Strong ground motion simulation during the November 1759 Earthquake along Serghaya Fault in the metropolitan of Damascus, Syria

The seismic hazard potential for metropolitan of Damascus, Syria is mainly controlled by earthquakes along Serghaya Fault which is a branch of Dead Sea Fault System. In this study, strong ground motion due to the November 1759 Earthquake along the fault of Serghaya was estimated with a numerical simulation technique. In the simulation, the Kostrov-like slip-velocity function was used as an input to the discrete wave number method to simulate the strong ground motions in a broadband frequency range. In order to model the incoherent rupture propagation which can excite large high-frequency waves, random numbers are added to arrival time of circular rupture front. MMI intensities calculated from the synthetic ground motions are compared with the observed values by Ambraseys and Barazangi (J Geophys Res 94:4007-4013, 1989). The calculated intensities are in good agreement with the observed ones at the most sites that validate appropriateness of the proposed source model. The PGA and PGV in the eastern region of Damascus city are higher than those in the western region due to the effects of local site amplification. The simulated high-frequency (1.0–6.0 Hz) ground motions for the sites in the Damascus city are higher than the design requirements defined by the Syrian building code. Furthermore, the simulated high-frequency ground motions for sites in the focal region are bigger than the design requirements in the case of the near-fault factors and are not considered. That demonstrates the appropriateness of considering the near-fault factors for a site near the focal region as introduced by the new building code.     

Reconstructing the Kolka surge on September 20, 2002 from the instrumental seismic data

The process of the Kolka rock and ice avalanche on September 20, 2002 in the Karmadon Gorge, North Ossetia is reconstructed based on analyzing the instrumental seismic records. The results of calculating the velocities of the rock-ice mass movement on the interval from the Maili Glacier to the Karmadon Gate agree with the results of mathematical modeling the avalanche flow in a gorge. The macroseismic effect of the surge impact on the rocks in the region of the Karmadon Gate is investigated from seismic data and the results of surveying the territory carried out by the authors in 2003–2004.     

Distribution of slip along an earthquake fault

IntroductionInearthquakeandengineeringseismology,fortheexplanationofthehigh-frequencycontentsinearthquakegroundmotion,itisoftenassumedthatalargeearthquakeiscomposedofmanysmallereventswithavarietyofsizes(Frankel,1991).Thesesmalleventscomefromtheruptureoftheasperitiesalongtheearthquakefault,showingthecharacteristicsoffractals(Aki,1981).Thisworkingassumptioncanexplainsomeoftheimportantpropertiesofseismicsourcesuchasthehigh-frequencyfall-offofsourcespectra.Ontheotherhand,however,beinglimitedbyobs…     

Assessing the intensity of the September 17, 2003, Khoito-Gol earthquake from instrumental and macroseismic data

The present study is devoted to the assessment of shaking intensities due to the September 17, 2003, earthquake occurring in the Khoito-Gol basin (southwestern flank of the Baikal Rift System). The instrumental and macroseismic data used here were acquired during an investigation into the impact of this seismic event. The highest intensity of shaking, VI, was recorded at Khoito-Gol, the human settlement that was the nearest to the instrumental epicenter. A nonuniform distribution of intensity was found for different directions from the epicenter. A scatter of as much as two intensity units was recorded at one settlement.     

用浅层地震勘探资料研究蓟运河断裂的第四纪活动特征

蓟运河断裂是天津地区东北部的一条重要断裂,是张家口—渤海构造带的组成部分.由于未对蓟运河断裂的活动性进行过专门探测研究,其空间展布及第四纪活动性一直存在争议.经广泛收集资料确定蓟运河断裂的大致展布,并布设9条人工地震测线,采用可控震源对该断裂进行探测.结果表明:蓟运河断裂不是一条南北贯通的断裂,其大致分为北西段和南东段...     

利用背景噪声互相关研究汶川地震震源区地震波速度变化

利用2007年3月至2009年3月四川数字地震台网的宽频带连续波形资料,通过计算地震背景噪声互相关提取台站对间的经验格林函数,在0.1～0.5 Hz频带下测量每天经验格林函数与参考经验格林函数的走时偏移,进而得到各台站对在该时段内的相对地震波速度变化.结果表明,2008年5月12日汶川Ms8.0级地震造成了震源区地震波速度的急剧降低,最大降幅达0.4%;大致以安县为界,余震带西南部地区在汶川主震后波速降即达到最大值,而东北部地区的最大波速降一般出现在主震后的1~4个月,相对地震波速度变化的这种分段特性与地震序列的时空分布特征有较好的对应关系;在震源区外围的四川盆地也观测到了震后波速降低,而川西高原内部则没有出现显著的波速变化.进一步的分析和计算结果表明主震的静态应力变化和强地面运动引起的地表破坏都不能很好地解释震后波速的急剧降低,地震导致的断层区内部结构破坏和周边介质应力状态改变可能是波速变化的主要原因.     

