D.A.Walker 的答复

我感谢Forsyth等对南纬18°地震活动性质的澄清,同时我认为地震活动与厄尔尼诺之间的关系是不清楚的。我也相信偏离洋脊轴线的地震活动本身未必跟厄尔尼诺有直接关系,并相信由远震记录得到的发生于遥远洋脊系上的许多地震是一种不伴随火山活动、其震中没有热液成分的洋脊外地震。然而,远震记录到的异常地震活动事件在发生时间上似乎与厄尔尼诺有某种同步性。怎么会是这样的?沿着洋脊系异常高的地震活动水平往往伴生异常的     

Chronology of Vesuvius’ activity from A.D. 79 to 1631 based on archeomagnetism of lavas and historical sources

The activity of Vesuvius between A.D. 79 and 1631 has been investigated by means of precise archaeomagnetic dating of primary volcanic deposits and taking into account the stratigraphy of lavas and tephra, historical written accounts, archaeological evidence related to the developing urbanisation, and radiocarbon ages. We found that the historical records are highly useful in constraining the timing of the main events, even if the data are often too scarce and imprecise for ascertaining the details of all phases of activity, especially their magnitude and emplacement of all the deposit types. In addition, some eruptions that took place in the 9^th and 10^th centuries appear to be unnoticed by historians. The archaeomagnetic study involved 26 sites of different lavas and 2 pyroclastic deposits. It shows that within the 15 centuries which elapsed between A.D. 79 and 1631, the effusive activity of Vesuvius clustered in the relatively short period of time between A.D. 787 and 1139 and was followed by a 5-century-long repose period. During this time Vesuvius prepared itself for the violent explosive eruption of 1631. The huge lavas shaping the morphology of the coast occurred largely through parasitic vents located outside the Mount Somma caldera. One of these parasitic vents is located at low elevation, very close to the densely inhabited town of Torre Annunziata. Among the various investigated lavas, a number of which were previously attributed to the 1631 eruption, none is actually younger than the 12^th century. Therefore it is definitively concluded that the destructive 1631 event was exclusively explosive.Editorial handling: J. McPhie     

A review of: “Principles of Geodynamics, 3rd edition. By Adrian E. Scheiddeger. Springer-Verlag,Berlin-Heidelberg-New York,xvii + 395pp. DM165, U.S. $73.30 (ISBN 3-540-11323-1). 1982.”

Abstract

Edited by J.-P. Zhan and J. Zinn-Justin, Elsevier, 1993. XXIV+ 615 pp., US$248.50, hardbound (ISBN-0-444-81797-2).     

A simplified 3 D.O.F. model of A FEM model for seismic analysis of a silo containing elastic material accounting for soil–structure interaction

The purpose of this study is the evaluation of dynamic behavior induced by seismic activity on a silo system, containing bulk material, with a soil foundation. The interaction effects between the silo and bulk material, as well as the effects produced between the foundation of the silo and the soil, were taken into account. Proposed simplified approximation, as well as the finite model, were used for analysis. The results, from the presented approximation, were compared with a more rigorous obtainment method. Initially, the produced simplified approximation, with elastic material assumption for the grain, could determine the pressures on the dynamic material along with displacements along the height of the silo wall and base shear force, etc., with remarkable precision. Some comparisons, via a change of soil and/or foundation conditions, were also made regarding the seismic pressure of the dynamic material pressure, displacement and base shear forces for both squat and slender silos. Comparing the analytical predictions to results from the numerical simulations produced good results. It can be concluded that the model can be used effectively to perform a broad suite of parametric studies, not only at the design stage but also as a reliable tool for predicting system behavior under the limit state of the system. The results and comprehensive analysis show that displacement effects and base shear forces generally decreased when soil was softer; however, soil structure interaction (SSI) did not have any considerable effects on squat silos and therefore need not be taken into practice.     

对Y.Y.Kagan和D.D.Jackson“VAN地震预报的统计检验:评述和思考”一文的答复

本文仅限于回答再次由 Kagan 和 Jackson(1996)提出的那些观点,尽管对此我们已经在其他对 Kagan(1996)和 Jackson(1996)的答文中作过讨论。例如我们证明他们关于“……大多数 VAN 参数在1987～1989年检验期后作了调整,亦即,反推调整”的观点并不正确。而另一方面我们却同意他们的结论:“这一问题的观点不同,说明地震学界需要一套评估地震预报方法的总方案”,应用这套方案应接着对到目前为止发布的 VAN 预报进行评估(包括从1987～1995的9年时间),而不是仅限于这场争论中讨论的1987～1989年间。Kasan 和 Jackson(1996)还将 Aceves 等(1996)和 Kagan(1996)的检验结果进行了对比并得出这样的结论,即如果目录中包含余震或只是去掉部分余震,则两项检验都表明 VAN 方法优于泊松零假设。另一方面,Kagan 和 Jackson(1996)称,“如果余震被尽可能全部删去”,VAN 方法并不比泊松零假设更为优越。然而我们将阐明,在后一种情况的“减丛集”过程中会出现以下情况:对主震的成功预报同样会被去掉;而且会将成功的预报变成失败的;我们的结论与 Aceves 等(1996)的基本一致。     

对D.A.Rhoades和F.F.Evison的“VAN地震预报”的答复

Ｒｈｏａｄｅｓ和Ｅｖｉｓｏｎ５ Ｍｕｌａｒｇｉａ和Ｇａｓｐｅｒｉｎｉ的程序中的技术缺陷，在如何对一个地震预报方法实施正确统计评估的方法上做了有益的评论并提出了十分重要的建议。我们认为统计学家们今后要认真遵循这些建议。     

对D.D.Jackson的“应用于VAN方法的地震预报评估标准”一文的答复

我们早期的文章表明,VAN 方法并非不符合 Jackson(1996)提出的必要条件(1)和(2)。对评估成功而言,非主观的事后决定也是需要的,这是因为,绝大多数 VAN 预报,其ΔM、Δr 以及Δt 值都是在被讨论的1987～1989年时段以前发表的,只有在极少数与地震电信号地电活动新现象的观测有关的情况下(29次中的3次),Δt 值才是在1988年确定的。此外,一次仔细的审验——从物理观点看——表明,VAN 方法确实满足 Jackson 的3个有理判据(被候选预报技术所遵从)。