共查询到20条相似文献,搜索用时 15 毫秒
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利用纯S波波形拟合方法,输入纯S波波形,使用传递矩阵计算了层状介质自底面传到地表约100 km厚度、32 s的理论地震波形;引进快速模拟退火法进行反演搜索理想模型,用理论波形与观测波形的相关系数作为约束函数,选择同一台站几个震例的理论波形与实际波形吻合最好的模型作为该台站下方的可接受速度结构模型.收集深源远震的清晰S波记录波形,我们共得到了陕西省境内秦岭造山带中段及其邻近区域13个地震台站下方的S波速度结构.结果显示,秦岭造山地带、渭河盆地及鄂尔多斯块体的地壳结构之间存在很大的差异,各个块体有其各自的构造特点;不过三个块体的地壳厚度都显示了由东向西逐渐增加的变化趋势. 相似文献
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J. L. Bonner D. C. Pearson W. S. Phillips S. R. Taylor 《Pure and Applied Geophysics》2001,158(11):2017-2039
—?During 1997 and 1998, twelve chemical explosions were detonated in boreholes at the former Soviet nuclear test site near the Shagan River (STS) in Kazakhstan. The depths of these explosions ranged from 2.5 to 550 m, while the explosive yield varied from 2 to 25 tons. The purpose of these explosions was for closure of the unused boreholes at STS, and each explosion was recorded at local distances by a network of seismometers operated by Los Alamos National Laboratory and the Institute of Geophysics for the National Nuclear Center (NNC). Short-period, fundamental-mode Rayleigh waves (Rg) were generated by these explosions and recorded at the local stations, resultingly the waves exhibited normal dispersion between 0.2 and 3 seconds. Dispersion curves were generated for each propagation path using the Multiple Filter Analysis and Phase Match Filtering techniques. Tomographic maps of Rg group velocity were constructed and show a zone of relatively high velocities for the southwestern (SW) region of the test site and slow propagation for the northeastern (NE) region. For 0.5?sec Rg, the regions are separated by the 2.1?km/sec contour, as propagation in the SW is greater than 2.1?km/sec and less in the NE region. At 1.0 sec period, the 2.3?km/sec contour separates the two regions. Finally, for 1.5 and 2.0 sec, the separation between the two regions is less distinct as velocities in the NE section begin to approach the SW except for a low velocity region (<2.1?km/sec) near the center of the test site. Local geologic structure may explain the different regions as the SW region is composed predominantly of crystalline intrusive rocks, while the NE region consists of alluvium, tuff deposits, and Paleozoic sedimentary rocks. Low velocities are also observed along the Shagan River as it passes through the SW region of the test site for shorter period Rg (0.5–1.0?sec). Iterative, least-squares inversions of the Rg group velocity dispersion curves show shear-wave velocities for the southwestern section that are on average 0.4?km/sec higher than the NE region. At depths greater than 1.5?km the statistical difference between the models is no longer significant. The observed group velocities and different velocity structures correlate with P-wave complexity and with spatial patterns of magnitude residuals observed from nuclear explosions at STS, and may help to evaluate the mechanisms behind those observations. 相似文献
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基于微动技术探测盆地浅部地层速度结构1 总被引:1,自引:0,他引:1
本文介绍了利用微动技术探测地表浅层速度结构的方法,并在江苏常州地区一个凹陷盆地内进行了一次野外台阵观测试验,采集场地数据的质量良好.利用空间自相关法得到了不同半径下的自相关函数曲线,该场地的自相关函数显示,对于半径较大的台阵,其自相关系数较好;根据自相关函数提取了场地的频散曲线.通过设定初始模型,利用邻域反演算法得到了该场地的基本速度结构和各层深度分布范围;最后通过与场地附近的人工地震剖面进行对比分析表明,试验结果所揭示的土层结构与浅层人工地震勘探解释结果接近. 相似文献
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Artificially enhancing recharge rate into groundwater aquifer at specially designed facilities is an attractive option for increasing the storage capacity of potable water in arid and semi‐arid region such as Damascus basin (Syria). Two dug wells (I and II) for water injection and 24 wells for water extraction are available in Mazraha station for artificial recharge experiment. Chemical and stable isotopes (δ2H and δ18O) were used to evaluate artificial recharge efficiency. 400 to 500*103 m3 of spring water were injected annually into the ambient shallow groundwater in Mazraha station, which is used later for drinking purpose. Ambient groundwater and injected spring water are calcium bicarbonate type with EC about 880 ± 60 μS/cm and 300 ± 50 μS/cm, respectively. The injected water is under saturated versus calcite and the ambient groundwater is over saturated, while the recovered water is near equilibrium. It was observed that the injection process formed a chemical dilution plume that improves the groundwater quality. Results demonstrate that the hydraulic conductivity of the aquifer is estimated around 6.8*10?4 m/s. The effective diameter of artificial recharge is limited to about 250 m from the injection wells. Mixing rate of 30% is required in order to reduce nitrate concentration below 50 mg/l which is considered the maximum concentration limit for potable water. Deuterium and oxygen‐18 relationship demonstrates that mixing line between injected water and ambient groundwater has a slope of 6.1. Oxygen‐18 and Cl? plot indicates that groundwater salinity origin is from mixing process, and no dissolution and evaporation were observed. These results demonstrate the efficiency of the artificial recharge experiments to restore groundwater storage capacity and to improve the water quality. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Hussam Eldein Zaineh Hiroaki Yamanaka Yadab Prasad Dhakal Rawaa Dakkak Mohamad Daoud 《Journal of Seismology》2013,17(4):1295-1319
