给定内插高程异常值的精度时对GPS水准网格间距的考虑   总被引：7，自引：0，他引：7  

陈俊勇 《测绘学报》2003,32(2):130-133

在已布设GPS水准网的地区，若需内插其中任意一点的高程异常值时，应该了解该内插值的精度。导出了该内插点高程异常值的精度评定方法，并具体给出在我国C级GPS水准网中，该内插点高程异常推估值精度和该地区的地形和栅格重力异常分辨率的数学关系式和实例。在给定内插点高程异常值精度的局域大地水准面时，按不同地形和栅格重力异常分辨率的密度，根据这些数学关系式，可以设计间距合理的B级或C级GPS水准网。  相似文献   

Study of Aeromagnetic Data Over Part of Eastern Ghat Mobile Belt and Bastar Craton     

S.P. Anand  Mita Rajaram   《Gondwana Research》2003,6(4):859-865

A portion of the aeromagnetic anomaly map of India, from 17⁰ to 20⁰ N and 78^o to 84^o E has been analysed to understand the tectonics of the region. The distribution of magnetic sources in the study region are clearly brought out in the analytic signal map and found to be associated with charnockitic rocks, iron formation and trap flows. The Godavari Graben is devoid of any magnetic sources. High-grade charnockitic rocks on surface and sub-surface, flank the shoulders of the Godavari Graben on either side. From the analysis of magnetic data, Sileru Shear Zone (SSZ) is identified as the contact of the Bastar craton and the Eastern Ghat Mobile Belt (EGMB). The Eastern Ghat is divided into two blocks: Block-N north of Srikakulam is devoid of magnetic sources while the charnockitic rocks are the main magnetic carriers in Block-S. The difference in magnetic characteristics of the two blocks has been attributed to the difference in metamorphic history. Block-N has an over print of amphibolite facies metamorphism while Block-S to the south depicts granulite facies metamorphism. The Euler solutions within the EGMB shows that the magnetic sources along SSZ is shallower than the south east implying that the exhumation process in the EGMB has a differential rate.  相似文献   

Chemical, Isotopic, and Fluid Inclusion Evidence for the Hydrothermal Alteration of the Footwall Rocks of the BIF-Hosted Iron Ore Deposits in the Hamersley District, Western Australia     

Makoto Haruna    Takahiro Hanamuro    Kaoru Uyeda    Hirokazu Fujimaki  Hiroshi Ohmoto 《Resource Geology》2003,53(2):75-88

Abstract. The petrography, chemical, fluid inclusion and isotope analyses (O, Rb-Sr) were conducted for the shale samples of the Mount McRae Shale collected from the Tom Price, Newman, and Paraburdoo mines in the Hamersley Basin, Western Australia. The Mount McRae Shale at these mines occurs as a footwall unit of the secondary, hematite-rich iron ores derived from the Brockman Iron Formation, one of the largest banded iron formations (BIFs) in the world. Unusually low contents of Na, Ca, and Sr in the shales suggest that these elements were leached away from the shale after deposition. The δ¹⁸O (SMOW) values fall in the range of + 15.0 to +17.9 per mil and show the positive correlation with calculated quartz/sericite ratios of the shale samples. This suggests that the oxygen isotopic compositions of shale samples were homogenized and equilibrated by postdepositional event. The pyrite nodules hosted by shales are often rimmed by thin layers of silica of varying crystallinity. Fluid inclusions in quartz crystals rimming a pyrite nodule show homogenization temperatures ranging from 100 to 240C for 47 inclusions and salinities ranging from 0.4 to 12.3 wt% NaCl equivalent for 18 inclusions. These fluid inclusion data give direct evidence for the hydrothermal activity and are comparable to those of the vein quartz collected from the BIF-derived secondary iron ores (Taylor et al, 2001). The Rb-Sr age for the Mount McRae Shale is 1,952 ± 289 Ma and at least 200 million years younger than the depositional age of the Brockman Iron Formation of ∼ 2.5 Ga in age. All the data obtained in this study are consistent with the suggestion that high temperature hydrothermal fluids were responsible for both the secondary iron ore formation and the alteration of the Mount McRae Shale.  相似文献   

An Unusual Texture: Skeletal Sphalerite in Pyrite from Dajing Tin-polymetallic Deposit, China     

Yu Wang Wang    Jing Bin Wang  Li Juan Wang 《Resource Geology》2003,53(1):67-72

Abstract. Skeletal sphalerite with stellar, cruciform and snowflake-like (or cauliflower-like) shapes included in pyrite is widely found in the Dajing tin-polymetallic deposit. It occurs only in chalcopyrite-pyrite mineralization stage. The compositions of all sphalerites in the chalcopyrite-pyrite stage are characterized by high Cu content (3.9 - 7.0 wt% with a mean of 5.4 wt%), while the skeletal crystal sphalerite has higher zinc and cadmium contents, and lower copper and iron contents, compared with other sphalerites of the same stage. The skeletal crystal sphalerite in pyrite is possibly generated by exsolution.  相似文献   

Pull-down basin in the central part of Japan due to subduction-induced mantle flow     

