延怀盆地上地壳热流体特征及其与地震活动的关系

系统研究了延怀盆地上地壳热流体的温度、水化学、气体化学与同位素化学特征 ,确定热水成因与大气降水渗入有关 ,并计算了热储温度与水循环深度 ,认为热水活动对中小地震活动有一定的控制作用并影响断裂活动强度     

滇西地区断层气体成因研究

本文讨论了滇西地区由温泉释放的断层气体中各主要组分(He、H_2、Ar、N_2、CO_2、CH_4、Hg)的分布特征及其成因机制。 作者指出,滇西地区断层气体中直接来自地幔的He是微不足道的,较高水平的He释放(>100ppm)可能直接来自地层中的火成岩;H_2的释放与地层岩性无关,而与深大断裂的活动或地震活动有成因联系;洱源地区九台等泉点中CH_4含量达2—3％,同位素测定表明,它是典型的无机成因,是该区深部热动力变质作用的产物;滇西地区断层气体中Hg的分布特征表明,并不是所有的活动性断裂都有高含量的Hg释放。具有较高含量的幔源CO_2和Hg释放是红河断裂的两个最重要的地球化学特征。     

新疆地下热水特征及其与地震活动的关系

新疆地下热水广泛分布于昆仑山、天山和阿尔泰山。温泉和地震活动与大地构造、板块运动有着密切的联系。动态观测资料分析表明,热水温度变化不仅受到地震的作用,而且显示出某些地震前兆信息。分析了地下热水的化学成分、气体组分、微量元素、放射性元素,认为某些热水具有低矿化、高碱性、高氟、高氦等独特性质,有可能是形成于地壳深部或上地幔的深成水     

综合地球物理勘探在齐齐哈尔地区低温地热系统调查中的应用——以HLD1井为例

随着我国"蓝天保卫战"打响,以及快速经济社会发展对清洁能源的需求急剧增加,地热资源因资源量巨大、分布广泛、清洁、可再生、利用率较高等优点,逐渐成为人们关注的热点.本文针对齐齐哈尔龙安桥地区的地热资源开展综合地球物理调查研究,方法包括有可控源音频大地电磁测深、大地电磁测深与反射地震勘探,通过对地热能控热要素——盖层、热储层、热源与导热通道的综合分析,查明了控热要素的空间配置关系,确立了该地区地热系统的成因模式,为该区低温地热资源调查提供有益的指导.通过研究发现,盖层主要为白垩系嫩江组与明水组的泥岩层,盖层厚度大,其中以嫩江组为主的低阻盖层主体埋深范围620 ～ 1020 m;热储层主要为白垩系泉头组、青山口组和姚家组的砂岩层,热储层厚度中等,主要埋深范围1050～ 1350 m;热源——盆地下部与基底的花岗岩、花岗斑岩等酸性岩体富含放射性元素,其衰变生热,以及下部幔源热向上热传导产生的热量;导热通道为热储层内部及下部断裂构造,这些断裂为热量的传导及热液的运移提供了运输通道.最后提出了该区的低温地热系统的成因模式为"层控热盖热储-岩体放射生热与地幔热共同供热-热传导与断裂通道共同导热"的热水系统成因模式.     

新疆地下水热水特征及其与地震活动的关系

新疆地下热水广泛分布于昆仑山,天山和阿尔泰册。温泉和地震活动与大地构造,板块运动有着密切的联系。动态观测资料分析表明,热水温度变化不仅受到地震的作用,而且显示出某些地震前兆信息。分析了地下热水的化学成分,气体组分,微量元素,放射性元素,认为某些热水具有低矿化,高碱性,高氟,高氦等独特性质,有可能是形成于地壳深部或上地幔地深成水。     

