中国东北及邻区大陆边缘构造

中国东北及邻区大陆边缘包括两个构造带。内带由裂解的古陆碎块组成，其北部与古亚洲洋的演化有关，南部与古太平洋演化有关。外带由中生代地体组成。它们是晚古生代到早中生代的洋壳碎块与晚中生代的深海沟堆积组成的混杂体带。古亚洲洋封闭后到现代太平洋板块活动前，即由泥盆纪到侏罗纪曾存在过另一个大洋－古太平洋，其洋底扩张活动形成了上述的构造带。晚侏罗世后本区发育左旋平移断裂系，晚白垩世一早第三纪形成了大陆缘火山－     

边坡岩体块体稳定性分析系统的开发与研究

提出了复杂形态块体几何建模的切割法, 在此基础上, 对石根华等人提出的块体理论作了改进和完善。并基于Windows操作平台, 开发了一套实用方便、实用的边坡岩体块体稳定性分析系统。经大量的实例 (例如三峡工程船闸高边坡 )检验结果表明, 该系统可以作为对边坡中复杂形状块体稳定性进行现场快速评价的实用工具。     

Evaluating assumptions for seismic assessment of existing buildings

This paper evaluates the American FEMA 356 and the Greek GRECO (EC 8 based) procedural assumptions for the assessment of the seismic capacity of existing buildings via pushover analyses. Available experimental results from a four-storeyed building are used to compare the two different sets of assumptions. If the comparison is performed in terms of initial stiffness or plastic deformation capacities, the different partial assumptions of the procedures lead to large discrepancies, while the opposite occurs when the comparison is performed in terms of structural performance levels at target displacements. According to FEMA 356 assumptions, effective yield point rigidities are approximately four times greater than those of EC 8. Both procedures predicted that the structure would behave elastically during low-level excitation and that the structural performance level at target displacement for a high-level excitation would be between the Immediate Occupancy and Life Safety performance levels.     

浙东沿海海蚀地貌及其与断块差异运动的关系

本文阐述了浙江东部沿海海蚀地貌的分布特征,认为高位古海蚀地貌是浙江东部一种普遍存在的现象,这些海蚀地貌确系古海面遗迹,但它们今日之分布高度乃是长时期构造抬升作用的结果。同期海蚀地貌的分布高度不同,除在形成时受到各种因素制约外,断块间的差异升降运动也是其影响因素之一。     

Silica-undersaturated sapphirine, spinel and kornerupine granulite facies rocks, NE Strangways Range, Central Australia

Small pods of silica-undersaturated Al-rich and Mg-rich granulite facies rocks containing sapphirine, pleonastic spinel, kornerupine, cordierite, orthopyroxene, corundum, sillimanite and gedrite are scattered throughout the NE Strangways Range, Central Australia. These are divided into four distinct rock types, namely orthopyroxene-rich aluminous granofels and metapelitic gneisses containing sapphirine, spinel or kornerupine. Two granulite facies metamorphic events are recognized, of which only the first (M1) is considered in this paper. Peak metamorphic mineral parageneses indicate that the M1 thermal maximum occurred at approximately 900–950 °C and 8–9 kbar. All samples are characterized by profuse and diverse coronitic and symplectic reaction textures. These are interpreted as evidence for the sequential crossing of the following reactions in the system FMAS: cordierite + spinel + corundum = sapphirine + sillimanite, cordierite + spinel = orthopyroxene + sapphirine + sillimanite, sapphirine + spinel + sillimanite = orthopyroxene + corundum, sapphirine + sillimanite = cordierite + orthopyroxene + corundum. Phase stability relationships in FMAS and MASH indicate an anticlockwise P–T path terminated by isobaric cooling. Such a path is exemplified by early low-P mineral parageneses containing spinel, corundum and gedrite and the occurrence of both prograde and retrograde corundum. Reaction textures preserve evidence for an increase in aH₂O and aB₂O₃ with progressive isobaric cooling. This hydrous retrogression resulted from crystallization of intimately associated M1 partial melt segregations. There is no evidence for voluminous magmatic accretion giving rise to the high M1 thermal gradient. The M1 P–T path may be the result of either lithospheric thinning after both crustal thickening and burial of the supracrustal terrane, or concomitant crustal thickening and mantle lithosphere thinning.     

