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1.
多年来,胜利探区多波多分量地震采集所得资料的信噪比和分辨率较低,无法取得较好的应用效果.为此,以胜利垦71区块为先导实验区开展了多波采集方法研究.首先,通过单点三分量检波器与常规检波器小面积组合分析了该区转换波发育情况,认为该区转换界面较强,转换波特征明显,转换横波速度约为纵波速度的1/2;然后,通过数字三分量检波器的室内各种组合研究,进行了超线元叠加,由此可以有效地改善资料的信噪比,并对分辨率基本没有影响;最后,利用三分量检波器扩展排列进行转换波最佳偏移距的设计,通过垂直排列追踪放炮进行最佳非纵距设计,从而得出该区多波采集的最佳观测系统参数.通过上述合理的设计和多项试验研究,在垦71地区多波采集中,数字检波器Z分量剖面的频率优势非常明显,分辨率明显高于常规检波器的纵波剖面,对于搞清小断层及微幅度构造具有重要的意义;同时,转换横波能量强、信噪比和分辨率高,使多波采集取得了较好的效果. 相似文献
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Acquisition and processing of high-resolution reflection seismic data from a survey within the complex terrain of the Bavarian Folded Molasse 总被引：1，自引：0，他引：1
A high‐resolution reflection seismic survey was carried out in the southern part of the Bavarian Molasse Basin in 1998 and 1999. The survey aimed to investigate the near‐surface structure of the complicated transition from the unfolded Foreland Molasse to the Folded Molasse, and the Folded Molasse to the internally complicated thrust systems of the Helveticum, the Ultrahelveticum and the Rhenodanubian Flysch. The study is linked to the TRANSALP seismic project, and the results help to fill the gap between the surface and the upper 300–500 ms two‐way traveltime (TWT), typical of deep‐reflection seismic experiments. The environmental conditions encountered in the study area required that particular attention be paid to the acquisition parameters for the three seismic lines (each about 4 km long). The energy source was a small vibrator; the geophone spread, spacing and frequency range were adjusted to image reflectors, which were expected to dip steeply southwards. In general, the unprocessed field records did not show signals that could be attributed to specific reflectors. Individual trace processing considerably improved the data quality, taking into account the influence of the Quaternary cover and also the strong lateral velocity variations of the shallow subsurface. The effects of the various processing steps, such as muting, refraction statics, residual statics and velocity analysis, are discussed. To assess the NMO velocities, the qualitative analysis of the seismic energy in a common‐shotpoint gather offered advantages over an analysis in a common‐midpoint gather or in a stacked section, and proved to be very effective. As demonstrated along the Miesbach 9801 line, low‐velocity zones extend locally down to about 400 ms, adjacent to zones of extremely high velocities close to the surface, reflecting steeply dipping strata. Besides the Quaternary cover on top, the Miesbach 9801 and Miesbach 9802 lines exhibit many horizontal reflections, in places down as far as 1400 ms TWT, indicating the sedimentary sequences of the unfolded Foreland Molasse. The southern part of both lines is dominated by southward‐dipping reflection bands, indicating units of the Folded Molasse. The reflection pattern shown by the Miesbach 9901 line suggests that there is almost no Quaternary cover. Southward‐dipping elements reflect the internal structure of the Folded Molasse, whereas a rather diffuse reflection signature may be attributed to Rhenodanubian Flysch units. 相似文献
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《Journal of Applied Geophysics》2006,58(2):87-98
A geophysical campaign to characterize the subsurface of a contaminated site down to a depth of several tens of meters was carried out under the HYGEIA-CEE project. On this site, seismic techniques were combined to image the geological structures; i.e. seismic reflection, P-wave tomography and spectral analysis of surface waves. Because these techniques consider different wave components in the processing, they can be expected to provide complementary information concerning the site lithology. The special feature of this experiment is the fact that the same seismic acquisition device, consisting of a mobile central unit, a drop-weight seismic source, and a sensor line of gimbal mounted geophones, was used for each of the techniques. Two perpendicular seismic lines were set up in the field for testing two geophone spacings. Three processing procedures, one each for the seismic reflection, P-wave tomography and spectral analysis of surface waves, were developed for producing seismic images from the P-wave reflectivity, the first P-wave arrivals and the dispersion of Rayleigh waves, respectively. The images show good complementarity in terms of investigation depth. The results are also in good agreement with available borehole data: the sandy layers seem to be related to low velocities, since the high velocities are better explained by the presence of clayey and gravelly intervals. The contribution and the limits of this seismic multi-approach method is discussed. 相似文献
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M. Corciulo A. Zollo M. Vassallo P. Dell'Aversana S. Morandi 《Geophysical Prospecting》2008,56(4):541-553
In order to retrieve a 2D background velocity model and to retrieve the geometry and depth of shallow crustal reflectors in the Southern Apennines thrust belt a separate inversion of first arrival traveltimes and reflected waveforms was performed. Data were collected during an active seismic experiment in 1999 by Enterprise Oil Italiana and Eni-Agip using a global offset acquisition geometry. A total of 284 on-land shots were recorded by 201 receivers deployed on an 18 km line oriented SW–NE in the Val D'Agri region (Southern Apennines, Italy).