京北地区热水水文地球化学特征与地热系统的成因模式

京北地热田包括小汤山和沙河2个次级地热田,呈三角形展布,东南部边界为黄庄-高丽营断裂,西南部边界为南口-孙河断裂,北部边界为阿苏卫-小汤山断裂。热储层为蓟县系雾迷山组、铁岭组和寒武系—奥陶系碳酸盐岩岩溶裂隙含水层,热储盖层为青白口系页岩、石炭系—二叠系砂页岩和侏罗系火山岩隔水层。该地热田地温场的平面特征是在小汤山镇和汤11井区出现2个高温区;垂向特征是随埋深加大,地温升高,但热储层内垂向增温率较低,热储盖层垂向增温率较高。该区雨水、地下冷水和热水的氢氧同位素组成基本上都落在克雷格降水线上,表明区内热水来源于大气降水。在地下水化学三线图解中,该区热水位于城区热水的下方,说明京北热水比城区热水更靠近冷水补给区。热水的3H值表现出北高南低的特点,14C年龄也由北往南逐渐增大,说明热水自北向南流动。由此认为,由北部山区渗入地下的大气降水,经小汤山以北的十三陵—桃峪口岩溶水分布区,跨过阿苏卫-小汤山断裂后发生深循环并被地热加温,流入京北地区后在该地区赋存,形成热田。根据上述特征,建立了京北地热田地热系统的成因模式并定义为京北中低温对流型地热系统     

区域地震活动与西安地区地下热水活动相关性的研究

根据西影井热水水位的观测资料,分析了区域地震活动与西安地区地下热水活动的相关性,结果表明西安地区地下热水活动与区域地震活动明显相关;西安地区地下热水活动与西安及邻区的地震活动最为密切,表明它们均受长安-临潼活动断裂的控制,西安市抽取地下热水的影响范围主要局限于西安及邻区,即临潼-长安活动断裂的展布区.     

利用合成地震图研究东北地区壳幔介质结构

本文采用计算合成地震图与分布在东北地区的11个地震台记录的深源远震波形对比分析的方法,研究该区壳幔结构.结果表明,东北地区地下100km 以上壳幔介质为分层结构,并存在有低速层.莫霍界面较清晰.地壳厚度在31.8——35.8km 之间.      

长白山天池火山地热区逸出气体的物质来源

根据天池火山地热区逸出气体的化学成分和稳定同位素组成,讨论了这些气体的物质来源.提出该区逸出气体主要源自壳内幔源岩浆残留体;长白地热区可能与古火山喷发通道相连,其下方有一稳定的地热水和深源气储库,储库热水温度约(166±9)℃;锦江地热区逸出气体可能是通过活动构造带快速由深部向地表迁移的.     

腾冲热海地区现代幔源岩浆气体释放特征

详细讨论了腾冲热海地区逸出气体的化学和氦、碳同位素组成及其在地表的分布特征结果表明,该区地壳浅部存在幔源岩浆侵入活动;现代幔源岩浆挥发组分通过活动断裂带源源不断地向外释放,其主要成分是ＣＯ_２,还有少量的Ｈｅ,Ｈ_２,ＣＨ_４,Ｈ_２Ｓ和ＣＯ等．研究区内南北向断裂最深,它可能与得到幔源岩浆挥发组分直接补充的深部热储直接相通．逸出气体的氦、碳同位素组成特征指示,现今在热海地区壳内活动的幔源岩浆与导致区内最新火山喷发的幔源岩浆之间可能存在着渊源和继承关系．     

Implementation and verification of a masonry panel model for nonlinear dynamic analysis of infilled RC frames

The effect of infill panels on the response of RC frames subjected to seismic action is widely recognised and has been subject of numerous experimental investigations, while several attempts to model it analytically have been reported. In this work, the implementation, within a fibre-based Finite Elements program, of a double-strut nonlinear cyclic model for unreinforced masonry panels is carried out. The adequacy of the model in predicting the cyclic/seismic response of multi-storey infilled reinforced concrete frames is then verified through comparisons against experimental results.     

