单道地震技术在海洋地质调查中的应用——以威海褚岛北部海域为例

单道地震调查技术方法是海洋地震调查的主要手段之一,海上单道地震具有配置灵活、施工效率高、中—浅部地层分辨率较高、应用面广等特点,在海洋地质调查领域应用广泛。该文简要介绍了单道地震的工作原理,并以威海褚岛北部海域为例,通过分析该区单道地震资料,结合探测目的及仪器性能,制定了针对性的试验方案,确定了分辨率较高的参数优化组合,获得了高质量、高分辨率的海底地层资料。通过对实测单道地震剖面的比较和分析,结合钻孔数据,对威海褚岛北部海域地层进行分层划分及地层单元体系域分析,得出威海褚岛北部海域中—浅地层结构特征及海底地质灾害特征。通过对威海褚岛北部海域单道地震调查应用实例的分析,阐述了海上单道地震在数据采集、处理和解译方面的相关技术。     

威海市近海海域浅地层结构及灾害地质特征

通过对2 131km高分辨率浅地层剖面资料分析和研究,揭示了威海市近海海域浅地层结构特征,分析了海洋灾害地质因素类型及分布特征,并绘制了主要灾害地质因素分布图。威海市近海海域65m以浅地层共分为5层,第一层为全新世泥质楔形体,地层厚度8~15m;第二层为末次盛冰期以来的海侵层,厚度一般小于3m;第三层为MIS2期的陆相沉积层,地层厚度3~8m;第四层为MIS3期的海相沉积层,厚度3~6m;第五层未完全揭示。近海海域灾害地质因素主要包括埋藏下切谷、浅部断层、浅层气、海底沙波沙脊、浅埋起伏基岩等5种类型;埋藏下切谷主要分布在南部海域U3地层单元中;浅部断层主要分布在南部海域水深大于20m的海底堆积平原;浅层气主要分布在北部海域,东部和南部海域面积较小;海底沙波沙脊主要分布在荣成成山头外海海域;浅埋起伏基岩主要分布在基岩海岸和岛屿较近的海域。     

浅层地下水物探探测方法选择

浅层地下水探测是物探工作重点关注领域之一,本文从地球物理特征出发,结合工作实例,分析电阻率层析成像技术、电测深、大地电磁法、甚低频及浅层地震等方法在地下水探测中的效果,分析各方法探测中优缺点。本文从成本、效率、探测深度、地形条件等不同因素考虑,给出了不同条件下物探方法的选择。文中对不同勘探深度给出了不同的综合勘探手段组合,100m以浅优选层析成像技术、电测深、瞬变电磁法、浅层地震等方法组合,500m以深选择CSAMT法、EH法等组合。     

Shallow water body data processing based on the seismic oceanography

Physical properties of sea water,such as salinity,temperature,density and acoustic velocity,could be demarcated through degradation of energy caused by water absorption,attenuation and other factors.To overcome the challenging difficulties in the quick monitoring of these physical properties,we have explored the high resolution marine seismic survey to instantly characterize them.Based on the unique wavefield propagating in the sea water,we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure.This approach improves seismic data with high signal-to-noise ratio and resolution.The seismic reflection imaging can map the sea water structure acoustically.Combined with the knowledge of local water body structure profile over years,the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition.This model can also be updated with instant observation and the complete data processing system.The present study has the potential value to many applications,such as 3D sea water monitoring,engineering evaluation,geological disaster assessment and environmental assessment.     

水域地震映像在火成岩发育区的应用与探讨——以厦门某海底隧道勘察为靶区

以厦门某海底隧道勘察为靶区，采用电磁气泡震源系统激发地震波，在火成岩发育区进行水域地震映像实验，较好地查明了海底水深界面、淤泥（砂层）和基岩面的分界线。实验结果表明，水域地震映像法对海域火成岩发育区是一种有效的物探方法，可以为海域地质勘察提供可靠的地质参考依据；利用水域地震映像勘探既可以较好地弥补钻探缺陷，又能极大地节约经济成本。     

Seismic acquisition parameters analysis for deep weak reflectors in the South Yellow Sea