The two-step procedure allows for the retrieval of a reliable velocity model by using a non-linear tomographic inversion and reflected waveform semblance data inversion. The tomographic model shows that the P wave velocity field varies vertically from approximately 3 km/s to 6 km/s within 4 km from the Earth's surface. Moreover, at a distance of approximately 11 km along the profile, there is an abrupt increase in the velocity field. In this zone indeed, an ascent from 2 km depth to 0 km above sea level of the 5.2 km/s iso-velocity contour can be noted. The retrieved velocity can be associated with Plio-Pleistocene clastic deposits outcropping in the basin zone and with Mesozoic limestone deposits. The inversion of waveform semblance data shows that a P-to-P reflector is retrieved at a depth of approximately 2 km. This interface is deeper in the north-eastern part of the profile, where it reaches 3 km depth and can be associated with a limestone horizon. 相似文献
The two-step procedure allows for the retrieval of a reliable velocity model by using a non-linear tomographic inversion and reflected waveform semblance data inversion. The tomographic model shows that the P wave velocity field varies vertically from approximately 3 km/s to 6 km/s within 4 km from the Earth's surface. Moreover, at a distance of approximately 11 km along the profile, there is an abrupt increase in the velocity field. In this zone indeed, an ascent from 2 km depth to 0 km above sea level of the 5.2 km/s iso-velocity contour can be noted. The retrieved velocity can be associated with Plio-Pleistocene clastic deposits outcropping in the basin zone and with Mesozoic limestone deposits. The inversion of waveform semblance data shows that a P-to-P reflector is retrieved at a depth of approximately 2 km. This interface is deeper in the north-eastern part of the profile, where it reaches 3 km depth and can be associated with a limestone horizon. 相似文献
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Shallow reflection and refraction seismic studies were carried out in Greece in the eastern leg of the Chalkidiki peninsula, in order to test the validity of reports in history books which describe a legendary canal built by the engineers of King Xerxes during the major Persian invasion of Europe through Greece in the 5th century B.C. In the narrowest part of the Athos peninsula, where it is 2 km wide, an 85 m profile was topographically defined almost centrally between the two coastlines. The position of this profile was based on palaeogeographical, geomorphological and topographic studies and observations. A sledgehammer was used as the seismic source for the shallow target. Despite the presence of significant urban and coherent noise, a final stacked section was produced by a suitable choice of acquisition and processing parameters. Both the reflection and refraction seismic studies illustrated clearly the existence of a channel-like structure of trapezoid cross-section, almost midway between the two opposite sides of the peninsula. 相似文献
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Tatiana Pertuz Alireza Malehmir Jordan Bos Bojan Brodic Yinshuai Ding Richard de Kunder Paul Marsden 《Geophysical Prospecting》2022,70(1):79-94
A prototype electromagnetic vibrator, referred to here as E-Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E-Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two-dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E-Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E-Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E-Vib source for improved targeting in hardrock geological settings. 相似文献
7.
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
8.
