以拉张正断层作用为主的京西盆岭活动构造区(112°～116.2°N,38.3°～41.5°E)自BC231年以来共记载和记录15次M6～7.5地震.本研究计算每一次强震产生的以及逐次积累的库仑破裂静应力变化,并分析强震之间的应力触发关系.结果显示在14次后发的强震中,有10次发生在先发强震产生的积累库仑破裂静应力变化为正的触发区,触发率为71％.所有15次历史强震作用共同引起研究区积累库仑破裂静应力变化的正值区,主要分布于六棱山北麓断裂中段、怀涿盆地北缘断裂、新保安沙城断裂、桑干河断裂以及蔚县盆地南缘断裂,并使得这些断裂(段)的强震危险性有所增加,这可为分析研究区的未来强震危险性提供参考.

本文对龙蟠-乔后断裂,采用1/5万数字高程模型和2.5m分辨率的ALOS遥感影像,在ENVI 4.5平台上将二者融合,获取三维可视化卫星遥感影像.从不同的角度、尺度,对三维影像进行构造地貌解译,获得断裂的展布和活动性质.之后选择部分场点考察验证,发现地质地貌体的断错特征与影像上分析的一致,说明三维影像的构造地貌解译在获得断裂几何展布研究中完全适用.本文应用该方法对龙蟠-乔后断裂的研究表明:龙蟠-乔后断裂由北向南依次经过老母增、龙蟠东、鸿文、雄古、北高寨、龙门邑、桃园、东富乐、岩峰场等;依据断裂几何不连续、走向变化、活动性质变化等,由北向南分为龙蟠段、鸿文段、九河段、剑川盆地段、东富乐段.龙蟠段与鸿文段为左旋左阶斜列;鸿文段与九河段为左旋左阶斜列,九河段走向相较鸿文段和南侧的剑川段逆时针旋转约5°,九河盆地的发育与走向变化相关;九河段与剑川盆地段为左旋右阶斜列,剑川盆地的发育不仅与龙蟠-乔后断裂相关,更可能与丽江-小金河断裂的活动也相关;剑川盆地段与东富乐段为左旋右阶斜列,斜列区为拉分性质的沙溪盆地.综上可知,龙蟠-乔后槽谷的形成与断裂最新几何结构和运动性质仅在部分段落上一致,从这个角度看槽谷的形成不排除古河道等其它因素的影响.

Contemporary tectonic stress field on boundaries of active tectonic blocks in and around western China mainland is obtained from the data of Harvard CMT solution and reliable focal mechanism solutions from 1920to 1999selected by Xu Zhonghuai.We obtained the stress field by testing input and checking FMSI code ( Gephart ) many times.Most of the maximum principalstressσ 1 axes on active tectonic boundaries are horizontal.To the west of 90°E in and around western China mainland,the horizontalσ 1 axes are nearly in N--S direction.In the northeastern area of Qingzang plateau,the horizontalσ 1 axes are nearly NE--SW.In the southeastern area of Qingzang plateau,the horizontalσ 1 axes turn around clockwise around eastern end of Himalaya arc.The minimum principal stressσ 3 axes show two dominant dip angles.In Xiyu active tectonic block region and on some segments of the northeastern edge of Qingzang plateau,the σ 3 axes are steep,while in the Qingzang block region theσ3axes are horizontal. So there are more thrust earthquakes in the Xiyu block region and on some segments of the northeastern edge of Qingzang plateau than in the Qingzang plateau block region.The stress field on the same active tectonic boundary is heterogeneous.On north Tianshan belt,south Tianshan belt,west Qinling-Delingha belt,Minshan--Longmenshan belt and Anninghe--Xiaojiang belt,the heterogeneity is relatively weak.On west Kunlun belt,Haiyuan--Qilian belt,east Kunlun belt,Mani--Yushu belt,Lancangjiang belt and western belt of west Yunnan block,the heterogeneity is relatively strong.The heterogeneity on Kalakunlun--Jiali belt and Himalaya belt is more notable.Due to limited focal mechanism data,this paper only gave the stress field on some segments of the active tectonic block boundaries.

this paper compares the seismicity between eastern Asia,western Asia and eastern Mediterranean regions.Seismicity includes not only the analysis of earthquake time-space-magnitude distribution pattern,but also the structure and dynamic background.The synthetic analyses show that seismicity and deformation of eastern Asia,western Asia and eastern Mediterranean region are closely related to the interaction(convergence collision,subduction and velocity) between Eurasia plate and surrounding plate(North America,Pacific,Philippine sea,India,Arab and Africa plate).There are macroscopic earthquake epicenter distributions with a pattern of alternate contraction and dissipation,and symmetrical fault trends in the eastern Asia,western Asia and eastern Mediterranean region.But there are some differences for seismicity and dynamic background in the plate boundary and inland area of these regions.

Using the earthquake sequence data of MS7.0~7.9 earthquakes since 1966 in mainland China,we study the characteristics of magnitude difference distribution between main shocks and their strong aftershocks and the spatial distribution characteristics of strong aftershocks away from their main shocks.The results show that the magnitude difference distribution obeys intercepted exponential distribution and obtain the B value of 0.72 for the whole earthquake sequences and the B value of 0.73 for the strike-slip earthquake sequences,while the spatial distribution of strong aftershocks obeys normal distribution and the dominated distribution area of strong shocks of strike-slip earthquakes is 5~59 km and 10~29 km for the no-strike-slip earthquakes.