板块地震迁移链与汶川地震

从1956年开始沿印度洋—亚洲和太平洋板块边界的地震迁移触发了2008年5月12日M8.0中国汶川地震。迁移链为东西两条,彼此相向迁移,在缅甸弧附近的中国大陆汇合,并触发地震。迁移持续约50年。与此相类似的迁移发生在1902—1957年,迁移触发了1950年西藏东部M8.5地震和1957年蒙古M8.3地震。预计1956—2008地震迁移可能尚未结束,可能会继续触发大地震。     

汶川地震断裂带滑移行为、物理性质及其大地震活动性——来自汶川地震断裂带科学钻探的证据

断裂带物质组成、结构及其物理性质是理解断裂变形机制和地震破裂过程的基础和关键,断裂带地震（黏滑）和非地震（蠕滑）滑移行为不仅对了解地震活动性和山脉隆升过程具有重要意义,而且直接为防震减灾提供科学依据.我们以穿过龙门山映秀—北川和灌县—安县断裂带的汶川地震断裂带科学钻探（WFSD）岩心和地表出露的断裂带为研究对象,通过对断裂岩组成、结构、显微构造和钻孔物性测井数据进行分析研究,确定了龙门山逆冲断裂带滑移行为和物性特征,初步探讨了大地震活动性和有关断裂带的隆升作用：（1）映秀—北川断裂带倾向NW,浅部倾角~65°,发育的断裂岩厚约180~280 m,由碎裂岩、假玄武玻璃（地震化石）、断层泥和断层角砾岩组成.断裂带具有高自然伽马、高磁化率值、低电阻率、低波速等物理性质以及对称型破碎结构.断层泥普遍具有摩擦热效应的高磁化率值和石墨化作用特征,是古地震滑动的岩石记录.表明映秀—北川断裂带为经常发生大地震的断裂带,晚新生代以来类似汶川地震的大地震复发周期小于6000—10000年,具有千年复发周期特征.（2）灌县—安县断裂带倾向NW,浅部倾角~38°,发育的断裂岩厚约40~50 m,仅由断层泥和断层角砾岩组成,具有典型的"压溶"结构,表现出蠕滑性质.除压溶作用外,定向富集的层状黏土矿物和微孔隙的发育使断层强度变弱.断裂带具上盘破碎的非对称型破碎结构,除具低磁化率值特征外,其他物性与映秀—北川断裂带一致.（3）根据断裂岩厚度与断层滑移量相关经验公式关系,以及断层产状,粗略估算映秀—北川断裂带自中生代以来累积垂直位移量大于9 km,灌县—安县断裂带累积垂直位移量小于3 km.映秀—北川断裂带长期大地震产生的累积垂直位移量是龙门山隆升的主要贡献.     

Characteristics of fault rocks and paleo-earthquake source along the Koktokay-Ertai fault zone,Xinjiang,China

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几种仪器烈度算法在汶川地震与芦山地震中的可靠性比较

破坏性地震发生后, 特别是在通信中断的情况下, 利用仪器烈度快速估计地震动强度(烈度)的分布情况, 可为开展最有效的地震应急救援提供决策依据. 该文介绍了现有的几种仪器烈度算法, 并利用汶川地震与芦山地震中获得的强震加速度记录对各种算法的可靠性进行了比较. 结果表明, 在这两次地震中只利用地震动峰值参数确定仪器烈度的算法可靠性较低, 而考虑反应谱特性的算法可靠性更高. 在未得到更多强震数据的检验前, 建议采用袁一凡提出的仪器烈度算法, 或利用谱烈度值确定仪器烈度的算法, 或利用加速度反应谱值确定仪器烈度的算法.     

A fault model of the 1946 Nankaido earthquake derived from tsunami data

A fault model of the 1946 Nankaido earthquake (M = 8.2) is determined by the use of tsunami records of Uwajima, Shimotsu and Hososhima which were located within or near the area of major coseismic crustal deformation. Synthetic tsunamis computed for various fault models are matched with the observed tsunamis to determine the fault parameters. A low-angle thrust model slightly revised from a previous model by Ando is consistent with the observed tsunamis. The duration of faulting is constrained as less than 10 min based upon the tsunami. The fault is divided into an eastern and a western segment corresponding to areas associated with and without aftershocks, respectively. The fault area and dislocation for the western segment are 150 × 70 km² and 6 m, and those for the eastern segment are 150 × 70 km² and 3 m, respectively. The total seismic moment is 4.7 × 10²⁸ dyn·cm, significantly smaller than that obtained from a geodetic model by Fitch and Scholz, but still larger than that of the seismic model by Kanamori. The discrepancy in seismic moment between the seismic and the present models (RAN2) could be interpreted in terms of a slow dislocation on the fault, but this interpretation does not match the seismic intensity distribution and damage pattern, and the slow-slip model for the Nankaido earthquake is rejected. The discrepancy between the two seismic moments is considered insignificant within error involved in data and modeling assumptions. If the revised geodetic model (RAN2) is modified, the seismic moment required to explain the observed tsunamis would be reduced further by ～30%. If we consider the uncertainties involved in the fault model of Kanamori and the fault-finiteness effect affecting the amplitude of seismic waves, the seismic moment required to interpret the seismic-wave data could be increased, possibly being more than twice that of Kanamori. Thus, the two seismic moments from the different data sets could be close to each other within allowable tolerance. This implies that the rise time of the Nankaido earthquake was short enough to generate short-period seismic waves from both the western and the eastern fault segments.     