Estimating permeability from field measurements of seismic attenuation in fractured chalk

Broadband (100–4000 Hz) cross‐hole seismic data have been acquired at a borehole test site where extensive hydrological investigations have previously been performed, including in situ estimates of permeability. The rock type is homogeneous chalk and fractures and bedding planes have been identified from well logs. High values of seismic attenuation, Q= 22 ≤ 27 ≤ 33, were observed over a 10 m depth interval where fracture permeability values of 20–50 darcy had been recorded. An attempt has been made to separate the attenuation due to scattering and intrinsic mechanisms. The estimated values of intrinsic attenuation, Q= 31 ≤ 43 ≤ 71, have been reproduced using a number of current theories of seismic‐wave propagation and fluid‐flow‐induced seismic attenuation in cracked and fractured media. A model that considers wavelength‐scale pressure gradients is the preferred attenuation mechanism. Model parameters were obtained from the hydro‐geological and seismic data. However, we conclude that it is not possible to use seismic Q to measure rock permeability remotely, principally because of the inherent uncertainties arising from model parameterisations.     

Seismic safety of high concrete dams

China is a country of high seismicity with many hydropower resources. Recently,a series of high arch dams have either been completed or are being constructed in seismic regions,of which most are concrete dams. The evaluation of seismic safety often becomes a critical problem in dam design. In this paper,a brief introduction to major progress in the research on seismic aspects of large concrete dams,conducted mainly at the Institute of Water Resources and Hydropower Research(IWHR) during the past 60 years,is presented. The dam site-specific ground motion input,improved response analysis,dynamic model test verification,field experiment investigations,dynamic behavior of dam concrete,and seismic monitoring and observation are described. Methods to prevent collapse of high concrete dams under maximum credible earthquakes are discussed.     

海域天然气水合物的地震研究进展

海域天然气水合物的地震研究是在岩石物性分析成果的指导下，用地震技术进行真假BSR的识别和含水合物沉积层物性预测.海域天然气水合物地震研究的进展主要表现在：物性分析理论模型由简单模型发展到最大程度模拟实际情况的复杂模型；地震勘探方法已由常规的单道、多道地震发展到多频地震、高分辨率二维、三维地震和海底多分量地震；地震资料处理由常规处理发展到突出BSR特征的“三高”和叠前时间偏移处理；从利用速度、振幅结构研究识别天然气水合物发展到AVO、多属性判别、多弹性参数和多物性参数反演识别天然气水合物、预测其物性参数.这些新技术、新方法的应用，加快了海域天然气水合物调查进度，提高了天然气水合物地球物理识别的可靠性.     

Direct migration of ambient seismic data

Utilising ambient seismic energy naturally propagating in the Earth as an alternative approach to active body-wave seismic investigations has been a topic of interest for a number of decades. However, because ambient surface-wave arrivals typically are of much greater amplitude than ambient body-wave energy, significant data signal processing and long recording times are required to mitigate this and other coherent noise sources, and to correlate sufficient reflected body-wave energy to converge to a stable image. Even for these scenarios, identifying and validating imaged body-wave reflection events remain challenging. In active-source investigations, extended imaging condition gathers are used to examine velocity (in)accuracy. Herein, we develop an ambient direct migration approach that uses a novel ambient (deconvolution) extended imaging condition. We simulate synthetic ambient-wavefield seismic data for two different models and use a field data set from Lalor Lake in Manitoba, Canada, to conduct a series of numerical experiments to demonstrate the velocity sensitivity and long-term stationarity of ambient-wavefield seismic data in the migration image domain. Tests with varying global velocity perturbations show a characteristic reflector moveout in deconvolution extended imaging condition gathers that can serve as a diagnostic of reflected ambient body-wave energy. We illustrate that this imaging formalism, under idealised circumstances, gives comparable results to conventional seismic methods, which extends the use of extended imaging condition gather-based image validation to ambient-wavefield seismic data scenarios. We assert that this may be a valuable tool for the validation of ambient migration techniques that to date have yielded largely inconclusive results.     

