红河断裂带两侧地块地震震源参数研究     

叶建庆  张建国  杨晶琼  谢英情 《地震研究》2007,30(3):241-247

利用云南区域数字地震遥测台网资料,采用Brune圆位错模型对1998年12月至2006年8月云南境内M≥3地震和越南北部M>2地震测算震源参数。结果表明,红河断裂两侧活动块体的地震活动和震源参数存在较为明显的差异。就地震矩与震级的标度关系而言,滇西南块体与美国加州圣安德列斯断层和滇西实验场及其周边地区的结果一致,但与华南块体和越南北部地区有差异;从应力降的测算结果看,华南块体西缘的云南及越南北部地区的年均值为7.29MPa,滇西南块体为4.48MPa,两块体北部地震的应力降大于南部地区,应力降由北向南逐渐减小;就地震位错年均值而言,华南块体为12.3mm/a,滇西南块体为6.6mm/a。  相似文献   

1975年海城7.3级地震在朝鲜半岛的震害及对日本九州地区的影响s          下载免费PDF全文

李裕澈  秋教昇  石川有三 《地震学报》2007,29(2):214-221

1975年中国海城7.3级地震波及整个朝鲜半岛，乃至日本九州地区. 本文系统收集了该震有关资料，并通过整理分析勾画出其烈度分布，以探讨该震的震害特点. 在半岛的北部， 除局部地区为Ⅵ度之外，大部分地区为Ⅴ度区，其震害情况与相同烈度的典型特征基本相符； 半岛南部大部分地区为Ⅳ度区. 然而，韩国首尔等大城市，除高层建筑强烈振动之外，还有人出现眩晕症状等特别的感觉，个别街区变压器跳闸造成一时停电. 这些可能是大震的长周期波在远场的效应所致.   相似文献   

Variations in Melt Productivity and Melting Conditions along SWIR (70{degrees}E-49{degrees}E): Evidence from Olivine-hosted and Plagioclase-hosted Melt Inclusions   总被引：1，自引：0，他引：1  

Font  L.; Murton  B. J.; Roberts  S.; Tindle  A. G. 《Journal of Petrology》2007,48(8):1471-1494

Melt inclusion and host glass compositions from the easternend of the Southwest Indian Ridge show a progressive depletionin light rare earth elements (LREE), Na₈ and (La/Sm)_n, but anincrease in Fe₈, from the NE (64°E) towards the SW (49°E).These changes indicate an increase in the degree of mantle meltingtowards the SW and correlate with a shallowing of the ridgeaxial depth and increase in crustal thickness. In addition,LREE enrichment in both melt inclusions and host glasses fromthe NE end of the ridge are compatible with re-fertilizationof a depleted mantle source. The large compositional variations(e.g. P₂O₅ and K₂O) of the melt inclusions from the NE end ofthe ridge (64°E), coupled with low Fe₈ values, suggest thatmelts from the NE correspond to a variety of different batchesof melts generated at shallow levels in the mantle melting column.In contrast, the progressively more depleted compositions andhigher Fe₈ values of the olivine- and plagioclase-hosted meltinclusions at the SW end of the studied region (49°E), suggestthat these melt inclusions represent batches of melt generatedby higher degrees of melting at greater mean depths in the mantlemelting column. Systematic differences in Fe₈ values betweenthe plagioclase- and the olivine-hosted melt inclusions in theSW end (49°E) of the studied ridge area, suggest that theplagioclase-hosted melt inclusions represent final batches ofmelt generated at the top of the mantle melting column, whereasthe olivine-hosted melt inclusions correspond to melts generatedfrom less depleted, more fertile mantle at greater depths. KEY WORDS: basalt; melt inclusions; olivine; plagioclase; Southwest Indian Ridge  相似文献   

Cold Air Activities in July 2004 and Its Impact on Intense Rainfalls over Southwest China   总被引：1，自引：0，他引：1       下载免费PDF全文

