菏泽5.9级地震前后水准测量与承压水变化关系的研究

利用深层承压水头观测结果,对东明——菏泽长水准测线8——9号测段的高差变化进行了回归计算和相关分析。认为菏泽市城区9号测点下沉的主要原因是受深层承压水头变化的影响。排除地下水影响因素后证实,1983年11月7日菏泽5.9级地震前后仅3mm左右的升降变化,表明9号测点对这次中强地震仅能反映微弱的形变信息量。     

华东地区测震学指标异常配套和中强震对应关系初探

本文分析了部分地震学指标的物理意义。通过对华东地区1970年以来14个指标的全时间扫描,并使用华东地区Ms≥5.0地震进行对应,结果表明,选取Rm值、b值和AC值进行同步异常分析,能显著提高华东地区的有震报震率,但有漏报。对目前华东地区异常集中区(南黄海及其沿岸地区)进行时间扫描,结果显示该异常集中区未出现同步异常,认为该区域短期内发生中强地震的可能性不大。     

印尼苏门答腊MW9.0级地震对全球及中国大陆地震趋势影响研究的反思

本文对2004年12月26日印尼苏门答腊以西发生MW9.0级地震后所做的地震趋势预测做了反思,指出:关于全球特大地震近年可能连发,特大地震对几年内世界7级以上地震年频度没有明显影响,但未来几年内7级以上强震可能集中在这次特大地震附近或相关构造上的预测意见是正确的;而有关近年中国大陆及川滇地区可能发生7级强震的预测是错误的;并认为,2001年昆仑山口西8.1级地震释放了已积累的应变可能是这次特大地震不能触发中国大陆及川滇地区发生强震的重要原因。     

Sliding mode fuzzy control: Theory and verification on a benchmark structure

A sliding mode fuzzy control (SMFC) algorithm is presented for vibration reduction of large structures. The rule base of the fuzzy inference engine is constructed based on the sliding mode control, which is one of the non‐linear control algorithms. In general, fuzziness of the controller makes the control system robust against the uncertainties in the system parameters and the input excitation, and the non‐linearity of the control rule makes the controller more effective than linear controllers. For verification of the present algorithm, a numerical study is carried out on the benchmark problem initiated by the ASCE Committee on Structural Control. To achieve a high level of realism, various aspects are considered such as actuator–structure interaction, sensor noise, actuator time delay, precision of the A/D and D/A converters, magnitude of control force, and order of control model. Performance of the SMFC is examined in comparison with those of other control algorithms such as H_{mixed 2/∞}, optimal polynomial control, neural networks control, and SMC, which were reported by other researchers. The results indicate that the present SMFC is efficient and attractive, since the vibration responses of the structure can be reduced very effectively and the design procedure is simple and convenient. Copyright © 2000 John Wiley & Sons, Ltd.     

芦山M7．0地震余震分布特征

使用双差定位方法,对2013年4月20日08时02分芦山 M 7．0地震后近10天的余震进行重新定位,获得精度较高的重定位结果;在此基础上,对余震空间分布特征进行研究,推测芦山主震的发震断层可能为大川-双石主断裂东侧的一条次级隐伏逆冲断层。     

Earthquake probabilities and magnitude distribution (M ≥ 6.7) along the Haiyuan fault, northwestern China

Introduction Haiyuan fault is a major seismogenic fault in north-central China. One of the most devastat-ing great earthquake in the 20th century occurred near Haiyuan in northwestern China on Decem-ber 16, 1920. More than 220 000 people were killed and thousands of towns and villages weredestroyed during the devastating earthquake. A 230 km long left-lateral surface rupture zone wasformed along the Haiyuan fault during the earthquake with maximum left-lateral displacement of10 m. Pale…     

Relocation of shallow earthquakes in southern Alaska using Joint Hypocenter Determination method

A subset of 2660 shallow earthquakes (0–50 km) that occurred from 1988 to 1996 in south central Alaska between 155°W and 145°W and 59°N and 63°N was relocated using the joint hypocenter determination (JHD) method. Both P- and S-wave observations recorded by the regional seismic network were used. Events were relocated in twenty different groups based on their geographic location and depth using two velocity models. As a result of the relocation, the majority of the hypocenters shifted downward, while the epicenter locations did not change significantly. The distribution of the shallow subduction zone earthquakes indicates the existence of two seismically independent blocks, with one block occupying the northeastern part and the other occupying the central and western parts of the study area. The boundary between the blocks is marked by a 15 to 20 km wide seismicity gap to the southeast of 149.5°W and 62°N. The analysis of the fault plane solutions for shallow subduction zone earthquakes shows that an overwhelming majority of the solutions represent normal, oblique-normal or strike-slip faulting with predominant WNW-ESE orientation of T-axes. This indicates a down-dip extensional regime for the subducting slab at shallow depths. Very few earthquakes yielded fault plane solutions consistent with thrusting on a contact zone between the overriding and subducting plates. This result may be an indication that currently either the strain energy is not released at the contact zone or it is associated with aseismic motion.     

四川芦山7.0地震和汶川8.0地震震源区地壳岩石圈变形特征分析

地壳和岩石圈变形特征研究对于深入了解中强地震的深部孕震环境具有重要科学意义.本文联合P和S波远震接收函数偏移成像结果,对发生过芦山7.0地震和汶川8.0地震的龙门山断裂带及附近区域地壳和岩石圈结构进行分析.结果揭示出在青藏高原向四川盆地过渡的龙门山断裂带,Moho面和岩石圈底界面(LAB)呈现出强烈变形,特别是芦山地震和汶川地震震源区下方地壳出现了错断、下凹,岩石圈也呈现下凹变形特征.这种地壳及岩石圈变形所代表的高应力的积累可能是汶川和芦山地震发生的重要深部地球动力学背景.     

地震红外长波辐射短期异常特征分析

利用NOAA卫星资料反演的地震长波辐射值OLR对黑龙江及其周边2003年以来8次中强地震进行了追踪研究.结果显示,震前2个月左右OLR场值存在明显的高值异常区,未来震中距离高值区中心点250km(优势距离为160km).该方法对黑龙江及其周边4级以上地震短期判定可能具有一定的指示价值,也为利用卫星遥感技术预测未来可能发震区域并及时做出短期预测预警提供了新途径.     

桥梁沉井基础抗震性能研究现状及展望

随着国内外大跨桥梁特别是跨海桥梁建设的迅速发展,沉井基础在桥梁基础中所占的比例越来越大。虽然沉井基础作为1种刚性基础具有良好的力学性能,然而震害实践表明沉井基础在地震作用下也并非万无一失。通过分析国内外典型桥梁沉井基础的震害特征发现,沉井基础的地震破坏与桩基础有显著差异,且与埋置深度有直接关系;研究表明:地震作用下沉井基础的破坏机理及地基承载力与静力作用下明显不同,但目前在该方面的研究还较为欠缺;总结和对比了现有几种沉井基础-土相互作用研究方法,并分析了几种研究方法的优缺点和适用场合;同时也归纳和对比了各国抗震规范对桥梁沉井基础的基本规定、适用范围、计算方法和构造规定等方面的内容。最后结合现有的研究现状对沉井基础抗震性能研究的发展方向进行了展望,此外,随着我国跨海、跨江及跨库区大跨桥梁建设的发展,地震力和波浪力等多灾害因素共同作用下深水沉井基础桥梁破坏机理及设计方法的研究势在必行。