复杂地形下浅层折射波地震勘探解释方法探讨

在一些地形起伏较大的地区(如水电站坝址等)开展折射波法地震工作时,地形影响相当严重,给常规解释工作带来很大困难。如不采取相应的措施消除地形影响,有意义的地质现象可能遗漏或掩盖,真假异常难以分辨,有时甚至可能会造成假象,影响解释结果的可信度。     

浅层地震折射波法综述

浅层地震折射波法是在工程地质、水文地质及环境地质勘查中广泛应用的地震探测方法之一。在工程地质调查中,根据不同的场地地质条件和勘察目的,合理地正确应用浅层折射波法可以取得较明显的岩土工程勘察效果。本文简要地回顾了浅层地震折射法的发展历史,对各种新近发展的折射波解释方法进行了简单的介绍和比较,并列举了工程勘察中的应用领域。     

折射波时距曲线及解释剖面的自动绘制

本文提出并解决了折射波时距曲线及解释剖面的自动绘制问题。通过自动的绘制，输出美观、准确的时距曲线及解释剖面，避免了清绘等过程，节省了大量的人力、物力。     

反射波地震勘探中折射波资料的应用

在反射波地震勘探中通常会将折射波作为干扰波,本文详细分析了折射波与反射波时距曲线的区别与联系,并通过三个应用实例说明,在反射波地震勘探中,充分利用折射波资料,有时会大大提高勘探效率和勘探精度,并可使地震资料解释依据更加充分。     

覆盖开关在水中地震折射波法中的运用

介绍了浅层地震折射波法在铁路桥基础勘查中的应用。使用覆盖开关,采用互换法,提高了野外数据采集速度,降低了成本。     

地震层析成像在工程勘测中的应用

目前,地震层析成像在许多工程勘测和矿产勘探部门开始试用,迫切需要有这方面的指南性的文章。本文综合介绍地震层析成象的原理、数据采集技术、图象重建的理论和方法,并通过一个成功的应用实例说明方法的应用效果。作为一种新的物探方法,地震层析成象的应用仍然存在许多问题,如非线性图像重建,文章对存在问题及对策作了详细讨论。     

折射波资料在北黄海盆地地震资料解释中的应用

北黄海盆地地质构造复杂,在反射地震资料中,部分地区中、深层反射不清,造成地震资料解释的多解性.笔者分析了该区反射波与折射波时距曲线的区别和联系,充分挖掘反射地震资料的潜力,利用其中的折射波资料,分析盆地的折射波特点,计算出基底速度,弥补反射资料速度分析的不足;利用折射波速度,推断地质属性,划分地震层位,提高了北黄海盆地中、深层地震资料解释的精度,使地震资料解释更加合理.     

地震反射层析成像方法的研究及其在工程中的应用

本文提出的地震反射层析成像方法,基于射线原理,应用叠前反射波的走时资料,逐层反演地下介质结构。它是在局部范围内,将地层各界面视为平面,求取界面、速度参数,全剖面的成像只需反复进行局部反演。用该方法处理了三板溪水电站工区的两个地震剖面,处理结果与钻孔资料对比,一致性较好。     

Exploiting Lateral Resolution of Near-Surface Seismic Refraction Methods

The 1D τ-p inversion algorithm is widely employed to generate starting models with most computer programs that implement refraction tomography. However, this algorithm emphasizes the vertical resolution of many layers, and as a result, it frequently fails to detect even large lateral variations in seismic velocities, such as the decreases that are indicative of shear zones. This study presents a case that demonstrates the failure of the 1D τ-p inversion algorithm to define or even detect a major shear zone that is 50 m or ten stations wide. Furthermore, the majority of refraction tomography programs parameterize the seismic velocities within each layer with vertical velocity gradients. By contrast, the 2D generalized reciprocal method (GRM) inversion algorithms emphasize the lateral resolution of individual layers. This study demonstrates the successful detection and definition of the 50-m wide shear zone with the GRM inversion algorithms. The existence of the shear zone is corroborated by a 2D analysis of the head wave amplitudes and by numerous closely spaced orthogonal seismic profiles carried out as part of a later 3D refraction investigation. Furthermore, a 1D analysis of the head wave amplitudes indicates that a reversal in the seismic velocities, rather than vertical velocity gradients, occurs in the weathered layers. While all seismic refraction operations should aim to provide as accurate depth estimates as is practical, the major conclusion reached in this study is that refraction Inversion algorithms that emphasize the lateral resolution of individual layers generate more useful results for geotechnical and environmental applications. The advantages of the Improved lateral resolution are obtained with 2D profiles in which the structural features can be recognized from the magnitudes of the variations in the seismic velocities. Furthermore, the spatial patterns obtained with 3D investigations facilitate the recognition of structural features that do not display any intrinsic variation or "signature" in seismic velocities.     

Structural Characteristics of the Basement beneath Qiangtang Basin in Qinghai-Tibet Plateau: Results of Interaction Interpretation from Seismic Reflection/Refraction Data