我国绝对重力观测技术应用研究与展望

简要介绍了近年来运用高精度绝对重力仪,开展和建立我国2-5×10-8ms-2精度的绝对重力基准和绝对重力网工作;回顾了近年来中国学者利用绝对重力观测技术在地壳运动、地震监测与预报及地球动力学等研究方面所取得的成就;并探讨了未来进一步的应用前景.     

A comparison of cross-hole electrical and seismic data in fractured rock

Cross‐hole anisotropic electrical and seismic tomograms of fractured metamorphic rock have been obtained at a test site where extensive hydrological data were available. A strong correlation between electrical resistivity anisotropy and seismic compressional‐wave velocity anisotropy has been observed. Analysis of core samples from the site reveal that the shale‐rich rocks have fabric‐related average velocity anisotropy of between 10% and 30%. The cross‐hole seismic data are consistent with these values, indicating that observed anisotropy might be principally due to the inherent rock fabric rather than to the aligned sets of open fractures. One region with velocity anisotropy greater than 30% has been modelled as aligned open fractures within an anisotropic rock matrix and this model is consistent with available fracture density and hydraulic transmissivity data from the boreholes and the cross‐hole resistivity tomography data. However, in general the study highlights the uncertainties that can arise, due to the relative influence of rock fabric and fluid‐filled fractures, when using geophysical techniques for hydrological investigations.     

Estimation of the behavior factor of existing RC-MRF buildings

In recent years, several research groups have studied a new generation of analysis methods for seismic response assessment of existing buildings. Nevertheless, many important developments are still needed in order to define more reliable and effective assessment procedures. Moreover, regarding existing buildings, it should be highlighted that due to the low knowledge level, the linear elastic analysis is the only analysis method allowed. The same codes (such as NTC2008, EC8) consider the linear dynamic analysis with behavior factor as the reference method for the evaluation of seismic demand. This type of analysis is based on a linear-elastic structural model subject to a design spectrum, obtained by reducing the elastic spectrum through a behavior factor. The behavior factor (reduction factor or q factor in some codes) is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural capacities. The behavior factors should be defined based on several parameters that influence the seismic nonlinear capacity, such as mechanical materials characteristics, structural system, irregularity and design procedures. In practical applications, there is still an evident lack of detailed rules and accurate behavior factor values adequate for existing buildings. In this work, some investigations of the seismic capacity of the main existing RC-MRF building types have been carried out. In order to make a correct evaluation of the seismic force demand, actual behavior factor values coherent with force based seismic safety assessment procedure have been proposed and compared with the values reported in the Italian seismic code, NTC08.     

Seismic studies of piip crater break-through

To establish the structure of volcanic vents in adventive craters, seismic studies have been carried out on Piip crater break-through formed in October–December 1966 on the northern flank of Kliuchevskoi volcano. The studies were carried out by refraction method on longitudinal and nonlongitudinal profiles. An approximate seismic section has been obtained together with several refracting horizons. An injection area of magmatic melt is established and its size in plan is 100×40 m, which is identified with the upper part of the channel feeding Piip break-through with magma. By parametric measurements on an incandescent lava flow the longitudinal wave velocitiesV=750?850 m/sec have been computed. Special investigations established an area of microearthquakes located on the northern extension of explosion funnel line.     

Paleoseismological investigations in the pleistoseismal zone of the 1885 Belovodskoe earthquake,North Tien Shan

The results of paleoseismological investigations to find the epicentral area of the Belovodskoe earthquake are presented. New data on prehistoric earthquakes have been obtained resulting from a seismic deformation study using trenching. It is found that seismic dislocations during the reactivation of the fault by the 1885 earthquake did not extend east of the Sokuluk River. In addition, the age and kinematic features of a paleoearthquake located in the area between the Sokuluk and Alamedin rivers are specified. This earthquake occurred in the interval of 887–1533 cal BC and was no less than 7.1 in magnitude. The minimal estimated earthquake source length is 32 km and the reverse-fault amplitude is 3.8 m.