华北文安-蔚县-察哈尔右翼中旗剖面S波资料的地质解释

通过对文安—蔚县—察哈尔右翼中旗深地震测深剖面S波资料的处理解释 ,获得本区二维壳幔速度结构和波速比结构。该区的上、中地壳主要由花岗岩组成 ,整体呈脆性 ,其速度比γ值为 1 72左右 ;下地壳的γ值一般为 1 78;上地幔顶部的γ值在 1 82左右 ,表明下地壳与上地幔顶部整体呈塑性的特征。根据波组及γ值横向变化特征 ,推断了该区的几条深大断裂 ,结合本地区的地震活动 ,推测地震的孕育发生不仅与构造相关 ,而且与该区的岩石性质有关     

香河-北京-涿鹿及其相邻地区壳幔构造与速度结构特征

通过对北西向的宁河—北京—涿鹿宽角反射／折射剖面西段测深资料的二维处理、计算以及综合解释研究,获得了该段壳幔速度结构和深部构造的基本特征。结果表明：不同区域的壳幔速度结构在纵向和横向上均具有明显的非均匀性,壳幔深部构造呈现明显的层状结构和东浅西深的倾斜状态,地壳厚度由香河以东的３２～３３ｋｍ向西至北京西部的西山山区、怀来南部以及涿鹿迅速加深至３９～４０ｋｍ,其中北京为３６．５ｋｍ左右,并且在香河的西侧存在着延伸至Ｍ界面的深断裂     

GWK-201型测氦仪及其观测资料分析

简要介绍了一种新型测氦仪———GWK - 2 0 1型测氦仪 ,分析了聊古一井 1998年 9月 1日至 1999年 11月 30日的逸出气氦观测资料。结果表明 :该资料的正常动态为近直线型 ,并且在附近 4 0级地震前有显著的异常显示 ,对今后的地震预报研究具有一定的参考价值     

塔里木盆地中部地震转换波测深及其解释

沿塔里木盆地中部的库车—塔中—塔南测线,首次进行了地震转换波测深。探测结果表明,本区岩石圈具有明显的层状－块体结构,地壳厚度４０～５０ｋｍ,隆起区约为４０ｋｍ,凹陷区约为５０ｋｍ。上地壳的厚度在盆地中部明显减薄,中地壳波速相对偏高（ＶＰ＝６．４～６．５ｋｍ／ｓ）,下地壳上部普遍存在低速薄层,结晶地壳的速度高于周围青藏高原和天山地区的波速,波速结构表明地壳具有陆壳性质,地壳内存在具有逆冲性质的深部断裂。综合解释认为,自新生代以来,在印度－欧亚板块边界的强大挤压力作用下,岩石圈内包括结晶基底面和莫霍面在内的各深部界面（岩层）的准同步挠曲变形和地壳刚性块体沿深部逆冲断裂的调整运动,是塔里木盆地岩石圈中主要的深部动力学过程     

小江断裂带中段盆地的发育阶段及其与区域构造运动的关系

小江断裂带中段新生代发育的系列盆地，根据其发育阶段可分为始新世—渐新世、上新世—早更新世、中更新世—晚更新世和晚更新世—全新世４个阶段，并根据发育持续性可分为继承性、阶段性、复活性、新生性４种类型。由大比例尺填图所获资料及前人成果，介绍了各阶段盆地的分布特征和成因机制，讨论了盆地发育与区域构造运动、断裂活动的关系     

