Wenchuan Earthquake： Way of thinking is changed   总被引：9，自引：0，他引：9  

Yong Chen Li Li Juan Li Gang Li 《《幕》》2008,31(4):374-377

On 12 May, 2008, at 14：28：04 local time, an Ms 8.0 earthquake struck the Wenchuan County, Sichuan Province, in southwest China （Figure 1）. This quake left about 70,000 people dead, 18,000 missing and over 370,000 injured. In the 75 days after the main shock, 20,000 aftershocks were recorded, which included 241 with Ms≥4.0, 205 with 4.0≤M≤4.9, 30 with 5.0≤Ms≤5.9, and 6 with Ms≥6.0. The largest aftershock took place 13 days after the main shock, in Qingchuan County, 110 km northeast of the epicenter of the quake （Chen, 2008）. The losses from the quaketriggered geological disasters accounted for over a third of the total quake losses, which is extremely rare in the history of earthquake disasters. Secondary disasters, such as landslides, rockslides, landfalls, debris flows, etc., were widely distributed. Large numbers of buildings collapsed, including ones with steel reinforcing in the area of the epicenter. Infrastructure was badly damaged. In many areas, communications, and power and water supplies were cut off. The earthquake left over 35 large quake-dammed lakes, which threatened further disasters in the catchment areas.  相似文献   

High‐pressure metamorphism in Taiwan: from oceanic subduction to arc‐continent collision?     

O. Beyssac  F. Negro  M. Simoes  Y. C. Chan  Y. G. Chen 《地学学报》2008,20(2):118-125

Abstract The Taiwan orogen has been the focus of a number of models of mountain building processes, but little attention has been paid to high‐pressure (HP) metamorphic rocks that are found as exotic blocks intermingled within the deepest units of the mountain belt. In this study, we re‐appraise from updated petrological and thermodynamic databases the physical conditions of HP metamorphism in Taiwan, and we combine our findings with available geochronological data to estimate the thermal history of these rocks. Our results indicate that peak metamorphic conditions of ～550 °C and 10–12 kbar have been followed by a rapid isothermal decompression, with exhumation possibly as rapid as burial. These units have subsequently been stored at a pressure of ～3 kbar for ～4–5 Myr, before their final exhumation, probably facilitated by the accretion of passive margin sequences during the Late Cenozoic collision. Therefore, HP units in Taiwan maintain a record of processes at depth from the early stages of oceanic subduction to the present arc‐continent collision.  相似文献   

Flexural isostatic response of the Alps to increased Quaternary erosion recorded by foreland basin remnants,SE France     

Jean‐Daniel Champagnac  Peter Van Der Beek  Gaël Diraison  Samuel Dauphin 《地学学报》2008,20(3):213-220

We test the hypothesis that flexural isostatic compensation of the mass removed by enhanced Quaternary erosion is responsible for uplift of the Western European Alps and their forelands. We use two well‐preserved and well‐dated (1.8 Ma) abandonment surfaces of foreland basin remnants in SE France (the Chambaran and Valensole plateaux) as passive benchmarks for tilting of the foreland. Estimating their initial slope from morphometric scaling relationships, we determine bulk post‐depositional tilting of 0.5–0.8% for these surfaces. The calculated isostatic response of the Alpine lithosphere to erosional unloading, using the method recently proposed by Champagnac et al. [Geology 35 (2007) 195–198] , yields a predicted tilting of 0.3–0.4% in the considered areas, explaining approximately half of the determined post‐depositional tilting. Such long‐term deformation being insensitive to cyclic loading/unloading because of glaciations, we suspect the other half to be related to as yet undetermined long‐wavelength and long‐lived tectonic process(es).  相似文献   

川中—川南地区上三叠统沉积相研究   总被引：7，自引：1，他引：6  

施振生  杨威  金惠  朱秋影  刘满仓  郭长敏 《沉积学报》2008,26(2):211-220

综合分析岩心、露头剖面和测井资料,认为川中—川南地区上三叠统发育三角洲相和湖泊相,其中,三角洲相可进一步划分为三角洲平原、三角洲前缘和前三角洲三个亚相,湖泊相则可细分为滨湖和浅湖两个亚相。不同时期三角洲相和湖泊相发育程度不同。须一段、须三段、须五段和须六段以湖泊沉积为主,由东向西,水体逐渐加深。须二段和须四段以三角洲沉积为主,湖泊沉积分布范围较小。须二段发育时期,研究区北部构造活动强烈,沉积物供给充分,三角洲相主要由北向南延伸;须四段沉积时期,由于北部构造活动逐渐减弱,东南部沉积物供给增加,三角洲相主要由东南向西北方向延伸。随着周缘构造活动的变化,研究区沉积范围逐渐扩大。早期沉积范围仅局限于宜宾—泸州以北地区,中晚期沉积范围扩大,宜宾—泸州以南地区开始接收沉积。  相似文献   

