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1.
H. C. Soffel Ch. Bücker H. Gebrande E. Huenges E. Lippman J. Pohl A. Rauen A. Schult K. M. Streit F. Wienand 《Surveys in Geophysics》1992,13(1):1-34
The project of an ultradeep drill hole (KTB) in the Oberpfalz area at the western margin of the Bohemian Massif has completed a pilot drill hole to a depth of 4000.1 m in April 1989. This well is situated only about 200m away from the main drill hole aimed at 10 km depth where drilling started in September 1990. The cores of the pilot well have a diameter of 9.4 cm or 10.16 cm, respectively. In addition to cores and cuttings there was also mud available for geochemical, petrological and some geophysical measurements. The pilot drill hole has a core recovery length of as much as 3042.6 m (about 76%), among which 193.1 m were obtained by rotary drilling and 2849.5 m by wireline drilling. Several petrophysical parameters were measured in a specially established field laboratory at the drill site immediately after sampling in order to obtain as good as possible in-situ values. Results for the following parameters are reported: density, natural gamma ray activity, velocities of seismic longitudinal and shear waves, thermal conductivity, electrical resistivity, natural remanent magnetization, magnetic susceptibility, porosity and inner surface. The methods of measurement are characterized briefly and the results of the pilot drill hole are presented and discussed in connection with the lithology and the geophysical anomalies, which have been observed on the surface. 相似文献
2.
A three-dimensional (3-D) kinematic migration algorithm for media in which migration velocity varies linearly with depth is developed, implemented and tested. The algorithm is based on the concept that a single reflection or diffraction in a (zero- or finite-offset) trace may have originated at any point on a constant traveltime surface within the Earth defined by the observed two-way traveltime. The envelope of all such constant time surfaces, for all observed reflections and diffractions produced by one reflector, is the desired migrated 3-D image. The optimal envelope position in depth is determined, beneath each point on a regular grid, by a statistical imaging condition; an incremental function of depth containing the number of constant time surfaces passing through that depth increment is cross-correlated with a Gaussian function whose width is chosen to correspond to the vertical scale of the features of interest. The numerical procedures are based on the observation that, in a medium in which velocity varies linearly with depth, ray segments are circular so traveltimes can be computed analytically. Also, traveltimes are independent of azimuth so the 3-D problem can be collapsed into an equivalent 2-D problem. The algorithm is illustrated and tested by application to synthetic data and to scale-model data from the Seismic Acoustics Laboratory at the University of Houston. 相似文献
3.
—Prestack migration finds increasing application in processing crustal seismic data. However, less effort has been made to incorporate slowness information in the imaging process. The combination of slowness information with migration leads to an improved image in the depth domain, especially by reducing migration artefacts and noise. A slowness-driven isochrone migration scheme is introduced for migration of 2-D seismic data. Instantaneous slowness information p(x, t) is extracted from the data using correlation analysis in moving time and space windows. Slowness values resulting from spatial coherent energy (signal) and incoherent background noise are distinguished by the simultaneous evaluation of an instantaneous coherence criterion g(x, t). In slowness-driven isochrone migration this information is used for locally weighting the amplitude A(x, t) smearing on the isochrone surface. In particular, slowness p and coherence criterion g determine position and sharpness of a Gaussian weighting function. The method is demonstrated using two synthetic data examples and is subsequently applied to two deep crustal data sets, one wide-angle (along DEKORP4) and one steep-angle reflection seismic observation (KTB8506). Both data sets were collected in the surroundings of the KTB drill site, Oberpfalz, as part of the German DEKORP project. 相似文献
4.
2000年8月21日～10月20日，德国大陆超深钻井(KTB)进行了为期60天的新一轮注水诱发地震实验．在对KTB台网所记录到的2 700多次地震的原始波形进行分析和处理的基础上，对其中的237次地震进行了精确定位．定位时，先采用和达法剔除了误识的非KTB诱发地震事件；然后，使用大折刀法求得了台站偏差的最佳值，以及中误差和平均误差；最后应用Geiger法进行修定，从而保证了237个事件定位的中误差达到0.1 km的高精度．定位结果显示，在大于9.3 km(几乎是主井底的深度)没有发生诱发地震．这一现象表明，在这个深度，应力可能低于摩擦强度，以至于由注水引起的孔隙压力的变化不足以诱发地震；在这样的深度不存在可渗透的、取向恰当的断层．这个深度也可能是这一区域内的地震活动性的最大深度，即在这一相对稳定地区的板块内部，主井底已接近脆-延性转换带．并用实验室的结果和超深钻井中所观测到的热流值资料解释了这一现象． 相似文献
5.