《全球扭动构造——-地球演化学说》简介

《全球扭动构造———地球演化学说(GlobalWrenchTectonics—TheoryofEarthEvolution)》是挪威古地磁学家K.M. Storetvedt2003年的新作,篇幅 397页,是他 1997年出版的《我们演化中的星球(OurEvolvingPlanet)》一书的续篇。印度的H.C. Sheth在 1998年《全球构造新概念通讯(NewConceptsInGlobalTectonicsNewsletter)》第 7期上,曾对《我们演化中的星球》一书作过较全面的介绍与评述。《全球扭动构造———地球演化学说》一书为了把新的全球框架置于正确认识地球科学的适当位置,在第一章和第二章中阐述了包括魏格纳大陆漂移和板块构造在内的,试图统一全球地质现象内在联系的研究史。第三章快速展示了有关地球起源、内部结构、以及能量转换过程的一些关键性问题。在第四、五章中勾画了新的动力-构造系统原理。最后第六、七章扩展了应用上述理论解释实际地质问题的能力,侧重研讨了阿尔卑斯时期印度洋—南极—东南亚区域的构造发育,以及从太古代到中古生代构造格局的变迁。Storetvedt教授的理论,与由地球地极游移和行星旋转速度幕     

任意曲线上二维重磁位场转换的B样条函数法

重磁位场转换在重磁资料解释中是十分重要和必要的。随着物探仪器的改进和资料解释精度要求的提高,人们对位场转换方法的研究越来越深入。本文提出一种原理简单、计算精度高的新方法--B样条函数法,应用其插值、求导、求积的性质,以解决曲线上二维重磁位场转换的两类问题。一是Z_α分量向H_α分量的转换及向上延拓,二是水平和垂向导数的换算及磁位的计算。 样条函数为分段多项式函数。B样条函数是用σ函数逼近的一类样条函数,其节点     

唐山地震前后地下水位动态图象及其形成演化模式

对唐山地震前后地下水位动态图象的生成方法、时空演化特征及其形成演化模式的研究表明,唐山地震前后地下水位动态图象正负区和异常特征区的时空演化具有明显的规律性和阶段性。负值区的演化具有“收缩—扩展—急速扩展—发震”的特征;异常特征区的演化显示“迁移—扩展—稳定—发震—消失”的特征;滑动变差值显示“增大—减小—发震—急速减小”的变化过程。探讨了地下水位动态图象演化与构造变形、断层运动和上地幔物质上涌的关系,提出了唐山地震地下水位动态图象“场—区—源”的演化模式     

波前重建法折射成像及应用研究

根据实际工作需要对传统的地震折射资料解释方法的适用范围进行了讨论,指出了传统折射资料解释方法所存在的问题。采用重建波前的方法进行折射成像,通过改进震源函数,并在反演过程中使用有限差分技术解程函方程,进行波场外推,从根本上解决了传统折射资料解释方法存在的问题,计算精度高,速度快。通过理论模型和实际资料的对比计算和验证,效果良好。     

应用形变和重力资料分析腾冲火山区岩浆的活动特征

文中对腾冲火山区1998—2004年水准及重力观测资料进行了分析,发现垂直形变量大多在±10mm之内,重力变化为几十μGal,火山锥体和断层附近点位活动异常较大,可综合应用多源mogi模型和断层模型解释,断层的活动可使相邻测点的形变方向相反;垂直形变和重力的逐年变化表明火山岩浆处于一种活动状态。将火山区点位各时间段的重力梯度展布在形变-重力关系解释图中,发现数据主要落在Ⅰ、Ⅱ、Ⅳ和Ⅴ区,结合形变量对压力源等效体积的估算,初步认为火山区岩浆目前活动程度较低,暂没有喷发的危险     

Refraction traveltime and amplitude corrections for very near- surface inhomogeneities

