汶川地震区绵竹小岗剑沟泥石流发展趋势

小岗剑沟是汶川地震区内一条典型的泥石流沟,位于绵远河的左测,流域面积1.36 km2,沟床平均纵比降412‰。该沟在2008年"5.12"汶川地震后多次暴发泥石流,掩埋从沟口通过的汉(旺)清(平)公路,给四川省绵竹市清平乡的地震灾后重建造成重大危害。通过初步分析,小岗剑沟泥石流的形成过程为:暴雨作用下沟因上游良好的汇流条件而产生山洪→山洪冲刷堆积在沟道内的松散固体物质形成小规模泥石流→泥石流沿大比降沟道向下运动,因具有强大动能而具有强大冲刷下切侵蚀能力,下切侵蚀下游沟床质以及沟口的老台地→在沟口形成大规模泥石流。地震后4 a内共暴发泥石流10次,将沟口老堆积体下切侵蚀深度达35 m,泥石流冲出固体物质50×104m3。目前,沟内仍有固体物质量334.3×104m3,可能参与泥石流活动的动储量为156.8×104m3。如此大量的松散固体物源,使小岗剑沟可能还暴发大规模泥石流。通过泥石流形成因素分析,该沟泥石流活动总体呈强度下降趋势,泥石流活动类型:震后一段时间内为输移控制型、然后为输移控制型向松散固体物质控制型过渡,最后发展成为松散固体物质控制型。通过这些分析,为泥石流治理提供科学支撑。     

Brief Introduction to the "Catalogue of Recent Chinese Earthquakes (1912～1990, M_S≥4.7)

This paper briefly introduces the principles and methods for compiling the "Catalog of Recent Chinese Earthquakes (1912 ～ 1990, MS≥4.7)." This new catalog is compiled by revising and supplementing the 1983 version of the Catalog of Chinese Earthquakes.     

Probabilistic Estimation of Hazard on Engineering Site Based on the Intensity of Historic Earthquakes and A Preliminary Comparison with Seismic Hazard Analysis

This paper introduces a new method to estimate the seismic hazard on engineering site.The method is mainly based on intensity data of historical earthquakes.The obvious feature of the method is to use some ideas of seismic hazard analysis and considering regional seismicity tendency.The authors depict the comprehensive method to estimate the related parameters and predict the seismic hazards for 14 sites as practical examples.Some problems are also discussed.Compared with seismic hazard analysis,this method has certain advantages,such as simpler computation,lower uncertainty and smaller sensitivity factor.Moreover total hazard P(I≥i)of a site can be examined with real historic data.The result given by the method in this paper can be more stable than that given by seismic hazard analysis nowadays.     

On Shear-wave Splitting in Tangshan Region

Shear-wave splitting in Tangshan region is studied by using digital seismic data.Analyzing 3-component digital seismic data in Tangshan strong ground motion array,it is found that almost all earthquakes occurred during 1982 to 1984 have significant shear-wave splitting.The polarization directions of faster shear waves in 7 stations are near EW,which are consistent with the axis of maximum principal compressive stress obtained from earthquake fault mechanisms and geodetic surveys.The crack densities of the 7 stations are roughly estimated,0.019 for TS01,TS02 and TS15,0.015 for TS03,TS07 and TS18 and 0.024 for TS19,by using the average time delay of slow shear-wave at the 7 stations.     

中国低纬地区地磁场Z分量日变特征

根据我国低纬地区的台站资料，分析了地磁场Ｚ分量的静日变化特征，得到的主要结果是：（１）日变幅随季节和太阳黑子数的变化而变化；（２）低点出现时间大约在地方时１２时左右，并随季节有所变化；（３）最大值出现时间大约在地方时６时左右，在赤道电射流影响区其受季节的影响较大。     

Tectonic Characteristics and Evolution of the Taiwan Strait

The Taiwan Strait is a part of the continental-margin rift of eastern China, which can tectonically be divided into the Taiwan Strait basin, southwestern Taiwan basin and Penhu-Beigang uplift. The basins are structurally semi-graban down-faulted ones in character. The Cretaceous-Cenozoic sedimentary strata in the basins have a maximum thickness of over 10,000 m. The formation and development of the Taiwan Strait rift were not only affected by both the East China Sea basin and South China Sea basin but also closely related to the Central Range collision orogen of Taiwan. In the Cenozoic, the Taiwan Strait area experienced, under the influence of a multiple of tectonic mechanisms, three stages of evolution: poly-centre downfault-ing, down warping-faulting and foreland basin formation. The depositional centres of the basins migrated from west to east during the Tertiary, resulting in the thinning of the Palaeogene strata from west to east but that of the Neogene in the reverse direction. All this determine     

Continental- Margin Structure of Northeast China and Its Adjacent Areas

The continental margin of Northeast China and its adjacent areas is composed of two tectonic belts. The inner belt is a collage made up of fragments resulting from breakup of an old land with the north part related to the evolution of the Palaeo-Asian Ocean and the south part to the evolution of the Palaeo - Pacific Ocean. The outer belt is a Mesozoic terrane, which is a melange made up of fragments of the Late Palaeozoic to Early Mesozoic oceanic crust and the Late M esozoic trench accumulations.There existed another ocean-the Palaeo - Pacific Ocean during the period from the closing of the Palaeo-Asian Ocean to the opening of the modern Pacific Ocean or from the Devonian to Jurassic, and the ocean-floor spreading of the Palaeo - Pacific Ocean led to the formation of the above-mentioned tectonic belts. The development of the strike-slip fault system after the Late Jurassic and the formation of an epicontinental volcano -plutonic rock belt in the Late Cretaceous to Early Tertiary are attributed to the i     

1992年黄海5.3级地震

对黄海5.3级地震序列研究表明,该序列属于一个典型的主-余震型地震。震源机制解的结果表明,该区主压应力方向基本上和华北地区主压应力方向一致。通过对5.3级地震前区域地震活动分析结果说明,该地震是在区域地震活动中期异常背景的情况下发生的,即存在明显的地震活动增强和孕育空区。     

菏泽5.9级地震前后S值的时空变化

运用地震活动度(S)的计算模型对1983年菏泽5.9级地震前后,周围地区进行了时空扫描,发现了在主震前2-3年的时空分布上,S值都有一个异常升高的过程。     

JWP-2全集成电路可调稳频板设计——华北地区遥测地震台网联网论文续六

JWP-2稳频电路全部采用集成电路,应用锁相环频率合成技术,频率可调,性能稳定,组装调试方便,可做为原WP-1稳频电路板的更新换代产品.适当改进功放电路部分,可用在台网的768记录器及其它中小型交流同步电机稳频稳速电路中.