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81.
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
82.
83.
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
84.
We present a new 2-D analytical solution of the fourth-order differential equation, which describes the flexure of a thin elastic plate.
The new analytical solution allows the differential equation for an elastic plate to be solved for any irregular shaped topography with a high spatial resolution. We apply the new method to the Central Andes. The flexural rigidity distribution calculated by this technique correlates well with tectonic units and the location of fault zones, for example, the Central Andean Gravity High correlates with the presence of a rigid, high-density body. 相似文献
The new analytical solution allows the differential equation for an elastic plate to be solved for any irregular shaped topography with a high spatial resolution. We apply the new method to the Central Andes. The flexural rigidity distribution calculated by this technique correlates well with tectonic units and the location of fault zones, for example, the Central Andean Gravity High correlates with the presence of a rigid, high-density body. 相似文献
85.
86.
Young Hong Shin Houze Xu Carla Braitenberg Jian Fang Yong Wang 《Geophysical Journal International》2007,170(3):971-985
87.
松辽盆地深部反射地震探查 总被引:14,自引:4,他引:14
概述了近年来用近垂直反射地震方法研究不同大地构造单元的地壳结构和深部构造问题所取得的基本成果,说明了在松辽盆地内所进行的两次深反射地震探查,包括位置、科学目标、资料采集、处理技术和基本结果,利用延长排列所得到的约42km长共炮点资料,求出松辽盆地地壳平均速度约为6.197km/s。通过初步解释,认为在上部地壳存在多组低角度断裂、中下部地壳构造具有更为复杂的震相、Moho震相比较清晰,多处出现与Moho震相斜交的震相。 相似文献
88.
利用中国陆地 10条GGT地球物理资料编制中国岩石圈篱笆图 ,并加以说明。通过对地球物理特征和地质学分析 ,认为以大兴安岭—太行山—武陵山重力梯级带和青藏高原周边重力梯级带为界 ,可把中国陆地划分 3个岩石圈构造单元。中国陆壳既有三分结构也存在二分结构 ;对地壳中存在的低速带、高导带和天然地震带进行了划分。以大兴安岭—太行山—武陵山重力梯级带为界 ,两侧盆地具有不同的地球物理特征 ,这些特征与构造运动、均衡调整过程有关。莫霍面几乎遍布全国 ,它具有内部结构。下部地壳底部存在的地球物理异常与莫霍面有关 ,也可能与岩石圈地幔的变化有关。 相似文献
89.
缅北中部,印缅岛弧及弧后盆地东侧、新生代造山带的前缘推覆构造带中,分布有许多脉金矿床及矿点,构成金矿带。矿带、矿田、矿床及矿体的形成、分布及其规模,受不同级别的近南北向逆冲断裂,及其间派生的北东向张性扩容断裂组成的剪切断裂带控制。可渗透的下麦尔组下部中一粗粒砂岩,起着很好的容矿作用。下麦尔组上部泥岩、细砂岩、粉砂岩和页岩互层单元,在携金热液的迁移、氧化硅的沉淀和矿质沉积定位等方面,可能起到圈闭作用。 相似文献
90.
Jake Hancock 《Cretaceous Research》2001,22(6):677
The Aptian/Albian boundary, as currently placed, presents problems which have not yet been solved and possibly never will be. No detailed definition of recent years can be applied on a world-wide scale, which will be needed for any definition acceptable to the Subcommission on Cretaceous Stratigraphy. The only satisfactory and workable solution is to choose a completely new position. It is suggested that this should be at the base of the Zone of Lyelliceras lyelli. This would change the start of the Albian from appproximately 112 Ma to 109 Ma but it would be a standard which should be recognizable on all five continents. 相似文献