The Mesozoic-Paleozoic marine residual basin in the South Yellow Sea (SYS) is a significant deep potential hydrocarbon reservoir. However, the imaging of the deep prospecting target is quite challenging due to the specific seismic-geological conditions. In the Central and Wunansha Uplifts, the penetration of the seismic wavefield is limited by the shallow high-velocity layers (HVLs) and the weak reflections in the deep carbonate rocks. With the conventional marine seismic acquisition technique, the deep weak reflection is difficult to image and identify. In this paper, we could confirm through numerical simulation that the combination of multi-level air-gun array and extended cable used in the seismic acquisition is crucial for improving the imaging quality. Based on the velocity model derived from the geological interpretation, we performed two-dimensional finite difference forward modeling. The numerical simulation results show that the use of the multi-level air-gun array can enhance low-frequency energy and that the wide-angle reflection received at far offsets of the extended cable has a higher signal-to-noise ratio (SNR) and higher energy. Therefore, we have demonstrated that the unconventional wide-angle seismic acquisition technique mentioned above could overcome the difficulty in imaging the deep weak reflectors of the SYS, and it may be useful for the design of practical seismic acquisition schemes in this region.     

Numerical simulation for accuracy of velocity analysis in small-scale high-resolution marine multichannel seismic technology

When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positive results have been achieved in submarine geological research, particularly in the investigation of marine gas hydrates. However, the amount of traveltime difference information is reduced for the velocity analysis under conditions of a shorter spread length, thus leading to poorer focusing of the velocity spectrum energy group and a lower accuracy of the velocity analysis. It is thus currently debatable whether the velocity analysis accuracy of short-arrangement multichannel seismic detection technology is able to meet the requirements of practical application in natural gas hydrate exploration. Therefore, in this study the bottom boundary of gas hydrates (Bottom Simulating Reflector, BSR) is used to conduct numerical simulation to discuss the accuracy of the velocity analysis related to such technology. Results show that a higher dominant frequency and smaller sampling interval are not only able to improve the seismic resolution, but they also compensate for the defects of the short-arrangement, thereby improving the accuracy of the velocity analysis. In conclusion, the accuracy of the velocity analysis in this small-scale, high-resolution, multi-channel seismic detection technology meets the requirements of natural gas hydrate exploration.     

浅层地震反射波法在石膏矿采空区调查中的应用

随着人们对地下矿产资源的过度开采,地下空间形成了较大区域的采空区。采空区出现后,其上覆岩层平衡条件被破坏,使得上覆岩层产生移动变形,直到破坏、塌落,导致地表建筑物变形、破坏,地表大面积下沉、凹陷,形成大面积的采空塌陷区。采空区的存在使矿山生产面临很大的安全问题。近年来,矿山采空区的危害越来越受到人们的重视,在采空区调查中,各种地球物理方法起到了重要的作用,国内外以往探测实践表明,较为常用的物探测量方法有:高密度电阻率法、瞬变电磁法、CSAMT法、浅层地震反射波法、放射性土壤氡气测量法等,但每种物探方法的应用均具有一定的条件,需要根据岩石物性特征、场地条件、探测深度、环境影响等因素选择合适的地球物理方法。地震反射波法具有抗干扰能力强、分辨率较高等优势,被较多应用于矿山采空区的调查中。该文以临沂市兰陵县某石膏矿采空区为例,采用浅层地震反射波法对该石膏矿采空区进行调查,通过对获得的地震剖面资料进行处理和解释,取得了较好的探测效果,其技术方法可为同类采空区的探测提供借鉴和指导。     

利用SH横波反射资料中的勒夫面波反演浅部横波速度结构

由于勒夫波速度与纵波速度无关,勒夫波多道分析方法具有频散曲线简单、能量清晰、反演过程中未知参数少、对初始模型依赖小、反演结果稳定、分辨率高等特点。实验结果表明,利用浅层SH横波反射地震数据中的勒夫面波信息,反演得到近地表横波速度结构,在浅层地质构造、断层位置、上断点埋深等方面与浅层SH横波反射地震剖面以及地质钻孔数据吻合较好。该方法可为地下构造解释提供更多依据,提高探测成果的可靠性。     

重庆地区三维P波速度结构成像研究

利用重庆数字地震台网目录记录到的2009-01~2018-10重庆地区的地震数据资料,采用双差层析成像方法得到重庆地区的上地壳三维速度结构模型。研究表明,浅层地壳速度结构与地质构造的分布呈现出较高的相关性：石柱地区褶皱基底缺失,断裂两侧速度结构差异较大;华蓥山基底断裂两侧速度结构差别明显,可能与两侧结晶基底的深度和物性有关;巫溪断裂的高速区可能与地幔深处的物质上溢有关。     

