Application of the Double-difference Relocation Method Combined with Waveform Cross-correlation on the Three Gorges Reservoir Seismicity     

Luo Jiahong  Ma Wentao  Li Chunzheng 《中国地震研究》2017,31(3):368-380

In this paper, we use the double difference location method based on waveform cross-correlation algorithm for precise positioning of the Three Gorges Reservoir (TGR) earthquakes and analysis of seismic activity. First, we use the bi-spectrum cross-correlation method to analyze the seismic waveform data of TGR encrypted networks from March, 2009 to December, 2010, and evaluate the quality of waveform cross-correlation analysis. Combined with the waveform cross-correlation of data obtained, we use the double difference method to relocate the earthquake position. The results show that location precision using bi-spectrum verified waveform cross-correlation data is higher than that by using other types of data, and the mean 2 sig-error in EW, NS and UD are 3.2m, 3.9m and 6.2m, respectively. For the relocation of the Three Gorges Reservoir earthquakes, the results show that the micro-earthquakes along the Shenlongxi river in the Badong reservoir area obviously show the characteristics of three linear zones with nearly east-west direction, which is in accordance with the small faults and carbonate strata line of the neo-tectonic period, revealing the reservoir water main along the underground rivers or caves permeated and induced seismic activity.The stronger earthquakes may have resulted from small earthquakes through the active layers.  相似文献   

Variability of the useful life of reservoirs in tropical locations: A case study from the Burdekin Falls Dam,Australia     

Michelle Cooper  Stephen E. Lewis  Thomas C. Stieglitz  Scott G. Smithers 《国际泥沙研究》2018,33(2):93-106

Large dam construction for irrigation, hydropower, water supply, and flood control in tropical to sub-tropical areas increased markedly after 1950. Many of the dams built during this period have filled with sediment and no longer perform to their original design specifications; in many cases, forecast dam life was greatly overestimated. This study investigates the useful life of Burdekin Falls Dam (BFD), northeastern Australia and compares the findings with other tropical reservoirs. Using two independent methods it is estimated that between 61 and 65 million m³ of sediment has been deposited in the reservoir over the 24 years of operation through 2011. This sediment volume equates to an average of 0.15% of capacity lost per year since construction was completed. If current sediment loads/climate regimes persist, reservoir capacity will be reduced by 50% after 345 years. However, the useful life of the BFD reduces to just 276 years when drawdown data are considered; these data show reservoir use would be affected once 40% of storage was filled with sediment, with a 60% drawdown return period of 1 in 15 years. When compared to similar large tropical to sub-tropical reservoirs, the BFD has a slightly longer reservoir useful life than dams in India and a much longer half-life than for both similar-sized and larger dams in China, Brazil, and Iran. Properties of the BFD that promote a longer useful life include a lower trap efficiency, relatively low annual sediment load delivered to the reservoir, limited sediment deposition behind the dam wall (and uniform distribution of deposited sediment), and the export of highly turbid annual floodwaters before settling and deposition of any remaining sediment within the reservoir.  相似文献   

过零点个数地震属性理论诠释及应用     

张军华  桂志鹏  刘显太  王军  张云银  蒋龙 《地球物理学进展》2020,(1):258-264

在地震解释与储层预测中,地震属性扮演着重要角色.在砂砾岩储层研究过程中,常规属性效果并不理想,无法满足实际应用的需要.而过零点个数,虽是一种不被人经常使用的地震属性,但我们发现在砂砾岩体油藏预测中应用效果良好.为此,研究过零点个数地震属性的定义与计算方法,讨论子波主频、砂岩厚度、泥岩夹层和地层韵律性等与它的关系,通过模型测试与实际资料应用对其做较全面的诠释.研究表明:(1)对于单一界面地震记录,过零点个数不随子波主频和波长的变化而变化;(2)砂岩厚度与过零点个数呈正相关,厚砂岩的过零点个数要比薄砂岩大;(3)砂体间存在的泥岩夹层,厚度变化对过零点个数影响较小,但它会影响波组的形态;(4)不规则沉积与均匀沉积相比,过零点个数属性值要大,因此,此属性比较适合多期次发育的砂砾岩体或其他薄互层结构的储层预测.总的来说,过零点个数地震属性能够有效地识别砂砾岩体发育区,可为此类储层预测提供了一种新的优势属性.  相似文献   