The performance of refraction inversion methods that employ the principle of refraction migration, whereby traveltimes are laterally migrated by the offset distance (which is the horizontal separation between the point of refraction and the point of detection on the surface), can be adversely affected by very near‐surface inhomogeneities. Even inhomogeneities at single receivers can limit the lateral resolution of detailed seismic velocities in the refractor. The generalized reciprocal method ‘statics’ smoothing method (GRM SSM) is a smoothing rather than a deterministic method for correcting very near‐surface inhomogeneities of limited lateral extent. It is based on the observation that there are only relatively minor differences in the time‐depths to the target refractor computed for a range of XY distances, which is the separation between the reverse and forward traveltimes used to compute the time‐depth. However, any traveltime anomalies, which originate in the near‐surface, migrate laterally with increasing XY distance. Therefore, an average of the time‐depths over a range of XY values preserves the architecture of the refractor, but significantly minimizes the traveltime anomalies originating in the near‐surface. The GRM statics smoothing corrections are obtained by subtracting the average time‐depth values from those computed with a zero XY value. In turn, the corrections are subtracted from the traveltimes, and the GRM algorithms are then re‐applied to the corrected data. Although a single application is generally adequate for most sets of field data, model studies have indicated that several applications of the GRM SSM can be required with severe topographic features, such as escarpments. In addition, very near‐surface inhomogeneities produce anomalous head‐wave amplitudes. An analogous process, using geometric means, can largely correct amplitude anomalies. Furthermore, the coincidence of traveltime and amplitude anomalies indicates that variations in the near‐surface geology, rather than variations in the coupling of the receivers, are a more likely source of the anomalies. The application of the GRM SSM, together with the averaging of the refractor velocity analysis function over a range of XY values, significantly minimizes the generation of artefacts, and facilitates the computation of detailed seismic velocities in the refractor at each receiver. These detailed seismic velocities, together with the GRM SSM‐corrected amplitude products, can facilitate the computation of the ratio of the density in the bedrock to that in the weathered layer. The accuracy of the computed density ratio improves where lateral variations in the seismic velocities in the weathered layer are known.     

A new direction for shallow refraction seismology: integrating amplitudes and traveltimes with the refraction convolution section

The refraction convolution section (RCS) is a new method for imaging shallow seismic refraction data. It is a simple and efficient approach to full‐trace processing which generates a time cross‐section similar to the familiar reflection cross‐section. The RCS advances the interpretation of shallow seismic refraction data through the inclusion of time structure and amplitudes within a single presentation. The RCS is generated by the convolution of forward and reverse shot records. The convolution operation effectively adds the first‐arrival traveltimes of each pair of forward and reverse traces and produces a measure of the depth to the refracting interface in units of time which is equivalent to the time‐depth function of the generalized reciprocal method (GRM). Convolution also multiplies the amplitudes of first‐arrival signals. To a good approximation, this operation compensates for the large effects of geometrical spreading, with the result that the convolved amplitude is essentially proportional to the square of the head coefficient. The signal‐to‐noise (S/N) ratios of the RCS show much less variation than those on the original shot records. The head coefficient is approximately proportional to the ratio of the specific acoustic impedances in the upper layer and in the refractor. The convolved amplitudes or the equivalent shot amplitude products can be useful in resolving ambiguities in the determination of wave speeds. The RCS can also include a separation between each pair of forward and reverse traces in order to accommodate the offset distance in a manner similar to the XY spacing of the GRM. The use of finite XY values improves the resolution of lateral variations in both amplitudes and time‐depths. The use of amplitudes with 3D data effectively improves the spatial resolution of wave speeds by almost an order of magnitude. Amplitudes provide a measure of refractor wave speeds at each detector, whereas the analysis of traveltimes provides a measure over several detectors, commonly a minimum of six. The ratio of amplitudes obtained with different shot azimuths provides a detailed qualitative measure of azimuthal anisotropy and, in turn, of rock fabric. The RCS facilitates the stacking of refraction data in a manner similar to the common‐midpoint methods of reflection seismology. It can significantly improve S/N ratios.Most of the data processing with the RCS, as with the GRM, is carried out in the time domain, rather than in the depth domain. This is a significant advantage because the realities of undetected layers, incomplete sampling of the detected layers and inappropriate sampling in the horizontal rather than the vertical direction result in traveltime data that are neither a complete, an accurate nor a representative portrayal of the wave‐speed stratification. The RCS facilitates the advancement of shallow refraction seismology through the application of current seismic reflection acquisition, processing and interpretation technology.     

