The earthquake sequence of May 1951 at Jucuapa, El Salvador     

N.N. Ambraseys  J.J. Bommer  E. Buforn  A. Udías 《Journal of Seismology》2001,5(1):23-39

Three earthquakes that happened over two days in May 1951 caused extensive damage to villages in a small area of eastern El Salvador (Central America). Contemporary hypocentral solutions indicated focal depths, confirmed by re-calculations using available seismic data, of the order of 90 km, suggesting events associated with the subducted Cocos plate. Macroseismic observations strongly indicate that the earthquakes were of very shallow focus and this is supported by wave-form modeling and the appearance of seismograms recorded in Guatemala. A re-evaluation of the location and source characteristics for these events is presented, together with a fault plane solution and additional macroseismic evidence. The implications for seismic hazard and risk assessment in Central America, where shallow earthquakes of moderate magnitude, frequently occurring in clusters, pose the greatest threat to settlements which, like the area affected by these events, are concentrated along the axis of Quaternary volcanoes.  相似文献   

A note on the useable dynamic range of accelerographs recording translation   总被引：2，自引：0，他引：2  

M. D. Trifunac  M. I. Todorovska 《Soil Dynamics and Earthquake Engineering》2001,21(4)

Since the late 1970s, the dynamic range and resolution of strong motion digital recorders have leaped from 65 to 135 dB, opening new possibilities for advanced data processing and interpretation. One of these new possibilities is the calculation of permanent displacement of the ground or of structures, associated with faulting or with non-linear response. Proposals on how permanent displacements could be recovered from recorded strong motion have been published since 1976. The analysis in this paper concludes that permanent displacements of the ground and of structures in the near-field can be calculated provided all six components of strong motion (three translations and three rotations) have been recorded, and the records are corrected for transducer rotation, misalignment and cross-axis sensitivity.  相似文献   

Evolution of accelerographs, data processing, strong motion arrays and amplitude and spatial resolution in recording strong earthquake motion   总被引：1，自引：0，他引：1  

M. D. Trifunac  M. I. Todorovska 《Soil Dynamics and Earthquake Engineering》2001,21(6)

This paper presents a review of the advances in strong motion recording since the early 1930s, based mostly on the experiences in the United States. A particular emphasis is placed on the amplitude and spatial resolution of recording, which both must be ‘adequate’ to capture the nature of strong earthquake ground motion and response of structures. The first strong motion accelerographs had optical recording system, dynamic range of about 50 dB and useful life longer than 30 years. Digital strong motion accelerographs started to become available in the late 1970s. Their dynamic range has been increasing progressively, and at present is about 135 dB. Most models have had useful life shorter than 5–10 years. One benefit from a high dynamic range is early trigger and anticipated ability to compute permanent displacements. Another benefit is higher sensitivity and hence a possibility to record smaller amplitude motions (aftershocks, smaller local earthquakes and distant large earthquakes), which would augment significantly the strong motion databases. The present trend of upgrading existing and adding new stations with high dynamic range accelerographs has lead to deployment of relatively small number of new stations (the new high dynamic range digital instruments are 2–3 times more expensive than the old analog instruments or new digital instruments with dynamic range of 60 dB or less). Consequently, the spatial resolution of recording, both of ground motion and structural response, has increased only slowly during the past 20 years, by at most a factor of two. A major (and necessary) future increase in the spatial resolution of recording will require orders of magnitude larger funding, for purchase of new instruments, their maintenance, and for data retrieval, processing, management and dissemination. This will become possible only with an order of magnitude cheaper and ‘maintenance-free’ strong motion accelerographs. In view of the rapid growth of computer technology this does not seem to be (and should not be) out of our reach.  相似文献   

澜沧-耿马等强震迁移活动与地电前兆场时空关系     

李晓玲  汪志亮  余素荣 《地震》1996,(3)

研究1988年11月至1990年10月近2a时间内,在22°～36°N,98°～104°E地区连发性的5次6级以上迁移地震与地电前兆的时空关系。结果表明,这组连发性迁移强震发生之前,地电前兆在南北两地区观测到两个应力相对集中区。随着南部系统内应力不断向北调整,发生了多次强震。这组连发性的强震孕育,包括它们各自前兆场分布和发育,彼此并不是孤立的,而是彼此呼应的。  相似文献   

