中国地磁台网的K指数测量结果分析

Ｋ指数以０,１,……,９的数字分为１０级,以３小时为一时段,简单、直观、清晰地表示出地磁场受太阳微粒辐射而形成的扰动变化的程度。Ｋ指数测量是地磁台日常工作的重要内容之一。正确地区别Ｋ变化与非Ｋ变化是测量Ｋ指数的基本要求和关键所在。我国地磁台站从１９８９年开始用规则日变化ＳＲ代替“铁曲线”来识别Ｋ变化与非Ｋ变化,使测量方法与国际上的通行做法相一致。本文通过对我国地磁台站的Ｋ频次分布统计指出,在采用新     

地磁场Z分量的年变化

利用河北省及邻区共８个台的绝对磁测Ｚ分量的资料,分析了地震磁场Ｚ分量的年变化。结果是,曲线相对长斜线而言,一年中形成两个峰值,时间在４月份和１０月份前后。前年１、７、１２月份为低值,７月份最低。相对长斜线的年变量大幅度各台变化不大,有从南往北逐渐加大迹象,但是各台的年变化幅度又随时间而有较大差异。主伙同时间里各台Ｚ分量的变化差异,主要是各地长期变化速率不同引起的。认识了地磁场Ｚ分量这些变化特征和规     

Evidence for the Blake event in volcanic rocks from Lipari (Aeolian Archipelago)

Palaeomagnetic and geochronological measurements have been carried out on the late Pleistocene basaltic–andesitic unit of Monte Chirica–Costa Rasa, on the island of Lipari (Aeolian Archipelago). The lava flow sequence is about 10  m thick and has been sampled in detail. Magnetic properties are rather uniform; Curie temperatures of 540° to 580 °C, and the saturation IRM reached at applied values of 0.1  T point to titanomagnetite as the main magnetization carrier. Thermal and AF demagnetization have shown the presence of secondary magnetization components. These were removed mostly at 450°–500 °C or 20–30  mT, indicating a highly stable ChRM with directions from transitional to reverse. Where a ChRM could not be isolated by application of the demagnetization techniques, the converging remagnetization circles method gave a mean ChRM value fully comparable with that obtained from other methods. ⁴⁰Ar/³⁹Ar determinations were performed on two lava flows, in the lower and upper parts of the sequence. The former shows a transitional ChRM direction and a whole-rock age of 157±12  ka, the latter a reverse direction, a whole-rock age of 143±17  ka and a ground-mass age of 128±23  ka. The radiometric data and the reconstructed stratigraphy, which indicate ages of 150±10  ka and 104±3.5  ka, respectively, for the volcanic units at the bottom and top of the Monte Chirica–Costa Rasa unit, suggest that the reverse directions recorded in Lipari are related to the Blake event.     

Electromagnetic core–mantle coupling—I. Explaining decadal changes in the length of day

Measured changes in the Earth's length of day on a decadal timescale are usually attributed to the exchange of angular momentum between the solid mantle and fluid core. One of several possible mechanisms for this exchange is electromagnetic coupling between the core and a weakly conducting mantle. This mechanism is included in recent numerical models of the geodynamo. The 'advective torque', associated with the mantle toroidal field produced by flux rearrangement at the core–mantle boundary (CMB), is likely to be an important part of the torque for matching variations in length of day. This can be calculated from a model of the fluid flow at the top of the outer core; however, results have generally shown little correspondence between the observed and calculated torques. There is a formal non-uniqueness in the determination of the flow from measurements of magnetic secular variation, and unfortunately the part of the flow contributing to the torque is precisely that which is not constrained by the data. Thus, the forward modelling approach is unlikely to be useful. Instead, we solve an inverse problem: assuming that mantle conductivity is concentrated in a thin layer at the CMB (perhaps D"), we seek flows that both explain the observed secular variation and generate the observed changes in length of day. We obtain flows that satisfy both constraints and are also almost steady and almost geostrophic, and therefore assert that electromagnetic coupling is capable of explaining the observed changes in length of day.     

地磁场总强度空间线性相关在预报武定,丽江强震中的应用及机理

介绍了地磁场空间线性相关的计算方法。详细阐述了利用此方法在预报武定地震 (1 995年 1 0月 2 4日 ,MS6.5)及丽江地震 (1 996年 2月 3日 MS7.0 )中的应用。笔者对此方法进行了理论推导 ,结果表明相关参量与台站经纬度的选择有关 ,而地磁场的空间线性相关的规律与台站的经纬度选择无关。该结果对台组的选择起到了指导作用     

中国（东亚）地磁台链建设及其观测与国际地磁卫星台网

本文对中国（东亚）地磁台链的漠河,北京十三陵,三亚和南极长城站与中山站地磁台的建设及其观测研究做了较系统的总结,北京地磁中心,南极长城站与中山站地磁台是中国首批实现了数字化的地磁台,为中国地磁台链参加了国际地磁卫星（ＩＮＴＥＲＭＡＧＮＥＴ）奠定了基础,此外,本文对国际地磁卫星台网做了简单介绍。     

关岛地磁转换函数的变化

分析了１９９０￣１９９５年关岛地磁台１ｍｉｎ值资料,得出转换函数Ａｕ的时间变化与关岛１９９３年８月大地震似乎有一定的关系,考虑到地磁转换函数的地方时效应,文中还对分析结果的可靠性作了一些评估。     

临汾台地磁转换函数变化与邻区地震的关系

利用转换函数的方法对临汾台1988年1月至1998年12月地磁资料进行了计算处理，用所得到的转换函数A、B的模|A|、|B|及总方差δz的月变化，来考察地震前后地下电性结构的变化。对1988年以来发生在临汾台周边地区的3次Ms4.0以上地震前后临汾台地磁转换函数的变化情况进行了研究。结果表明：不同周期的转换函数A、B以及总方差δz在震前有明显变化。