Vertical geophone arrays in boreholes have been used for many years to study seismic velocities by investigating the first arrivals of records. The development of the vertical seismic profiling (VSP) technique shows possibilities of using the reflected events to close the gap between interpretation of conventional seismic data and physical observations made in the well. Reflected events recorded by vertical arrays (as in VSP) generally have higher signal-to-noise ratio, larger bandwidth and can easily be separated from multiples. The new Continuous Vertical Array (CVA) technique combines vertical arrays in several boreholes with a line of source points near the surface. The result is a multi-covered seismic line similar to that of a conventional seismic survey, but it retains the benefits of observations with vertical arrays. The possibilities of the new technique are discussed with the aid of theoretical considerations, model studies, and a first field case using nine boreholes 500 m apart with depths of 400 m. New data acquisition and processing techniques (mainly migration before stack) have been developed. The CVA-seismic method is still in the development stage but promises new possibilities for detailed surveys in difficult areas. 相似文献
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2005年,跨西安坳陷完成一条NW方向,69 km长的深地震反射剖面,首次获得该区域的地壳精细结构、主要断裂展布和深、浅构造关系图像.地震反射CMP叠加时间剖面显示,以反射事件C为界,地壳被分成上下两部分.上地壳由多组近水平反射带组成,具有分段连续性好、局部存在反射带明显错断或形态突变等特征,清晰地刻画出西安坳陷新生代沉积分层、坳陷底界、渭河断裂带、临潼-长安断裂带和秦岭山前断裂带的几何形态和关系.反射事件C是结晶地壳内宽度约0.5 s的反射带,最深处位于桩号30 km,底界约6.5 s,向西北缓慢抬升至5.5 s,向南东迅速抬升至5.5 s.下地壳有两个明显的反射事件RA、RB: RB是位于桩号40~47 km之间的局部反射团, 而RA为宽度约2 s、向坳陷倾斜的反射带.以桩号38 km为界,反射Moho形态截然不同,而且出现了显著的错断:大桩号方向,反射Moho为位于双程走时11~14 s水平的反射分段连续的过渡带,宽度约3 s;小桩号方向,反射Moho为一宽度约2 s、并向大桩号倾斜的反射分段连续的过渡带,其形态和反射事件RA相同.根据地震波速度资料,求得这几个反射带顶界的深度分别为:10.5~13.5 km(反射带C)、20.3~21.5 km(反射带RB)、16.8~34.3 km(反射带RA)和32~36.7 km(反射带Moho)左右.作者认为形态一致的反射事件RA和反射Moho很可能是古秦岭洋向华北地台俯冲的遗迹.此外,西安坳陷内错断新生界深达反射事件C的渭河和临潼-长安断裂带和莫霍错断的存在,表明该地区地壳现今活动性很强,是未来强震发生值得注意的地区. 相似文献
11.
In recent years some authors have given a certain amount of attention to towed seismic reflection acquisition systems. Based on some of these works we sought to design and test a system making use of currently available geophones instead of specifically designed sensors as employed in some previous works. Thus, bearing in mind that the geophone's characteristics are achieved in the conditions that they are originally designed to be employed in, i.e., coupled with a spike driven into the ground, we devoted our attention to some of the variables involved in the geophone's performance, namely the total weight, the effect of a spikeless geophone and the surfaces on which the geophone is placed. Previously, we had experimentally verified some variations in the signal response due to coupling geophones in different surface materials, such as hard soil, asphalt and concrete pavement and we noticed that these surface materials were in fact an important factor in the overall response. Hence, these materials, or as we also called them coupling agents, could be employed as a base material in the construction of a mobile seismic acquisition device composed of blocks of a certain size, on which the geophone would be then inserted and thus making it into a spikeless surface towable system. Therefore, various materials were tested in order to select one that could maintain a similar fidelity to that of the spike coupled geophone and thus contribute towards building a more time efficient and towable geophone and block system. Pinging tests revealed variations in the coupling frequency and damping characteristics of each coupling agent and from all of these tested materials one was selected for field comparative tests with the normally planted geophones with spike coupling. Finally a seismic reflection profile was acquired simultaneously with both systems, i.e., spike coupling versus cement block coupled geophones. This field test showed similar results in terms of signal levels and frequency content and therefore it was possible to observe the presence of the same reflectors and other seismic events in either of the time sections. With this experiment we propose not only a system that allows a time efficient seismic field operation but we also aim to encourage more research into the response dependency of the coupling agent of which the towable base block is made of. 相似文献
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B Damotte 《Journal of Applied Geophysics》1993,29(3-4)