The seismic hazard potential for metropolitan of Damascus, Syria is mainly controlled by earthquakes along Serghaya Fault which is a branch of Dead Sea Fault System. In this study, strong ground motion due to the November 1759 Earthquake along the fault of Serghaya was estimated with a numerical simulation technique. In the simulation, the Kostrov-like slip-velocity function was used as an input to the discrete wave number method to simulate the strong ground motions in a broadband frequency range. In order to model the incoherent rupture propagation which can excite large high-frequency waves, random numbers are added to arrival time of circular rupture front. MMI intensities calculated from the synthetic ground motions are compared with the observed values by Ambraseys and Barazangi (J Geophys Res 94:4007-4013, 1989). The calculated intensities are in good agreement with the observed ones at the most sites that validate appropriateness of the proposed source model. The PGA and PGV in the eastern region of Damascus city are higher than those in the western region due to the effects of local site amplification. The simulated high-frequency (1.0–6.0 Hz) ground motions for the sites in the Damascus city are higher than the design requirements defined by the Syrian building code. Furthermore, the simulated high-frequency ground motions for sites in the focal region are bigger than the design requirements in the case of the near-fault factors and are not considered. That demonstrates the appropriateness of considering the near-fault factors for a site near the focal region as introduced by the new building code. 相似文献
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天津滨海地区浅层剪切波速与基底构造关系研究 总被引:1,自引:0,他引:1
剪切波速是反映土体动力学特性的重要物理量之一,在土木工程抗震中有广泛的应用.本文收集整理了天津滨海地区500余口横波测井资料,在经纬向与垂直向以0.01°×0.01°x1m的三维网格进行线性插值,获得了天津滨海地区近地表剪切波速空间分布的精细图像.根据资料分布与地质构造背景,选取2个代表性波速剖面进行分析.结果表明,滨海地区浅部剪切波速结构具有明显的分层特征与横向不均匀性,进一步的分析认为,不同地质构造单元的速度结构具有明显差异,在大型区域或边界断裂两侧波速结构或受到扰动或受到明显影响,充分显示了天津滨海地区基底构造与断裂活动对晚第四纪沉积发展和地层发育的控制以及对工程地震地质条件评价的影响. 相似文献
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Haley A. Schneider W. Andrew Jackson Ken Rainwater Danny Reible Stephen Morse Paul B. Hatzinger Uriel Garza-Rubalcava 《Ground water》2019,57(6):915-924
The fate and transport of groundwater contaminants depends partially on groundwater velocity, which can vary appreciably in highly stratified aquifers. A high-resolution passive profiler (HRPP) was developed to evaluate groundwater velocity, contaminant concentrations, and microbial community structure at ∼20 cm vertical depth resolution in shallow heterogeneous aquifers. The objective of this study was to use mass transfer of bromide (Br−), a conservative tracer released from cells in the HRPP, to estimate interstitial velocity. Laboratory experiments were conducted to empirically relate velocity and the mass transfer coefficient of Br− based on the relative loss of Br− from HRPP cells. Laboratory-scale HRPPs were deployed in flow boxes containing saturated soils with differing porosities, and the mass transfer coefficient of Br− was measured at multiple interstitial velocities (0 to 100 cm/day). A two-dimensional (2D) quasi-steady-state model was used to relate velocity to mass transfer of Br− for a range of soil porosities (0.2–0.5). The laboratory data indicate that the mass transfer coefficient of Br−, which was directly—but non-linearly—related to velocity, can be determined with a single 3-week deployment of the HRPP. The mass transfer coefficient was relatively unaffected by sampler orientation, length of deployment time, or porosity. The model closely simulated the experimental results. The data suggest that the HRPP will be applicable for estimating groundwater velocity ranging from 1 to 100 cm/day in the field at a minimum depth resolution of 10 cm, depending on sampler design. 相似文献
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利用主动震源检测汶川地震余震引起的浅层波速变化 总被引:9,自引:6,他引:9
为了监测汶川地震后断裂带附近的波速变化,2008年6月,我们利用快速响应探测系统,在龙门山断裂带北端进行了为期3周的连续观测实验.实验使用电动落锤作为主动震源,GPS连续同步授时的高精度数采作为接收系统.利用记录到的高时间精度观测数据,结合互相关时延检测技术,计算了P波和面波走时的相对变化,来表征地下波速的变化.我们观测到两次面波波速的异常变化,变化幅度最高达到2%,远远大于气压变化所能引起的波速变化.结合该时段内地震活动记录,我们认为面波的波速变化是由在附近发生的两次地震事件的同震效应引起的,该观测结果同理论计算结果相符. 相似文献
