四川省北川县擂鼓盆地地壳稳定性与城镇选址

Crustal Stability of the Leigu Basin in Beichuan County,Sichuan Province and Its Possibility for a New Town Site

5·12汶川地震造成四川多座县城遭受毁灭性破坏,北川县城几乎被地震夷为废墟,因此灾后重建选址成为震后迫切需要开展的工作。野外地质调查和综合分析认为,尽管北川县擂鼓镇所在的擂鼓盆地处于强烈活动构造带,但盆地处于活动断裂的下盘,盆地基底整体性较好,内部断裂不甚发育,是活动构造带中的相对稳定地块,即"安全岛"。这个地区在北川县地震灾后重建中具有重要的利用价值。本文基于野外活动断裂和地震地质灾害调查,运用李四光先生的"安全岛"理论,初步论证了擂鼓盆地的地壳稳定性,并从环境工程地质角度分析了擂鼓盆地的工程地质和水文地质条件,对北川县地震灾后重建规划和灾民安置场地选址具有重要意义。

Owing to the fact that several county towns in Sichuan were badly damaged, especially Beichuan County was in ruin by the Wenchuan earthquake on May 12,2008, selection for town sites has become the important task for reconstruction of earthquake-striking areas. Field investigation and comprehensive analysis show that the basin is of good basement and has no fractures developed inside the basement, although it is located in an intensive active tectonic zone. The basin is in a relatively state block-so called safety island. Thus the Leigu basin is of practical value for reconstruction of Beichuan County. Based on field investigation of active faults and seismic hazards, applying the theory of Safety Island originated by Prof. Li Siguang, this paper discusses the crustal stability of Leigu basin, and analyzes the characteristic of the engineering geological and hydrological conditions, which can provide geological evidences for reconstruction and relocation of Beichuan earthquake-hit area.