CHEN Yan  DING Yihui 《Acta Meteorologica Sinica》2007,21(3):302-319

The severe rainfall events in the mid-summer of July 2004 and the roles of cold air in the forma- tion of heavy precipitation are investigated by using daily observational precipitation data of China and NCEP/NCAR reanalysis.The results show that the severe rainfalls in Southwest China are closely related to the cold air activities from the mid-high latitudes,and the events take place under the cooperative effects of mid-high latitude circulation and low latitude synoptic regimes.It is the merging of a cold vortex over mid-latitudes with the northward landing typhoon and eastward Southwest China Vortex,as well as the abrupt transformation from a transversal trough into an upright one that causes three large alterations of mid-high atmospheric circulation respectively in the early and middle ten days of this month.Then,the amplitude of long waves soon magnifies,leading to the unusual intrusion of cold air to low-latitude areas in the mid-summer.Meanwhile,the warm and humid southwest summer monsoon is quite active.The strong interactions of cold air and summer monsoon over Southwest China result in the large-scale convective rain- falls on the southern side of cold air. With regard to the activities of cold air,it can influence rainfalls in three prominent ways.Firstly,the incursion of upper-level cold air is often accompanied by partial southerly upper-level jet.The ascending branch of the corresponding secondary circulation,which is on the left front side of the jet center,provides the favorite dynamic upward motion for the rainfalls.Secondly,the southward movement of cold air contributes to the establishment of atmospheric baroclinic structure,which would lead to baroclinic disturbances.The atmospheric disturbances associated with the intrusion of cold air can destroy the potential instability strat- ification,release the convective available potential energy(CAPE)and finally cause convective activities.In addition,the advection processes of dry and cold air at the upper level along with the advection of humid and warm air at the lower level are rather significant for the reestablishment of potential instability in the precipitation area,which is one of the crucial factors contributing to persistent rainfalls.  相似文献   

日本90年代区域差异的现状与趋势   总被引：6，自引：2，他引：4  

贾绍凤 《地理科学进展》1998,17(3):60-68

在都道府县层次上,日本的经济区域差异已比较小。从ＧＤＰ的人均生产额来说,最高的东京都与最低的奈良县之比为３倍左右;从人均分配所得来说,最高的东京与最低的冲绳县之比只有２倍左右。所以分配的差异比生产的差异更小。但人口密度和经济密度的区域差异仍很突出。人口密度的差异达到７０多倍。经济密度的差异更达到１６０多倍。日本经济区域差异的缩小主要发生在６０、７０年代,在８０年代反而有所扩大,９０年代主要由于泡沫经济的破灭又有所缩小。在今后几年,在泡沫经济破灭、东亚经济危机等暂时因素和较高的经济发展水平、越来越注重环境和福利的价值观等长远因素的作用下,日本的区域差异还将进一步缩小。  相似文献   

Sapphirine-bearing granulites and related high-temperature metamorphic rocks from the Higo metamorphic terrane, west-central Kyushu, Japan   总被引：7，自引：0，他引：7  

Y. OSANAI  T. HAMAMOTO  O. MAISHIMA  & H. KAGAMI 《Journal of Metamorphic Geology》1998,16(1):53-66

The Higo metamorphic unit in west-central Kyushu island, southwest Japan is an imbricated crustal section in which a sequence of units with increasing metamorphic grade from high (northern part) to low (southern part) structural levels is exposed. The basal part of the metamorphic sequence representing an original depth of 23–24  km consists mainly of garnet–cordierite–biotite gneiss, garnet–orthopyroxene gneiss, orthopyroxene-bearing amphibolite and orthopyroxene-bearing S-type tonalite. These metamorphic rocks underwent high amphibolite-facies up to granulite facies metamorphism with peak P – T  conditions of 720  MPa, 870  °C. In addition sapphirine-bearing granulites and related high-temperature metamorphic rocks also occur as tectonic blocks in a metamorphosed peridotite intrusion. The sapphirine-bearing granulites and their related high-temperature metamorphic rocks can be subdivided into five types of mineral assemblages reflecting their bulk chemical compositions as follows: (1) sapphirine–corundum–spinel–cordierite (2) corundum–spinel–cordierite (3) garnet–corundum–spinel–cordierite (4) garnet–spinel–gedrite–corundum, and (5) orthopyroxene–spinel–gedrite. These metamorphic rocks are characterized by unusually high Al₂O₃ and low SiO₂ contents, which could represent a restitic nature remaining after partial melting of pelitic granulite under the ultra high-temperature contact metamorphism at the peak metamorphic event of the Higo metamorphic unit. The metamorphic conditions are estimated to be about 800  MPa and above 950  °C which took place at about 250  Ma as a result of the thermal effect of the regional gabbroic rock intrusions.  相似文献   

