关于唐山地震前震中区地应力测值张性跳动的原因

唐山地震前,地震主断裂附近的陡河站和赵各庄站都观测到垂直于该断裂方向的地应力张性跳动,根据地震前跨该断裂的水准观测数据,认为这是地壳沿该断裂的局部凸起使地表附近沿该方向出现张性裂隙的反映。在其扩展的过程中,测量元件与张裂隙前沿的相对位置将发生变化。通过对张裂隙前沿附近应力场的分析,不仅可以说明当裂隙前沿在元件附近经过时与裂隙垂直的元件测值为什么突然上升后又下降恢复到原来的水平,而且可以说明另外两个与该元件呈60°交角的元件的同时刻测值变化不大的原因。     

Localized thermal anomalies in haloclines of coastal Yucatan sinkholes

A temperature spike is reported in the haloclines of three Yucatan sinkholes along a 1 km NW-SE transect from 5 to 4 km inland from the Caribbean coast. The temperature spike decreases in magnitude from 3.5 degrees C to 0.2 degrees C, approaching the coast. The anomaly does not vary diurnally and does not extend down into the underlying sea water. These conditions are inconsistent with explanations such as radiation absorption within the halocline, in situ microbially mediated sulfate reduction within the halocline and the underlying sea water, and sulfide oxidation by photosynthetic purple and green bacteria within the halocline. One explanation consistent with the shape and halocline location of the temperature spike involves a localized sea water convection cell operating near the coast. Cold sea water from the Caribbean Sea enters the coastal limestone at depths of a few hundred meters and heats up because of the geothermal gradient, buoyantly rising in vertical fractures within the unconfined aquifer. Blocked by the less dense fresh water, the movement stops in the halocline where the warm sea water mixes with brackish water. The convection cycle would be completed by the coastward movement of cooling brackish water. The observed temperature anomalies could possibly be snapshots of this warm layer moving coastward.     

对同震观测应力-应变阶跃的研究

一、引言地震是当地壳内的应力积累超过岩石破裂强度引起大范围的岩体破裂造成的。因此,对地应力(应变)及其变化的观测一直受到人们的特别关注。我国用钻孔地应力-应变观测进行地震预报,是1966年在李四光的倡导下开展起来的,已经有30多年的历史。30多年来,经过众多研究人员的不懈努力,钻孔地应力-应变观测在理论上和技术上不断改进,日臻完善。最近10多年来,钻孔地应力(应变)观测系     

Observations of remote coseismic stress step-changes

The study on stress triggering and stress shadow is a frontier subject of current seismologic research. One of the problems presently encountered is the lack of reliable observation of real coseismic stress changes at locations remote to the epicenter. At Changping Station near Beijing, coseismic step-changes were recorded for the Mw6.3 Zhangbei quake on 10 January, 1998 and the Mw5.8 Zhangbei quake on 11 March, 1999, by a RZB borehole component strainmeter. Based on analyses of these recordings, this paper shows observed coseismic step-changes of the horizontal component of strain tensor. The strain step-changes reach the order of 10?8 and, correspondingly, stress step-changes reach as high as 10?4 MPa. The results are significantly higher than linear elastic theoretical values. However, as self-checking can be carried out with the 4 groups of data recorded by the 4-component strainmeter, it has proved that the results are reliable.     

国外钻孔应变观测的发展现状

简要论述了钻孔应变观测在人类对地壳运动的研究中扮演的越来越重要的角色 .这种观测已经被美国、日本、秘鲁、澳大利亚、南非、冰岛、意大利等国家用于对板块运动、地震、火山、水库、油田等众多方面的观测研究 .指出这种观测日益成熟 ,迅速向多分量和综合探头发展 .介绍了根据这种观测结果 ,地震应变阶、慢地震、地震前兆以及火山喷发预测等方面的研究取得的重要进展 .     

Application of observed strain steps to the study of remote earthquake stress triggering

IntroductionModernseismologysuggeststhatearthquakesarecausedbyfaultslippingtriggeredbytec-tonicstressesaccumulatedtoacertainextent;andthefaultslip,inturn,releasesstresses.Infact,whenanintensivequakeoccurs,thefracturingoftheseismogenicfaultdoesnotleadtothereleaseofallthestressesbut,accordingtothegeometricrelationsamongthefaults,releasesstressesonsomeofthefaultstomakethemmorestable,whileaccumulatesstressesonotherfaultstomakethemtendtoslip.Asanapproximation,thestrengthofthefaulttobeysByerleylawby…     

国外钻孔应变观测的发展现状

简要论述了钻孔应变观测在人类对地壳运动的研究中扮演的越来越重要的角色. 这种观测已经被美国、日本、秘鲁、澳大利亚、南非、冰岛、意大利等国家用于对板块运动、地震、火山、水库、油田等众多方面的观测研究. 指出这种观测日益成熟，迅速向多分量和综合探头发展. 介绍了根据这种观测结果，地震应变阶、慢地震、地震前兆以及火山喷发预测等方面的研究取得的重要进展.      

新发现的唐山地震大断层

在对唐山地面塌陷的研究中发现了一条与唐山地震相关的大断层,该断层至少长90km,地面垂直错距3m,明显具有铲形正断层特点。该断层倾向NW,可分为南、北2段。南段的确定主要依据震后地面形变野外调查、水准形变资料、航片解译和石油地球物理勘探资料;北段的存在则有强烈线状喷沙冒水分布以及地震反射测深资料作为证据。唐山地震主震的余震大致分布在该断层地表出露迹线的NW侧,这种位置关系显示了新发现的断层对唐山地震的控制性