The accurate location of the injection-induced microearthquakes in German Continental Deep Drilling Program 总被引：1，自引：0，他引：1
Introduction The scientific drilling belongs to the International Lithosphere Program and is one of the four lithospheres explorations. So far there are more than ten countries, which have taken the scientific drilling. The German Continental Deep Drilling Program was later than the others and is the sec-ond deep drilling, but is the most significant scientific super deep drilling in the world. The Ger-man Continental Deep Drilling Program (Kontinentales Tiefbohrprogram der Bundesrepub… 相似文献
6.
Summary We have analysed magnetovariational data of ten temporary field stations deployed as a 2-D array covering about 50 km square of a SFR/FRG border area adjacent to the KTB superdeep drill site. Single- and inter-station induction vectors were computed by frequency and time domain analyses. The distribution of induction vector characteristics was analysed, interpreted in terms of the electrical conductivity distribution across the array, and correlated with geological phenomena. 相似文献
7.
郯庐断裂带是中国东部规模最大的构造活动带,有着复杂的形成演化历史,对中国东部的区域构造、岩浆活动、矿产资源的形成和分布以及现代地震活动都有重要控制作用.2010年在郯庐断裂带中南段的江苏宿迁市附近,采用深地震反射探测方法对郯庐断裂带及其两侧地块的岩石圈结构进行了解剖.结果表明,该区莫霍面和岩石圈底界均向西倾,其中,地壳厚度约为31~36km,岩石圈厚度约为75~86km,且岩石圈厚度在郯庐断裂带下方出现突变.郯庐断裂带在剖面上表现为由多条主干断裂组成的花状构造,其内部发育有断陷盆地和挤压褶皱,具有伸展、挤压和走滑并存的构造形迹,暗示郯庐断裂带的形成和演化经历了多期复杂的构造活动.这一断裂带错断了近地表沉积层,向下切割莫霍面和岩石圈地幔,属岩石圈尺度的深大断裂构造系统.软流圈高温高压热物质沿断裂带的上涌、岩浆底侵或热侵蚀作用造成岩石圈出现拉张伸展和岩石圈减薄,并可能使岩石圈组构及其物质成分发生改变.本项研究结果不但可进一步加深对郯庐断裂带深、浅部结构的认识,而且还可为分析研究华北克拉通东部的深部过程和浅部构造响应提供资料约束. 相似文献
8.
This paper presents a new method for the measurement on core samples of their electrical resistivity, its anisotropy and heterogeneity. The equipment used has been developed in the field laboratory of the German Continental Deep Drilling program KTB in the north-east of Bavaria on the western rim of the Bohemian Massif. The apparatus measures the resistivity at a fixed frequency as a function of the drill core azimuth and along the core by moving point electrode configurations. From these azimuth and depth dependences, mean values of resistivity and additional information about its anisotropy and heterogeneity are determined. Geometrical averaging is used, because the resistivity data follows a log normal distribution. The quantitative parameters ‘azimuth factor’, corresponding to horizontal anisotropy, and ‘heterogeneity factor’ are introduced. The depth logs of resistivity, azimuth factor and heterogeneity factor, measured on cores obtained from the KTB main drill hole (gneisses and amphibolites) at depths between 4150 m and 8080 m are presented. The geometrically averaged mean values of resistivity of gneisses and amphibolites are in the same range (? 103Ωm). The resistivities tend to decrease with depth. The stress release of the drill cores during recovery produces microcracks which may partially account for this effect. Reduced resistivities (down to 150 Ωm) within an amphibolite core correlate with an alteration zone. One sample of this core displays alteration from fresh to completely altered. This sample is also electrically heterogeneous (heterogeneity factor ? 2). Other samples with uniform low alteration are more homogeneous heterogeneity factor ? 1.4). In general, higher anisotropies are observed in gneisses (mean azimuth factor 2.8), lower anisotropies in amphibolites (mean azimuth factor 1.3). Examples of isotropic and homogeneous samples, as well as anisotropic and heterogeneous samples are also presented. 相似文献
9.
苏鲁超高压变质带北部地球物理调查（1）─-深反射地震 总被引：17，自引：8，他引：9
苏鲁超高压变质带是世界上研究陆一陆碰撞俯冲和壳幔作用的最佳地质场所之一．为了解超高压变质带岩石的形成、折返和相应的动力学过程,必须了解该区的地壳和浅地幔构造．本文介绍了该区北部的地质情况和进行深反射地震调查取得的成果,包括（１）在五莲─青岛断裂南侧超高压变质岩片向北倾斜,呈现叠复组构,反映岩片的折返;（２）根据地震资料推测在１４６Ｍａ前后胶南地块的隆升一伸展构造内幕;（３）超高压变质岩片厚约１２ｋｍ,由于含有大量相辉岩透镜体,地震波速高达６．８─７．３ｋｍ／ｓ;（４）莫霍面附近有许多楔形反射体,反映陆一陆碰撞;（５）石门地区７ｋｍ深处存在高波速的强反射体,可作为在该区进行大陆科学钻探的候选场址． 相似文献
10.