A brief study of applications of the generalized reciprocal method and of some limitations of the method

An analysis of the generalized reciprocal method (GRM), developed by Palmer for the interpretation of seismic refraction investigations, has been carried out. The aim of the present study is to evaluate the usefulness of the method for geotechnical investigations in connection with engineering projects. Practical application of the GRM is the main object of this study rather than the theoretical/mathematical aspects of the method. The studies are partly based on the models and field examples presented by Palmer. For comparison, some other refraction interpretation methods and techniques have been employed, namely the ABC method, the ABEM correction method, the mean‐minus‐T method and Hales' method. The comparisons showed that the results, i.e. the depths and velocities determined by Palmer, are partly incorrect due to some errors and misinterpretations when analysing the data from field examples. Due to the limitations of the GRM, some of which are mentioned here, stated by Palmer in his various publications, and other shortcomings of the method (e.g. the erasing of valuable information), the GRM must be regarded as being of limited use for detailed and accurate interpretations of refraction seismics for engineering purposes.     

THE RESOLUTION OF NARROW LOW-VELOCITY ZONES WITH THE GENERALIZED RECIPROCAL METHOD1

The depth to the surface of a refractor and the seismic velocity within the refractor are very often intimately related. In the shallow environment, increased thicknesses of weathering occur in areas of jointing, shearing or lithological variations, and these zones of deeper weathering can have lower subweathering refractor velocities. This association is important in geotechnical investigations and in the measurement of weathering thicknesses and sub-weathering velocities for statics corrections for reflection seismic surveys. Algorithms, which employ forward and reverse traveltime data and which explicitly accommodate the offset distance through the process known as refraction migration, are necessary if detailed structure on a refractor and rapid lateral variations of the seismic velocity within it are to be resolved. These requirements are satisfied with wavefront construction techniques, Hales’ method and the generalized reciprocal method (GRM). However, these methods employ refraction migration in fundamentally different manners. Most methods compute an offset distance with an often imprecise knowledge of the seismic velocities of the overlying layers. In contrast, the GRM uses a range of offset distances from less than to greater than the optimum value, with the optimum value being selected with a minimum-variance criterion. The approach of the GRM is essential where there are undetected layers and where there are rapid variations in the depth to a refractor and the seismic velocity within it. In the latter situations the offset distance necessary to define the seismic velocities can differ considerably from the value required to define depths. The efficacy of the GRM in resolving structure and seismic velocity is demonstrated with three model studies and two field examples.     

Combination of common-midpoint-refraction seismics with the generalized reciprocal method

A useful method for increasing the signal/noise ratio of refracted waves is Common-Midpoint (CMP)-refraction seismics. With this technique the shallow underground can be described in detail using all information (amplitude, frequency, phase characteristics) of the wavetrain following the first break (first-break phase). Thus, the layering can be determined and faults, weak zones, and clefts can be identified. This paper deals with the optimization of CMP-refraction seismics used in combination with the Generalized Reciprocal Method (GRM). Theoretical studies show a close relationship of both methods to the kinematics of wave propagation. Velocities and optimum offsets determined by the GRM can be used directly in the partial Radon transformation in CMP-refraction seismics. The integration of refracted waves leads to an increase in the signal/noise ratio but simultaneously the integration boundaries must be restricted to deal only with selective parts of the investigated refractor. The result of this process is an intercept-time section which can be converted directly to a depth section using standard refraction seismic techniques. Another possibility of depth conversion is the transformation of this intercept-time section to a `pseudo-zero-offset section', known from reflection seismics. Thus, zero-offset sections can be migrated using wave-equation techniques such as Kirchhoff migration.     

Alternating field demagnetization of rocks,and the problem of gyromagnetic remanence

Alternating field (a.f.) demagnetization has proved to be a very reliable technique for separating the magnetization components of rock samples. The method is subject to errors caused by either imperfection of the technique or by intrinsic properties of a rock. Recently, Stephenson [1,2] introduced the term gyroremanent magnetization (GRM) for a disturbing remanent magnetization that can be acquired by magnetic material during tumbling or stationary a.f. demagnetization. The implications for the routine a.f. demagnetization of anisotropic rock samples seemed to be very serious. Here, however, a method is presented on how to avoid the effect of GRM on results obtained from stationary a.f. demagnetization.     

