广西灵山断裂北段古地震事件初步研究

目前国内古地震研究主要集中于中国西部、华北等强震构造区，华南大陆因地处中强地震构造区，很少发生7.0级以上地震，古地震遗迹少。同时华南大陆气候湿润，雨水较多，人类改造活动频繁，古地震遗迹难以保存，鲜有与古地震研究相关的报道，广西灵山震区的古地震研究弥补了华南大陆古地震研究少的缺陷。本文采用槽探、地表破裂带分析及测年等方法，揭露了在广西灵山断裂北段曾发生至少4次地震事件，其中3次古地震事件，1次历史地震事件，时间分别为距今约>36 300、25 000、13 090、80 a(最后者即1936年6级地震)，4次地震事件强度有逐渐减弱的趋势。该4次地震事件的平均重复间隔约12 073 a，比中国西部、华北等地的一些古地震复发间隔长，主要原因在于灵山震区构造活动强度相对较弱。

Preliminary study of paleoearthquakes in the northern section of the Lingshan fault,Guangxi.

Presently paleoearthquake research in China mainly focuses on the strong seismotectonic provinces in the western and northern parts of the country. The South China Block (SCB) is located across the medium strong seismotectonic provinces where earthquakes of MS≥7.0 seldom occur. Traces of paleoearthquakes in SCB are hard to preserve due to high humidity, frequent rainfall and human activities in the region; as a result no detailed paleoearthquake studies are available. This research on the Lingshan paleoearthquakes, therefore, may fill the gap in the study of paleoearthquakes in South China. Based on our analysis of trenching, surface rupture and dating, it could be concluded that historically there were at least four earthquake events in the northern section of the Lingshan fault, and three of those were paleoearthquake events. They occurred around >36300, 25000, 13090 and 80 a B.P., respectively, following a trend of decreasing magnitude. The average time interval of the four earthquake events was about 12073 a and apparently longer compared with that of earthquakes occurred in the western and northern China, mainly due to relatively low tectonic activities in the Lingshan region.