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龙门山断裂带是否存在类似汶川5.12大地震的地质记录,是地震科学工作者所关注的科学问题之。处于中央断裂带中段和北段分界地区的北川-邓家一带,古地震研究对认识整个龙门山断裂带的大地震复发特征有重要意义。沿北川-邓家地震地表破裂带,可能有过早期活动,并兼顾是否有较多细粒第四纪沉积物,以便能较清晰地分析、判断古地震事件以及采集测年样品,所以我们在沙坝1组、和尚坪和邓家海光6组等3个地点开挖了4个探槽,并进行了断错地貌的实测,发现了该地区明显的古地震遗迹,以及该地区特殊的正断层地表破裂样式。通过探槽和实测地貌情况与前人在龙门山中央和前山断裂带的古地震研究结果的对比分析,结果显示该地区至少发生过两次地震事件(包括5.12地震事件在内),与龙门山中央和前山断裂大部分地点已揭露的古地震事件相吻合。而通过对该地区地貌侵蚀特征与地震陡坎的高度变化分析,可以得出该地区之前的地震事件与5.12地震的大小相近。
Whether there is a Longmenshan fault zone similar to the Wenchuan 5.12 Earthquake geological record is a scientific issue of concern for earthquake scientists. The study of paleoseismicity in the Beichuan-Dengjia area, which is located in the middle section of the central fault zone and the northern section, is of great significance for understanding the characteristics of the recurrence of large earthquakes across the Longmen Shan fault zone. There may be early events along the surface rupture zone of the Beichuan-Dengjia earthquake, taking into account whether there are more fine-grained Quaternary sediments in order to be able to analyze and judge paleoearthquakes more clearly and to collect dating samples so that we Shaba 1, Hepingping and Dengjiahai 6 groups of three sites such as excavation of the four trenches, and the fault survey of the landforms and found the obvious paleo-earthquake ruins in the area, as well as the region’s special normal fault Surface rupture pattern. Through the comparison between the results of the trenches and the measured geomorphology and the paleo-earthquake research results of the predecessors in the central Longmenshan and the Qianshan fault zone, the results show that at least two seismic events (including 5.12 earthquake events) occurred in this area, The paleoearthquakes that have been uncovered in most of the central and previous parts of the Qianshan fault coincide. By analyzing the features of the landform erosion and the height changes of the earthquake scarp in the area, it can be concluded that the previous earthquake events in this area are similar to the magnitude of the 5.12 earthquake.