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991.
胶莱盆地白垩纪构造应力场与转换机制 总被引:14,自引:3,他引:14
通过对胶莱盆地断层滑动矢量的收集与测量,利用计算机程序反演了盆地白垩纪的古构造应力场演化历史,并据此将盆地的发育划分为三个伸展阶段和三个挤压反转阶段,分别为早白垩世早-中期莱阳期伸展,与造山期后应力松弛重力坍塌有关;早白垩世中-晚期青山期伸展,受早白垩纪早期以后广泛的岩石圈减薄、大陆裂陷制约;晚白垩世王氏期伸展,与郯庐断裂及牟平-即墨断裂右旋走滑有关。三期伸展之间存在构造挤压反转,最后阐明各期盆地发育的地球动力学背景。 相似文献
992.
Link between convection and meridional gradient of sea surface temperature in the Bay of Bengal 总被引:2,自引:0,他引:2
We use daily satellite estimates of sea surface temperature (SST) and rainfall during 1998–2005 to show that onset of convection
over the central Bay of Bengal (88–92°E, 14–18°N) during the core summer monsoon (mid-May to September) is linked to the meridional
gradient of SST in the bay. The SST gradient was computed between two boxes in the northern (88–92°E, 18–22°N) and southern
(82–88°E, 4–8°N) bay; the latter is the area of the cold tongue in the bay linked to the Summer Monsoon Current. Convection
over central bay followed the SST difference between the northern and southern bay (ΔT) exceeding 0.75°C in 28 cases. There was no instance of ΔT exceeding this threshold without a burst in convection. There were, however, five instances of convection occurring without
this SST gradient. Long rainfall events (events lasting more than a week) were associated with an SST event (ΔT ≥ 0.75°C); rainfall events tended to be short when not associated with an SST event. The SST gradient was important for the
onset of convection, but not for its persistence: convection often persisted for several days even after the SST gradient
weakened. The lag between ΔT exceeding 0.75°C and the onset of convection was 0–18 days, but the lag histogram peaked at one week. In 75% of the 28 cases,
convection occurred within a week of ΔT exceeding the threshold of 0.75°C. The northern bay SST, T
N
, contributed more to ΔT, but it was a weaker criterion for convection than the SST gradient. A sensitivity analysis showed that the corresponding
threshold for T
N
was 29°C. We hypothesise that the excess heating (∼1°C above the threshold for deep convection) required in the northern
bay to trigger convection is because this excess in SST is what is required to establish the critical SST gradient. 相似文献
993.
994.
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. 相似文献
995.
2-D Crustal thermal structure along Thuadara-Sindad DSS profile across Narmada-Son lineament,central India 总被引:1,自引:0,他引:1
Central India is traversed by a WSW-ENE trending Narmada-Son lineament (NSL) which is characterized by the presence of numerous
hot springs, feeder dykes for Deccan Traps and seismicity all along its length. It is divided in two parts by the Barwani-Sukta
Fault (BSF). To the west of this fault a graben exists, whereas to the east the basement is uplifted between Narmada North
Fault (NNF) and Narmada South Fault (NSF). The present work deals with the 2-D thermal modeling to delineate the crustal thermal
structure of the western part of NSL region along the Thuadara-Sindad Deep Seismic Sounding (DSS) profile which runs almost
in the N-S direction across the NSL. Numerical results of the model reveal that the conductive surface heat flow value in
the region under consideration varies between 45 and 47mW/m2. Out of which 23mW/m2 is the contribution from the mantle heat flow and the remaining from within the crust. The Curie depth is found to vary between
46 and 47 km and is in close agreement with the earlier reported Curie depth estimated from the analysis of MAGSAT data. The
Moho temperature varies between 470 and 500°C. This study suggests that this western part of central Indian region is characterized
by low mantle heat flow which in turn makes the lower crust brittle and amenable to the occurrence of deep focused earthquakes
such as Satpura (1938) earthquake. 相似文献
996.
C. Panneerselvam C. Selvaraj K. Jeeva K. U. Nair C. P. Anilkumar S. Gurubaran 《Journal of Earth System Science》2007,116(3):179-186
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. 相似文献
997.
福建尤溪梅仙矿田铅锌银矿床特征及找矿方向 总被引:1,自引:0,他引:1
梅仙矿田铅锌银矿是福建省目前已发现规模最大的铅锌矿产地。自上世纪90年代以来,矿田内陆续发现和评价了丁家山、峰岩2处大型规模的铅锌矿床。矿床产于闽中裂谷带中新元古代东岩组绿片岩中,属块状硫化物型矿床。 相似文献
998.
渗漏是严重影响堤坝安全的主要形式,确定渗漏通道的位置是进行堤坝渗漏整治的前提和基础。温度场探测堤坝渗漏的研究是其中一种较便捷的方法,但是在理论上还需要进一步完善。在库水和地下水存在着温度差异的基础上,考虑堤坝发生集中渗漏后,渗漏通道中的地下水与周围土体进行热量交换,造成渗流通道附近地层温度发生改变,建立起温度场对渗漏通道的反演模型。在前人研究的基础上,考虑地温梯度的影响,可以建立有集中渗漏通道影响下的二维热传导方程,进而以现场测井的温度数据作为边界条件,对泛定方程进行求解,最终得到渗漏通道的位置。计算结果和实测结果的对比表明,通过温度场反推渗漏通道参数的方法是可行的。 相似文献
999.
温度植被干旱指数(TVDI)在复杂山区干旱监测的应用研究 总被引:11,自引:1,他引:11
对地观测卫星(EOS)中分辨率成像光谱仪(MODIS)传感器因具有高时间分辨率、高光谱分辨率、适中的空间分辨率等特点,非常适合大范围、长时期、动态的干旱监测。本文选取云南省红河州地区为研究对象,利用MODIS植被指数和陆地表面温度产0品建立高原多山地区NDVI- T_s空间,并由此建立了复杂山区的温度植被干旱指数(TVDI)。利用该方法检测2006年3、4两个月的云南省红河地区的地表干旱情况,同时结合当地气象局信息和野外同步观测的表层土壤温度、湿度数据对该指标进行定量验证,结果表明,TVDI与土壤湿度显著相关,该方法可以用来对大区域干旱进行检测,能很好的用于山区的干旱预警与监测。 相似文献
1000.
1961-2004年乌鲁木齐城市化过程中的冷化效应 总被引:4,自引:2,他引:4
利用乌鲁木齐和达坂城1961-2000年月平均气温,2001-2004年月平均最低气温和月平均最高气温资料,分析了乌鲁木齐和达坂城两地平均温Tm、平均最高温Tmax、平均最低温Tmin及其对应值的差值(ΔTu-rm、ΔTu-rmax、ΔTu-rmin)随时间的变化趋势特征。结果表明,乌鲁木齐城市化过程中冷化效应和热岛效应同时存在。近40多年来,乌鲁木齐年Tmm、Tmax有微弱的下降趋势,春季、夏季Tm、Tmax、Tmin和秋季Tm、Tmax均呈下降趋势,以夏季最为显著,而冬季Tm、Tmax、Tmin呈上升趋势;乌鲁木齐和达坂城之间年、春季、夏季和秋季ΔTu-rm、ΔTu-rmax、ΔTu-rmin均呈显著的下降趋势,冬季气温差值显著上升。降水量的增加、城市绿化和城市灌溉面积的增大,可能对乌鲁木齐城市化过程中的气候冷化产生了影响。 相似文献