“孤石”精细探测物探方法研究 ——以福州滨海快线为例

孤石在我国南方花岗岩地区普遍存在,其发育无规律性,埋藏及分布较为随机;城市地铁盾构施工孤石探测是公认的技术难题。以福州滨海快线（机场—大鹤站）区间孤石分布区为研究区开展了微动、等值反磁通瞬变电磁、高密度电法、探地雷达探测方法综合勘察试验,从抗干扰能力、施工效率和探测效果方面进行了对比分析,发现因浅表存在高阻砂层屏蔽,高密度电法在15 m以浅具有较高勘察精度、受地下线网影响明显,探地雷达在砂层中的有效勘察深度仅4 ～ 5 m;优选出对于孤石体精细探测的物探方法,“微动 + 等值反磁通瞬变电磁”的组合方法具有抗干扰、较好探测效果,与钻孔验证结果吻合。     

一维HHT变换在探地雷达数据处理中的应用

探地雷达(GPR)噪声信号通常具有非稳态、非线性特征,为去除这些噪声提高GPR图像解译的准确性,对利用HHT方法去噪进行了研究。首先阐述HHT的基本理论,然后通过对探地雷达数值模拟信号中噪声的去除验证基于HHT方法的可行性,最后将该方法用于探地雷达隧道地质超前预报的数据处理中。通过研究表明:该方法可以用于探地雷达信号的去噪,通过Hilbert变换得到三特征参数图像与EMD分解后合成图像进行对比验证,从而达到提高GPR信号解译精度的目的。     

Temporal observations of a seasonal snowpack using upward‐looking GPR

An increase of the spatial and temporal resolution of snowpack measurements in Alpine or Arctic regions will improve the predictability of flood and avalanche hazards and increase the spatial validity of snowpack simulation models. In the winter season 2009, we installed a ground‐penetrating radar (GPR) system beneath the snowpack to measure snowpack conditions above the antennas. In comparison with modulated frequency systems, GPR systems consist of a much simpler technology, are commercially available and therefore are cheaper. The radar observed the temporal alternation of the snow height over more than 2·5 months. The presented data showed that with moved antennas, it is possible to record the snow height with an uncertainty of less than 8% in comparison with the probed snow depth. Three persistent melt crusts, which formed at the snow surface and were buried by further new snow events, were used as reflecting tracers to follow the snow cover evolution and to determine the strain rates of underlaying layers between adjacent measurements. The height in two‐way travel time of each layer changed over time, which is a cumulative effect of settlement and variation of wave speed in response to densification and liquid water content. The infiltration of liquid water with depth during melt processes was clearly observed during one event. All recorded reflections appeared in concordance with the physical principles (e.g. in phase structure), and one can assume that distinct density steps above a certain threshold result in reflections in the radargram. The accuracy of the used impulse radar system in determining the snow water equivalent is in good agreement with previous studies, which used continuous wave radar systems. The results of this pilot study encourage further investigations with radar measurements using the described test arrangement on a daily basis for continuous destruction‐free monitoring of the snow cover. Copyright © 2010 John Wiley & Sons, Ltd.     

昆明地震台地面与井下地震计地震记录震级偏差

选取昆明基准地震台观测山洞内放置的宽频带地震计BBVS-60及井下放置的GL-S60B深井宽频带地震计记录资料,采用新的震级国家标准（GB17740-2017）,对地面及井下地震记录计算M_L、m_b、m_B（BB）、M_S、M_S（BB）等5种震级,得到2种地震计的震级偏差。结果显示,M_L平均偏差0.18,m_b、m_B（BB）平均偏差0,M_S平均偏差-0.02,M_S（BB）平均偏差-0.01。     

THE DELINEATION OF THREE-DIMENSIONAL SHALLOW GEOMETRY OF ACTIVE FAULT BASED ON TLS AND GPR: A CASE STUDY OF AN NORMAL FAULT ON THE NORTH MARGIN OF MAOYABA BASIN IN LITANG,WESTERN SICHUAN PROVINCE