浅地震剖面揭露南秦岭隐伏断裂特征——以丹江断裂为例

采用浅层地震反射勘探方法对南秦岭构造带内丹江断裂进行地球物理勘探，通过数据处理与分析，获取包括断裂在隐伏区的几何展布形态、上断点埋深及断层性质在内的高分辨率浅地震剖面；对部分测线的地震剖面成果与钻孔资料进行对比验证解译。研究表明，浅地震反射对该区域隐伏探测行之有效，该方法可为隐伏活动断层探测提供参考。     

Application of Gaussian beam pre-stack depth migration in rugged seabed

Strong fluctuation of seabed, abrupt variation in depth and dip of seabed bring seismic imaging problems, such as irregular reflection waves, obvious multiple waves, serious lateral wave development, poor imaging on base surface and depression structure, low signal-to-noise ratio of middle and deep layers. In this paper, Gaussian beam migration imaging method is used to analyze the imaging effect of rugged seabed in deep water area, and the ray tracing method of wavefront construction method is used to analyze the kinematic characteristics of seismic waves. By improving the design of seismic data acquisition and observation system, imaging quality of fine structures is improved.     

浅地震反射剖面揭示地震小区划覆盖层厚度及隐伏断裂——以九江芳兰规划区为例

以九江芳兰规划区为例，利用浅层地震反射方法获取小区划工区的覆盖层厚度，并查明周边隐伏断裂位置及特征。结合钻孔资料对比解译，对地震小区划工作提供基础地震地质信息，同时为该区的活断层探测和地震危险性评价提供参考资料。     

茅山断裂带及邻区精细速度结构的双差层析成像研究

选取2008~2018年茅山断裂带及周边82个测震台站记录到的516个近震Pg、Sg到时数据,采用双差地震层析成像方法对茅山断裂带及邻区进行地震重定位和三维P波速度结构的联合反演,并分析溧阳历史上两次破坏性地震与速度结构的关系。结果表明,地震重定位后残差显著降低,研究区大部分地区横向分辨率可达0.2°。P波的速度结构横向差异变化比较明显,反演后的速度与初始速度模型之间的变化率基本在±10%左右。茅山断裂带两端呈现高速特征,中段表现为低速结构。溧阳震源区1974年MS5.5地震发生在深变质岩系内的低速层上,而1979年MS6.0地震发生在深变质岩系与浅变质岩系边界上,这两次地震的发震原因可能与具有塑性流变特性的低速体和速度梯度较大的转换复合位置容易产生应力集中有关。     

Distribution and Characteristics of Hazardous Geological Features in the Marine Coastal and Offshore Areas of Zhejiang Province,East China Sea

Newly acquired high-resolution shallow seismic profiles(7069 km in length) in the coastal and offshore areas of Zhejiang Province, East China Sea, China, have revealed eight marine hazardous geological features: shallow gas, sand ridges, erosion ditches, scarps, irregular bedrock features, underwater shoals, buried paleo-channels, and submarine deltas. Based on the seismic profiles, we have constructed a marine geological map of these hazardous features. Shallow gas accumulations are common and occur mainly in two separate nearshore regions that cover 4613 and 3382 km~2 respectively. There are also scattered shallow gas accumulations in the offshore area, typically accompanied by paleo-channels that occur mainly in the middle of the study area. Sand ridges, erosion ditches, scarps, and irregular bedrock features are found mainly in the northeast of the study area in association with each other. In the southeastern part of the study area, the sand ridges have a linear form and trend NW–SE, representing the western part of the linear sand ridges in the East China Sea. The maximum slope gradient is 1?, which suggests that this area is prone to landslides. These hazardous marine geological features are important to marine and engineering activities in this region.     

