活动断裂的变形特征及其大地震复发周期的估算

Deformation feature of active fault and recurrence intervals estimation of large earthquake

活动断裂是晚更新世10-12万年以来一直在活动,现在正在活动,未来一定时期内仍会发生活动的各类断裂。活动断裂控制着大地震的发生,是不同类型地震的发震构造。从活动断裂的变形特征来看,不同性质的活动断裂具有不同的发震构造模型,研究这些问题对认识强震的发震条件,划分潜在的震源区或地震危险区,评估发震构造和发震地点具有重要的意义。基于国内外对不同类型活动断裂的认识,结合近10年来在青藏高原地区对活动断裂的研究,总结了活动断裂的基本变形特征和对大地震复发周期估算的认识。研究表明,东昆仑断裂库塞湖段类似2001年Ms8.1级大地震的强震复发周期为250-350年,阿尔金断裂康西瓦段类似Ms7.4级大地震的强震复发周期为370-500年,而在青藏高原东缘的龙门山地区,类似2008年5月12日Ms8.0级汶川大地震的强震复发周期为3000-6000年。这些结果可能暗示着走滑断裂大地震的复发周期远短于逆冲断裂大地震的长复发周期,这是值得高度重视和深入研究的新课题。

Active faults are refer to all kinds of faults that have been active since 0.1-0.12 Ma of the Late Pleistocene, and are active at present and will be active in future. Active faults are causative structures of various earthquakes and are control of great earthquakes. According to the deformation features, model of causative structures are also different for different active faults, then researches related are important for studying the causative condition of great earthquake, determining potential focal region or seismic risk region, and evaluating causative structure and its location. In this paper, combining the researches on active faults in the Qinghai-Tibetan Plateau in recent ten years at home and abroad, we have summarized general deformation characteristics of active fault and estimation methods of large earthquake recurrence period. The results show that recurrence intervals is 250-350 years for great earthquake comparable to the 14/11/2001 Ms 8.1 earthquake on the East Kunlun fault, 370-500 years for great earthquake comparable to the Mw 7,4 earthquake on the Kangxiwar segment of the Altyn Tagh fault, and 3000-6000 years for great earthquake comparable to the 12/05/2008 Wenchuan earthquake in the Longmenshan area, the east margin of Qinghai-Tibet Plateau. The data indicate that recurrence period of large earthquake on strike-slip fault is possibly much less than that on thrust fault, which is a new subject should be highly emphasized and thoroughly studied.