本文分析了1900-2008年东亚大陆大三角地震区7.5级以上大地震的地震活动时空图像,认为:① 1902-1974年东亚大陆大三角地震区的7.5级以上浅源地震成组活动的主体地区,沿着大三角地震区的边界顺时针迁移,到了1997-2001年开始转移到大三角地震区的内部;②对于整个大三角地震区而言,近代7.5级以上浅源地震的震级(M)-时间(t)过程表明,地震活动是活跃和平静交替出现的幕式过程;③大三角地震区近代7.5级以上浅源地震的时空迁移图像的力学机制,可能是地震区内地震断层应力转移和耦合的相互作用.

The Wenchuan M8 earthquake occurred on the Longmenshan fault zone.Based on field investigation of the surface rupture and focal mechanism study of the aftershocks,we studied the geological relationship of main rupture,secondary rupture and trigged rupture.The main rupture is about 200 km long which can be divided into the south part and north part.The south part consists of two parallel fault zones mainly reverse,with several parallel secondary ruptures on the hanging wall of the main fault,and the north part is a single main fault zone characterized with lateral strike slip and reverse faulting.Comparing with 300 km long aftershock distribution,the surface rupture only occupy 200 km of them,and the left 100km on the northeast of the main rupture were triggered earthquakes.The Earthquake geology results of this paper may be useful for studying the earthquake risk evolution on the Longmenshan fault system.

The interaction zone between southern Tianshan and northern Tarim is located at the northeast side of Pamir. It is a region with high seismicity. We constructed a seismotectonic model for the west part of this zone from geological profiles, deep crust seismic detection and earthquake focal mechanisms data. Based on the synthesized geological features, deep crust structure, and earthquake focal mechanisms, we think that the main regional tectonic feature is that the Tianshan tecto-lithostratigraphic unit overthrusts on the Tarim block. The Tianshan tectonic system includes the Maidan fault and thrust sheets in front of the fault; The Tarim tectonic system includes the underground northern Tarim margin fault, conjugate faults in basement and overthrust fault in shallow. The northern Tarim margin fault is a high angle fault deep in the Tarim crust, adjusting different trending deformation between Tianshan and Tarim. It is a major active fault that can generate large earthquakes. The other faults, such as the Tianshan overthrust system and the Tarim basement faults in this area may generate moderately strong earthquakes with different styles.

The great Kunlun earthquake occurred on Nov. 14, 2001 in Qinghai Province, China. Five large aftershocks with magnitude larger than 5.0 occurred near the Kunlun fault after main shock. Calculations of the change in Coulomb failure stress reveal that 4 of 5 large aftershocks occurred in areas with Δσf>0 (10−2–10−1 MPa) and one aftershock occurred in an area with Δσf=−0.56 MPa. It is concluded that the permanent fault displacement due to the main shock is the main cause of activity of large aftershocks, but not the whole cause.

2000年1月15日在云南省姚安县发生了MS 6.5级地震,震后发生了7次M≥4.0级的较强余震.本文计算了姚安MS 6.5级主震后,主震和前震在7次强余震破裂面上诱发的库仑破裂应力变化(ΔCFS).结果表明,有5次较强余震发生在库仑破裂应力增加(ΔCFS＞0)的地区,增加的范围为10-2～10-1MPa.并对结果的可靠性进行了检验,发现在前震和主震的破裂面长宽度和位错量估计值分别取上下限的16种组合情况下,5次较强余震破裂面上的库仑破裂应力变化都为正,只是数值在10-3～10-1MPa之间变化,而另2次较强余震破裂面上的库仑破裂应力变化正负值发生变化.结果表明,主震和前震位错产生的库仑破裂应力变化是姚安MS 6.5级地震较强余震活动的重要原因.

In order to make a more effective use of the data from regional digital seismograph networks and to promote the study on shear wave splitting and its application to earthquake stressforecasting, SAM software system, i.e., the software on systematic analysis method of shear wave splitting has been developed. This paper introduces the design aims, system structure,function and characteristics about the SAM software system and shows some graphical interfaces of data input and result output. Lastly, it discusses preliminarily the study of shear wave splitting and its application to earthquake forecasting.

Western China continent and its surroundings is one of the most active seismic area in the world, where have occurred 16 great earthquakes with magnitude 8.0 since 1800 A.D. The recent great West of Kunlun Mountain Pass earthquake (36.1°N,90.9°E;M_s=8.1) of Nov. 14, 2001 occurred in the western China continent after 44 a of quiescence since the great Mongolia earthquake (M_s=8.3) occurred in 1957. The researches in this paper show that there is an episodic or cyclic seismic process of activity and quiescence alternatively, the 1957 Mongolia earthquake may be a beginning of new cycle in the studied area,and the great West of Kunlun Mountain Pass earthquake was the second event in the new cycle. Supposing temporal changes of the cumulative number of event in a cycle follow an exponential function, the next great earthquake (M_s≥8) in Western China continent and its surroundings will occur in 2026. If the process is approximately the Poisson one, the occurrence probabilities of the great earthquake (M_s≥8) in Western China continent and its surroundings before 2005, 2010 and 2015 will be 0.29, 0.53 and 0.70 respectively.

介绍了中国地震前兆台网中心数据信息网络服务系统,该系统建设采用全新思路,将地震前兆数据接收、管理、处理、共享融为一体,解决了前兆数据量大、结构复杂、难于管理的历史现状.文中从系统的组成、网络结构、技术特点介绍了地震前兆数据接收、管理、处理、共享四个关键环节的技术进步.尤其是地震前兆数据库建设,摒弃了当前常规数据库设计思路,突破了结构化数据类型的约束,使数据库中字段长度随时可调,字段中数据位数随时可变.文中还介绍了中国地震前兆台网中心在Internet网络基础上建立的Web服务器,使各地分析预报人员随时获取中国地震前兆台网中心数据信息网络服务系统中的历史数据和最新前兆数据,为地震前兆数据共享服务奠定了坚实的基础.