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2019年8月2日河北省唐山市路南区某矿井区发生ML2.4巷道塌陷,基于塌陷周边台站观测到的短周期瑞雷波,提取面波基阶群速度频散曲线,并利用迭代反演方法得到研究区域地下10 km深度范围内的一维剪切波速度结构,用于精定位分析。速度分析结果表明,研究区域浅表剪切波速度约为2.46 km/s;深度为2 km时,塌陷周边存在小范围的低速区,速度约为2.57 km/s;深度约为4 km时,剪切波速度达3.47 km/s;深度为5~9 km时,唐山东部沉积盆地内存在1个剪切波低速层。精定位分析结果表明,增加浅层速度模型有助于提高深度较小的地震定位精度;塌陷周边的低速区向下延伸近20 km,为地震多发区。 相似文献
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GUO Yang XU Jiajun LIN Chen JIN Xing YAO Huajian YANG Hongfeng CAI Huiteng 《中国地震研究》2019,33(2):265-275
112 short-period seismographs were set up in the 400km2 area of Pingtan Island and its surrounding areas in Fujian. The combined observations of the airgun source and ambient noise source were carried out using a dense array to receive the 387 airgun signals excited around the island and one month of continuous ambient noise recording. The 1-D P-wave and S-wave shallow velocity model of Pingtan Island is obtained by the inversion of the airgun body wave''s first arrival time data, and the reliability of the velocity model is verified by using the surface wave phase velocity dispersion curve, which can provide initial model for subsequent 3-D imaging. The experimental results show that this experiment is a successful demonstration of local scale green non-destructive detection, which can provide basic data for shallow surface structure research and strong vibration simulation of the Pingtan Island. 相似文献
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In this paper the authors have discussed the results of investigation of fine velocity structure in the basement layer of the Simao-Zhongdian DSS profile in western Yunnan region.The depth of upper Pz interface of the basement layer is about 0-3.5 km,and the depth of the lower P1 interface is 11.0-17.0 km.The velocity of the basement layer on the southern side of the Jinhe-Erhai deep fault is 5.70-6.30 km/s,and has increased to 6.30-6.50 km/s on the northern side.Their transitional zone is situated near Jianchuan County.Along the profile some localities,where the faults cut across the lateral variation of Pz interface velocity,are quite obvious in addition to the variation in depth.The velocity isopleths are relatively sparse in the southern region of JYQ S.P.(shot - point),near the DC S.P.,and in the south ZT S.P.The magma has apparently risen up along the deep faults to the upper crust in these localities,forming a large intrusive rock zone in the basement layer.In Jinggu region the basaltic magma has 相似文献
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土石混合滑坡体地表地形复杂,土、石混杂堆积,结构松散,探测难度大,目前尚缺乏有效的物探手段.本文首次尝试将小台阵二维微动剖面探测技术应用于衡阳市拜殿乡的土石混合滑坡体探测.探测结果揭示,该滑坡体上部为砂质黏性土层,含块石较多;下为全风化花岗岩层,岩性较为均匀,块石含量少,其顶部为该滑坡体潜在的滑动面.滑动面在滑坡体后缘较陡、中部较为平缓,从而后缘的重力失稳、滑动风险更大.滑坡体的滑床(中-强风化花岗岩、微-未风化花岗岩)埋深在10 m以下,起伏变化较大,但岩体相对致密、完整,稳定性好,不易滑动.探测结果与钻探资料较为吻合,为评价滑坡体稳定性、设计合理的治理方案提供了地球物理依据.
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A combination of stable isotopes (18O and 2H) and hydrochemistry has been applied to investigate storage processes in relation to aquifer storage and recovery (ASR) of the shallow alluvial Quaternary aquifer in Damascus basin. The stored water, entirely taken from the Figeh springs during flood periods, was injected in a single well having a brackish groundwater. Water samples were collected from four observation wells drilled in the Damascus University Campus (DUC) site during a 3‐year period (2006–2008). The injectant water, which deviates in its chemical and isotopic signatures from that of the ambient groundwater, shows that the stored water plume remains within close proximity to the injection well (IW) (<≈ 100 m). Thus, only two wells (W13 and W14) located at a distance less than 80 m from the injection point were affected by this injection. The observation wells located at longer distances from the IW (≈145 m and ≈ 600 m for wells W15 and WHz, respectively) were completely unaffected by the injection. Although most of the chemical and isotopic parameters usefully reflected the mixing process that occurs between the injectant water and ambient groundwater, the stable isotope (18O) and chloride (Cl−) were the most sensitive parameters that quickly reflect this signature. Using a simple mass balance, the calculated proportion of injectant water reaching the well W13 was in the range of 50–90%. This proportion was even lower (30–55%) in the case of well W14. Although the drought event prevailing during this study did not much help to inject further amounts of water, higher than the injected volume (0·2416 M m3) and also not favourable to better evaluate the fate and subsurface hydrological processes, these findings offer encouragement to continue the ASR activities, as an alternative way for better management of water resources in this basin facing intensive problems. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献