Information about electrical anisotropy in and around the deep borehole of the German Continental Deep Drilling Program (KTB) has been acquired using three different methods: (1) Under surface temperature and pressure conditions, the azimuthal dependence of resistivity has been measured in horizontal planes perpendicular to the axes of drill cores. (2) Simulated in-situ conditions (high temperature and pressure) have been applied to mini cores drilled at different orientations to structural features such as foliation. The resistivity was then measured in the direction of the mini cores' long axes. (3) Under quasi-in-situ (downhole) conditions, the azimuthal dependence of resistivity has been measured in horizontal planes using the Azimuthal Resistivity Imager (ARI), a down hole logging tool.These investigations have shown that electrical anisotropy is strongly related to structural features. The anisotropy of gneisses is the highest due to the strong foliation (averaged anisotropy factor 2.8). Lamprophyres are most isotropic (factor 1.2). Most rocks from KTB are amphibolites with intermediate anisotropies (factor 1.3). The anisotropies measured under surface temperature and pressure conditions and quasi-in-situ conditions on amphibolites are approximately the same, whereas anisotropies under simulated in-situ conditions are partially higher.Furthermore, the anisotropies measured on the cm to m scale using the various methods outlined above shall be compared with large scale anisotropies of the km scale measured around KTB using Magneto Tellurics. 相似文献
11.
苏鲁超高压变质带北部地球物理调查(1)─—深反射地震 总被引：7，自引：0，他引：7
苏鲁超高压变质带是世界上研究陆一陆碰撞俯冲和壳幔作用的最佳地质场所之一．为了解超高压变质带岩石的形成、折返和相应的动力学过程,必须了解该区的地壳和浅地幔构造．本文介绍了该区北部的地质情况和进行深反射地震调查取得的成果,包括（１）在五莲─青岛断裂南侧超高压变质岩片向北倾斜,呈现叠复组构,反映岩片的折返;（２）根据地震资料推测在１４６Ｍａ前后胶南地块的隆升一伸展构造内幕;（３）超高压变质岩片厚约１２ｋｍ,由于含有大量相辉岩透镜体,地震波速高达６．８─７．３ｋｍ／ｓ;（４）莫霍面附近有许多楔形反射体,反映陆一陆碰撞;（５）石门地区７ｋｍ深处存在高波速的强反射体,可作为在该区进行大陆科学钻探的候选场址． 相似文献
12.
Parsimonious post‐stack migration is extended to three dimensions. By tracing single rays back along each incident wave direction (as determined by a local slant stack at the receivers), the ray tracing can be embedded in the migration. This approach significantly reduces the computer time and disk space needed because it is not necessary to build and save image time maps; 3D migration can be performed on a workstation or personal computer rather than using a supercomputer or cluster. The location of a reflector in the output image is defined by tracing a zero‐offset ray to the one‐way traveltime (the image condition); the orientation of the reflector is defined as a surface perpendicular to the raypath. The migration impulse response operator is confined to the first Fresnel zone around the estimated reflection point, which is much smaller than the large isochronic surface in traditional Kirchhoff depth migration. Additional efficiency is obtained by applying an amplitude threshold to reduce the amount of data to be migrated. Tests on synthetic data show that the proposed implementation of parsimonious 3D post‐stack Kirchhoff depth migration is at least two orders of magnitude faster than traditional Kirchhoff migration, at the expense of slightly degraded migration image coherence. The proposed migration is expected to be a useful complement to conventional time migrations for fast initial imaging of subsurface structures and for real‐time imaging of near‐offset sections during data acquisition for quality control. 相似文献
13.
14.
The structure of the crust and the crust-mantle boundary in the Vogtland/West Bohemian region have been a target of several
seismic measurements for the last 25 years, beginning with the steep-angle reflection seismic studies (DEKORP-4/KTB, MVE-90,
9HR), the refraction and wide-angle experiments (GRANU’95, CELEBRATION 2000, SUDETES 2003), and followed by passive seismic
studies (receiver functions, teleseismic tomography). The steep-angle reflection studies imaged a highly reflective lower
crust (4 to 6 km thick) with the Moho interpreted in a depth between 30 and 32 km and a thinner crust beneath the Eger Rift.
