪声实验数据进行了讨论,分析了矿区噪声的特点.分别利用远参考方法和基于大地电磁时间序列依赖关系的去噪方法对实验数据进行了处理.研究结果表明:矿区近场源噪声的频率一般大于0.1 Hz,远参考方法可以压制高频部分近场源噪声,但在0.1 Hz附近仍存在跳点;基于大地电磁时间序列依赖关系的去噪方法也可以压制矿区强相关噪声,抑制近场源效应,其效果要好于远参考的处理;两种方法结合可以更好的压制强噪声,基本消除了近场源效应,有效提高了大地电磁测深数据的信噪比. 相似文献
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大地电磁测深法基于天然电磁场,其存在信号弱频带宽的特点,因此很难获得无噪声的数据,而传统的大地电磁数据处理方法面临着噪声环境日益复杂、对于海量数据的处理效率不高和难以剔除持续性噪声等诸多挑战.机器学习方法是一种基于统计分析的数据驱动方法,能够发现数据内部的结构和规律,从而对未来时刻和未知状态进行预测和判断.本文从大地电磁噪声分析入手,基于目前在大地电磁数据处理中研究和应用较为广泛的神经网络、字典学习等机器学习方法,分析了其方法原理、应用领域及优缺点,并与传统方法做了对比.发现机器学习方法在海量数据处理、大地电磁噪声模式识别和特征提取、数据预测等方面具有巨大的优势.同时,提高泛化能力和将机器学习方法与大地电磁理论相结合等仍是目前需要进一步探索的问题.随着计算机技术的发展和三维探测的实用化,机器学习方法在大地电磁数据处理中的应用将更加广泛. 相似文献
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《地震学报》2017,(1)
以2013年4月20日芦山MS7.0地震震后5月3—24日距主震震中约7km处所观测到的大地电磁数据为基础,分析地下电阻率变化与较大余震(MS3.0)活动的关系.为确保用于地震异常分析的观测数据的可靠性,基于大地电磁方法的特点,使用稳定估算(robust)技术和相干度因子约束等方法得到各频点一定数量的自功率谱和互功率谱,再根据视电阻率和相位曲线的分布形态,剔除引起视电阻率和相位曲线突变的谱值之后得到高质量的视电阻率和相位曲线.此外,根据曲线形态和误差分布来判断数据质量,剔除可能受到干扰影响的数据,以获得能够真实地反映地下电阻率变化的视电阻率分析结果.结果显示:观测期内的yx极化模式的视电阻率值总体呈非单调的增大趋势,最大增幅达27%;yx极化模式的视电阻率值几乎在每个相对集中的较大余震丛集后均会出现高值,而较大余震丛集期间对应的则是视电阻率低值.从物理机制上分析地震的电阻率效应源于微裂隙内孔隙流体的变化,故推测芦山地震余震期间电阻率的增加趋势是由于震后应变释放区应力恢复和孔隙度恢复所致. 相似文献
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最近开发了一种针对二维大地电磁野外数据进行处理解释的新反演方法。该方法以加入阻抗相位信息的一维大地电磁连续介质曲线对比法为基础 ,把一维反演得到的电阻率和相位的数据集作为二维反演的初始模型 ,使用二维有限单元法做正演模拟。在程序的后继迭代中 ,深度方向上用一维反演修改模型的电阻率和深度值 ,沿测线方向由二维有限元作修改 ,反演结束可得到一个接近真实电性分布的电阻率数据集 ,并绘制成电阻率断面图。对模型的反演实验结果显示 ,该反演方法能够较真实地反映地下电性分布 ,而且避免了偏导数矩阵的计算 ,其原理简单 ,计算速度快 ,表明该反演方案是可行的 相似文献
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《国际泥沙研究》2014,(4)
正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and 相似文献
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《中国科学:地球科学(英文版)》2014,(3)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献
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Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored. 相似文献
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《水文科学杂志》2013,58(6)
Abstract The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca2+, Mg2+, Na+, K+, Cl?, SO4 2?, HCO3 ?, NO3 ?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region. 相似文献
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《中国科学:地球科学(英文版)》2014,(12)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献