岷县漳县6.6级地震极震区峰值加速度估算

Estimation of Peak Ground Acceleration in Magistoseismic Area of the Minxian-Zhangxian M_S6.6 Earthquake

简述了2013年7月22日岷县漳县6.6级地震极震区破坏特;针对调查中发现的砖柱铁门地震破坏现象,应用力学分析原理估算了极震区地震水平峰值加速度。估算结果表明,极震区禾驮乡拉路村地震水平峰值加速度在5.1～5.4m/s2,即0.52～0.55g左右,大于《中国地震烈度表》Ⅷ度区参考的水平向地震峰值加速度,这可能与研究区黄土及山坡的双重放大效应有关。因此在灾后恢复重建及该区未来的抗震设防中应考虑这两方面的作用影响。

The horizon important parameter tal peak ground acceleration （PGA） distribution in an earthquake is a very and can be used as a reference for the determination of seismic intensity. In Minxian--Zhangxian Ms6.6 earthquake disaster region, there is only Minxian seismostation in in- tensity region got the seismic records and in intensity region there is no seismic record. During site investigation, a kind of brick doorpost was noticed in Lalu village in Hetuo town, meizoseismal area. The doorpost with iron door broke in the earthquake and the doorpost without iron door kept in good condition, which can be used to estimate the PGA in this area. Based on the field investigation, the destruction features in meizoseismal area of the Minxian--Zhangxian Ms6.6 Earthquake are sketched and the damage to the brick doorpost with iron door in earth- quake are described and analysed. The seismic intensity ~ region is about 706 km2 and the most serious damage area include Yongguang, Yongxing and Lalu villages, most of them located in the high half slope covered by thick loess. According to the characteristics of the doorpost and its break, the earthquake horizontal PGA was estimated by mechanics analysis theory using a simpli- fied strut-node model, which can be used as a reference for seismic intensity division and post-dis- aster reconstruction design. The results show that the earthquake horizontal PGA of Lalu village in Hetuo town, meizoseismal area, is up to 5.1~5.4 m/s2 , namely 0.52~0.55 g, which is much greater than the reference value of eight-degree region in the Chinese Earthquake Intensity Scale.Judging by the related study about the influence of local topography on ground motion in moun- tain region of southern Gansu province and the seismic records observed on Shangcheng platform in Wenxian during Wenchuan Ms8.0 earthquake, the high PGA may be caused by the amplifica- tion effects of both high mountain slope and thick loess in study area. Compared with the PGA value of seismic record by seismostation in Minxian--Zhangxian Ms6. 6 earthquake and Lushan Ms7.0 earthquake, the PGA value is usually much higher than the reference value in the Chinese Earthquake Intensity Scale of the same intensity region. Therefore, these two effects should be considered for the post-disaster reconstruction and seismic fortification in the future and the forti- fication criterion should be increased for villages in high half slope area.