基于近似支持向量机的流体识别因子融合     

李文秀  文晓涛  李天  刘松鸣  李雷豪  杨吉鑫 《地球物理学进展》2020,(1):139-144

通过叠前反演获得的单参数或组合参数都有一定的流体识别能力,但如何将多种流体识别因子有效融合是目前进行流体识别的一个难题.利用人工参与进行流体性质的综合解释是目前流体识别因子融合的主要途径,但这种方法人为干扰较大,不确定性强.鉴于此,本文提出了一种基于近似支持向量机的流体识别方法.该方法首先以实际工区测井资料为依据,优选出对工区内储层所含流体特征敏感的流体识别因子作为输入参数,然后通过近似支持向量机进行流体性质的判别,实例证明该方法的识别结果客观准确,是一种可靠的流体识别方法.  相似文献   

稳定分层水库水质的季节性变化特征及扬水曝气水质改善   总被引：1，自引：0，他引：1  

巨拓  黄廷林  马卫星  周子振 《湖泊科学》2015,27(5):819-828

为了解深水型水库水体的热分层结构、水质特征及扬水曝气系统对水质的改善情况,对水温、溶解氧、p H、叶绿素a、营养盐、溶解性有机碳浓度等水质指标进行为期一年的监测,探讨各项指标的季节性变化规律.结果表明,黑河水库水体呈单循环混合模式,在3-10月形成自然热分层,水体的热分层导致相应水库水质明显分层.黑河水库为偏碱性水体,叶绿素a、总磷、总氮、铵态氮和溶解性有机碳浓度平均值分别为2.21μg/L、0.022 mg/L、1.32 mg/L、0.20 mg/L和2.93 mg/L,表明黑河水库处于中-富营养状态.热分层期底部水体溶解氧浓度在0~7.9 mg/L之间,平均值为2.9 mg/L,氮磷质量比在41~100之间,表明黑河水库是一个底部季节性缺氧、高营养盐型水库.在水库自然热分层末期,应用扬水曝气技术,不仅改善了底部水体的厌氧/缺氧环境,抑制了厌氧/缺氧条件下内源污染物的释放和藻类的增殖,而且还使得水库水体提前混合,实现了强制混合与水体自然混合过程的有机衔接,延长了水质持续改善的作用时效,有效地改善了水环境,保障了安全供水.  相似文献   

基于EFDC模型的河道型水库藻类生长对流域污染负荷削减的响应——以广东长潭水库为例   总被引：1，自引：0，他引：1  

李一平  王静雨  滑磊 《湖泊科学》2015,27(5):811-818

将环境(EFDC)模型应用于广东梅州的河道型水库——长潭水库,经过模型的验证,建立长潭水库水生态数学模型,模拟出水库在现状污染负荷下的藻类生长情况,以叶绿素a浓度为指标,研究水库在丰水年与枯水年富营养化改善程度对不同流域污染削减方案的响应关系.结果表明:现状污染负荷削减10%,在丰水年库尾、库中和库首点位的叶绿素a平均浓度分别降低13.99%、12.00%和10.35%;枯水年3个代表点位叶绿素a平均浓度分别下降8.42%、5.63%和2.10%.污染削减20%的情况下,丰水年3个代表点位的叶绿素a浓度分别降低26.78%、19.25%和17.04%,枯水年对应的降低幅度分别为11.72%、7.97%和5.12%;库尾地区表现出河道的特征,在污染负荷削减的情况下藻类生长能够受到有效遏制,库首地区则表现出湖泊的特性,枯水年这一特征表现更加突出,污染削减20%的情况下,叶绿素a的平均浓度仅降低5.12%.  相似文献   

Experimental quantification of the seismoelectric transfer function and its dependence on conductivity and saturation in loose sand          下载免费PDF全文

