新丰江水库区1989年11月26日4.5级地震的主要特征

本文总结分析了发生在新丰江水库老震区，距1962年6.1级主震27年的1次4.5级地震的活动和特点，认为此次4.5级地震及其伴生的小震群仍系新丰江水库诱发地震序列的中晚期强余震。     

冬季青藏高原对东移大槽动力影响的研究：Ⅲ.模拟试验结果的分析

具体分析了本文Ⅱ的模拟试验结果。结果表明，该试验较清楚地再现了青藏高原地形对西风气流的影响，也显示了不同地形、急流的有无、强度和位置以及初始槽强度和基本气流斜压性的强度对东移槽的影响。这些结果有的清楚地再现了过去熟知的或还不很清楚的地形影响事实，有的可为东移槽的预报提供着眼点。     

Application of stress-pore pressure coupling theory for porous media to the Xinfengjiang reservoir earthquakes

Theory of the coupling of stress-pore pressure in the saturated, elastic porous media is used in the study of the formation mechanism of the Xinfengjiang reservoir-induced earthquakes. Based on the results, it is believed that compared with the mechanism of additional stress in the vicinity of the reservoir, the mechanism of the coupling of additional stress and pore pressure may be more well-founded for the occurrence of reservoir-induced earthquakes.     

Earthquakes in the Czech Republic and Surrounding Regions in 1995–1999

In the time span from January 1995 to December 1999 the Czech National Seismological Network (CNSN), consisting of ten permanent digital broadband stations, several local networks and two data centers, detected and recorded 9530 regional natural seismic events, 27 greater than magnitude 2. Most of these events were located by the Czech Seismological Service (CSS), and the most prominent of them were analyzed in detail. A large number of quarry blasts were recorded as well but were not included in the analysis. We provide basic information on the configuration of the CNSN and on the way of routine data processing employed by the CSS in this paper. The over-all regional seismicity monitored by the CNSN in 1995–1999 is briefly reviewed. The main results of observations and evaluation of the local (NW-Bohemia/Vogtland, South Bohemia, Sudeten) and induced (Kladno, Píbram, Upper Silesia, Lubin/Poland) seismic activity within this period are presented in a condensed form. Finally, a summary on macroseismic observations on the territory of the Czech Republic in 1995–1999 is also presented.     

印尼苏门答腊8.7级大震对中国陆区的影响

发生在2004年12月26日的印尼苏门答腊8．7级地震，是全球有地震台网以来100多年中记录到的少数几次特大地震之一。初步汇集了在中国陆区观测到的地震活动、地壳形变、地下流体等多学科震时和震后效应的异常变化，包括地震活动性（特别是云南地区）的显著增强；地壳形变观测，尤其是钻孔应变观测记录到地壳应力-应变的震时和震后显著变化，以及地下水温度、化学成分、特别是水位的突出变化。同时，还从库仑破裂应力触发、动态应力触发以及下地壳和上地幔流动变形机制等方面，对这些大震效应作了一些成因机理讨论。     

流动注射分光光度法同时测定水中挥发酚及氰化物

在单针进样器的基础上，增加一个三通流路同时进样，在线消解-流动注射分光光度法测定水中挥发酚及氰化物。实验结果表明，挥发酚浓度在0mg/L～0．2mg／L、氰化物浓度在0mg/L～0．5mg／L范围内具有良好的线性关系。通过在线气体扩散分离技术，提高了分析速度，每小时可完成12个～15个样品的分析。方法的相对标准偏差〈5％，回收率在90．4％～108．5％之间。     

Locally triggered seismicity in the central Swiss Alps following the large rainfall event of August 2005

In 2005 August, an unusual series of 47 earthquakes occurred over a 12-hr period in central Switzerland. The earthquakes occurred at the end of 3-d period of intensive rainfall, with over 300 mm of precipitation. The highest seismicity occurred as two distinct clusters in the region of Muotatal and Riemenstalden, Switzerland, a well-known Karst area that received a particularly large amount of rainfall. The large increase in seismicity, compared to the background, and the short time delay between the onset of the intense rainfall and the seismicity strongly suggest that earthquakes were triggered by rainfall. In our preferred model, an increase in fluid pressure at the surface due to a large amount of rain leads to a local increase in pore fluid pressure at depth. The increase in pore fluid pressure will reduce the shear strength of a porous medium by counteracting normal stress and, at the end, provoke failure. The series of triggered earthquakes in central Switzerland occurred in regions that have been seismically active in the past, showing similar hypocentre locations and magnitudes. This suggests that these earthquakes occurred on existing faults that were critically stressed. We modelled the intense rainfall as a step increase in fluid pressure at the surface that migrates to greater depths following the solution of the one-dimensional diffusion equation in a homogeneous half space. This allowed us to estimate the hydraulic diffusivity by plotting triggered seismicity in a time–depth plot. We found values of hydraulic diffusivity in the range from 0.01 to 0.5 m² s⁻¹ for our study area. These values are in good agreement with previous studies on earthquakes that were triggered by fluids, supporting the idea that the observed earthquake series was triggered by the large amount of rainfall.     

Modeling forced pool–riffle hydraulics in a boulder-bed stream, southern California

The mechanisms which control the formation and maintenance of pool–riffles are fundamental aspects of channel form and process. Most of the previous investigations on pool–riffle sequences have focused on alluvial rivers, and relatively few exist on the maintenance of these bedforms in boulder-bed channels. Here, we use a high-resolution two-dimensional flow model to investigate the interactions among large roughness elements, channel hydraulics, and the maintenance of a forced pool–riffle sequence in a boulder-bed stream. Model output indicates that at low discharge, a peak zone of shear stress and velocity occurs over the riffle. At or near bankfull discharge, the peak in velocity and shear stress is found at the pool head because of strong flow convergence created by large roughness elements. The strength of flow convergence is enhanced during model simulations of bankfull flow, resulting in a narrow, high velocity core that is translated through the pool head and pool center. The jet is strengthened by a backwater effect upstream of the constriction and the development of an eddy zone on the lee side of the boulder. The extent of flow convergence and divergence is quantified by identifying the effective width, defined here as the width which conveys 90% of the highest modeled velocities. At low flow, the ratio of effective width between the pool and riffle is roughly 1:1, indicating little flow convergence or divergence. At bankfull discharge, the ratio of effective width is approximately 1:3 between the pool and downstream riffle, illustrating the strong flow convergence at the pool head. The effective width tends to equalize again with a ratio of 1:1 between the pool and riffle during a modeled discharge of a five-year flood, as the large roughness elements above the pool become drowned out. Results suggest that forced pool–riffle sequences in boulder-bed streams are maintained by flows at or near bankfull discharge because of stage-dependent variability in depth-averaged velocity and tractive force.     

Non-stationary random vibrations of a shear beam under high frequency seismic effects

Band-limited, non-stationary random vibrations of a shear beam are studied in order to investigate high frequency seismic effects on building structures. A solution for the evolutionary spectral density of the shear beam response to a time segment of band-limited white noise is given in a closed form. The root mean square (rms) and peak response of the shear beam are studied for two characteristic frequency bands: the conventional 1–4 Hz and higher frequency 4–16 Hz, characteristic for rockburst ground motion. Applying the criterion of equal excitation intensity with constant rms velocity, both responses are analyzed in detail and compared. The “switching off” fundamental mode for high frequency excitations results in characteristic overshoot of the stationary response level by the non-stationary rms response and an amplification of the response in the upper part of the shear beam.