华北陆块、秦岭地块和扬子陆块构造演化的古地磁证据

通过对河北井陉和湖北宜昌、兴山的39个采样点、392个样品进行的古地磁测试,以及7个采样点、71个样品中的原生剩磁以及笔者前期研究结果,系统分析了三大块体的古地磁极位置、古地磁偏角以及古纬度自寒武纪以来的变化特征,并进行了古地理复原。研究表明,三块体为不同地质构造单元,寒武纪时,华北陆块、秦岭地块以及扬子陆块自北到南顺序排列于北纬2.9°、南纬5.5°以及南纬17.0°。秦岭地块北侧和南侧分别存在一古洋盆,此时华北陆块和扬子陆块相距约1400Km左右;三块体向北漂移的过程中伴随着旋转运动;三块体开始拼合的时间为晚二叠纪至早三叠纪之间,华北陆块和秦岭地块完全拼合的时间为早三叠纪至中三叠纪之间,三块体完全拼合的时间为中三叠纪至晚白垩纪之间;晚白垩纪以后,一体化的三块体继续向北漂移,并于第四纪到达现今地理位置。     

华北断块区地震幕与气温异常

本文利用1951-1980年期间中国气温资料研究了1966-1976年间华北断块区地震幕活动与1960年2月-1977年1月气温异常之间的关系。主要结论如下:1.华北断块及其邻近地区1960年2月天气异常增温到1977年1月天气异常降温过程与地震幕活动开始和结束的时间相关联;1967年5月、1973年1月、1975年9月和1976年2月的气温异常与该地震幕中1969年7月18日渤海7.4、1975年2月4日海城7.3和1976年7月28日唐山7.8级三次地震密切相关。2.气温异常时问和异常范围之间以及它们与地震能量之间都有较高的可信度,表明气温异常与地震幕之间有成因上的联系。3.从1960年2月气温异常开始到1976年7月28日唐山7.8级地震发生时的16.5年可按0.618~N划分为18个时段,4次7.0级以上地震和5次气温异常发生的时间恰好位于某几个时间段上。     

Study on Statistical Features About Weak Earthquake Activity Before Moderately Strong Earthquakes in the Middle Northern Part of the Qinghai-Xizang （Tibet） Block

In regards to the earthquakes recording M ≥ 5.0 that occurred in middle northern part of the Qinghai-Xizang （Tibet） Block from 1970 - 2003, in this study we describe the temporal and spatial centralization features of the weak earthquakes and the enhancement and anomalous quiescence of their seismic activity before main shocks through 4 parameters, which are basically not correlated： earthquake time centralization degree parameter Ct, earthquake space centralization degree parameter Cd, η value and weak earthquake frequency and so on. On the basis of calculation results, it has been seen that before earthquakes with M ≥ 5.0 took place in the middle northern part of the Qinghal-Xizang （Tibet） Block, the frequency of weak earthquakes often shows ascent and drop, their strength shows an obvious enhancement and the centralization distribution with time and space is evident.     

红河断裂带两侧地块地震震源参数研究

利用云南区域数字地震遥测台网资料,采用Brune圆位错模型对1998年12月至2006年8月云南境内M≥3地震和越南北部M>2地震测算震源参数。结果表明,红河断裂两侧活动块体的地震活动和震源参数存在较为明显的差异。就地震矩与震级的标度关系而言,滇西南块体与美国加州圣安德列斯断层和滇西实验场及其周边地区的结果一致,但与华南块体和越南北部地区有差异;从应力降的测算结果看,华南块体西缘的云南及越南北部地区的年均值为7.29MPa,滇西南块体为4.48MPa,两块体北部地震的应力降大于南部地区,应力降由北向南逐渐减小;就地震位错年均值而言,华南块体为12.3mm/a,滇西南块体为6.6mm/a。     

Kriging Regionalized Positive Variables Revisited: Sample Space and Scale Considerations

Frequently, regionalized positive variables are treated by preliminarily applying a logarithm, and kriging estimates are back-transformed using classical formulae for the expectation of a lognormal random variable. This practice has several problems (lack of robustness, non-optimal confidence intervals, etc.), particularly when estimating block averages. Therefore, many practitioners take exponentials of the kriging estimates, although the final estimations are deemed as non-optimal. Another approach arises when the nature of the sample space and the scale of the data are considered. Since these concepts can be suitably captured by an Euclidean space structure, we may define an optimal kriging estimator for positive variables, with all properties analogous to those of linear geostatistical techniques, even for the estimation of block averages. In this particular case, no assumption on preservation of lognormality is needed. From a practical point of view, the proposed method coincides with the median estimator and offers theoretical ground to this extended practice. Thus, existing software and routines remain fully applicable.