共查询到19条相似文献，搜索用时 93 毫秒
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根据云南地区的基阶瑞利波相速度频散资料，用面波层析成像方法反演得到该区域中上地壳S波速度结构. 给出了研究区域内在4个深度上的S波速度水平分布图像和沿100.5°E、24°N、25°N、26°N及27°N的S波速度-深度剖面图. 结果表明：在小江断裂与红河断裂围成的川滇菱形块体内，26～30km深度处的速度明显低于周边地区，其南段从地表到15km深度均为明显的低速区域. 云南地区的强震（M＞6.0）震中位置与S波速度分布图像具有明显的相关性，主要分布于高速与低速的过渡区域. 相似文献
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龙门山断裂带精细速度结构的双差层析成像研究 总被引：21，自引：11，他引：10
利用川西流动地震台阵、汶川地震震后应急台网记录到的P波到时资料，对2008年5月至2008年10月期间发生的汶川地震余震序列应用双差层析成像方法进行了地震震源和三维P波速度结构的联合反演.结果显示，联合反演获得的地震重定位结果与基于一维地壳参考模型的双差定位方法结果相近；研究区15 km以上速度结构与地表断裂分布密切相关，20 km以下深度呈现北东向和北西向交错结构.汶川地震破裂带南段龙门山断裂带之间上地壳呈现高速异常，速度结构的非均匀变化是控制余震分布和主震破裂传播的主要因素；联合反演结果给出了小鱼洞-理县方向存在隐伏断裂的速度结构证据，同时发现，破裂带北东段可能沿新发断裂扩展；结果确认了汶川地震起始段的高角度逆冲断裂特征，也确认了前山断裂和中央断裂在约20 km深度合并到脆韧转换带的特征. 相似文献
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腾冲火山地热区地壳结构的地震学研究 总被引：23，自引：7，他引：23
根据腾冲火山地热区实施的人工地震测深剖面资料 ,用有限差分反演和正向走时拟合方法确定了地壳二维 P波速度结构 .地壳模型显示 ,在腾冲的热海热田附近上地壳存在低速异常体 ,它与火山地热活动可能有关 .测线的二维地壳结构上显示出两条地壳断裂 :龙陵—瑞丽断裂和腾冲断裂 ,其中腾冲断裂可能切穿莫霍界面 .同时 ,根据远震波形资料反演腾冲热海热田地区的 S波速度结构 ,也显示出该地区上地壳存在 S波的低速异常 .本文从深部结构方面探讨腾冲火山的成因 .腾冲火山地热区地壳具有低 P波和 S波速度、低电阻率、高热流值和低 Q值 ,以及上地幔也具有低 P波速度的特点 .由此推测地壳内岩浆来源于上地幔 ,腾冲附近地区存在的上地壳低速度异常可与岩浆的分异作用相联系 .与地球上大多数的活动火山一样 ,腾冲火山位于移动板块之间的边界附近 ,属于“板块边界”火山 相似文献
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利用10～184 s基阶瑞利波频散曲线反演得到了中国西部及邻近区域地壳上地幔(0～300 km)的S波速度结构.反演采用了传统的两步法,即通过时频分析获得频散曲线后,首先利用Occam方法反演出各周期面波速度在二维网格结点上的分布,然后反演每个结点下方的S波速度结构,从而给出研究区域的三维速度结构. 相似文献
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区域地壳速度结构对于地震定位和地球动力学特征认识十分重要，一直是地震反演研究的主要内容。利用收集到的基于背景噪声面波成像方法的瑞利面波相速度数据，我们对苏北—南黄海地区地下三维S波速度结构开展了深度反演，进而探讨苏北—南黄海盆地地质结构与地震构造的关系。面波层析成像结果表明区域速度结构模型与地质特征基本一致，速度结构清晰刻画出了苏北—南黄海沉积盆地的主要沉积构造范围和基底起伏。反演结果还揭示了南黄海盆地中地壳内存在一显著的低速层，与历史强震集中分布区高度一致，表明浅源强震活动与壳内的低速层密切相关。 相似文献
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双平面波拟合法是一种新的面波成像方法,反演中考虑地震波场中的非平面波成分,提高反演的分辨率.本文利用双平面波拟合法,反演获得鄂尔多斯地区上地幔岩石圈的速度结构.所用资料为国家数字地震台网69个宽频带地震仪和北京大学34个流动数字地震台观测到的地震波面波资料.首先从面波记录中提取了研究区域20~125 s瑞利波相速度频散曲线,进而得到各个周期瑞利波相速度异常分布图.结果显示,短周期瑞利波相速度异常与地表的构造特征吻合较好,中长周期的瑞利波相速度可以反映出上地幔岩石圈的速度异常分布以及构造特征.由研究区20~125 s的瑞利波相速度分布图可以反演得到地表到地下200 km范围内的三维剪切波速度结构.结果显示,鄂尔多斯块体内部稳定均一,活化或改造的痕迹不明显;鄂尔多斯块体西南缘受到青藏高原的强烈作用,有大量地幔物质流动的痕迹存在;中央转换带下超过200 km深度存在地幔物质上涌,可能与太平洋板块的俯冲和青藏高原板块的挤压有关. 相似文献
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通过最新收集的大量高质量的地方震和远震事件的到时数据进行联合反演,我们确定了日本俯冲带约700km深度的P波和S波速度层析成像。我们还使用远震瑞利波的振幅和相速度,确定了日本及其附近海域下方20~150s周期基阶瑞利波的二维相速度图像。研究区精细三维S波层析成像可通过地方震和远震事件的S波到时,及瑞利波相速度数据进行联合反演得到。我们的反演结果揭示:一维原始速度模型中,俯冲太平洋板块和菲律宾海板块呈现明显的高速区。在板块上方的地幔楔和太平洋板块下方的地幔中存在显著的低速异常。俯冲板块和周围地幔之间速度有明显的差异,表明温度、水含量和/或部分熔融程度有显著的横向变化。地幔楔低速异常是由板块脱水作用和地幔楔拐角流造成。在日本东北太平洋板块下方显示片状的低速区,这可能反映了地幔深部热上涌以及地幔柱软流圈的俯冲作用。我们的结果表明不同的地震数据联合反演,对于得到地壳和地幔可靠的层析成像图像是非常有效和重要的。 相似文献
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本文用单台多重滤波方法测定了经过青藏高原地区瑞利波群速度频散曲线。所得基阶瑞利波的观测周期为5.0-56.0秒,速度标准偏差为0.08-0.15公里/秒,一阶瑞利波的观测周期范围为10-16秒,速度标准偏差为0.05-0.13公里/秒。利用广义线性反演方法对频散曲线进行反演,可得出一个由五层构成的地震横波速度地壳模型。在27-40公里之间存在低速层,其横波速度为3.29公里/秒,比上一层低0.21公里/秒。 相似文献
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浅层面波法调查表层速度结构多用于非沙漠区的工程与环境领域。本文利用多道面波分析(MASW)技术针对塔克拉玛干沙漠地区特殊地质情况,对所采集的浅层多道面波资料进行处理分析得到沙漠区表层速度结构;同时对该地区所获得的地震大炮记录上的面波进行了处理、分析和对比,探讨了沙漠区利用大炮面波法调查表层结构的可行性。实践表明,多道面波资料可以得到很好的浅层速度结构,而大炮记录则可得到详尽的深层地质结构,将二者相结合便得到测区表层60m范围内的速度结构信息,也证明了在沙漠区利用大炮面波记录提取表层地下介质结构是可行的。 相似文献
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Studying surface structure in desert areas using multiple kinds of surface wave data 总被引：1，自引：0，他引：1
Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan Desert area, we use the multi-channel analysis of surface wave （MASW） method to process multi-channel shallow surface wave records to determine the near surface velocity structure in the desert area. We also process, analyze, and compare the surface waves in many-trace records extracted from the oil exploration shot gathers in the area. We show that the MASW method can determine detailed shallow velocity structure in desert areas and the many-trace records can be used to get detailed deep geological structure. The combination of the two different datasets can obtain the exact velocity structure upper 60 m depth in the survey area. 相似文献
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Multichannel analysis of surface wave method with the autojuggie 总被引：2，自引：0，他引：2
Gang Tian Don W. Steeples Jianghai Xia Richard D. Miller Kyle T. Spikes Matthew D. Ralston 《Soil Dynamics and Earthquake Engineering》2003,23(3):61-65
The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the ‘autojuggie’) is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys. 相似文献
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A joint analysis of down-hole (DH) and multichannel analysis of surface waves (MASW) measurements offers a complete evaluation of shear wave velocity profiles, especially for sites where a strong lateral variability is expected, such as archeological sites. In this complex stratigraphic setting, the high “subsoil anisotropy” (i.e., sharp lithological changes due to the presence of anthropogenic backfill deposits and/or buried man-made structures) implies a different role for DH and MASW tests. This paper discusses some results of a broad experimental program conducted on the Palatine Hill, one of the most ancient areas of the city of Rome (Italy). The experiments were part of a project on seismic microzoning and consisted of 20 MASW and 11 DH tests. The main objective of this study was to examine the difficulties related to the interpretation of the DH and MASW tests and the reliability limits inherent in the application of the noninvasive method in complex stratigraphic settings. As is well known, DH tests provide good determinations of shear wave velocities (Vs) for different lithologies and man-made materials, whereas MASW tests provide average values for the subsoil volume investigated. The data obtained from each method with blind tests were compared and were correlated to site-specific subsurface conditions, including lateral variability. Differences between punctual (DH) and global (MASW) Vs measurements are discussed, quantifying the errors by synthetic comparison and by site response analyses. This study demonstrates that, for archeological sites, VS profiles obtained from the DH and MASW methods differ by more than 15 %. However, the local site effect showed comparable results in terms of natural frequencies, whereas the resolution of the inverted shear wave velocity was influenced by the fundamental mode of propagation. 相似文献
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Zheng-Qin He 《地震科学（英文版）》1993,6(3):631-639
