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16世纪初云南永胜发生过一次破坏性地震，长期以来其强度判定成为疑难问题。本文通过解读《明实录》以及地方志中相关史料记载认为，由于对《明实录》相关记述解读有误，以及采信了“石门阙”“田陷成湖”等地方志衍袭夸大、与自然规律相矛盾的记载，并“捆绑”了大理、鹤庆等2次破坏性地震，《中国历史强震目录》高判了此震强度，导致其地震影响场有悖于地震影响衰减的一般规律。本文分析表明，此地震时间为“弘治十五年七月己亥（1502年8月31日）”，强度≤7级。此永胜地震的强度问题会影响该地区未来地震的危险性分析、判断等。 相似文献
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C. Clarke G. Lodato S. Y. Melnikov M. A. Ibrahimov 《Monthly notices of the Royal Astronomical Society》2005,361(3):942-954
We present the results of a photometric monitoring campaign of three well-studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken at Maidanak Observatory between 1981 and 2003. When combined with photometric data in the literature, this data base provides a valuable resource for searching for short time-scale variability – both periodic and aperiodic – as well as for studying the secular evolution of these systems. In the case of V1057 Cyg (which is the system exhibiting the largest changes in brightness since it went into outburst) we compare the photometric data with time-dependent models. We show that prior to the end of the 'plateau' stage in 1996, the evolution of V1057 Cyg in the V –( B − V ) colour–magnitude diagram is well represented by disc instability models in which the outburst is triggered by some agent – such as an orbiting planet – in the inner disc. Following the end of the plateau phase in 1996, the dimming and irregular variations are consistent with occultation of the source by a variable dust screen, which has previously been interpreted in terms of dust condensation events in the observed disc wind. Here we instead suggest that this effect results from the interaction between the wind and an infalling dusty envelope, the existence of this envelope having been previously invoked in order to explain the mid-infrared emission of FU Orionis systems. We discuss how this model may explain some of the photometric and spectroscopic characteristics of FU Orionis systems in general. 相似文献
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