Takeshi Kudo  Koshun Yamaoka   《Tectonophysics》2003,367(3-4):203-217

The driving force for the basin subsiding against isostatic balance in and around Lake Biwa in the Kinki district, Japan is discussed. The lake region is characterized by strong negative Bouguer anomalies, especially by a steep horizontal gradient zone of gravity anomaly running along the western margin of the lake. The large negative anomaly (>50 mgal) cannot be explained by low-density sediments beneath it. A down-warping structure extending to the Moho depth should be taken into account. This conjecture has been strongly supported by a short-period receiver function imaging, which shows a clear offset of about 8 km for the Moho discontinuity under the steep gravity gradient zone.A question arises as to what is the driving force to create such a large down-warping structure. We consider that the subduction of the shallow-dipping slab under the region (Philippine Sea Slab) may cause crustal deformation by dragging the viscous mantle downward. In order to verify this model, we simulated the induced mantle flow due to the subduction of the Philippine Sea Slab and the pressure distribution on the crust–mantle boundary. This numerical experiment showed that the induced flow makes a strong negative pressure zone under the lake region if the slab has a vertical offset along the direction of subduction. This offset of the slab is consistent with plate models deduced from hypocentral distributions and Sp phases of the deep-focus earthquakes.  相似文献   

冬季北极涛动和华北冬季气温变化关系研究   总被引：33，自引：6，他引：33  

何春  何金海 《南京气象学院学报》2003,26(1):1-7

利用北极涛动指数（AOI）、NCEP／NCAR40a再分析资料中的海平面气压（SLP）、850、500、200hPa等压面高度场资料及中国160站月平均气温资料，运用小波分析，经验正交函数（EOF）分析等方法，分析了华北冬季气温和冬季北极涛动指数的变化特征及其关系。结果表明它们之间存在有着显著相关，特别是在年代际尺度上关系尤其密切。华北在20世纪70年代初以前为持续冷冬，80年代中期之后变为持续暖冬，其间相对正常，而冬季北极涛运指数亦存在类似的3个阶段，冬季北极涛动高（低）低数年，华北地区为暖（冷）冬年。其原因在于，北极涛动在于对流层低层和高层都可激发类似EU遥相关型的异常，通过影响西伯利亚高压和东亚大槽影响华北地区气温。强（弱）涛运年大气环流具有弱（强）东亚冬季风特征，西伯利亚高压减弱（增强），亚洲大陆地面东北风减弱（增强），高空东亚大槽减弱（增强）。  相似文献   

欧亚冬季雪盖异常及其与ENSO循环的关系     

王静  孙照渤 《南京气象学院学报》2003,26(1):38-46

利用 NOAA- NESDIS提供的 1 973— 2 0 0 0年北半球雪盖面积资料 ,研究了欧亚冬季雪盖的时空特征 ,发现欧亚大陆中高纬地区积雪有明显的整体性分布特征 ,而50°N以南的冬季积雪随纬度的变率较大 ;欧亚大陆中高纬地区冬季积雪呈东西反位相分布。利用小波分析发现 ,冬季欧亚积雪具有显著的 3～ 4 a周期。最后指出 ,欧亚积雪异常引起的下垫面热力异常可能为次年 El Nino事件的爆发提供触发条件。  相似文献   

2002年北半球大气环流特征及其对中国气候异常的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

艾子 《气象》2003,29(4):24-27

2002年春末夏初一次新的厄尔尼诺事件形成；1～12月北半球大气环流的主要特征表现为：中纬度地区纬向环流盛行，西太平洋副热带高压持续偏强偏西，我国大部地区气温偏高，降水呈南多北少分布；欧亚地区夏季500hPa位势高度距平场上，中高纬从西到东呈现为“ - ”分布形式，贝加尔湖地区为正距平中心，7月在贝加尔湖地区出现典型阻高；东亚夏季风偏强，南亚夏季风及热带对流指数偏弱；夏季赤道辐合带偏弱等。在上述大气环流的影响下，我国的天气气候发生了异常。  相似文献   

Geoid determination using adapted reference field, seismic Moho depths and variable density contrast   总被引：4，自引：0，他引：4  

H. A. Abd-Elmotaal  N. Kühtreiber 《Journal of Geodesy》2003,77(1-2):77-85

 The traditional remove-restore technique for geoid computation suffers from two main drawbacks. The first is the assumption of an isostatic hypothesis to compute the compensation masses. The second is the double consideration of the effect of the topographic–isostatic masses within the data window through removing the reference field and the terrain reduction process. To overcome the first disadvantage, the seismic Moho depths, representing, more or less, the actual compensating masses, have been used with variable density anomalies computed by employing the topographic–isostatic mass balance principle. In order to avoid the double consideration of the effect of the topographic–isostatic masses within the data window, the effect of these masses for the used fixed data window, in terms of potential coefficients, has been subtracted from the reference field, yielding an adapted reference field. This adapted reference field has been used for the remove–restore technique. The necessary harmonic analysis of the topographic–isostatic potential using seismic Moho depths with variable density anomalies is given. A wide comparison among geoids computed by the adapted reference field with both the Airy–Heiskanen isostatic model and seismic Moho depths with variable density anomaly and a geoid computed by the traditional remove–restore technique is made. The results show that using seismic Moho depths with variable density anomaly along with the adapted reference field gives the best relative geoid accuracy compared to the GPS/levelling geoid. Received: 3 October 2001 / Accepted: 20 September 2002 Correspondence to: H.A. Abd-Elmotaal  相似文献   

扰动重力边值问题与实际数据处理的研究   总被引：3，自引：0，他引：3  

吴晓平  李姗姗  张传定 《武汉大学学报(信息科学版)》2003,(Z1)

讨论了应用GPS测量重力点的大地高 ,从而获得地面点的扰动重力 (或称纯重力异常 )值这样新的重力边值条件 ,如何从理论与实际上确定重力场的问题。  相似文献