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761.
从历史地震资料记载点数量的变化情况入手研究了中国大陆5个地区的历史地震资料记载的完整性,结果表明由于明朝以后地方志的发展历史地震资料才趋于完整。 相似文献
762.
763.
A destructive shock with magnitude of 6.3 occurred on 2 June 2007 at 21h34min56s UT in Pu’er region (23.0°N, 101.1°E), Yunnan Province, China. The data from DEMETER satellite during the period from 23 May to 2 June, i.e., ten days before the earthquake and one day just on the day of earthquake occurrence, were analyzed. Among the 284 orbits of DEMETER during the period, 29 orbits with the trace passing through the region within 1 888 km from the epicenter were selected to be studied. Seven anomalous events were found on the dataset of the seven orbits among the 29 ones. There existed synchronous perturbations on the variations of the spectrogram of the electric field and the variations of the density and temperature of the ions and electron, in contrast with the variations of its surround- ing area. And five events appeared in the space within 1 888 km from the epicenter while the other two were out of the studied area. Electrostatic turbulences were also recorded with the synchronous perturbations with that in the electron density and ions density in plasma in the region near the epicenter in the five events, which seems to sug- gest that there be some physical relation between these events and the preparation processes of Pu’er earthquake. 相似文献
764.
Haruko Sekiguchi Masayuki Yoshimi Haruo Horikawa Kunikazu Yoshida Sunao Kunimatsu Kenji Satake 《Journal of Seismology》2008,12(2):185-195
We studied the long-period ground motions in the Osaka sedimentary basin, Japan, which contains a 1- to 3-km thickness of
sediments and is the site of many buildings or construction structures with long-natural period. We simulated the broadband
ground motions likely to be produced by the hypothetical Nankai earthquake: the earthquake expected to give rise to the most
severe long-period ground motion within the basin. For the simulation, we constructed multiscale heterogeneous source models
based on the Central Disaster Management Council of Japan (CDMC) source model and adopted a hybrid computation method in which
long-period motion and short-period motion are computed using a 3-D finite difference method and the stochastic Green’s function
method, respectively. In computing long-period motions, we used a 3-D structure model of the crust and the Osaka sedimentary
basin. The ground motions are estimated to have peak velocities of 50–90 cm/s, prolonged durations exceeding 300 s, and long
predominant periods of 5–10 s in the area with great thickness of sediments. The predominant periods are in agreement with
an approximate evaluation by 4 H/V
s where H and V
s are the thickness of the sediment and the average S wave velocity, respectively. 相似文献
765.
The optimal seismic design of structures requires that time history analyses (THA) be carried out repeatedly. This makes the optimal design process inefficient, in particular, if an evolutionary algorithm is used. To reduce the overall time required for structural optimization, two artificial intelligence strategies are employed. In the first strategy, radial basis function (RBF) neural networks are used to predict the time history responses of structures in the optimization flow. In the second strategy, a binary particle swarm optimization (BPSO) is used to find the optimum design. Combining the RBF and BPSO, a hybrid RBF-BPSO optimization method is proposed in this paper, which achieves fast optimization with high computational performance. Two examples are presented and compared to determine the optimal weight of structures under earthquake loadings using both exact and approximate analyses. The numerical results demonstrate the computational advantages and effectiveness of the proposed hybrid RBF-BPSO optimization method for the seismic design of structures. 相似文献
766.
地震预报具有明显的双重属性: 科学性和社会性。 该文着重对地震预报科学性的问题做了评述, 强调地震预报必须以一定的科学理论为指导, 以科学的观测资料为基础, 以预报经验为借鉴。 文中对当前中国地震“活跃期”与“平静期”的划分以及根据地震前兆持续时间将地震孕育过程划分“长、 中、 短、 临”四个阶段和相应的地震“渐近式”预报程式, 和“以场求源”的预报思路做了简要的评论。 此外, 强调论及地震预报必须以浅源地震发生的物理实质及对孕震物理过程的基本认识作为思考问题的基本出发点。 相似文献
767.
应用模糊数学原理,将我国现行建筑抗震设计规范(GB 50011-2001)划分场地类别的依据模糊化,用正态分布作为等效剪切波速与覆盖层厚度的隶属函数,对不同场地条件特征周期值进行模糊综合评判,给出了高层建筑结构地震作用计算步骤。结果表明,模糊综合评判方法使得建筑抗震设计中的设计反应谱更符合实际,高层建筑结构地震作用的计算更为准确。 相似文献
768.
769.
770.
Bihong Fu Xinglin Lei Khaled Hessami Yoshiki Ninomiya Takashi Azuma Hisao Kondo 《Journal of Geodynamics》2007,44(3-5):160-172
The December 26, 2003 Mw 6.6 Bam earthquake is one of the most disastrous earthquakes in Iran. QuickBird panchromatic and multispectral satellite imagery with 61 cm and 2.4 m ground resolution, respectively provide new insights into the surface rupturing process associated with this earthquake. The results indicate that this earthquake produced a 2–5 km-wide surface rupture zone with a complex geometric pattern. A 10-km-long surface rupture zone developed along the pre-existing Bam fault trace. Two additional surface rupture zones, each 2–5 km long, are oblique to the pre-existing Bam fault in angles of 20–35°. An analysis of geometric and geomorphic features also shows that movement on the Bam fault is mainly right-lateral motion with some compressional component. This interpretation is consistent with field investigations, analysis of aftershocks as well as teleseismic inversion. Therefore, we suggest that the 2003 Bam earthquake occurred on the Bam fault, and that the surface ruptures oblique to the Bam fault are caused by secondary faulting such as synthetic shears (Reidel shears). Our fault model for the Bam earthquake provides a new tectonic scenario for explaining complex surface deformations associated with the Bam earthquake. 相似文献