Upper Silurian–Middle Devonian radiolarian zones of the Yokokurayama and Konomori areas in the Kurosegawa Belt, Southwest Japan     

M. Umeda 《Island Arc》1998,7(4):637-646

Five radiolarian zones, from the Upper Silurian to Middle Devonian, are discriminated from the tuffaceous successions of the Joryu and Nakahata Formations of the Yokokurayama Group of the Yokokurayama area and the Konomori area in the Kurosegawa Belt, Southwest Japan. The definition of the zones is based on the first appearance biohorizon of the characteristic species. The zones are the Pseudospongoprunum sagittatum, Futobari solidus, Trilonche (?) sp. A, Glanta fragilis and Protoholoeciscus hindea zones, in ascending order. The preliminary age assignments for the zones are discussed on the basis of the comparison with other previous documented faunas. The age determination of the formations suggests the presence of unconformities and the episodic sedimentation of the tuffaceous strata in the Yokokurayama Group.  相似文献   

K–Ar ages of the basaltic rocks from Far East Russia: Constraints on the tectono-magmatism associated with the Japan Sea opening     

Satoshi Okamura  Yuri A. Martynov  Katsuhiko Furuyama  & Keisuke Nagao 《Island Arc》1998,7(1-2):271-282

K–Ar ages of the Cenozoic basaltic rocks from the Far East region of Russia (comprising Sikhote-Alin and Sakhalin) are determined to obtain constraints on the tectono-magmatic evolution of the Eurasian margin by comparison with the Japanese Islands, Northeast China, and the formation of the back-arc basin. In the early Tertiary stage (54–26 Ma), the northwestward subduction of the Pacific Plate produced the active continental margin volcanism of Sikhote-Alin and Sakhalin, whereas the rift-type volcanism of Northeast China, inland part of the continent began to develop under a northeast–southwest-trending deep fault system. In the early Neogene (24–17 Ma), a large number of subduction-related volcanic rocks were erupted in connection with the Japan Sea opening. After an inactive interval of the volcanism ∼ 20–13 Ma ago, the late Neogene (12–5 Ma) volcanism of Sikhote-Alin and Sakhalin became distinct from those of the preceding stages and indicated within-plate geochemical features similar to those of Northeast China, in contrast to the Japan Arc which produces island arc volcanism. During the Japan Sea opening, the northeastern Eurasian margin detached and became a continental island arc system, and an integral part of continental eastern Asia comprising Sikhote-Alin, Sakhalin and Northeast China, and the Japan Arc with a back-arc basin. The convergence between the Eurasian Plate, the Pacific Plate and the Indian Plate may have contributed to the Cenozoic tectono-magmatism of the northeastern Eurasian continent.  相似文献   

Biostratigraphy and depositional facies of the Cretaceous-Tertiary boundary strata in Amakusa-Shimojima,Kyushu, Western Japan     

M. Tashiro  A. Taira  T. Matsumoto 《Cretaceous Research》1980,1(1):13-26

The Upper Himenoura Subgroup exposed in the island of Amakusa-Shimojima, Kyushu, Japan shows an example of the terminal Cretaceous stratigraphic record in the circum Pacific region. This sequence is a part of the Upper Cretaceous intra-arc basins of southwest Japan. Four cycles of upward coarse-graded facies are recognized. Each cycle consists of a basinal mud facies in the lower part and a tide-dominated shallow marine to brackish coarse clastic facies in the upper part. Biostratigraphic correlation chiefly based on ammonites, inocerami and trigoniids indicates that this sequence is Campanian to Maastrichtian in age. The occurrence of the above three fossils decreases upward and is terminated at the top of the sequence, being replaced by a molluscan assemblage similar to the Danian. This suggests that the sedimentation may have continued to the very end of the Cretaceous period and possibly to the beginning of the Tertiary.  相似文献   

黄河三角洲短期暴雨预报系统   总被引：1，自引：0，他引：1  

张经珍  郝家学  候淑梅  孙忠欣 《气象》1998,24(9):46-50

在天气学分析的基础上,利用１９９０～１９９５年日本数值预报产品与实时资料相结合,研制黄河三角洲短期暴雨预报系统,经１９９６年使用效果较好。  相似文献