The refraction and wide-angle reflection seismic studies (CELEBRATION 2000) revealed strong wide-angle reflections in a depth
of 26–28 km interpreted as the top of the lower crust. Long coda of these reflections indicates strong reflectivity in the
lower crustal layer, a phenomenon frequently observed in the Caledonian and Variscan areas. The receiver function studies
detected one strong conversion from the base of the crust interpreted as the Moho discontinuity at a depth between 27 and
37 km (average at about 31 km). The discrepancies in the Moho depth determination could be partly attributed to different
background of the methods and their resolution, but could not fully explain them. So that new receivers function modelling
was provided. It revealed that, instead of a first-order Moho discontinuity, the observations can be explained with a lower
crustal layer or a crust-mantle transition zone with a maximum thickness of 5 km. The consequent synthetic ray-tracing modelling
resulted in the model with the top of the lower crust at 28 km, where highly reflective lower crustal layer can obscure the
Moho reflection at a depth of 32–33 km. 相似文献
15.
利用长白山天池火山区三维空间深地震测观测系统所采集的反射P波走时资料,采用层析成像技术,重建了该区地壳界面构造形态和速度分析图像。界面成像结果表明：研究区地壳界面总体上显示了由北西向东南加深的趋势;马鞍山—三道白河断裂和富尔河—红旗河断裂是本区两条主要的深部构造,尤其是马鞍山—三道白河断裂,北北东向穿越天池火山口,其两侧的地壳界面存在明显的错断,预示了该处地壳厚度陡变或深大断裂带的存在,速度成像结果显示在10km深度,明显的P波低速异常分布在天池周围;15km深度上它表现为一个近南北向的P波低速异常条带,其延展尺度南北向为80~90km,东西向30~40km;随着深度的增加,P波低速异常分布在天池西侧,其尺度有明显的缩小,分布范围更加集中,而且低速扰动幅度更大。这种P波速度异常的变化图像在一定程度上反映了天池火山口下方壳内岩浆系统的空间分状况。 相似文献
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17.
S.G. Smith 《Earth and Planetary Science Letters》1976,32(1):62-68
A 45-km square seismic reflection profiling grid survey was made in the part of the Herodotus basin where there is a large thickness of strongly deformed sediment, to determine the nature and cause of the deformation. The survey showed that the area has sediment ponded between highs in the underlying deformed sedimentary sequence, which becomes more deformed with increasing depth. The deepest continuous reflector that can be seen is probably reflector M. The seismic velocity above this is 3.2 km s?1; a velocity could not be obtained from below this reflector. A map of depth to reflector M shows small rises superimposed on a strong linear north-south rise. There are no magnetic anomalies associated with any of these rises, so they are not caused by doming above igneous intrusions. The structures could be caused by syn-depositional folding, or sedimentary diapirism, of which sedimentary diapirism seems the most probable. 相似文献
18.
为了实验大容量气枪震源陆地水体流动激发反射地震探测效果,在长江中下游安徽省铜陵段,采用气枪船长江航道流动激发、沿江岸布设反射地震仪器接收的非纵弯线工作方式,得到了反映测线经过地区地壳深部结构和构造特征的反射地震数据。原始资料信噪比较低,但部分资料不同部位仍可辨认出来自地壳及莫霍面反射波组。就传播距离而言,地震波传播的水平距离最大可达21km,垂直深度可达30km以上。在数据处理中,根据原始资料特点,针对性采用了非纵弯线面元定义、三维层析静校正、叠前多域去噪及组合反褶积技术,最终得到的叠加时间剖面上具有丰富的壳内反射波组。结果显示,测线经过地区的地壳结构为双层结构,总厚度为30.0～36.0km。上地壳呈现隆坳相间的反射特征,下地壳存在多组叠层状弧型反射波组,莫霍面反射特征清晰,由2～3个反射同相轴组成,呈现SW端向NE段抬升的形态。剖面经过地区存在一个切穿下地壳和莫霍面的深部断裂,应该是长江深断裂的反映。研究结果充分说明,大容量气枪震源可应用于陆地流动水体地壳精细结构的深地震反射探测。 相似文献
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20.
—In addition to the near normal-incidence observations within the German DEKORP 2 project in 1984, wide-angle observations have been carried out on a parallel profile across the boundary between the Saxothuringian and Moldanubian crust, approximately 50 km NE of the main transect to control three-dimensional variations. Explosion sources have been used for the entire survey, providing excellent conditions for wide-angle registrations. A velocity model has been derived on the basis of in- and off-line refraction measurements using a kinematic raytracer which was extended to three dimensions by interpolation of 2-D velocity fields between parallel sections. Although prestack-migration of the data led to aliasing effects due to large shot and geophone spacing, stable results were obtained by forming envelopes after single-shot migration. The migrated sections reveal a strongly reflective Moho at about 31 km depth and a steeply (50°) dipping intracrustal reflector, which seems to be related to the border between the two Variscan units. 相似文献