The French Ecors program was launched in 1983 by a cooperation agreement between universities and petroleum companies. Crustal surveys have tried to find explanations for the formation of geological features, such as rifts, mountains ranges or subsidence in sedimentary basins. Several seismic surveys were carried out, some across areas with complex geological structures. The seismic techniques and equipment used were those developed by petroleum geophysicists, adapted to the depth aimed at (30–50 km) and to various physical constraints encountered in the field. In France, Ecors has recorded 850 km of deep seismic lines onshore across plains and mountains, on various kinds of geological formations. Different variations of the seismic method (reflection, refraction, long-offset seismic) were used, often simultaneously. Multiple coverage profiling constitutes the essential part of this data acquisition. Vibrators and dynamite shots were employed with a spread generally 15 km long, but sometimes 100 km long.Some typical seismic examples show that obtaining crustal reflections essentialy depends on two factors: (1) the type and structure of shallow formations, and (2) the sources used. Thus, when seismic energy is strongly absorbed across the first kilometers in shallow formations, or when these formations are highly structured, standard multiple-coverage profiling is not able to provide results beyond a few seconds. In this case, it is recommended to simultaneously carry out long-offset seismic in low multiple coverage.Other more methodological examples show: how the impact on the crust of a surface fault may be evaluated according to the seismic method implemented (vibroseis 96-fold coverage or single dynamite shot); that vibrators make it possible to implement wide-angle seismic surveying with an offset 80 km long; how to implement the seismic reflection method on complex formations in high mountains.All data were processed using industrial seismic software, which was not always appropriate for records at least 20 s long. Therefore, a specific procedure adapted to deep seismic surveys was developed for several processing steps. The long duration of the vibroseis sweeps often makes it impossible to perform correlation and stack in the recording truck in the field. Such field records were first preprocessed, in order to be later correlated and stacked in the processing center. Because of the long duration of the recordings and the great length of the spread, several types of final sections were replayed, such as: (1) detailed surface sections (0–5 s), (2) entire sections (0–20 s) after data compression, (3) near-trace sections and far-trace sections, which often yield complementary information.Standard methods of reflection migration gave unsatisfactory results. Velocities in depth are inaccurate, the many diffractions do not all come from the vertical plane of the line, and the migration software is poorly adapted to deep crustal reflections. Therefore, migration is often performed graphically from arrivals picked in the time section. Some line-drawings of various onshore lines, especially those across the Alps and the Pyrenees, enable to judge the results obtained by Ecors. 相似文献
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为进一步深入研究夏垫断裂的发震构造及活动性,在夏垫断裂震中区开展浅层地震勘探,布设小道距、高密度地震勘探测线,对地震反射剖面进行综合解释。以潘各庄段为中心,向两侧展开布设,共布设浅层地震勘探测线12条,测线总长约18 km。野外数据采集采用中间激发、双边不对称接收、满覆盖次数不少于12次的观测系统。原始资料经过常规处理和精细处理,获得了高质量的反射波叠加时间剖面。地震反射时间剖面揭示的波组变化特征明显,断裂特征清晰,解释夏垫断裂为倾向SE、视倾角约为72°的正断层;同时展现了自小石各庄至南张岱延伸约20 km范围内夏垫断裂的空间展布及浅部构造特征,解释测线范围内夏垫断裂走向约为N40°E。在此基础上,结合微地貌测量和以往研究成果,推测夏垫断裂为全新世活动断裂,其中夏垫断裂中心段伴随次断裂发育和断层绕射波,该特征向两侧减弱,与断裂陡坎的分布和连续的高差变化相对应,同时验证了夏垫镇潘各庄附近为震中的结果。探测结果所揭示的夏垫断裂的空间展布及地层结构特征与地质资料吻合。 相似文献
17.
Colin M. Sayers 《Geophysical Prospecting》2009,57(2):187-192
Natural fractures in reservoirs play an important role in determining fluid flow during production and knowledge of the orientation and density of fractures is required to optimize production. Variations in reflection amplitude versus offset (AVO) are sensitive to the presence of fractures but current models used to invert the seismic response often make simplified assumptions that prevent fractured reservoirs from being characterized correctly. For example, many models assume a single set of perfectly aligned fractures, whereas most reservoirs contain several fracture sets with variable orientation within a given fracture set. In addition, many authors only consider the azimuthal variation in the small offset amplitude versus offset and azimuth response (the variation in AVO gradient with azimuth), while the effect of fractures on amplitude versus offset and azimuth increases with increasing offset. In this paper, the variation in the reflection coefficient of seismic P -waves as a function of azimuth and offset due to the presence of multiple sets of fractures with variable orientation within any fracture set is used to determine the components of a second-rank fracture compliance tensor α ij . The variation in the trace of this tensor as a function of position in the reservoir can be used to estimate the variation in fracture density with position in the reservoir and may be used to choose the location of infill wells in the field. The principal axes of α ij reveal the most compliant direction within the reservoir and may be used to optimize the trajectory of deviated wells. The determination of the principal axes of α ij requires wide azimuth acquisition and the use of the small-offset amplitude versus offset and azimuth (the azimuthal variation of the AVO gradient) may give misleading results. 相似文献
18.
