重磁异常正反演可视化实时方法技术改进

摘 要 给出了2∙5D 多边形截面棱柱体重磁异常的简化表达式及其偏导数;提供了实用的可 视化模型建立、修改、实时正反演中的一些具体方法技术。借助这一操作方便、功能强大的 图形化实时反演系统‚资料解释工作者可以综合利用各种地质资料对计算过程实现引导和控 制‚使其解释思想及技术方案得到充分体现‚从而提高计算速度和质量。     

重力异常视深度滤波及应用

为了解观测面以下位场场源体产生的异常,设计了一种波数域的滤波器,该滤波器可在无需岩石物性资料的前提下用于位场数据的反演．对位场资料用解析法和差分法上、下延拓,以消除浅表干扰源的影响,并最后下延至观测面以下,根据下延后场的极值确定场源的质心深度．理论模型的试算和实际资料的处理均获得了令人满意的效果．     

The study on the interannual variation and the mechanism of the south china sea monsoon

l.Intr0ductionTheonset0ftheSouthChinaSea(SCS)monsoonisasignofthecomingoftheAsianmonsoon.Inaverage,theonsetoftheSCSmonsoonisinthemiddleofMay,butitsstrengthandtheonsetdatediffergreatlyfromoneyeartoanother.TheanomaliesoftheSCSmon-soonhighlydePendonnotonIytheprecipitationinSCS,butalsotheanomaliesofthecircu-lationintheworld.WhyisthemonsoononsetearliestinSCS?Whatisthemechanismoftheonsetanditsvariation?Thisisascientificproblemthatisinterestedinbymeteorologistsbothathomeandabroad.TaoandChen…     

山西五台山地区照山一带基岩地球化学异常特征研究

本文通过五台山地区典型地段—照山一带基岩地球化学测量及异常特征的研究 ,并结合区域地质、构造等特征的综合分析 ,提出Au、Ag、Cu、Bi、As为区域金 (铜 )矿地球化学勘查的最佳指示元素组合 ;确定出三个较为重要的矿化带 (区 ) :一个是下龙宿沟—上龙宿沟铜—金矿化带 ,另一个是土岭铁建造金矿化带 ,第三个是台峪口金异常区 ;金矿化的形成受条带状铁建造的发育程度以及区域变质变形作用过程中热流体活动的叠加改造等共同制约。     

Structure of Réunion Island (Indian Ocean) inferred from the interpretation of gravity anomalies

Réunion is a volcanic edifice whose origin is related to a hot spot in the Indian Ocean. Only 3% of its volume is emergent. Many geological and geophysical studies were carried out on Réunion Island during the 1980's but few of them allow study of the internal structure of the edifice. Several gravity surveys have been carried out on the island since 1976 and we have compiled the available data set. The lack of data on the western side of the island led us to conduct a regional survey in 1993 to obtain a more homogeneous distribution of the stations. Computation of Bouguer anomalies for different correction densities accounts for the variable density of the rocks constituting the edifice and provides a distribution of gravity anomalies interpreted as dense bodies of intrusive rocks inside the edifice. Two very large intrusive complexes can be unambiguously recognised: one beneath Piton des Neiges and one beneath the Grand Brûlé area. Both have been penetrated by geothermal exploration drill holes and the first is also known from outcrop observations. 2.5D simple models were constructed to reveal the geometry and extent of the buried intrusives. They are deeply rooted, extending several kilometres below sea level, and extensive (20–25 km long and 10–13 km wide for the Piton des Neiges complex, 12–15 km long and some kilometres wide for the Grand Brûlé complex). The development of such complexes implies that the activity of the two volcanic centres was long lasting and remained stable while the volcanoes were growing. The Grand Brûlé complex has been interpreted as relics of an old volcano named Alizés Volcano. The interpretation of the gravity maps suggests the presence of a ridge of dense rocks to the North of the axis joining the centres of Piton des Neiges and Piton de la Fournaise volcanoes. By analogy with the other structures, 2.5D models show that this structure would culminate between 0 and 1 km below sea level and be 15 km wide. This complex induces a maximum anomaly in Takamaka Valley and we thus propose to name it Takamaka Volcano. No geological evidence of the nature of these dense rocks is available but the ridge coincides with structures revealed by magnetic and seismic data. Interpretation of the Bouguer anomaly maps suggests that the inner gravity structure of Piton de la Fournaise is not characterised by the presence of a voluminous dense body but probably by more restricted concentrations of dense rocks. Some structures can be recognised: along the present NE and SE rift zones and in the previous central part of Piton de la Fournaise to the West of the present summit. The recent eastward migration of the centre of activity of Piton de la Fournaise accounts for the lack of a large positive anomaly beneath the active craters.     

基于密集台阵的青藏高原东北缘地壳精细结构及九寨沟地震震源区结构特征分析

基于青藏高原东北缘密集宽频带野外流动观测台阵以及固定台站资料,利用双差层析成像方法对地震位置和研究区的地壳速度结构进行了反演.最终用于联合反演的地震事件合计9644个.结果显示青藏高原东北缘速度结构具有明显的横向不均匀性.从整体上看,青藏高原地区表现为低速异常,鄂尔多斯表现为高速异常,而扬子地块亦表现为高速异常.不同深度处速度结构表现不一致,同一深度处P波速度结构和S波速度结构也有明显差异.由西秦岭北缘断裂带、临潭-宕昌断裂以及礼县-罗家堡断裂围限的地震活动强烈的区域中,P波速度结构由深度0 km时呈现的低速异常,逐渐过渡到5 km时高低速相间分布的特征;而S波速度结构在此区域中,由近地表0 km时高低速相间分布的特征,逐渐过渡到30 km时几乎表现为低速异常.2017年8月8日九寨沟7级地震所在的塔藏断裂、岷江断裂和雪山断裂围限区域,在深度20 km处的P波速度结构和周围存在明显差异,九寨沟地震处于高速异常与低速异常的过渡带内.此外,2013年7月22日发生在青藏高原东北缘的岷漳县6.6级地震,震源区所在的临潭-宕昌断裂附近的P波速度结构在15 km深度处也有明显特征,震源位置所在区域也处于高低速过渡带.该区域这种地壳内部高低速过渡带可能是应力比较容易积累而发生中强地震的一个重要场所.     

