岷江上游干扰岸坡主要表生地质灾害分布特征及成因浅析

岷江上游地处我国著名的南北向地震带的中段，因其特定的地质环境导致区内表生地质灾害极为严重。通过对岷江上游（汶川以上）河段的崩塌、滑坡、泥石流等表生地质灾害的调查研究，其分布沿岷江两岸具有明显的分段特征与河谷地貌分段基本一致，它们形成发展与特定地形地貌、易崩滑或软弱地层、特殊的构造部位、降雨等密切相关。     

Optimum multiple tuned mass dampers for structures under the ground acceleration based on DDMF and ADMF

Multiple tuned mass dampers (MTMD) consisting of many tuned mass dampers (TMDs) with a uniform distribution of natural frequencies are taken into consideration for attenuating undesirable vibration of a structure under the ground acceleration. A study is conducted to search for the preferable MTMD which performs better and is easily manufactured from the five available models (i.e. MTMD‐1 – MTMD‐5), which comprise various combinations of the stiffness, mass, damping coefficient and damping ratio in the MTMD. The major objective of the present study then is to evaluate and compare the control performance of these five models. The structure is represented by its mode‐generalized system in the specific vibration mode being controlled by adopting the mode reduced‐order approach. The optimum parameters of the MTMD‐1 – MTMD‐5 are investigated to reveal the influence of the important parameters on their effectiveness and robustness using a numerical searching technique. The parameters include the frequency spacing, average damping ratio, tuning frequency ratio, mass ratio and total number. The criteria selected for the optimum searching are the minimization of the maximum value of the displacement dynamic magnification factor (DDMF) and that of the acceleration dynamic magnification factor (ADMF) of the structure with the MTMD‐1 – MTMD‐5 (i.e. Min.Max.DDMF and Min.Max.ADMF). It is demonstrated that the optimum MTMD‐1 and MTMD‐4 yield approximately the same control performance, and offer higher effectiveness and robustness than the optimum MTMD‐2, MTMD‐3, and MTMD‐5 in reducing the displacement and acceleration responses of structures. It is further demonstrated that for both the best effectiveness and robustness and the simplest manufacturing, it is preferable to select the optimum MTMD‐1. Copyright © 2002 John Wiley & Sons, Ltd.     

Oxydation expérimentale de Fe-tourmalines et corrélation avec une déprotonation des groupes hydroxyleAnnealing in oxidising conditions of Fe-tourmalines and correlated deprotonation of OH groups

Annealing at 400?T?600 °C (40?P?60 MPa and HM buffer-controlled f(O₂)) of tourmalines synthesised at the same T and P with NNO buffer induces an oxidation of Fe²⁺ into Fe³⁺ in some Y sites only (Mössbauer Spectroscopy data). Annealing in the same conditions of natural tourmalines is consistent with these results. FTIR spectroscopy shows that oxidation of Fe²⁺ into Fe³⁺ is charge-balanced by deprotonation of the external OH₍₃₎ groups. To cite this article: Y. Fuchs et al., C. R. Geoscience 334 (2002) 245–249.     

Optimum multiple tuned mass dampers for structures under the ground acceleration based on the uniform distribution of system parameters

The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1～US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.     

Preliminary data on chemical changes in the Aral Sea during low-level periods from the last 9000 years

The withdrawal of the Aral Sea tributaries (Amu and Syr Daria) for cultures has led to significant falls of its level and an important increase in its salinity. During the Holocene, a succession of low and high water inputs occurred. Silty deposits correspond to the high levels and carbonates to the low levels. This study makes a distinction between the Syr Daria and the Amu Daria water inputs during low-level periods by using mineralogical and chemical compositions of the carbonates deposits. Waters from the Syr Daria are more sulphatic and have a low iron content in comparison with that of the Amu Daria. The Syr Daria was the major tributary around 7500, 4956 and 970 yr?BP, whereas around 6200 and 3610 yr?BP, inflow also from the Amu Daria is observed. To cite this article: L. Le Callonnec et al., C. R. Geoscience 337 (2005).     

福州盆地及其周围地区地壳深部结构与构造的初步研究

1986-1988年,福建省地震局在福州盆地及其周围地区完成了五条地震测深剖面:宁德-永春剖面;洪懒-宁德剖面;莲峰-福州（尚干）剖面;南平-永泰-平潭非纵剖面;并在宁德-古田-嵩口首次试验扇形剖面观测系统,结果表明,扇形剖面对确定断裂是有效的. 根据对地震波走时的正、反演计算,用理论地震图和射线追踪方法进一步修改和完善,得到了福州盆地及其周围地区地壳深部为高、低速相间的速度分布特征.地壳介质速度为6.40km/s,在中地壳普遍发育一层速度为5.80-5.90 km/s、厚度约5.0 km的低速层.Moho面深度30-33 km,福州盆地为一Moho面隆起区,隆起幅度达3.0 km.北西向断裂发育,其中,闽江断裂在纵剖面和扇形剖面均有明显的反映,并切割到Moho面2.0-3.0 km. 反射波谱频方法计算得到福州盆地地壳Q值仅120-150,比邻近地区明显偏低,中地壳低速层Q值为40-80,是一典型的低速-高导-低Q（高衰减）结构层,此层上界面埋深14-15 km,与居里面埋深较一致.这些结果为福州地区的地热资源远景预测和开发提供了地壳深部结构和某些地球物理场背景.     