J. Holzhauer  D. Brito  C. Bordes  Y. Brun  B. Guatarbes 《Geophysical Prospecting》2017,65(4):1097-1120

Under certain circumstances, seismic propagation within porous media may be associated to the conversion of mechanical energy to electromagnetic energy, which is known as a seismo‐electromagnetic phenomenon. The propagation of fast compressional P‐waves is more specifically associated to the manifestations of a seismoelectric field linked to the fluid flows within the pores. The analysis of seismoelectric phenomena, which requires the combination of the theory of electrokinetics and Biot's theory of poroelasticity, provides us with transfer function that links the coseismic seismoelectric field E to the seismic acceleration . To measure the transfer function, we have developed an experimental setup enabling seismoelectric laboratory observation in unconsolidated quartz sand within the kilohertz range. The investigation focused on the impact of fluid conductivity and water saturation over the coseismic seismoelectric field. During the experiment, special attention was given to the accuracy of electric field measurements. We concluded that, to obtain a reliable estimate of the electric field amplitude, the dipole from which the potential differences are measured should be of much smaller length than the wavelength of the propagating seismic field. Time‐lapse monitoring of the seismic velocities and seismoelectric transfer functions were performed during imbibition and drainage experiments. In all cases, the quantitative analysis of the seismoelectric transfer function was in good agreement with theoretical predictions. While investigating saturation variations from full to residual water saturation, we showed that the ratio undergoes a switch in polarity at a particular saturation , which also implies a sign change of the filtration, traducing a reversal of the relative fluid displacement with respect to the frame. This sign change at critical saturation stresses a particular behaviour of the poroelastic medium: the dropping of the coseismic electric field to zero traduces the absence of relative pore/fluid displacements representative of a Biot dynamically compatible medium. We concluded from our experimental study in loose sand that the measurements of the coseismic seismoelectric coupling may provide information on fluid distribution within the pores and that the reversal of the seismoelectric field may be used as an indicator of the dynamically compatible state of the medium.  相似文献   

Marine transient electromagnetic sounding of deep buried hydrocarbon reservoirs: principles,methodologies and limitations          下载免费PDF全文

Pavel O. Barsukov  Edward B. Fainberg 《Geophysical Prospecting》2017,65(3):840-858

The possibility of a time‐domain electromagnetic sounding method using excitation and measurement of vertical electric fields to search for and identify deeply buried reservoirs of hydrocarbons offshore is investigated. The method operates on source–receiver offsets, which are several times less than the depth of the reservoir. Geoelectric information is obtained from the transient responses recorded in the pauses between the pulses of electric current in the absence of the source field. The basics of the method, as well as its sensitivity, resolution, and the highest accessible depth of soundings for various geological conditions in a wide range of sea depths, are analyzed. For the analysis, 1D and 3D geoelectric models of hydrocarbon reservoirs are used. It is shown that under existing technologies of excitation and measurement of vertical electric fields, the highest accessible depth of soundings can be up to 4 km. Technology for the inversion and interpretation of transient responses is demonstrated on experimental data.  相似文献   

Diurnal,seasonal and inter-annual variability of fish density and distribution in the Three Gorges Reservoir (China) assessed with hydroacoustics     

《Limnologica》2017

Environment conservation of the Three Gorges Reservoir (TGR) requires reliable assessment of fish resources and variation of their distribution. The goal of this study was to determine the best season and the diurnal period to estimate fish density in the TGR using acoustic surveys as a monitoring tool. To find out diurnal migration pattern of fishes in the TGR, we conducted reduplicated 24-h hydroacoustical surveys in the forequarter of the TGR, which covered different habitats (mainstream, tributary bay), seasons (summer, winter) and years (2012–2015). Measurements were performed using SIMRAD EY60 split beam echosounder with frequency 120 kHz. Additionally, zooplankton and environmental parameters were measured. The results showed more than ten times differences between the day and night fish density estimates, probably resulting either from the horizontal migrations between the littoral and open water or vertical migrations. Differences were higher during winter than during summer, and higher in the tributary bay than in the mainstream. Clear vertical migrations were observed both in the tributary bay (amplitude 15 m) and in the mainstream (amplitude 35 m), but only during winter time. Inter-annual estimates of fish density showed generally decreasing trend with years. especially well pronounced in the tributary bay. We also observed high seasonal and diurnal variability in fish distributions, which can significantly affect the accuracy and precision of biomass estimate, indicating importance of choosing appropriate timing for fish monitoring. According to our results, in order to receive the most reliable estimates of fish density in the TGR, hydroacoustic surveys should be performed during summer at night time.  相似文献   

Reservoir operation by staging due to climate variability     

Chongxun Mo  Peng Liu  Huanhuan Zhong  Dayang Wang  Ya Huang 《水文科学杂志》2018,63(6):926-937

The changing environment enhances the hydrological cycle and increases the frequency of extreme floods. In this paper, the impacts of climate variability on flood season segmentation are determined and the scientific basis for determining corresponding flood limiting water levels (FLWLs) is provided. Climate variation was determined and then the flood season was divided into several sub-seasons using the results of the set pair analysis method (SPAM) and four indices; peak floods crossing the transitional periods were sampled to obtain a design flood hydrograph; and, finally, seasonal FLWLs were determined for reservoir operation. The performance of this reservoir staging operation was evaluated for a case study in the Chengbihe Reservoir, China.  相似文献