龙门山前山断裂南段强震崩塌与1327年天全地震

Landslides Triggered by Earthquake in South Longmenshan Fault and Tianquan Earthquake in 1327

具有强震孕育能力的龙门山前山断裂南段附近地区的强震事件仅有以史料记载的1327年天全地震和仪器记载的1970年大邑6.2级、2013年芦山7.0级地震,这些地震均引发大量的崩塌、滑坡。调查对比发现,沿龙门山断裂南段大川-双石断裂沿线的典型地段分布的历史地震崩塌范围和运移距离都大于芦山地震所触发的崩塌,崩塌的方量和粒径表现为南西往北东逐步减少、减小的趋势。崩塌调查、崩塌体埋藏物和表生地衣相对年代学测试结果、史料记载与震例对比和地震有感半径与震级经验公式计算综合表明,1327年天全地震引起的地面震动大于芦山地震,是天全县"大岩崩"地名和双石镇"晒经书"景观形成的主要原因,1327年天全地震的震中可能位于龙门山断裂南段大川-双石断裂附近的天全响水溪一带,震中烈度≥Ⅸ度,震级≥7.0。

According to history and instruments, south Longmenshan fault, which is considered a seis- mogenic structure, has experienced three strong shocks： the 1327 Tianquan, the 1970 Dayi, and the 2013 Lushan earthquakes. These earthquakes triggered rockfall and landslides. We survey the typical landslide and the historical earthquake landslides along the Dachuan-Shuangshi fault across the earthquake area and find the distribution range and transport distances triggered by historical earthquakes greater than the Lushan earthquake. The density, volume and particle size triggered by the historical earthquake reduces from southwest to northeast along the fault. Results from the rock fall of the his- torical earthquakes and the Lushan earthquake, based on relative chronological tests of buried object and epigenetic lichen, and the formula of sensible radius and epicenter, show that the ground vibration is more heavily triggered by the Tianquan earthquake in 1327. Vibrations from the 1327 earthquake may have triggered the Tianquan county ＂Dayanbeng＂ and Shuangshi town ＂Shaijingshu＂. The histor- ical earthquake epicenter may be located in the southwest section of the Dachuan-Shuangshi fault, near Tianquan county Xiangshuixi town. The intensity from the epicenter is greater than 9, and the magnitude of the paleo-earthquake may be great than or equal to the Lushan earthquake.