Deep structure of the Racha earthquake source zone from seismic tomography data

The Racha earthquake of 1991 was the strongest of the earthquakes recorded in the Caucasus. It was studied by an international epicentral expedition. Unique data gathered by this expedition included records of aftershocks whose swarm was very intense. A 3-D velocity model is obtained from analysis of these data by the method of local earthquake tomography. The ancient crystalline basement and the sedimentary-volcanic Mesozoic-Cenozoic cover could be identified from cross sections of the P wave field. The eastern and western boundaries of an uplift in the basement of the Dzirulskii Massif are delineated. Linear low velocity heterogeneities correlating with the active Kakheti-Lechkhumi fault zone and two Trans-Caucasian linear fault zones are discovered in the basement. The cloud of aftershock hypocenters is shown to correlate with a reflector coinciding with the cover-basement interface.     

龙门山断裂带映秀-北川断裂的古地震及其复发间隔初步研究(英文)

The activity of the Longmenshan thrust belt has concentrated mainly on its Wenchuan-Maoxian Fault, Yingxiu-Beichuan Fault, and Guanxian-Jiangyou fault since the Quaternary time.     

昆仑山口西8.1级地震前青藏块体边界断层异常活动

系统分析了青藏块体边界断层的形变资料，研究了断层活动的动态过程及空间分布。结果表明，昆仑山口西8．1级地震前孕震影响范围达到青藏块体的周边地区；发震断层所在的构造带震前断层活动最为剧烈；加强对构造块体断层整体活动的宏观动态比较和分析，有助于判定未来强震发生的危险地段；震后应力将转移并集中到西秦岭构造带及其邻近地区。     

安宁河-则木河-小江地震带强震危险性趋势讨论

研究了川滇地震区强震活动期格局的变化,认为自1976年以来已进入川滇地震区的"中区"为主体活动的新活跃期,并将可能持续至少二三十年;1985～1996年初的川滇强震活跃幕已经结束,1996～2002年处于6级地震的少发时段.根据川滇中区历史上出现过的东带(E102°～103°线)、西带(E100°线)交替活动特征估计未来几年安宁河-则木河-小江地震带将可能是大地震发生带.     

沿地震带地震迁移的有序特征

对大华北的山西、燕山、华北平原和长江中下游地震带内的地震迁移规律、各带地震的迁移速度和地震序列特征进行研究,结果表明,各地震带是有机地联系在一起的,形成个统一体。     

Episodes and ages of seismic landslides along the Changma fault zone

ＥｐｉｓｏｄｅｓａｎｄａｇｅｓｏｆｓｅｉｓｍｉｃｌａｎｄｓｌｉｄｅｓａｌｏｎｇｔｈｅＣｈａｎｇｍａｆａｕｌｔｚｏｎｅＬａｉ－ＸｕｎＫＡＮＧ；（康来迅）ａｎｄＪｉａｎ－ＲｏｎｇＷＡＮＧ（王建荣）（ＥａｒｔｈｑｕａｋｅＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅｏ...     

读取地震目录自动截取波形程序

“九五”期间各个数字测震台网利用北京港震机电技术有限公司提供的EDSPRTP实时数据处理系统接收各个数字地震台站数据并将数据保存为EDAS格式的连续波形文件.本文介绍EDAS格式波形文件的结构以及利用C语言编写程序,从而实现通过读取地震目录文件得到地震事件的发震时刻和震级,然后自动截取地震波形并且保存该地震事件.     

祁连—海原断裂带库仑应力演化及地震危险性

祁连—海原断裂带是青藏高原东北缘重要的活动断裂带,调节着青藏高原北东向推挤作用和阿拉善地块的东西向运动.已有地震地质和数值模型结果显示,祁连—海原断裂带目前存在几个强震破裂空段且其上应力积累显著、断层闭锁程度高,2022年1月8日门源MS6.9地震即发生在祁连—海原断裂带西段的断层高闭锁、应力积累显著的破裂空段.为进一...     

Evaluation of the seismic moment of the April 20, 2013 Lushan earthquake

The April 20, 2013 Lushan earthquake which occurred in Sichuan, China had only moderate thrust. However, the computed seismic moments （M0） for the Lushan earthquake calculated by several institutions differ significantly from 0.4 × 1019 to 1.69 ×019 Nm, up to four times difference. We evaluate ten computed Mos by using normal mode observations from superconducting gravimeters in Mainland China. We compute synthetic normal modes on the basis of moment tensor solutions and fit them to the observed normal modes. Comparison of our results indicates that Mo is the main cause for some large differences between observations and synthetics. We sug- gest that a moment magnitude of Mw6.6, corresponding to a Mo of 0.97-1.08 × 1019 Nm, characterizes the size and strength of the seismic source of the Lushan earthquake.