Characterisation and multifaceted anisotropy assessment of Corvio sandstone for geological CO2 storage studies

We present a comprehensive characterisation of the physical, mineralogical, geomechanical, geophysical, and hydrodynamic properties of Corvio sandstone. This information, together with a detailed assessment of anisotropy, is needed to establish Corvio sandstone as a useful laboratory rock‐testing standard for well‐constrained studies of thermo–hydro–mechanical–chemical coupled phenomena associated with CO₂ storage practices and for geological reservoir studies in general. More than 200 core plugs of Corvio sandstone (38.1 and 50 mm diameters, 2:1 length‐to‐diameter ratio) were used in this characterisation study, with a rock porosity of 21.7 ± 1.2%, dry density 2036 ± 32 kg m^?3, and unconfined compressive and tensile strengths of 41 ± 3.28 and 2.3 ± 0.14 MPa, respectively. Geomechanical tests show that the rock behaves elastically between ～10 and ～18 MPa under unconfined conditions with associated Young's modulus and Poisson's ratio of 11.8 ± 2.8 GPa and 0.34 ± 0.01 GPa, respectively. Permeability abruptly decreases with confining pressure up to ～10 MPa and then stabilises at ～1 mD. Ultrasonic P‐ and S‐wave velocities vary from about 2.8–3.8 km s^?1 and 1.5–2.4 km s^?1, respectively, over confining and differential pressures between 0.1 and 35 MPa, allowing derivation of associated dynamic elastic moduli. Anisotropy was investigated using oriented core plugs for electrical resistivity, elastic wave velocity and attenuation, permeability, and tracer injection tests. Corvio sandstone shows weak transverse isotropy (symmetry axis normal to bedding) of <10% for velocity and <20% for attenuation.     

Analysis of Gravity Changes before and after the Akto MS6.7 Earthquake in 2016

This paper analyzes the characteristics of time sequence changes of gravity points near the epicenter, different changes of measuring lines and gravity changes of measuring areas in point-line-area manner respectively with the 5-period mobile gravity data through densified observation by the South Xinjiang Observation Network after the 2015-2016 Akto earthquake in Xinjiang. The gravity observation results before the earthquake indicate that the Wuqia-Bulungkol area near the epicenter presented the trend of gravity value increasing since 2015, but the gravity value decreased half a year before the earthquake, and witnessed a high gradient zone of gravity changes during some periods before the earthquake. The gravity observation results after the earthquake show that there is a trend of opposite changes in gravity difference on the northern and southern sides of Bulunkou, and good correspondence exists between the characteristics of gravity field changes near the epicenter before and after the earthquake and the geologic structure distribution in the area.     

内蒙古呼伦西白地区铌稀土多金属矿成矿特征及找矿标志

北山成矿带东缘的内蒙古呼伦西白地区近年来发现了多处铌稀土矿床(点),矿床(点)产于二叠纪二长花岗岩外接触带上,矿体赋存于滨浅海相碳酸盐岩-变碎屑岩内,其形态、产状、规模受构造-岩浆活动控制,并与磁异常对应,其中灰石山东北铌稀土矿区Nb2O5品位0.02%～0.56%、平均0.11%,REO品位0.13%～2.63%,平均0.93%,辉森乌拉西铌金矿区Nb2O5品位0.01%～0.1%,与白云鄂博Nb-REE-Fe超大型矿床特征类似,成矿潜力巨大。结合区域地质背景及铌稀土多金属矿成矿特征,初步认为区内该类型矿床的找矿标志为:二叠系滨浅海相碳酸盐岩-变碎屑岩地层、构造挤压形成的虚脱空间或韧-脆性转换部位、二叠纪二长花岗岩外接触带、放射性异常梯度带-磁异常位置、岩石蚀变(褐铁矿化、硅化、碳酸盐化等)和石英细网脉发育地段。对该地区铌稀土多金属矿成矿特征和找矿标志的研究有利于拓展北山地区三稀矿产的找矿思路,也可为此类矿产的找矿方向提供借鉴。     

北太平洋混合层深度异常及其与中国夏季降水的关系

利用GODAS逐月混合层深度(mixed layer depth,MLD)资料和中国160站逐月降水资料,分析了北太平洋MLD多年平均气候及异常特征,进一步研究了其对中国夏季降水年际异常的影响.结果表明:1)北太平洋30 ～ 40°N之间混合层最深,冬、春季明显大于夏、秋季.2)日期线附近的北太平洋中部海域是各季MLD年际异常共同最显著区域;仅夏季MLD年际异常与ENSO存在一定关系;秋、冬和春季MLD还存在明显年代际异常特征.3)当前冬北太平洋西部及中部MLD加深时,次年黄河下游部分地区、黄淮、江淮及长江以南大部分地区(广西南部除外)降水将偏少;河套地区、内蒙东部及东北大部降水可能偏多.