冉勇康^1,,
王虎^2,1,
陈立春¹,
陈文山³,
梁明剑^1,4,
徐锡伟^5,1
1. 中国地震局地质研究所, 活动构造与活动火山重点实验室, 北京 100029
2. 西南交通大学地球科学与环境工程学院, 成都 611756
3. 台湾大学地球科学系, 台北 106
4. 四川省地震局, 成都 610041
5. 中国地震局地壳应力研究所, 北京 100085

基金项目: 国家自然科学基金面上项目（41472179）和两岸合作重点项目（40821160550）以及汶川地震和芦山地震科学考察项目联合资助


详细信息

作者简介: 冉勇康, 男, 研究员, 主要从事活动构造与古地震研究.E-mail:ykran@263.net

中图分类号: P541;P315

收稿日期:2018-04-09
修回日期:2018-04-19
上线日期:2018-05-05

Late-Quaternary fault activity of the Longmen Shan fault zone—Evidence from paleoseismic trenching

RAN YongKang^1,,
WANG Hu^2,1,
CHEN LiChun¹,
CHEN WenShan³,
LIANG MingJian^1,4,
XU XiWei^5,1
1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China
2. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China
3. Department of Geosciences, Taiwan University, Taipei 106, China
4. Sichuan Earthquake Administration, Chengdu 610041, China
5. Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China


MSC: P541;P315

--> Received Date: 09 April 2018
Revised Date: 19 April 2018
Available Online: 05 May 2018


摘要
摘要:2018年5·12汶川地震后，龙门山断裂带的大地震活动特征一直是倍受关注的科学问题.而探槽古地震研究是最直接揭示活断层带晚第四纪大地震活动规律的重要途径.本文通过系统总结龙门山断裂带近十年来探槽古地震研究成果，全面分析了龙门山断裂带不同段落的晚第四纪大地震活动与复发特征.结果显示：龙门山断裂带的大地震活动具有明显的分段性，北川—映秀断裂和江油—灌县断裂中段（包括小鱼洞断裂）是全新世以来，最为活跃的段落，约距今6000年以来，发生过3次位移量近似相等的事件，分别发生在5920—5730 cal BP和3300—2300 cal BP，大地震活动具有3000年左右的准周期复发特征；北川—映秀断裂的北段具有独立破裂的能力，该段汶川地震前一次事件发生在大约665—1030 AD，可能是历史上记载的942 AD地震事件，另一次事件发生在8240—7785 BC；江油—灌县断裂的南段（大川—双石断裂）发震能力明显弱于断裂带中段和北段.现有古地震数据表明，沿北川—映秀断裂，除汶川地震以外，并未显示出不同段落间在全新世期间存在级联破裂的证据，这可能意味着2008年汶川M8地震是龙门山断裂带上罕见的巨大地震事件.另外，青川断裂上探槽揭露的古地震变形事件不像是断裂直接位错的结果，更可能是被动响应北川—映秀断裂右旋位错的现象.
关键词: 龙门山断裂带/
探槽/
古地震/
晚第四纪/
大地震活动

Abstract:The fault activity of the Longmen Shan fault zone has been focused since the Wenchuan earthquake occurred on May 12, 2018. Paleoseismic trenching has been suggested to be the most effective way to reveal Late-Quaternary fault rupture behavior. This paper integrates about 10-year paleoseismic studies on the Longmen Shan fault to further reveal its Late-Quaternary rupture behavior and recurrence characteristics. Herein we suggest that rupture behavior of the Longmen Shan fault shows segmentation characteristics. Fault activity of the middle segment of the Yingxiu-Beichuan and Jiangyou-Guanxian fault (including the Xiaoyudong fault) has been the most intense part since Holocene. Specifically, the segment ruptured three times since about 6000 years with a similar coseismic offset, the penultimate and third oldest event occurred at 3300—2300 cal BP and 5920—5730 cal BP, which indicates an average recurrence interval of about 3000 years. The northern segment of the Yingxiu-Beichuan fault had independent rupture behavior, the penultimate event on the segment ruptured at about 665—1030 AD that is associated with historical record 942 AD earthquake. The third oldest event occurred at 8240—7785 BC. The southern segment of the Jiangyou-Guanxian fault (Dachuan-Shaungshi fault) shows a weaker seismic potential than that of the middle and northern segments. The present paleoseismic data except for the 2018 Wenchuan earthquake that are associated with the Yingxiu-Beichuan fault suggest that no evidence has supported a cascading rupture behavior of the Yingxiu-Beichuan fault, which indicates that the 2018 Wenchuan earthquake might be an unusual great seismic event. Moreover, deformation evidence revealed from trenching on the Qingchuan fault might not be related to fault offset, but more possibly be related to responding deformation due to coseismic right-laterally offset of the Yingxiu-Beichuan fault.
Key words:Longmen Shan fault zone/
Trenching/
Paleoseismology/
Late Quaternary/
Seismic activity



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