The studies on configuration, character/property of the basement of Qiangtang basin is helpful for evaluating petroleum and nature gas resources as well as understanding the basin evolvement. Recently a moderate to high-grade metamorphic gneiss rock was found underlying beneath very low metamorphic Ordovician strata in Mayer Kangri to the north of the central uplift. That fact actually proved existence of the crystalline basement just the distribution and structures of pre-Paleozoic crystalline basement still remain puzzle. In recent years a number of active sources deep seismic profiling, to aim at lithospheric structure of northern Tibet and petroleum resources of the Qiangtang basin, had been conducted that make it possible to image the structure of the basement of the Qiangtang. Near vertical reflection profiles, included those acquired previously and those during 2004 to 2008, have been utilized in this study. By through the interaction process and interpretation between the reflection profiles and the wide-angle profile, a model with the detailed structure and velocity distribution from surface to the depth of 20 km of Qiangtang basin has been imaged.Based on the results and discussions of this study, the preliminary conclusions are as follows: (1) The velocity structure section (~20 km) that is interactively constrained by the refraction and reflection seismic data reveals that the sedimentary stratum gently lie until 10 km in the south Qiangtang basin. (2) The basement consists of fold basement (the upper) and crystalline basement (the lower).The fold basement buried at the average depth of 6 km with a velocity of 5.2–5.8 km/s. The shallowest appear at range of the central uplift. The crystalline basement is underlying beneath the fold basement at the average depth of 10 km with a velocity of 5.9–6.0 km/s except near Bangong-Nujiang suture. (3) The high-velocity body at the depth range of 3–6 km of the central uplift is considered as a fragment of the crystalline basement that perhaps was raised by Thermal or deformation. (4) The lower-consolidated fold basement show more affinity of Yangtze block but the crystalline basement seems more approximate to Lhasa terrene in geophysical nature. We have attempted to improve the resolution and reliability by interaction of the active seismic data and prove it effective to image complex basement structure. It will be a potential to process the piggy-back acquisition data and has wide prospects.     

折射静校正技术在宣东地震资料处理中的应用

当地震数据中存在较大的静校正量时，利用模型道与各道互相关求取时差的反射波静校正方法往往不能奏效，其主要原因是得不到好的模型道，当原始资料的信噪比很低时，这一问题更加突出，因此必须首先解决好野外一次静校正。近年来，针对复杂地形和地表结构的折射波静校正，总差分折射静校正方法和基于速度模型的反演静校正方法被广泛应用。在静校正问题严重的宣东地区为例，综合运用了这两种折射静校正方法进行三维地震资料的处理，取得良好效果。     

地震技术在隧道工程勘查中的应用

以折射波法及反射波法介绍了地震勘探技术在石柱槽隧道及大桠隧道探测断裂破碎带、断层中的应用情况，包括观测系统、处理方法及解释依据。结果表明地震技术在隧道工程勘查中具有良好的应用效果。实例说明，在隧道工程勘探中，因地震波能量衰减较快，除了选择合适的地震勘探方法、观测系统及工作参数外，还应特别注意选择较小的偏移距及道距。     

地震波法在煤层赋存条件解释中的应用

新疆含煤岩系大多沉积在中新生代拗陷型、断拗型及断陷型盆地中,煤层的赋存条件比较复杂,虽单层煤厚度可达100多m,但煤层沉积厚度在区域上变化较大,煤层煤组的尖灭、合并现象时有发生,使得新疆煤田煤组标定、归并工作变得非常复杂。根据新疆煤田地质特点和地震勘探中遇到的问题,结合实例探讨利用钻孔、单炮记录和折射波速度等资料确定煤层赋存情况的方法。利用折射波速度资料编制了新疆煤田勘查区地震波速度平面图,在钻孔验证的基础上,提出了在新疆哈密煤田依据其速度判断煤层赋存状态的辅助方法:①速度4 000～5800m/s的区域,其高速界面深度较浅,属无煤层赋存区;②速度3 000～4 000m/s,高速界面不明显,存在煤层赋存的可能性;③速度低于3 000m/s,其新近系、古近系及侏罗地层较厚、有煤层赋存的可能性,但煤层埋藏深度较深。     

地震波速层析成像方法研究进展

本文回顾了利用天然地震观测获取地下速度结构的方法。尽管有不同的新方法涌现,天然地震波速层析成像方法,尤其是多震相联合反演的格点层析成像方法,是当今使用广泛使用的层析成像方法之一,是对地球内部成像的最有效方式。波速层析成像方法的未来发展首先是提高第一手的观测资料,即增加接收地震波信息的地震台站分布密度;同时,通过多种地球物理方法联合反演相互约束可以给出较为严格的地球物理模型,并来降低了地球物理反演和解译的多解性,这是地球物理探测研究的趋势,也是天然地震波速层析成像方法的研究趋势。     

综合折射静校正方法在柴达木盆地的应用

在表层结构调查资料的约束下, 利用大炮初至折射静校正方法反演出精确、合理的表层结构模型, 进而求取炮点、检波点静校正量.选定柴达木盆地北极星工区04314测线进行地震模型数值模拟, 并对模型数据和野外地震资料进行多种静校正方法对比分析研究, 综合折射静校正方法的误差最小, 叠加效果最好.表明综合折射静校正方法结合了模型静校正和折射静校正的优点, 不仅较好地解决了影响剖面信噪比的短波长静校正问题, 同时也能解决产生虚假构造的长波长静校正问题.      

复杂地表条件剖分析射法静校正处理方法探索

通过分析在复杂地区使用常规静校正处理方法所暴露的问题，提出采用折射波垂直剖分法对地震资料进行静校正。首先建立近地表折射波剖分模型，用等问距或不等间距的垂向网格把折射波分成若丁个单元，每个单元的折射波速度近似为一常数，而不同单元间速度的变化则反映了整个近地表层速度的横向变化。在实际应用时可利用多张单炮记录相关正交求解速度。     

三维地震工程测量数据处理方法

利用坐标系的相互转换原理，通过AutoCAD2000的强大图形功能，在所设计的矢量图中准确量取已知点的实地坐标，再以赫尔默特坐标转换公式转换为数学模型，在电子表格软件Exce12000中进行所有激发点、检波点的坐标求解，获得设计坐标；外业放样数据亦可被导入Exce12000中进行筛选、排序而得到成果文件。该方法是处理三维地震工程测量数据的一种行之有效的新方法。