日照市近海海域灾害地质类型及特征分析

日照近岸海域灾害地质类型主要为埋藏下切谷、海底侵蚀、冲刷沟槽和冲刷陡坎及海底抛泥区等。通过对日照海岸带近岸海域的浅地层剖面和水深测量资料,开展主要地震地层界面的追踪和对比,结合沉积物粒度和地球化学特征,对近海海域潜在灾害地质因素进行分析对比,探讨了日照近海海区的灾害地质类型、特征和分布规律,为半岛蓝色经济区的海洋开发提供基础地质资料。     

基于无人机成像点云的禄丰恐龙谷南缘环状地貌空间特征探测实验分析

为了定量获取复杂地貌构造的特征参数,需要获取高精度、高分辨率的地形地貌数据。在复杂地貌特征探测中,基于无人机航测结合成像点云,可以快速、高效、安全、准确地完成复杂地貌空间探测任务。针对禄丰恐龙谷南缘环状地貌的典型局地场景,采用无人机测量技术获取测区高分辨率的地貌影像数据,构建实景三维场景模型并对其地貌特征进行探测分析研究。试验结果表明:①基于无人机成像点云构建0.2 m分辨率DEM数据能够精准表达研究区真实地貌特征。②通过构建环状场景"内-中-外"7条典型高程剖面线,对比分析证实了研究区地形呈现环形"盆缘"形态特征,内外两侧高程逐渐递减,并且"盆缘"外部剖面高程起伏变化剧烈,地形相较于内部地貌更加复杂。③为进一步探测提取微形地貌特征信息,利用无人机成像原理构建的精准DEM数据结合测区实景三维模型,定量提取了该区坡度、坡向、相对高差、等值线、山脊线、山谷线等相关参数进行精准定量测量及分析探讨。④利用立体三维模型的多视角目视解译与典型场景分析,可清楚辨别出测区冲沟发育以及地质体的节理层理面等微地貌特征。通过以上对地貌三维场景探测试验研究表明,利用实景三维模型能够快速准确呈现测区地貌形态特征,并且成像点云数据综合分析,能够量化、半量化揭示区域构造地质信息。总体而言,无人机测量技术与成像点云3D产品在地质调查中的应用具有实用意义,并具备独特的技术优势。      

Accuracy of the staggered-grid finite-difference method of the acoustic wave equation for marine seismic reflection modeling

Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity-pressure formulation of the acoustic wave equation to marine seismic modeling using the staggered-grid finite-difference method. The scheme is developed using a fourth-order spatial and a second-order temporal operator. Then, we define a stability coefficient (SC) and calculate its maximum value under the stability condition. Based on the dispersion relationship, we conduct a detailed dispersion analysis for submarine sediments in terms of the phase and group velocity over a range of angles, stability coefficients, and orders. We also compare the numerical solution with the exact solution for a P-wave line source in a homogeneous submarine model. Additionally, the numerical results determined by a Marmousi2 model with a rugged seafloor indicate that this method is sufficient for modeling complex submarine structures.     

浙江省台州-昌化深部构造特征探测

采用高分辨折射和宽角反射/折射综合地震探测方法，在浙江省中部沿黄岩、临海、东阳、桐庐、昌化进行深部构造探测，获得一条长约350 km的速度结构剖面。探测结果表明，地壳结构具有明显的多层性，存在3个速度间断面;基底速度结构图像揭示了速度结构的横向非均匀性，这种不均匀性既对应于地质构造单元的分界线或断裂构造带，也反映出东西部构造特征的差异性。     

山东省成武县土壤地球化学特征及土地质量现状

山东省成武县农业地质环境土壤地球化学调查是按浅层、深层土壤样品1点/4km2。测试N,P,K,Cu,Zn,B,Mo,Mn,F,As,Hg,Pb,Cr,Cd等14种指标。在统计这些指标的表层、深层土壤地球化学特征参数的基础上,对其与世界、全省同类参数的差异进行了分析,并分析了区内表层、深层土壤元素含量的相关性,认为该区表层土壤元素含量的显著特征是高F,Hg,Pb而低Mo;大部分元素在表层土壤中的含量继承了土壤母质的成分特征,但N,F,Hg,Pb等受人为活动和污染源的作用在表层土壤中明显富集。通过分析表层土壤营养元素有效量可知,P,K,Zn的有效量高;供肥能力强;而Mo,Cu,Mn明显偏低。利用易污染元素浅层土壤含量值,通过污染指数法,对全区土壤污染程度进行了评价;区内土壤无严重污染区存在,并且明显污染地段面积较小,呈零星分布,说明区内污染程度较轻。