It is crucial to reveal the surface traces and activity of active faults by obtaining high-precision microtopography and three-dimensional shallow geometry. However, limited by the traditional geological investigation methods in the field and geological condition factors, the measurement method on microtopography and shallow geometry of active fault is badly insufficient. In this study, the TLS and GPR are firstly used comprehensively to delineate the microtopography and shallow geometry of the normal fault scarp on the north margin of Maoyaba Basin in Litang. Firstly, the vertical displacements of two landforms produced by the latest two periods of normal faulting and the two-dimensional GPR profiles are obtained separately. Secondly, the three-dimensional measurement method of active fault based on TLS and GPR is preliminarily established. On this basis, three-dimensional model of fault scarp and three-dimensional images of subsurface geometry are also obtained. These data all reveal a graben structure at normal fault scarps. Thirdly, the fusion and interpretation of three-dimensional data from the surface and subsurface are realized. The study results show:1)the vertical displacements of the T₁ and T₂ terraces by the normal fault movement is 1.4m and 5.7m, the GPR profile shows a typical fault structure and indicates the existence of small graben structure with a maximum width of about 40m in the shallow layer, which further proves that it is a normal fault. 2)the shallow geometry of the normal fault scarp can be more graphically displayed by the three-dimensional radar images, and it also makes the geometry structure of the fault more comprehensive. The precise location and strike of faults F₁ and F₂ on the horizontal surface are also determined in the three-dimensional radar images, which further proves the existence of small graben structure, indicating the extensional deformation characteristics in the subsurface of the fault scarps. Furthermore, the distribution of small graben structure on the surface and subsurface is defined more precisely. 3)the integrated display of microgeomorphology and shallow geometry of normal fault scarp is realized based on the three-dimensional point cloud and GPR data. The fusion of the point cloud and GPR data has obvious advantages, for the spatial structure, morphological and spectral features from the point cloud can improve the recognition and interpretation accuracy of GPR images. The interpreted results of the GPR profiles could minimize the transformation of the surface topography by the external environment at the most extent, restore the original geomorphology, relocate the position and trend of faults on the surface and constrain the width of deformation zones under the surface, the geological structure, and the fault dislocation, etc. In a word, the TLS and GPR can quickly and efficiently provide the spatial data with multi-level and multi-visual for non-destructive inspection of the microgeomorphology and shallow structure for the active fault in a wide range, and for the detection of active fault in the complex geological environments, and it is helpful to improve the accuracy and understanding of the investigation and research on microtopography and shallow geometry of active faults. What's more, it also offers important data and method for more comprehensive identification and understanding of the distribution, deformation features, the behaviors of active faults and multi-period paleoseismicity. Therefore, to continuously explore and improve this method will significantly enhance and expand the practicability and application prospects of the method in the quantitative and elaborate studies of active faults.     

甚宽频带地震计噪声与环境耦合研究

首先以甚宽频带地震计为研究对象,分析垂直向的片簧系统理论模型,探讨气压变化对仪器的LP噪声影响;通过理论分析,得出垂直向的片簧系统受气压变化影响较大。根据片簧系统的理论模型,设计一种密封安装方法,通过实验探讨地震计噪声与环境耦合关系(气压、温度和底座变形的关系)。最后对实验数据进行功率谱噪声分析,结果显示抽真空后地震计三个分向的噪声均降低,其中在100 s处垂直向、东西和南北向分别降低了10 dB、5 dB和6 dB。     

易县台BBVS-120地震计记录重力固体潮能力分析

以河北省易县台BBVS-120甚宽频带地震计为研究对象,验证其垂直向地震记录波形中包含的长周期成分为重力固体潮,并运用小波变换方法提取地震记录中的固体潮信息;同时,通过对提取的固体潮信息进行Venedikov调和分析证明,易县地震台BBVS-120甚宽频带地震计可以记录重力固体潮信息。     

宽频数据在致密砂岩储层预测中的应用

西湖凹陷深层致密砂岩储层具有良好的勘探开发前景,受埋深影响,目的层地震资料品质较差.A构造通过斜缆宽频采集和处理获取宽频地震数据,提升了资料品质,然而应用常规子波提取方法对宽频数据进行子波提取并反演计算纵波阻抗,结果与井上实测数值差异较大,影响储层的定量解释.针对这一问题,提出统计性子波和确定性子波相结合的长短子波合并宽频子波提取方法,提取的宽频子波比常规子波低频丰富、旁瓣小,能更真实地反映地震信息,约束稀疏脉冲反演的纵波阻抗结果与测井曲线吻合度更高.基于宽频数据和常规数据分别进行约束稀疏脉冲弹性波阻抗反演,预测A构造优质储层分布,经已钻井证实,宽频数据比常规数据储层预测精度高,预测的储层展布特征与研究区地质沉积认识一致.结果表明:这种基于宽频子波提取的宽频资料应用方法有效降低了致密砂岩储层预测的多解性.     

人工挖孔桩桩底探测方法与应用

在石灰岩地区的建筑基础设计为挖孔桩时,需进行桩底岩溶探测。本文介绍了3种可行的桩底探测方法,主要对地质雷达法与地震反射波法两种物探方法的基本原理及具体探测技术进行了介绍,通过对物探方法与传统钻探法进行有效组合可以提高人工挖孔桩桩底探测的效率和准确性。     

基于小波能谱分析的岩溶区探地雷达目标识别

目前常用的根据记录波形的频率、振幅等特征进行岩溶区探地雷达目标识别的方式具有一定的局限性,为此提出了利用小波能量谱特征进行识别的新方法.通过对岩溶区典型样本进行分析,构造雷达信号各频率成分在各尺度上的能量特征向量,得到样本模型的能量谱,将待识别目标体的能量谱特征与之比对,数据分析和实际验证表明,小波特征能量谱具有直观地显示目标信号不同特征的优点,能有效地对岩溶区探地雷达剖面目标体进行识别.