震源谱的尾波多台多震综合求解方法

根据尾波观测的经验公式，选用北京遥测台网东部9个台站所记1989-1990年唐山地区10个地震的数字化记录，采用多台多震综合求解法，得到各地震的震源因子，并和单台多震法求得震源因子的平均值进行了比较．多台法所得震源因子精度明显优于单台法；且两者均比直达S波所求波谱比的精度提高1倍以上。提出了以一定的震源模型为基础，由震源因子求震源谱的方法．结果表明，ω一次方模型（即震源港高频部分与角频率ω的一次方成反比）较二次方模型更适合于本文所用的数据（震级范围为ML，3．0－5．2）．由于尾波能有效地消除震源辐射因子和单一路径的影响，故易于得到较多的资料和较高的精度，为研究震源的性质提供了一个有效的方法．     

基于自适应优化有限差分方法的全波VSP逆时偏移

与地面地震资料相比,VSP资料具有分辨率高、环境噪声小及能更好地反映井旁信息等优点.常规VSP偏移主要对上行反射波进行成像,存在照明度低、成像范围受限等问题.为了增加照明度、拓宽成像范围、提高成像精度,本文采用直达波除外的所有声波波场数据(全波),包括一次反射波、多次反射波等进行叠前逆时偏移成像.针对逆时偏移中的四个关键问题,即波场延拓、吸收边界条件、成像条件及低频噪声的压制,本文分别采用自适应变空间差分算子长度的优化有限差分方法(自适应优化有限差分方法)求解二维声波波动方程以实现高精度、高效率的波场延拓,采用混合吸收边界条件压制因计算区域有限所引起的人工边界反射,采用震源归一化零延迟互相关成像条件进行成像,采用拉普拉斯滤波方法压制逆时偏移中产生的低频噪声.本文对VSP模型数据的逆时偏移成像进行了分析,结果表明:自适应优化有限差分方法比传统有限差分方法具有更高的模拟精度与计算效率,适用于VSP逆时偏移成像;全波场VSP逆时偏移成像比上行波VSP逆时偏移的成像范围大、成像效果好;相对于反褶积成像条件,震源归一化零延迟互相关成像条件具有稳定性好、计算效率高等优点.将本文方法应用于某实际VSP资料的逆时偏移成像,进一步验证了本文方法的正确性和有效性.     

子波方法在云南人工地震测深资料处理中的应用

应用地震子波方法对云南人工地震测深资料进行了分析计算。结果反射波与折射波的处理存在明显差异。反射波较折射波对地层横向和纵向上的变化反应更为敏感。影响子波宽度的因素并非单一，特别是在云南这样地质结构极其复杂的地区。正是考虑到这些因素，仅选用了云南丰富的人工地震资料中的部分记录质量较好的数据进行计算。结果与常规方法的解释基本吻合。该方法虽不能对界面结构进行精确计算。但作为一种方法的应用研究和辅助解释还是有价值的。     

考虑到时误差的地震定位算法及其在四川地区2001-2008年地震定位的应用

精确的地震位置对于地震活动性、地震层析成像和地壳应力场反演具有相当重要的意义,对于地震速报也具有重要的应用价值。将观测到时的不确定性、台站高程、地震震源深度进行约束的同时,根据反演理论给出了地震震源位置精确估计和误差估计的方法。该算法联合考虑Pg波、Sg波、Pn波和Sn波的到时进行反演,数据量的增加可以增强地震位置的准确性,并可同时应用于地方震和区域地震。采用模拟数据对该地震定位算法进行检验发现,该算法在观测数据的不确定性不等时明显优于其他方法。将该算法应用于四川地区2001-2008年间的地震定位,得到的地震位置更加符合地震的丛集性并集中于断裂带附近。这些结果为四川地区的地震活动性、断层构造以及地震层析成像研究打下了基础,并且为汶川地震之前的地震活动前兆研究也提供了有益帮助。