蒲江—新津—成都—德阳断裂带——成都平原内一条代表性弱活动地震带的地震地质特征

活断层是地震的潜在策源地。然而不同的活断层上地震潜在能力有极大的差别。客观地评价活断层上地震潜在能力不仅是地震预报研究的需要,对国民经济建设的布局和抗震决策也极为重要。在这个意义上,对弱活动性断裂的研究与对强活动性断裂的研究具有同样的重要性。本文以弱活动的蒲江—新津—成都—德阳断裂带为例,讨论了该断裂的晚第四纪活动性,断裂带的地质结构以及断裂的切割深度等因素对该断裂带地震潜在能力的可能影响。     

A new area for earthquake resistant engineering: the control of seismic responses of structures

This paper summarizes the origin and idea of the control of civil engineering structures and reviews the state-of-the art of recent advances in structural control both theoretically and technologically. The prospects for structural control and key research objects to remain to be solved are put forward at last. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 375–380, 1993.     

扩频微波网桥在新疆测震网络中的应用

以频率为2.4 GHz和5.8 GHz设备为例,对扩频微波网桥在新疆测震网络中的应用范围进行阐述;根据实际工作中无线网桥的安装架设经验,对在不同条件、不同环境下可能出现的问题提出相应解决方案.     

The seismic shear of ductile cantilever wall systems in multistorey structures

The distribution of seismic base shear demand among ductile flexural cantilever walls, comprising the lateral load resisting system of a multistorey building, is studied. It is shown that the base shear force demand depends on the sequence of hinge formation at the wall bases, and this in turn depends on the relative wall lengths. Hence, the routine elastic approach in which the shear forces are allocated per relative flexural rigidity or (when some consideration is given to plastic hinge formation) to moment capacity at the wall base, may appreciably underestimate the shear force demand on the walls, particularly the shorter (usually the more flexible) ones. A simple procedure yielding the results of ‘cyclic’ pushover analysis is proposed to predict the peak seismic wall forces for a given total base shear when plastification is confined to the wall base. The effects of plastic hinges developing at higher floors on (1) shear distribution among the walls and (2) the in‐plane floor forces are also considered. Two numerical examples are presented to demonstrate the main points made. Copyright © 2004 John Wiley & Sons, Ltd.     

Seismic stratigraphy, buried beach ridges and contourite drifts: the Late Quaternary history of the closed Lago Cardiel basin, Argentina (49°S)

The results of a seismic stratigraphic analysis of a closed lake basin, Lago Cardiel, in southernmost South America are reported. Very few high-resolution, continental records spanning the Late Quaternary have been obtained from this region. Seismic sequence stratigraphic analysis allows a reconstruction of lake level variations. Two major hiatuses of unknown age occurred during the early evolution of the basin with the deposition of an alluvial fan in a restricted area in the intervening time period. Following the development of a relatively shallow lake during the late Pleistocene and a short desiccation pulse around 11 220 ¹⁴C yr BP, a transgression of over 135 m occurred at the beginning of the Holocene. The transgression was associated with the formation of beach ridges preserved in the lake stratigraphy on the floor of the modern Lago Cardiel at four different elevations. The preservation of largely unreworked beach ridges indicates a stepwise rise in the lake level. There is no seismic evidence of a major lowering of the lake below modern level during the entire Holocene. Deposition since the mid-Holocene is marked by strong lateral differences in sediment accumulation with a depocentre slightly to the north of the basin midpoint and a pronounced mounded distribution. Seismic reflection geometries, as well as sedimentological characteristics indicate a lacustrine contourite drift covering an area of 80–100 km². As Lago Cardiel is under the influence of westerly winds, these most likely drove lake circulation. The identification of drowned beach ridges and of contourite drifts illustrates that high-resolution seismic stratigraphy is not only a powerful tool in reconstructing past lake level elevations for closed lake basins, but it can also provide information about the rate of lake level changes and the presence and strength of lake currents.     

隧道地震响应数值模拟研究

在进行隧道地震响应的数值模拟研究时, 横向计算范围和人工边界等对计算结果有很大的影响。本文以黄草坪隧道为研究对象, 应用有限差分程序FLAC3D对其进行地震响应的数值模拟研究, 将横向计算范围分别取为隧道洞径的5倍、6倍、7倍、8倍、9倍和10倍, 并分别采用FLAC3D中的截断边界、自由场地边界和粘性边界进行计算。研究结果表明, 当地震波为P波时, 横向计算范围取为洞径的7至8倍, 人工边界采用自由场地边界或粘性边界是比较合理的。     

Seismic Hazard Analysis for the Bangalore Region

Indian peninsular shield, which was once considered to be seismically stable, is experiencing many earthquakes recently. As part of the national level microzonation programme, Department of Science and Technology, Govt. of India has initiated microzonation of greater Bangalore region. The seismic hazard analysis of Bangalore region is carried out as part of this project. The paper presents the determination of maximum credible earthquake (MCE) and generation of synthetic acceleration time history plot for the Bangalore region. MCE has been determined by considering the regional seismotectonic activity in about 350 km radius around Bangalore city. The seismotectonic map has been prepared by considering the faults, lineaments, shear zones in the area and historic earthquake events of more than 150 events. Shortest distance from the Bangalore to the different sources is measured and then peak ground acceleration (PGA) is calculated for the different source and moment magnitude. Maximum credible earthquake found in terms of moment magnitude is 5.1 with PGA value of 0.146 g at city centre with assuming the hypo central distance of 15.88 km from the focal point. Also, correlations for the fault length with historic earthquake in terms of moment magnitude, yields (taking the rupture fault length as 5% of the total fault length) a PGA value of 0.159 g. Acceleration time history (ground motion) and a response acceleration spectrum for the corresponding magnitude has been generated using synthetic earthquake model considering the regional seismotectonic parameters. The maximum spectral acceleration obtained is 0.332 g for predominant period of 0.06 s. The PGA value and synthetic earthquake ground motion data from the identified vulnerable source using seismotectonic map will be useful for the PGA mapping and microzonation of the area.     

带有横向约束的全局优化波阻抗反演方法及应用

地震波阻抗反演是一种基于地震数据得到波阻抗参数的非线性优化问题。不依赖于目标函数梯度信息的全局优化算法是求解地震波阻抗反演问题的有效方法。然而这类方法采用逐道反演的策略,忽略了相邻地震道的空间相关性,导致反演结果的横向连续性差。针对该问题,提出了一种融入旁道最优解的模型空间初始化方法约束波阻抗反演的搜索空间范围,以改善反演结果的横向连续性,进而提出了一种带有横向约束的多组变异差分进化地震波阻抗反演方法。合成地震记录算例表明,该方法相比于传统方法不仅具有更快的收敛速度,而且反演结果具有更好的横向连续性。此外,该方法被应用于胜利油田某区块的储层波阻抗参数反演,反演结果与测井资料有很好的一致性,且有效地刻画了储层砂岩厚度。