Precursory seismic crustal deformation in the area of southern Albanides

On the basis of growing evidence thatstrong earthquakes are preceded by a periodof accelerating seismicity of moderatemagnitude earthquakes, an attempt is madeto search for such seismicity pattern in NWAegean area. Accelerating seismic crustaldeformation has been identified in the areaof southern Albanides mountain range(border region between Greece, formerYugoslavia and Albania). Based on certainproperties of this activity and on itssimilarity with accelerating seismicdeformation observed before a strongearthquake which occurred in the sameregion on 26 May 1960 (M = 6.5), we canconclude that a similar earthquake may begenerated in the same region during thenext few years. This conclusion is inagreement with independent results whichhave been derived on the basis of the timepredictable model.     

大陆边缘沉积盆地流体逸散管道地震特征及其成因机制

流体逸散管道是深部流体向上运移所形成的通道,在大陆边缘沉积盆地中广泛发育。由地震资料显示,流体逸散管道主要由根部、过路区和末端3部分组成。由于形成机制、起源和流体成分的不同,其组成三要素有不同的表现形式,因此,流体逸散管道类型多样,具有不同的地震反射特征。水力压裂是文献中最常见的一种有关流体逸散管道形成机制的解释,但是,随着地震勘探的发展和研究的不断深入发现,水力压裂不足以解释所有类型的流体逸散管道,还存在其他的成因机制,包括流化侵蚀作用、局部空洞坍塌及同沉积模式等。从流体逸散管道组成三要素的角度描述了不同类型流体逸散管道的地震反射特征,并详细论述了其4种成因机制下的形成过程。     

Apports de la méthode sismique réflexion haute résolution à l'identification des structures profondes des formations tertiaires en Médoc (Gironde,France) : implications hydrogéologiques

Near Bordeaux (France), the Oligocene aquifer is a potential target for drinking water supply. A high-resolution seismic campaign and several exploration wells helped to clarify the geometry of this formation and, as a consequence, the Medoc Tertiary aquifers. The major information extracted from these new data is the existence of a soft deformation inducing two different deposit areas, showing different hydrogeological characteristics (thickness, type, hydraulic properties, etc.). The presence of an erosional gap area affecting the Oligocene formations lead us to propose a new image of groundwater flow in the area, in the context of a predicted intensive exploitation of this resource. To cite this article: F. Larroque, A. Dupuy, C. R. Geoscience 336 (2004).     

Analytical and experimental investigations on seismic performance of exterior beam–column subassemblages of existing RC‐framed building

Seismic performance of exterior beam–column subassemblages of reinforced concrete structure designed and detailed on the basis of the provisions of Eurocode and Indian Standards at different stages of their evolution is evaluated. Performance of the subassemblages designed and detailed according to the three different stages of codal evolution (gravity load design, ‘Nonductile’, and ‘Ductile’) is evaluated through analytical formulations and experimental investigations. In the ‘NonDuctile’ specimens, it has been observed that the shear distortion and degradation in stiffness and strength are significantly high. Performance of the ‘Ductile’ specimens based on Eurocode and Indian Standards is almost similar in terms of strength and stiffness degradation. Nevertheless, the specimen designed on the basis of Indian Standard shows higher energy dissipation at a given drift ratio. In the analytical study, shear and flexural failure of members of subassemblage and shear failure of the joint are considered as possible modes of failure of the beam–column subassemblage. For evaluating the shear strength of the joint region, a soften strut‐and‐tie model is used. Analytically obtained strengths based on the failure criteria of different components of the specimens have been first validated with experimental results and then used to determine the strength of the specimens. The investigation could indicate even the mode of failure at local level. It is utmost important to mention here that even the ductile specimens dissipate most of the energy through the development of damage in the joint region, which is neither desirable nor safe for the stability of whole structure. Copyright © 2013 John Wiley & Sons, Ltd.     

欧亚地震带地震活动和中国大陆地震

欧亚地震带及其与中国大陆相邻地域的地震活动和中国大陆地震之间存在有多种相关关系，这些相关关系对预测中国大陆地震活动趋势有一定的作用     

A technique for conducting seismic refraction experiments on the ocean bed using bottom shots

A technique has been devised for firing arrays of bottom shots on the ocean bed in depths upto 4000 m or more. Ten kilogram explosive charges are dropped from the surface while the shooting ship is navigated acoustically. They are detonated at preset times by an electronic timer which initiates an electrical detonator, detonating cord and cast PETN/TNT explosive. Ranges to ocean bottom seismographs, and the shot instants, can be calculated from the arrival-time differences of the direct and surface-reflected water waves. The accuracy, which is dependent on water-depth and range, was better than 22 m in range and 14 msec in shot instant for our experiments.     

A comparison of single‐run pushover analysis techniques for seismic assessment of bridges

Traditional pushover analysis is performed subjecting the structure to monotonically increasing lateral forces with invariant distribution until a target displacement is reached; both the force distribution and target displacement are hence based on the assumption that the response is controlled by a fundamental mode, that remains unchanged throughout. However, such invariant force distributions cannot account for the redistribution of inertia forces caused by structural yielding and the associated changes in the vibration properties, including the increase of higher‐mode participation. In order to overcome such drawbacks, but still keep the simplicity of using single‐run pushover analysis, as opposed to multiple‐analyses schemes, adaptive pushover techniques have recently been proposed. In order to investigate the effectiveness of such new pushover schemes in assessing bridges subjected to seismic action, so far object of only limited scrutiny, an analytical parametric study, conducted on a suite of continuous multi‐span bridges, is carried out. The study seems to show that, with respect to conventional pushover methods, these novel single‐run approaches can lead to the attainment of improved predictions. Copyright © 2007 John Wiley & Sons, Ltd.