胶东半岛乳山地区低角度韧性剪切带几何学、运动学特征:对中国东部岩石圈减薄作用的启示

大规模伸展构造是华北克拉通东部岩石圈减薄的重要表现形式。部分低角度韧性剪切带是地壳伸展变形后所展现的构造形式。本文研究了王格庄韧性剪切带的岩石学、几何学、运动学等特征显示:韧性剪切带走向近南北向,剪切带断层面倾向多变(倾向西、西南、西北方向)。大部分区域面理低角度倾向西,矿物拉伸线理近东西向,不对称旋转碎斑及S-C组构指示顶端指向西的剪切特征。结合研究区西侧与伸展构造相匹配的半地堑伸展盆地证据:本研究认为伸展构造的形成可能与西太平洋板块的后撤相关,即大规模伸展构造作用引发了华北克拉通东部的地壳减薄作用。     

Nouvelles données sur le téphra de Sarliève et le téphra CF7, marqueurs chrono-stratigraphiques de Grande Limagne (Massif central,France)

A trachytic tephra, discovered in the ancient lake of Sarliève, ‘Grande Limagne’, has been dated using the thermoluminescence technique. The obtained age, 16±4 ka ($\text{2}\text{σ}$), is older than that of the trachytic volcanoes of the Cha??ne des Puys, the ashes of which have already been locally recognised in the region. Its analysis confirms its originality. In the course of the comparisons made to search for its spring, it appears that the wide-dispersion tephra CF7, beforehand correlated by hypothesis to the Puy de Clierzou, probably originates from the Kilian crater or the Puy de Vasset. To cite this article: D. Miallier et al., C. R. Geoscience 336 (2004).     

岷江上游潜在性泥石流堰塞湖危害及判识

汶川地震造成泥石流形成条件的改变,其次生灾害堰塞湖的危害已开始显现。如何对震后潜在性泥石流堰塞湖进行判识,成为迫切需要解决的问题。选取岷江上游映秀至汶川段为研究区,通过分析震后泥石流形成条件的变化、典型泥石流堰塞湖的危害及松散物质储量,选取潜在性泥石流堰塞湖的判识指标,利用模糊物元可拓模型,建立潜在性泥石流堰塞湖的综合判识模式。通过判识,研究区形成泥石流堰塞湖可能性高的一级支沟有17条,主要集中分布在映秀镇至草坡乡段,此段将是今后受堰塞湖危害的高危地段。     

闽江河口湿地典型植物群落及交错带植硅体碳分布特征研究

湿地既是"碳汇"也是"碳源",研究发现,碳可以被长久稳定地封存在植硅体内,不同植物的植硅体封存碳的能力有明显差异。选取闽江河口鳝鱼滩湿地芦苇群落、短叶茳芏群落、互花米草群落及交错带为研究对象,研究这3种植物植硅体碳(Phytolith-Occluded Carbon,简称PhytOC)含量和储量的空间变化特征和影响因素,探讨PhytOC含量在纯群落和交错带的差异,为研究植物竞争和碳循环过程提供依据。结果表明:受水文条件、植物生长和空间扩展等影响,闽江河口湿地植物PhytOC含量整体表现为近岸区高于近海区,PhytOC储量表现为纯群落高于交错带。PhytOC含量依次表现为芦苇纯群落(4.14 mg/g) > 交错带芦苇(3.67 mg/g) > 与芦苇交错的短叶茳芏(3.08 mg/g) > 互花米草纯群落(2.70 mg/g) > 与互花米草交错的短叶茳芏(1.96 mg/g) > 交错带互花米草(1.86 mg/g) > 短叶茳芏纯群落(1.75 mg/g)。短叶茳芏与芦苇相互扩展中短叶茳芏植物整体及各器官PhytOC含量均升高,而与互花米草相互扩展时短叶茳芏除了根系、茎以外各器官PhytOC含量均下降。3种植物各器官在交错带中PhytOC储量分配比明显不同于纯群落,根系PhytOC储量的分配比上升,提高了根系竞争力。芦苇、短叶茳芏、互花米草通过植硅体封存的碳储量分别占植物碳储量的0.27%、0.15%和0.07%,但植物间的扩展过程影响了植物的PhytOC储量,其中短叶茳芏与互花米草形成的交错带中短叶茳芏下降幅度最高(56.29%),互花米草下降幅度最低(26.15%)。由此可见,植物的空间扩展对植物PhytOC含量、储量以及在不同器官的分配比都有一定的影响,短叶茳芏在与芦苇和互花米草竞争时分别采取不同的PhytOC分配机制。