Relocation and Genetic Analysis of Earthquakes in the West of Xietan Area of Three Gorges Reservoir

136 earthquakes,taking place in the west of Xietan area,recorded by portable stations deployed in the Three Georges reservoir area were relocated using the double difference algorithm.The relocations show that the root-mean-square deviations of the relocations in the directions of E-W,N-S and U-D are 0.38km,0.33km and 0.98km,respectively.The earthquakes in clasolite area with focal depths of about 4km～5km take on linear distributions from the shallow to deep parts.These earthquakes were deduced to be reservoir-induced earthquakes of fault fracture type.In contrast,the earthquakes in limestone pavement with the focal depths about 2km～3km take on slightly divergent distributions and have the characteristics of reservoir-induced earthquakes of the karst collapse type.     

Spatial variations of the 660-km discontinuity in the western Pacific subduction zones observed from CEArray triplication data

We examined the spatial variation of velocity structures around the 660-km discontinuity at the western Pacific subduction zones by waveform modeling of triplication data.Data from two deep earthquakes beneath Izu-Bonin and Northeast China are used.Both events were well recorded by a dense broadband seismic network in China (CEArray).The two events are located at approximately the same distance to the CEArray,yet significant differences are observed in their records:(1) the direct arrivals traveling above t...     

Relocation of aftershocks of the Wenchuan M_S8.0 earthquake and its implication to seismotectonics

From 14:28 (GMT+8) on May 12th,2008,the origin time of MS8.0 Wenchuan earthquake,to December 31th,2008,more than 10 000 aftershocks (M≥2.0) had been recorded by the seismic networks in Sichuan and surrounding areas.Using double difference algorithm,the main shock and more than 7 000 aftershocks were relocated.The aftershocks distribute about 350 km long.The depths of aftershocks are mainly between 10 km and 20 km.The average depth of aftershocks is about 13 km after relocation.In the southwest,the distribut...     

Rapid afterslip and short-term viscoelastic relaxation following the 2008 M_W7.9 Wenchuan earthquake

Significant postseismic deformation of the 2008 M W 7.9 Wenchuan earthquake has been observed from GPS data of the first 14 days after the earthquake. The possible mechanisms for the rapid postseismic deformation are assumed to be afterslip on the earthquake rupture plane and viscoelastic relaxation of coseismiclly stress change in the lower crust or upper mantle. We firstly use the constrained least squares method to find an afterslip model which can fit the GPS data best. The afterslip model can explain n...     

各向异性ATI介质剪切位错点源P波远场辐射

假设震源区为ATI介质,传播介质为全空间各向同性介质情况下,给出了剪切位错源P波远场辐射解析表达式,讨论了震源区各向异性对远场P波振幅和震源球的影响。结果表明,震源区裂隙密度,裂隙方位等参数的动态变化导致P波远场辐射花样也随之动态变化,同时也会造成非双力偶百分含量的动态变化。研究认为,在井中对中小地震的非双力偶机制进行...     

Curating NASA's extraterrestrial samples—Past, present, and future

The NASA Johnson Space Center Astromaterials Acquisition and Curation Office has the unique responsibility to curate NASA's extraterrestrial samples – from past and forthcoming missions – into the indefinite future. Presently curation includes documentation, preservation, preparation, and distribution of samples from the Moon, asteroids, comets, the solar wind, and the planet Mars. Each of these sample sets has a unique history and comes from a unique environment. The curation laboratories and procedures developed over forty years have proven both necessary and sufficient to serve the evolving needs of a worldwide research community. A new generation of sample return missions is being planned and proposed to destinations across the solar system. Curation must evolve to meet the increased challenges of these new samples.     

1982—1999年珠江流域归一化植被指数与降水年际变化分析

利用1982—1999年月平均归一化植被指数(normalized difference vegetation index,NDVI)和降水资料,采用经验正交函数(EOF)方法分别研究了珠江流域的NDVI和降水在年和年际尺度上的异常关系,并分析了NDVI与降水及其他一些气象因子的相关关系。研究发现流域NDVI和降水在年内异常上具有较好的空间一致性,在时间上具有1—2个月的滞后;年际尺度上两者异常空间差异明显,流域东部(下游)异常为负相关,西部(上游)异常为正相关。NDVI和各气候因子的相关关系存在明显的空间和季节差异:流域东部NDVI和降水负相关明显,和温度及太阳短波辐射正相关明显;流域西部NDVI和降水滞后正相关明显,和温度相关不明显;NDVI在夏季和降水呈显著负相关,在春、秋季节滞后于降水,呈明显正相关,且滞后3个月正相关最为明显。     

华北地区地壳水平运动演化特征研究

将华北地区划分为阴山-燕山、鄂尔多斯、山西、太行、冀鲁、胶辽6个块体，应用1995、1996、2001年GPS观测资料研究了这些块体的水平运动演化特征。结果显示出华北地区各块体的相对运动既有继承性也有差异性。华北各块体的总体水平运动趋势是向东漂移，但是个别块体，如鄂尔多斯块体，在1995～1996年期间出现了相对的西向运动。1995～1996年期间华北各块体的运动速率比1996～2001年期间的运动速率要大，特别是阴山-燕山块体。1995～1996年期间鄂尔多斯块体和相邻的山西块体表现为张性分离，阴山-燕山块体之间表现为左旋走滑，这一现象可能与1996～1999年期间发生在华北西北部的3个地震的孕震过程有关。进一步分析表明，加密的连续GPS观测可用于地震预报。     

地壳形变与地下水异常关系研究进展

地壳形变异常是地壳构造变动中直接的表现，也是物理含义最为明确的地震前兆之一。地下水异常能够提供多种形式的构造活动过程(包括地震)。这两类异常能够以不同的力式和特点反映出地震孕育过程中伴随的前兆信息，并成为地震预报的重要手段；而它们之间既相互联系又相互影响。因此，对两类异常关系的研究对于识别地震前兆特别是短临前兆至关重要。归类了地震孕育模型及其前兆异常机理，并对前兆异常机理进行归纳整理和简述，然后从机理和前兆方面综述了地壳形变与地下水异常关系的研究成果。     

应用GPS观测资料反演潜在震源参数

根据点源孕震力学模型 ,应用福建 台湾地区GPS位移速度资料反演 1999年台湾南投Mw7.6大震前的孕震参数。反演所得的震中与实际发生的地震震中相差 6 7km ,主压应力场方向为 319.9°,倾角 - 2 8.6° ,即仰角2 8.6° ,与用震源机制解得到的P轴方向和倾角分别相差 17°和 8.6° ,与菲律宾板块向亚洲板块挤压的方向是一致的。用土耳其地区GPS位移速率资料反演 1999年土耳其Mw7.6地震前的孕震参数 ,反演得到的震中与实际震中相差 70km ,主应力方位角和倾角分别为 16 2 .5°、11.5°,与震源机制解结果分别差 2 4 .5°和 1.5°。