中国大陆强地震时间间隔的概率          下载免费PDF全文

于利民  李钦祖  刁桂苓  孙佩卿  陈敬伟 《地球物理学报》1996,39(4):493-499

以东经１０８°线为界，把中国大陆分为东、西两部，东部取震级Ｍ≥６的地震、西部取Ｍ≥７的地震为强地震．利用有史以来全部地震资料，针对不同情况和不同时期，系统地研究了相继两次强地震之间的时间间隔，目的在于讨论一次强地震发生之后，下一次强地震何时发生．在所有情况下地震间隔数目都随时间间隔值的增大呈明显的趋势性减小．给出了８种情况下的间隔数目统计和相应的模拟函数，以及间隔值的经验概率和相应的函数模拟概率．由此可估计时间间隔为某个值的概率，也可估计时间间隔处于某个区间的概率．反之，对于给定的概率，可估计时间间隔的值或它所处的区间．  相似文献   

东昆仑活动断裂带的强震构造条件及未来强震危险区分析   总被引：4，自引：0，他引：4  

张瑞斌  赵培林  陈玉华 《高原地震》1996,(3)

通过对东昆仑活动断裂带强震构造条件的研究发现，这条断裂带的强震构造条件不仅与所处的区域地壳运动状况有关，而且与该活动断裂带的规模、形态，断裂带的构造组合及断裂带的运动条件等密切相关。在研究了东昆仑活动断裂带强震构造条件的基础上，还沿断裂带划出了三个未来强震危险区。  相似文献   

有序性分析与新疆7级强震预测     

王兰英  门可佩 《高原地震》1996,(4)

自然数可以视为反映世界客观本质的一种重要秩序，即信息，它不因加法处理而失真［１］。强地震在一定的时空范围内重复出现的现象称为有序性。自１７１６年以来，新疆及其邻区７级以上强震在时间上具有良好的有序性，有些强震在空间上亦表现出一定的有序性。强地震时间间隔值以６０、３０、４１、１９和１１年占据主导分布，并且相互之间关系密切。根据强震活动的有序性结构可进行预测：该地区未来Ｍ≥７强震可能发生在２００４年和２０１５年前后。  相似文献   

Amplitude Ratio of Regional Seismic Phases: An Efficient Indicator of Thermal State of the Lithosphere     

Gao Shiyu  Zhang Lianqiang  Tang Tianming  and Fu ChanghongInstitute of Geophysics  SSB  Beijing  China 《中国地震研究》1996,(2)

By analyzing seismograms of short period records at the Beijing SeismoJogicaJ Observatory, the present paper investigates the amplitude ratio of seismic phases. The results indicate that the amplitude ratio of Sn/Lg is correlated with the lithosphere structure, the thermal state, and strong earthquake occurrence in the region the seismic rays pass through. The significance of such a correlation in the study on the genesis and prediction of strong earthquakes is discussed.  相似文献   

El Ni?o影响热带大气季节内振荡的动力学研究   总被引：3，自引：0，他引：3  

李崇银  李桂龙 《大气科学》1996,20(2):159-168

根据El Ni?o期间热带大气状态的异常特征，确定了在简单大气动力模式中描写海温异常的参数化方法。然后利用斜压半地转两层模式从动力学上分析研究了El Ni?o对热带大气低频波的影响。理论分析同有关热带大气季节内振荡的资料分析结果完全一致，El Ni?o事件使热带大气季节内振荡减弱。  相似文献   

信息增益在地震趋势估计中的应用   总被引：2，自引：0，他引：2  

沈萍  冯国政 《中国地震》1996,12(4):378-382

从熵中信息增益的定义出发，将地震中的能量和频度作为一个整体考虑，研究了全球１９００－１９９２斫Ｍ≥６．０地震的信息增益。结果表明，强震前有信息增益减小的特点。信息增益方法的引入，为利用中小地震进入地震跟踪预报提供了一个新途径。  相似文献