Triggered-lightning properties inferred from measured currents and very close electric fields

Triggered-lightning properties, including dart-leader charge density, return-stroke propagation speed, dart-leader electric potential, dart-leader propagation speed, and dart-leader current, inferred from return-stroke current and very close electric field measurements, are presented. Although most of the estimates are based on relatively crude models, they are all generally in good agreement with independent measurements and/or theoretical considerations found in the literature. The results are likely to be applicable to subsequent strokes in natural lightning.     

青藏高原腹地现今地应力测量与应力状态研究

青藏高原腹地现今构造活动强烈，为了解强烈构造活动下的应力背景，我们在五道梁、风火山、雁石坪和安多不同构造部位的四个测点采用压磁应力解除法进行了现场应力实测工作，测量深度12～20m.测量结果表明, 最大主应力方向总体为北东向，与地质、地震以及大地测量等方面的研究成果基本吻合；最大主应力量值为36～68MPa（安多测点除外），与其他地区测量结果相比，属于中等偏高；安多测点最大主应力方向为北西西向，最大主应力量值为81MPa，与其他测点有较大差别，反映了板块缝合带附近现今应力状态的复杂性.     

个旧老厂锡多金属矿田陡石阶测区断裂构造地球化学异常特征

为对研究区内可能存在的隐伏矿体进行定位预测，指导下一步找矿工作，采用构造地球化学的研究方法，对区内断裂构造地球化学异常特征进行了详细的分析研究。结果表明，本区断裂构造中，主要成矿元素Cu、Pb、Zn、Ag、Sn、Mn的空间浓度分布趋势大致呈现西(北)高东(南)低之势；元素组合异常明显，呈NE向带状展布；主要成矿元素及与成矿相关元素的异常表现出10个浓集中心。这些特点的总结和运用，对指导矿山生产和进一步找矿都具有现实意义。     

江西安远热隆基本地质特征及其铀矿远景

江西省安远-寻乌地区位于地幔隆起部位，为一热隆伸展构造区，称安远热隆。在阐述安远热隆基本地质特征和地球物理(化学)场特征的基础上，提出热隆边部火山盆地中铀矿成矿潜力较大，具有进一步勘查的意义。     

Measuring magnetic field in the 'diamagnetic' ionosphere

Satellite magnetometers sometimes pass through regions of plasma, such as the terrestrial ionosphere, where the ionization is large enough that some of the original ambient field is excluded from the plasma. This reduction of field inside the plasma region comes from the 'diamagnetic' effect of the charged particles in their helical trajectory around the magnetic field lines. The (container of the) magnetometer will exclude the plasma, and a simple-minded approach, treating the ionosphere in the same way as for a conventional diamagnetic fluid, predicts that the field seen by the magnetometer will be somewhat larger than the (reduced) field in the plasma. However, the 'diamagnetic' properties of the ionosphere are quite different from those of a conventional diamagnetic. In particular, there is a 'reflection' of the ionospheric charged particles at the surface of the magnetometer, and the overall effect is that the magnetometer does actually measure the field present in the plasma before the magnetometer is inserted. Similarly, any leakage fields from the magnetometer have no effect in the magnetosphere.     

金沙江虎跳峡成因及形成时代探讨

虎跳峡是金沙江峡谷的典型代表,其成因及形成时代涉及金沙江-长江水系发育及其环境效应问题。文中分析研究了虎跳峡附近发育的夷平面、剥蚀面、阶地等区域性的层状地貌,并认为虎跳峡上下游河谷发育历史具有一致性;从地质构造上的分析表明,虎跳峡两侧的玉龙雪山、哈巴雪山为一相对完整的地块,不存在虎跳峡大断裂,因而虎跳峡峡谷是在区域地壳抬升、先成河深切作用下而形成的。根据相关盆地沉积物、玉龙雪山的冰川发育状况、前人在附近发现的哺乳动物化石等,初步认为虎跳峡峡谷形成于中更新世。     

山东济宁组群结构大城市地下水资源评价和应急供水探讨

阐述了济宁组群结构大城市地下水资源量与开发利用现状,指出因开采地下水产生的环境地质问题,根据现有水源地的开采潜力分析,提出河里、双庙、石桥、大南铺-新驿和济宁城区水源地适宜作为应急供水水源,并采用不同方法计算了应急供水总量.当济宁市城区水源地无法供水时,在无新增供水水源的情况下,其它应急水源地的供水保证程度(按2010年规划需水量计算)为60%,可基本满足城市生活供水需求.     

