推断勒夫波相速度的圆形台阵微震新技术

介绍了简单而又新颖的公式,使用微震的二分量,即圆形台阵记录的水平运动直接推断勒夫波相速度(cL)时,这些公式具有帮助作用。我们的公式与一般用于推断瑞雷波相速度(cR)的微震探测技术的空间自相关(SPAC)方法的公式类似。虽然SPAC方法现有的理论确实提供了估计cL的可能性,但这只能通过求解非线性的方程组才能实现,而其中待求解的未知数也包括cR以及瑞雷波?勒夫波的幂分配比。相反,在我们公式中cL是出现的唯一未知数。基于我们推荐公式——我们称为SPAC+L、SPAC-L和CCA-L(其中CCA表示无中心圆形台阵)法——的cL估算法的现场适用范围通过2个测试点的分析结果说明。在所提出的3种技术中,SPAC+L法由于表现最佳而出名。3种方法的有效波长范围下限是台阵半径r的2～5倍区域,上限是10～25r的区域。近年来,提出了类似的仅涉及cL的圆形台阵微震技术,但与它们相比,我们在此给出的方法,不是在数理计算上繁冗更少,就是在数学上更为简单。     

Development of damage probability matrices based on Greek earthquake damage data

A comprehensive study is presented for empirical seismic vulnerability assessment of typical structural types, representative of the building stock of Southern Europe, based on a large set of damage statistics. The observational database was obtained from post-earthquake surveys carried out in the area struck by the September 7, 1999 Athens earthquake. After analysis of the collected observational data, a unified damage database has been created which comprises 180,945 damaged buildings from/after the near-field area of the earthquake. The damaged buildings are classified in specific structural types, according to the materials, seismic codes and construction techniques in Southern Europe. The seismic demand is described in terms of both the regional macroseismic intensity and the ratio αg/ao, where αg is the maximum peak ground acceleration (PGA) of the earthquake event and ao is the unique value PGA that characterizes each municipality shown on the Greek hazard map. The relative and cumulative frequencies of the different damage states for each structural type and each intensity level are computed in terms of damage ratio. Damage probability matrices (DPMs) and vulnerability curves are obtained for specific structural types. A comparison analysis is fulfilled between the produced and the existing vulnerability models.     

An energy budget for the subtidal bivalve Modiolus barbatus (Mollusca) at different temperatures

Clearance rates, respiration rates and food absorption efficiencies of the commercially interesting subtidal bivalve Modiolus barbatus were measured at different temperatures under laboratory conditions and scope for growth calculated. Clearance rates were highest at temperatures from 20 °C to 28 °C, whereas respiration rate was maximal at 9 °C and minimal at 26 °C. Highest mean values of absorbed energy occurred at 20 °C and 26 °C. Scope for growth trend had negative values at 9 °C, 15 °C and 28 °C and positive values at temperatures 20 °C and 26 °C. The profitable thermal window for M. barbatus to have energy sufficient for growth and reproduction corresponded to <5 months per year. Seawater temperature increases will potentially impact the eco-physiological responses of subtidal M. barbatus causing life history traits to change with important repercussions for subtidal biodiversity in the Mediterranean.     

The ethno-demographic status of the Baltic States

The essay examines historic and current ethnodemographic trends in spatial and cultural contexts in the Baltic States. Fifty years of Soviet rule, with deliberate policies to dilute the relative homogeneity of the Balts through ethnocide, in-migration, and political dominance by Moscow, has left tensions between citizens of the Baltic States and illegal immigrants, mostly Russians. Estonians, and Latvians, in particular, fear ethnic and cultural extinction. The process of ethnic dilution and mixing under the Soviets is examined in terms of rural-urban contexts, the workplace, employment, housing, and education. Europe's smallest ethnic group, the Livs of Latvia, is also examined. Current demographic trends are analysed and prospects for ethnic harmony in these multi-ethnic societies are interpreted. A recurrent theme is that Latvia, with 52% of the population Latvian, is facing the most difficulties; Lithuania, with 80% Lithuanians, the least.     

黄土的力学性质与工程地质问题现状

据统计,目前全世界几乎每天都有一篇关于黄土工程力学性质的新文献问世。黄土具有一些特殊的性质:干燥时坚硬,遇水则变弱。这种性状常引起大规模沉降及湿陷。黄土的渗透系数小(0.5—1.5m/d),水分损失少,因而黄土上的建筑工地往往具有地下水位高的特点,引起地基浸湿。黄土区常有的“假喀斯特”现象,在地震时会引起泥石流和大规模滑坡。     

太古宙脉金矿床:地壳规模热液系统的产物

最近有关太古宙脉金矿床的成因争论集中在矿液来源和它们的抽送系统的规模上。产在以绿片岩相至低角闪岩相绿岩为容矿岩的较大型中温热液矿床,已引起人们十分关注,而对产在较低或较高变质程度背景中的金矿床却很少注意。但是,现在很明显的是,在西澳伊尔岗地块,大多数脉金矿床代表了一种“单一金(“gold-only”)矿床的相关(Coherent)成因群(genetic group),这一成因群是在大于15km 地壳剖面的各种构造格局中形成的,温-压条件估计从250℃、10~8Pa(次绿片岩相)到700℃、5×10~8Pa(低麻粒岩相)。依照矿化的构造型式和伴生围岩蚀变,它们代表着一种过渡群。有金矿床出现     

阿尔丹地盾通古恰(Tungurcha)绿岩带变质科马提岩和玄武岩的岩石学和地球化学特征

阿尔丹地盾西部是由两个省、即阿尔丹麻粒岩—片麻岩地体和奥廖克马花岗岩—绿岩地体组成。花岗岩—绿岩地体的下壳岩带,根据火山成因或火山—沉积岩石为主和变质程度,可分两种类型。奥隆多(Olondo)绿岩带是第一类型的典型实例,它以含有大量镁铁质—超镁铁质火山岩(已变质达中等的红柱石—矽线石级,T～560℃,P～4×10~8Pa)为特征。通古恰绿岩带是代表第二种类型,它含有丰富的碎屑岩和碳酸盐岩,已经受了高级的蓝晶石—矽线石级变质作用(T～600℃,P～5-6×10~9Pa)。阿尔丹地盾西部的通古恰绿岩带的上壳岩呈阳起石片岩和斜长角闪岩包体产在3.2Ga 的英云闪长质片麻岩内。地质和化学资料表明这些上壳岩是科马提岩和拉斑玄武岩。根据 A1/Ti 和 Gd/Yb 比     

地幔热柱和大陆的再造

热柱传递出的热约占地幔内热预算的10％左右。以前认为热柱起源于一个温度较高的热边界层,并认为该层极可能在地幔底部,而板块运动则是地幔顶部冷的、致密边界层(大洋岩石圈内)向下俯冲的结果。据此,驱动热柱的构造活动和板块构造活动很大程度上应是互相独立的过程。流体动力学模拟实验显示,地球内部的热柱起始于一个体积很大的“头”的上升,“头”的下部拖着一条窄细的管状“尾巴”并且通过它获得源源不断的热源物质。上升过程中,“头”部体积由于周围地幔的加入而大幅度增长。计算表明,一个起源于     

高速公路引起的部分城市生态问题

本文对交通运输系统建设和运营过程中出现的工程地质和社会经济问题的首次深层次全方位研究进行论述,其研究表明交通震动和冻胀比较常见,并对环境有着重要的影响。对不同地区生态系统高速公路影响程度的预测和评估亦作了一定的阐述。