Seismic reflection data were acquired across volcanic hosted massive sulfides (VHMS) of Vihanti in order to improve the understanding of the regional geological setting. Commercially processed seismic data from Vihanti are of good quality, but reprocessing can be used to extract additional information about geological structures. Especially, careful velocity analysis influences the quality of seismic images. Differentiating reflections caused by fractures from those caused by lithological contacts is very important for exploration and geological modeling. Reflections from fracture zones known from drilling stack with lower velocity (~ 5100 m/s) compared to typical stacking velocities of the Vihanti area (> 5500 m/s). The reprocessing also indicated that fracture zones are better imaged with low frequencies due to the better overall continuity of the fault zones at scales of hundreds of meters rather than at shorter seismic wavelengths.In full stacks, long offset data can mask structure close to the surface. More detailed seismic images of the shallow subsurface emerged by preferentially stacking short offset data wherever acquisition and processing lines lay close together and were nearly straight. Long offset data remains valuable for imaging deeper structures as well as dipping reflectors. Cross-dip-analysis revealed a bright diffractor located near the base of the Vihanti volcanic basin at 1.5 km depth. The seismic data allow a geological interpretation in which the Vihanti structure has developed through significant thrust faulting and displacement of the lithological contacts. Gentle folds that were formed prior to faulting are visible as undulating reflectivity in seismic sections. The reprocessed seismic section indicates a potential deep extension of the ore-hosting altered volcanic and calc-silicate rocks previously unexplored. 相似文献
19.
Ki Young Kim Jung Mo Lee Wooil Moon Chang-Eob Baag Heeok Jung Myung Ho Hong 《Pure and Applied Geophysics》2007,164(1):97-113
In order to investigate the velocity structure of the southern part of the Korean peninsula, seismic refraction profiles were
obtained along a 294-km WNW-ESE line and a 335-km NNW-SSE line in 2002 and 2004, respectively. Seismic waves were generated
by detonating 500–1000 kg explosives in drill holes at depths of 80–150 m. The seismic signals were recorded by portable seismometers
at nominal intervals of 1.5–1.7 km. Separate velocity tomograms were derived from first arrival times using a series expansion
method of travel-time inversion. The raypaths indicate several mid-crust interfaces including those at approximate depths
of 2–3, 15–17, and 22 km. The Moho discontinuity with refraction velocity of 7.8 to 8.4 km/s has a maximum depth of 37–39
km under the southern central portion of the peninsula. The Moho becomes shallower as the Yellow Sea and the East Sea are
approached on the west and east coasts of the peninsula, respectively. The depth of the 7.6 km/s velocity contour varies from
29.4 km to 36.5 km. The discrepancy in depth between the seismological Moho and the interpreted critically refracting interface
may result from the presence of a gradual transition between the crust and mantle. The velocity tomograms show particular
crustal structures including (1) the existence of an over 70-km wide low-velocity zone centered at 6–7 km depth under the
Okchon fold belt and Ryeongnam massif, (2) existence of high-velocity materials under the Gyeongsang basin, and (3) the downward
extension of the Yeongdong fault to depths greater than 10 km. 相似文献
20.
日喀则地质资料匮乏,地球物理勘探资料更加稀缺,该地区在此之前没有开展过地震勘探的工作.本文针对日喀则地区活动断裂,采用夯源为人工震源的浅层地震勘探方法,结合小折射调查低速层,详细讨论工作中的关键性技术问题;提出在该地区地质条件下实施隐伏断裂勘探时的地震仪器选择、方案设计、参数选取、数据处理、断层识别的基本方法;查明拉堆—乃东断裂、抓各落断裂、毕定—甲舍拉断裂、甲岗—谢通门断裂的走向、产状、上断点埋深及其在地表的垂直投影位置等主要参数.为日喀则地区的深浅构造关系等研究提供基础资料,填补该地区地球物理勘探资料的空白. 相似文献