发展中的板块边界:天山-贝加尔活动构造带

亚洲内陆的强地震密集地发生在天山-贝加尔一线,但该处并不存在一条连续的大断裂,学术界对这个问题的认识长期相左。文中分析了这条地震带的时空分布、分区特点、应力状态和活动周期,计算了欧亚大陆的布格重力异常场、均衡重力异常场,反演了上地幔的密度分布和剪切波速分布。发现在这个部位的70~250km的深部有一条北东向的密度、速度陡变带,它是新生代的冷地幔和热地幔的交界带,与浅部构造存在立交关系,对亚洲大陆的现今构造运动和应力场具有重要的控制作用。这个带的地震不同于传统意义上的板缘地震和板内地震,是一种因为深浅构造不同而造成的结构性地震,性质上为大陆内缘地震。文中还就深浅构造的空间立交关系、时间镜像关系进行了讨论,指出在南北地震带和伊朗东侧地震带的立交结构也与上地幔构造有关。天山-贝加尔活动构造带是正在发展中的板块边界,是大陆内部的一个典型构造,北侧为稳定的俄罗斯-西伯利亚次板块,南侧为活动的中国-东南亚次板块。     

Palynostratigraphy of the Erkovtsy field of brown coal (the Zeya-Bureya sedimentary basin)

The Erkovtsy brown coal field in the northwestern Zeya-Bureya sedimentary basin (129°–130° E, 46°–47° N) is structurally confined to southern flank of the Mesozoic-Cenozoic Belogor’e depression. The verified stratigraphic scheme of the coalfield sedimentary sequence is substantiated by palynological data on core samples from 18 boreholes sampled in the course of detailed prospecting and by paleobotanical analysis of sections in the Yuzhnyi sector of the coalfield (data of 1998 by M.A. Akhmetiev and S.P. Manchester). Sections of the Erkovtsy, Arkhara-Boguchan, and Raichikha brown-coal mines are correlated. Stratigraphic subdivisions distinguished in the studied sedimentary succession are the middle and upper Tsagayan subformations (the latter incorporating the Kivda Beds), Raichikha, Mukhino, Buzuli, and Sazanka formations.     

Fairweather atmospheric electricity at Antarctica during local summer as observed from Indian station,Maitri

Surface measurements of the atmospheric electrical parameters like Maxwell current, electric field and conductivity studied at the Indian station, Maitri (70.75° S, 11.75° E, 117 m above mean sea level), Antarctica, during austral summer have been analyzed for the years 2001 to 2004. A total of 69 days were selected which satisfied the ‘fairweather’ conditions, i.e., days with absence of high winds, drifting or falling snow, clouds, and fog effects. The diurnal variation curve of electric field and vertical current averaged for 69 fairweather days is a single periodic with a minimum at 03:00 UT and a maximum near 19:00 UT, which is very similar to the Carnegie curve. The correlation coefficient between these measured parameters has a high value (more than 0.9) for all the days. During fairweather days the measured current and field variations are similar and hence it is clear that the conductivity is more or less stable. During magnetically disturbed days, the dawn-dusk potential drop has clear influences on the diurnal variation and it modifies the conductivity. Apart from the day-to-day variation in low latitude thunderstorm activity, there are diurnal, seasonal, inter-annual variations in the electric potential and the currents, as well as solar influences on the measured parameters. This study will help us to examine the impact of solar and geophysical phenomena like solar flares, geomagnetic storms and substorms on the global electric circuit.