SEISMOLOGY AND GEOLOGY ›› 2014, Vol. 36 ›› Issue (4): 1228-1243.DOI: 10.3969/j.issn.0253-4967.2014.04.023

• CONTENTS • Previous Articles     Next Articles

TECTONIC CHARACTERISTICS OF STRONG EARTHQUAKES IN DALIANGSHAN SUB-BLOCK AND IMPACT OF THE MS6.5 LUDIAN EARTHQUAKE IN 2014 ON THE SURROUNDING FAULTS

CHENG Jia1,2, LIU Jie2, XU Xi-wei1, GAN Wei-jun3   

  1. 1. Key Laboratory of Active Tectonics &|Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. China Earthquake Networks Center, Beijing 100045, China;
    3. Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2014-11-28 Online:2014-12-30 Published:2015-01-07

大凉山次级块体内强震发生的构造特征与2014年鲁甸6.5级地震对周边断层的影响

程佳1,2, 刘杰2, 徐锡伟1, 甘卫军3   

  1. 1. 中国地震局地质研究所, 活动构造与火山重点实验室, 北京 100029;
    2. 中国地震台网中心, 北京 100045;
    3. 中国地震局地质研究所, 北京 100029
  • 作者简介:程佳,男,1982年生,中国地震局地质研究所在职博士研究生,现主要从事活动构造、地壳形变、强震模拟与预测方面的研究,E-mail:chengjiajc@gmail.com.
  • 基金资助:

    国家自然科学基金(41404043)和中国地震局"云南鲁甸6.5级地震专题研究"共同资助

Abstract:

The MS6.5 Ludian earthquake occurred on 3 August 2014 in Yunnan, China. The epicenter of this earthquake is located in the Dalingshan sub-block, a boundary region among the Bayan Har block, the Sichuan-Yunnan block and the South China block, which is dominated by the left-lateral and thrust-slip faults. The studies on the characteristics of the crustal deformation, the mechanism of strong earthquakes and stress changes after the MS6.5 Ludian earthquake in the Daliangshan sub-block will help us understand the tectonic implication of the earthquake and facilitate further in-depth studies in the region.
This article introduces the slip behavior around the Daliangshan sub-block and strong earthquake distribution on the faults. Using the GPS data in the southeastern Tibetan Plateau, this study analyzes the motions of sub-blocks bordering the Daliangshan sub-block and the slip behavior of the boundary faults in the block model, and estimates the crustal motion in the Daliangshan sub-block after removing the whole block motion of the sub-block. It can be shown clearly that the Daliangshan sub-block has absorbed the compression via the Xianshuihe Fault, the Anninghe Fault and the Longmenshan Fault. Due to the compression from the boundary faults, the crustal motion in the sub-block is mainly characterized by the north-northwest trending left-lateral strike-slip faults. The boundary faults of the Daliangshan sub-block are mainly characterized by strong earthquakes with magnitude larger than M7 in the history. But in the interior of the Daliangshan sub-block, there are mainly the moderate earthquakes. The MS6.5 Ludian earthquake ruptured the Baogunao-Xiaohe Fault, a left-lateral strike-slip fault associated with the main thrust Ludian-Zhaotong Fault and the Lianfeng Fault, where the whole thrust slip rate of the two faults is about 2.4mm/a.
Around the epicenter of the Ludian earthquake, there are strong earthquakes larger than M7 recorded in the nearby region, which might have impact on the occurrence of the Ludian earthquake. Also, the Ludian earthquake may further affect the occurrence of subsequent earthquakes. In this paper, we have calculated the static Coulomb failure stress changes (ΔCFS) on the fault plane of the Ludian earthquake induced by the 3 nearby big earthquakes, including the M7 1/2 earthquake in 1850 on the Zemuhe Fault and the M7 3/4 earthquake in 1733 on the Xiaojiang Fault. The MS6.5 Ludian earthquake ruptured the north-northwest trending Baogunao-Xiaohe Fault, which is associated with the main thrust fault system of the Zhaotong-Ludian Fault and Lianfeng Fault. In our results, the Ludian earthquake was promoted by the M7 3/4 in 1733 on the Xiaojiang Fault and the M7 1/2 in 1850 on the Zemuhe Fault earthquakes. From the Coulomb failure stress change calculation, the ΔCFS value is about 0.03MPa, which may advance the occurrence of the MS6.5 Ludian earthquake obviously. The calculations also showed opposite results of ΔCFS from the Ludian earthquake on the Yongshan MS5.0 earthquake of 17 August and on the Yuexi MS5.0 earthquake of 1 October in 2014. The former one is not much related to Ludian earthquake, but to the normal seismicity in the reservoir area as to the minus value of ΔCFS, while the Yuexi MS5.0 earthquake was promoted by the MS6.5 Ludian earthquake. Moreover, the MS6.5 Ludian earthquake has advanced, to a certain extent, the enhancement of Coulomb failure stress on the northern segment of the Daliangshan Fault, Ebian Fault, eastern segment of the Zhaotong-Ludian Fault and the southern segment of the Zemuhe Fault, and has enhanced the earthquake energy accumulation of these faults.

Key words: MS6.5 Ludian earthquake in 2014, Daliangshan sub-block, strong earthquake activity, Coulomb stress change, seismic hazards

摘要:

2014年8月3日, 在云南鲁甸发生MS6.5地震.该地震位于巴颜喀拉块体、川滇块体与华南块体三者之间的以挤压和左旋走滑为主要活动特征的大凉山次级块体内部.该次级块体吸收了来自川滇块体和巴颜喀拉块体的挤压作用, 主要以各边界断裂带的挤压作用和内部大凉山断裂带、峨边断裂带等NNW向的左旋走滑次级断裂为主要特征;在历史上大凉山次级块体边界上以7级以上强震活动为主要特征, 而在次级块体内部则以5级地震频繁活动为主.2014年鲁甸MS6.5地震发生在逆冲走滑断裂带内部的NNW向左旋走滑断裂上, 该地震主要受到了发生在小江断裂带上的1733年M7 3/4 和则木河断裂带上的1850年M7 1/2 强震的影响, 这两次地震对2014年鲁甸MS6.5地震有促进作用, 而2014年鲁甸6.5级地震促进了2014年10月1日越西5.0级地震的发生, 此外鲁甸地震对大凉山断裂带北段、峨边断裂带、昭通-鲁甸断裂带东段以及则木河断裂带南段有一定的库仑应力增强作用.

关键词: 2014年鲁甸6.5级地震, 大凉山次级块体, 强震活动, 应力触发, 地震危险性

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