观测应变阶在地震应力触发研究中的应用

对中国钻孔应变台网观测到的昆仑山口西MS8.1大地震的应变阶资料的研究结果表明:① 很多观测值与静力位错理论计算值不符合；② 北方地震较活跃地区的很多台站观测到异常大的应变阶，而南方构造运动较不活跃地区的台站虽然也观测到地震波动，但是应变阶不明显. 由此推断，地震的触发（可能是动态触发）作用对远场的实际地震应变变化具有重要影响. 也就是说，远场的构造活动（可能是断层活动）是否曾被地震触发，可能决定当地的应变场变化的主要特征. 进一步对昌平台1999年3月11日张北地震与1999年11月1日大同地震的观测资料对比分析表明:断裂带的分布情况对实际地震应变变化有直接影响. 这证明观测到的异常大的地震应变阶可能是地震触发了当地的断层活动的表现.      

地震断层面上的位错分布

1979年Imperial Valley地震、1989年Loma Prieta地震、1992年Landers地震、1994年Northridge地震、1995年阪神地震的地震断层面上的位错分布，满足分段的Gutenberg-地震位错 Gutenberg-Richter定律 b值Richter定律. 对于小位错，b值约为1；对于比较大的位错，b值大于1.      

3-D finite element modeling for evolution of stress field and interaction among strong earthquakes in Sichuan-Yunnan region

Introduction Sichuan-Yunnan region is a major area with frequent strong earthquakes in Chinese mainland, especially the middle-southern segment of South-North Seismic Zone, where many strong earth-quakes occurred in history. In the past 30 years, Sichuan-Yunnan region has two seismically active periods: one is from Tonghai earthquake in 1970 to Longling-Songpan earthquake in 1976, the other is from Lancang earthquake in 1988 to now. During this two periods, the M=7.7 Tonghai, M=7.1 Dagua…     

Developments of borehole strain observa- tion outside China

Introduction The Earth′s crust deforms in the regional tectonic stress field. Borehole strain observation isone important means for studies on the crustal deformation and the stress field. QIU and ZHANG(2002) have introduced the current situation of borehole strain observation in China. OutsideChina, early in September of 1968, Sacks of Carnegie Institution of Washington and Evertson ofUniversity of Texas firstly invented a borehole dilatometer in the world (Sacks, Evertson, 197…     

中国大陆科学钻探主孔2000米以上脆性变形构造应力场

在主孔2000米之内，存在复杂的脆性破裂系统和构造应力场。根据其充填物的特征，可划分为由石英、方解石和绿泥石等矿物充填的微破裂，发育石英、方解石等矿物薄膜或擦痕线理的微破裂和既无矿物充填、也无矿物薄膜的微破裂等3种不同类型的脆性应变现象，它们依次代表早、中、晚和深、中、浅3个不同构造层次的脆性变形。初步分析表明脆性变形阶段存在有以南东东-北西西向为主导的挤压作用、北东-南西向的区域挤压作用、南北向挤压作用和垂向伸展作用等4期构造应力场。郯庐断裂东侧的现代构造应力场在区域上具有极大的稳定性。在脆性和脆-韧性转换带，制约苏鲁高压-超高压变质带侵位的主导应力作用方式为自南东东往北西西方向的挤压，它在时间和空间上具有一定的稳定性。     

格尔木井水温异常特征及其与地震关系分析

简要介绍了格尔木井水温动态观测的环境与条件,在研究正常动态特征和影响因素的基础上,对水温异常的映震关系进行了分析,并成功地进行了一次短临地震趋势预测。探讨了水温异常的形成原因。     

Correlation Fractal and Multifractal Characteristics of Seismic Activity in the Taiwan Area, China

Based on the analysis of newly collected data of plate tectonics, distribution of active faults and crustal deformation, the Taiwan area is divided into two seismic regions and six seismic belts. Then, correlation fractal dimensions of all the regions and belts are calculated, and the fractal characteristics of hypocenteral distribution can be quantitatively analyzed. Finally, multifractal dimensions Dq and f(α) are calculated by using the earthquake catalog of the past 11 years in the Taiwan area. This study indicates that (1) there exists a favorable corresponding relationship between spatial images of seismic activity described with correlation fractal dimension analysis and tectonic settings; (2) the temporal structure of earthquakes is not single but multifractal fractal, and the pattern of Dq variation with time is a good indicator for predicting strong earthquake events.     

A CASE STUDY ON SANDSTORM

The favourable synoptic situation and climate background for a sandstorm process,which occurred in theperiod 9—16 April 1988,have been studied through analyzing weather maps,meteorological elements,satellitecloud pictures and sandstorm trajectories.The sand dust origin area,the directions and the paths of sanddust transport,and the extent the sand dust reached are also investigated.The results of measurments andanalysis indicate that the concentration of sand dust particles is 10 times greater than the normal.It is also shownthat the elements in the sand dust are lithophylic and come from natural source through the chemical composi-tion analysis of the sand dust,so that the sand dust has not been polluted by human activities.     

NUMERICAL EXPERIMENT OF THE INFLUENCES OF HEAT AND WIND STRESS ON THE EQUATORIAL OCEAN CIRCULATION

A time-dependent linear model on the equatorial beta plane is developed in this paper.Its verticalstructure consists of two active layers with equal density and temperature above the thermocline and aquasi-stationary layer with constant density below the thermocline.The results of nurnericat experiments show that the direct influence of heat on the equatorial ocean ismuch smaller than that of wind stress.Nevertheless,through the tropical ocean-atmosphere interaction,the change of wind stress resulting from the thermal forcing may set a determinant effect on the equilibriumand anomalous development of the ocean-almosphere circulation.