华北克拉通北缘隆化地区S型花岗岩的独居石年龄图谱   总被引：1，自引：0，他引：1  

凤永刚  刘树文  吕勇军  张臣  舒桂明  王长秋 《岩石学报》2008,24(1):104-114

位于华北克拉通北缘中段的隆化S型花岗岩由石榴石黑云母花岗岩、石榴石花岗岩以及片麻理化的黑云母花岗岩组成。其主体岩性石榴石黑云母花岗岩SiO_2和Al_2O_3含量分别为64.09%～69.6%以及14.6%～16.13%,K_2O/Na_2O>1.0,A/CNK>1,0,Mg~#在20.76～34.89之间变化,具有明显的Nb、Ta、P、Ti和Sr亏损以及Rb、K和Th富集。石榴石黑云母花岗岩(样品JB6031-1)采用独居石电子探针U-Th-Pb化学法进行测年,获得了2553±120Ma、2180±42Ma和1854±24Ma三个年龄峰值。一颗独居石内部成分分带上6个分析点定年结果构成2553±120Ma的峰值年龄,这一年龄与我们最新获得的2506±7Ma和2541±8Ma(继承锆石年龄)LA-ICP-MS锆石U-Pb同位素年龄相似,我们将这一独居石年龄解释为继承独居石的年龄,表明在赤城-隆化断裂以北存在太古宙陆块,并且在后期构造-热事件中发生部分熔融形成S型花岗岩。该独居石颗粒幔部成分分带上10个分析点的测年结果揭示的峰值年龄为2181±42Ma,该年龄也是出现频率最高的年龄值,我们建议2181±42Ma为S型花岗岩的结晶年龄,反映了S型花岗岩的侵位时代。独居石颗粒外部成分分带上8个分析点的测年结果构成1854±24Ma的峰值年龄,该年龄与华北克拉通中部带的变质年龄接近,我们将其解释为S型花岗岩的变质年龄,表明华北克拉通北缘的构造演化与中部带的构造演化密切相关。  相似文献   

滇西点苍山—哀牢山变质岩系锆石SHRIMP定年及其地质意义   总被引：21，自引：14，他引：7  

李宝龙  季建清  付孝悦  龚俊峰  宋彪  庆建春  张臣 《岩石学报》2008,24(10):2322-2330

滇西点苍山和哀牢山主体分别由下元古界苍山群和哀牢山群深变质岩系组成,被认为是前寒武纪结晶基底。选取点苍山的花岗闪长质糜棱岩(DCS-1)和哀牢山元江段黑云母花岗闪长质片麻岩(SM07-1)之中的锆石进行U-Pb SHRIMP定年。样品DCS-1和SM07-1测年结果分别为233±2.6Ma和239.8±2.8Ma。结合前人对滇西地区花岗质岩类所做的研究,揭示滇西地区在三叠纪经历一期在空间上广泛分布的岩浆事件,点苍山花岗质糜棱岩和哀牢山花岗质片麻岩的原岩为三叠纪侵位的花岗岩,其构造环境属于大陆裂谷,反映了滇西地区在三叠纪地壳物质的重新调整,而该变质岩系不是前寒武纪的结晶基底,其变质作用与山体出露地表过程和新生代构造作用有关。  相似文献   

GPS卫星反射信号增强技术研究     

杨进佩  刘中  朱晓华 《海洋湖沼通报》2006,(3):13-20

本文根据GPS卫星反射信号在海洋参数测量、无源雷达目标探测以及大地测绘中的应用,从天线接收、信号处理运算和多路径信号抵消角度,详细地研究了GPS卫星反射信号增强技术,给出了相应天线和电路结构及信号处理方法,并进行了计算机仿真,结果表明所提出的技术能增强GPS卫星反射信号。  相似文献   

UV-B辐射对海洋微藻抗氧化系统的影响   总被引：4，自引：1，他引：4  

于娟  唐学玺  李永祺  王晨  刘文明 《海洋科学》2002,26(12):49-53

研究了UV－B辐射对两种海洋微藻－小新月菱形藻（Ntzschia closterlum)和亚心形扁藻（Platymonas subcordiforming)的抗氧化系统的影响。结果表明：在本实验的辐射剂量范围内，随着UV－B辐射剂量的增强，两种藻的抗氧化防御系统的非酶性组分还原型谷胱甘肽（GSH）和类胡萝卜素（CAR）的含量随之下降；抗氧化防御系统的酶性组分超氧化歧化酶（SOD）和过氧化氢酶（CAT）的活性逐渐降低。加入外源性抗氧化剂GSH可减轻UV－B辐射对藻的伤害。分析表明海洋微藻的UV－B伤害是由于抗氧化防御系统遭到破坏而导致活性氧积累的结果。  相似文献   

DISCUSSION ON THE PLEISTOCENE HIGH SEA LEVEL ABOUT THE SHANDONG PENINSULA     

郭永盛  韩有松  杨光复  张铭汉 《海洋学报(英文版)》1984,3(2):238-245

It has for many years been controversial whether there was a Pleistocene high sea level on the Shandong Peninsula. Our investigations in recent years suggest that the red sandy sediments distributed around the Yuanyaodun village, Weihai County, the "Liukuang Red Bed" and the loess-like deposits near Penglai County should be terrestrial deposits, and there is will not a convincing evidence to confirm that abrasion landforms found above the 10m elevation oa the coast are of marine origin. From these, it is still not safe to say that a high sea level had occurred in the Shandong Peninsula during the Pleistocene.  相似文献   

中太平洋西部深海沉积物中的火山碎屑与粘土矿物     

何良彪  赵全基  张德玉  赵奎寰  彭汉昌  陈穗田 《海洋学报》1982,4(4):450-461

对于太平洋深海沉积物的研究虽有很久的历史(如1873-1876年“挑战者”号的科学考察),但对该区开展深入系统的岩石学和矿物学研究却是六十年代以后的事.随着研究手段的发展和进步,已积累了关于该区深海沉积物的大量资料.目前我国的海洋工作者也正在努力开展这方面的科学研究工作.  相似文献