Based on the short period surface wave recorded by DSS of Project 85009, the Rayleigh wave dispersion of phase velocity is determined with the periods from 0.3s to 1.07s in Lücan-Fanxian Profile in this paper. The profile is divided into 7 sections by their dispersion characteristics, and the shallow velocity structure is inversed for each section. It shows that velocity obviously increases at the bottom of Neogene in the eastern region of the profile; that not only does Rayleigh wave velocity evidently decreases but also its waveform conspiciously changes across Neihuang fault, Changyuan fault and Liaolan fault respectively, by which the corresponding surface positions of these faults can be exactly determined; and that not only is S wave velocity between Changyuan fault and Liaolan fault smaller than that of its two sides, but also the buried depth of Neogene bottom is obviously larger than that of the two sides. 相似文献
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地球物理勘探方法在岩土工程的应用已有很长一段时间,但其成效与工程师的期待往往有不小的落差,以致于在一般的工程应用上仍不普遍.近年来浅地表地球物理技术有显着的进展,特别是在走时速度层析成像(Traveltime Tomography)、电阻率层析成像法(Electrical Resistivity Tomography)及多道瞬态面波法(Multichannel Analysis of Surface Wave).本文首先介绍这些方法在台湾岩土工程的应用,主要包括地层土壤液化潜能评估、坝体的安全检测、土壤与地下水污染调查及地基改良的质量管控等,应用案例以台湾常使用的地球物理勘探方法逐一介绍.虽然许多成功案例与新的应用方向对于浅地表地球物理技术在岩土工程应用的推广起了鼓舞作用,本文从工程师的角度提出地球物理勘探工程大量应用的挑战与瓶颈,包括如何提升探测数据的客观性、数据反演非唯一性问题、探测深度与分辨率的限制、实际条件违背反演基本假设的情况、以及地物性质与工程性质链接的不确定性问题,并进一步针对这些问题说明相关研究的进展与实务对策.希冀透过上述探讨,降低物探师与工程师认知上的差距,提升地球物理勘探在工程的应用的合理性与普及性. 相似文献
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Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements 总被引：1，自引：0，他引：1
Jianghai Xia Richard D. Miller Choon B. Park James A. Hunter James B. Harris Julian Ivanov 《Soil Dynamics and Earthquake Engineering》2002,22(3)
Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated Vs and borehole measured Vs in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived Vs values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis. 相似文献
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Chih-Ping Lin Cheng-Chou Chang Tzong-Sheng Chang 《Soil Dynamics and Earthquake Engineering》2004,24(9-10):689
The multi-channel analysis of surface wave (MASW) method is a non-invasive method recently developed to estimate shear wave velocity profile from surface wave energy. Unlike conventional SASW method, multi-station recording permits a single survey of a broad depth range and high levels of redundancy with a single field configuration. An efficient and unified wavefield transform technique is introduced for dispersion analysis and on site data quality control. The technique was demonstrated in the assessment of soil liquefaction potential at a site in Yuan Lin, Taiwan. The shear wave velocity and liquefaction potential assessments based on MASW method compares favorable to that based on SCPT shear wave measurements. Two-dimensional shear wave velocity profiles were estimated by occupying successive geophone spreads at several sites in central western Taiwan, at some of which sand boils or ground cracks occurred during 1999 Chi Chi earthquake. Liquefaction potential analysis based on MASW imaging was shown to be effective for estimating the extent of potential liquefaction hazard. 相似文献
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多道面波分析（MASW）法是一种被广泛使用的浅层地震勘探方法.为解决埋入源近场效应对MASW法应用的影响，本文分析了埋入源产生的Rayleigh波传播机制，探讨了MASW法的排列参数对地震记录的影响，提出了确定最小偏移距的经验公式.通过对实际地质模型的有限元模拟，验证了经验公式的合理性.在以经验公式为指导的野外实测中，利用多种方法提取了相对可靠的频散曲线，采用基阶和高阶面波联合反演，所得的一维速度结构与钻孔资料具有很强的相关性，表明本文发展的最小偏移距估计方法具有一定的实际应用价值. 相似文献