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<正>The thermo-electric coefficients of twenty-six magnetite samples,formed either by magmatism or metamorphism,were tested by the thermo-electric instrument BHET—06.Results showed that the coefficient is of a constant value of about -0.05 mV/℃.It is emphasized that because every magnetite grain was tested randomly,the coefficient is independent of the crystallographic direction.This fact means the thermal voltage generated from a single magnetite crystal can be accumulated,and as a result a new thermo-electric field can arise when a gradient thermal field exists and is active within the earth's crust.Because magnetite is widespread in the earth's crust(generally appearing more in the middle-lower crust),there is more-than-random probability that the additional thermo-electric field can be generated when certain thermal conditions are fulfilled.We,therefore,used the thermo-electric effect of magnetite to study the mechanism responsible for the presence of abnormal geo-electric fields during earthquake formation and occurrence, because gradient thermal fields always exist before earthquakes.The possible presence of additional thermo-electric fields was calculated under theoretical seismological conditions,using the following calcu-lation formula:E= - 0.159(σ×△T×φ×ρ_2×[(h~2-2x~2)cosα+ 3hxsinα]/ρ_1(h~2 +x~2)~(5/2)).In the above formula,σis thermo-electric coefficient of magnetite,△T is the temperature difference acting on it,φis a sectional area on a block of magnetite vertically perpendicular to the direction of the thermal current.ρ_1 andρ_2 are the respective resistivities of magnetite and the crust,and h,α,and x,respectively,h is the depth of embedded magnetite block,αmeans the angle created by the horizontal line and ligature of the two poles of magnetite block,and x is the distance from observation point to projective center point of the magnetite block on earth surface.According to simulations calculated with this formula,additional thermo-electric field intensity may reach as high as n to n×10~2 mV/km.This field is strong enough to cause obvious anomalies in the background geo-electric field,and can be easy probed by earthquake monitoring equipment. Therefore,we hypothesize that geo-electric abnormalities which occur during earthquakes may be caused by the thermo-electric effect of magnetite. 相似文献
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震(前)兆远场异常与德令哈6.6级地震临震特征分析 总被引：4，自引：1，他引：3
简要叙述了2003年4月17日发生在青海德令哈6．6级地震及异常台站概况。采用甘肃省内11个地电台共61个测项(其中电阻率28个测项、自然电位28个测项、大地电场5个测项)及地震活动空间扫描图像(频度场、6值、GL值)进行筛选,从中检索到了15项异常指标。经对数据的处理与临震异常特征分析,结果表明：震(前)兆异常信息的出现为6．6级地震事件的发生提供了临震异常判据;这些异常判据也可为将来地震的预测预报提供一定的参考依据。 相似文献
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介绍了在2013年7月22日甘肃岷县漳县MS6.6地震前/后地电学科所做的震情研判和预测预报工作,评价了震中附近甘东南及邻区台站出现的地电阻率观测数据异常。认为:(1)在地震短临阶段和紧接震后提出的两个地震预测意见大致符合本次地震主震、余震发生的实际情况;(2)在数据异常中包括了与本次地震有关的前兆异常信息和由于台站观测环境变化引起的干扰数据异常,震前震后的震情预测意见有一定程度的有科学意义和启示,也存在明显的不确定性。最后强调了加大力度保护地电观测环境的重要性。 相似文献
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