对汶川地震宏观震中和极震区的认识

SOME INSIGHTS INTO THE MACRO-EPICENTER AND MEIZOSEISMAL REGION OF WENCHUAN EARTHQUAKE

汶川8.0级地震是近30年来世界范围内最严重的地震灾害之一。在大量的现场实地调查基础上,对汶川地震的极震区和宏观震中分布点进行了初步的研究,分析认为汶川地震极震区与地表破裂带关系极为密切,极震区烈度为Ⅺ度,表现为强烈的带状分布;宏观震中与传统的宏观震中的认定有较大的区别,不再是一个点,而是一组点。汶川县漩口镇蔡家杠村是宏观震中在西南段的起点,中间经由汶川县映秀镇、银杏乡,都江堰市虹口乡北部,彭州市小鱼洞镇北部、龙门山镇北部,什邡市红白镇北部,到绵竹市清平乡截止,跳过安县,再由北川县擂鼓镇起至漩坪乡、北川县城曲山镇、北川县陈家坝乡、平武县平通镇、南坝镇北部截止。宏观震中区是一条狭长的中间断开的线或窄带,这将在很大程度上影响我们对灾区的总体认识。

The Ms 8.0 Wenchuan earthquake is one of the most devastating earthquakes in recent 30 years in the world. Based on a number of on-the - spot investigations,preliminary research on the macro-epicenter and meizoseismal region has been done. The analysis reveals that the meizoseismal region, whose intensity is Ⅺ and shows obviously zonal distribution,is controlled by the rupture process and there exists a close relationship between the meizoseismal region and the rupture zone. What＇s more, the macro-epicenter of Wenchuan Earchquake is quite different from those of previous earthquakes,not just one point any more but a group of points. This group of points begins from the village of Caijiagang of Xuankou town of Wenchuan county,passes through Yingxiu town, Yinxing town of Wenchuan county,the north of Hongkou town of Dujiangyan city,the north of Xiaoyudong town and Longmenshan town of Pengzhou city, the north of Hongbai town of Shifang city, and ends at Qingping town of Mianzhu city. Skipping over Anxian county,it continues from Leigu town of Beichuan county to Xuanping town,Qushan town, Chenjiaba town, Pingtong town of Pingwu county, and ends at the north of Nanba town. The shape of the macro-epicenter area of the Wenchuan earthquake can be considered as a narrow belt or line, broken in the middle. This point of view will influence our overall understanding of quake-hit areas to a great extent. Besides, the realization that the macro-epicenter of a severe earthquake probably presents like a line is of great significance when we cope with severe earthquakes later, especially when determining key relief areas, planning the relief work, evaluating the earthquake situation, identifying key areas of scientific investigation and so on.