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大姚-姚安地区强震孕震机理——NW向褶皱节理的构造强化与活动
投稿时间:2016/5/10    点此下载全文
引用本文:常祖峰,张艳凤,李鉴林.大姚-姚安地区强震孕震机理——NW向褶皱节理的构造强化与活动[J].地质力学学报,2017,23(1):161-172
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作者单位
常祖峰 云南省地震局, 昆明 650041 
张艳凤 云南省地震局, 昆明 650041 
李鉴林 云南省地震局, 昆明 650041 
基金项目:国家自然科学基金项目(41472204);2014年度地震科技星火计划项目(XH14047);中国地质调查局地质调查项目“南北构造带活动构造体系综合调查与研究”(12120114002101)
中文摘要:以21世纪初滇中大姚-姚安-带接连发生的4次Ms 6.0~6.5级强震为例,通过分析该地区构造类型及其演化历史,结合川滇块体的现今运动特征和构造应力场,提出滇中构造区运动模型和特殊的孕震模式,探讨褶皱节理与地震活动的关系。研究表明,这些地震序列均有规律地沿北西方向展布,具有高度-致的沿北西向节理面右旋走滑的力学破裂机制。该地区断裂不发育,而是以北西向中生代褶皱构造为主。野外调查发现,该地区广泛发育与褶皱伴生的北西向纵向节理及北东向横向节理,前者较后者更为发育。这些节理密集成带,呈不等间距排列,带宽30~50 m,带内节理密度20~30条/m。节理面上发育有方解石脉和辉长岩脉,同时发育挤压片理化带、新鲜的水平擦痕和松软的断层泥,说明这些节理不仅与深部地壳有关联,而且近期有着新活动迹象。分析认为,在滇中块体南南东运动的背景下,这些地震是在现今北北西向挤压应力场作用下,北西向纵向节理发生构造强化、贯通、破裂的过程中产生的。“活节理”与活动断裂、活动褶皱等构造-样,是地球上广泛存在的活动构造之-。在特殊的构造环境和特定的构造应力场作用下,节理构造会演变为-种构造强化带或活化带,进而成为-种特殊的孕震构造。
中文关键词:地震  褶皱伴生节理  节理密集带  构造强化带
 
THE SEISMOGENIC MECHANISM OF STRONG EARTHQUAKES IN DAYAO-YAOAN AREA:STRUCTURE STRENGTHENING AND ACTIVITY OF THE NW STRIKE FOLD JOINTS
Abstract:At the start of this new century, four strong earthquakes of magnitude from 6.0 to 6.5 have successively occurred in Dayao-Yaoan region of central Yunan, we analyzed the structure and its evolution, combined with the modern motion characteristics and tectonic stress field of the Sichuan-Yunnan Block, to confirm the motion model and special seismogenic model of central Yunnan tectonic area and discuss the relationship between joints generated by folds and seismic. The research revealed that all these event sequences arranged in NW direction regularly, with highly consistent mechanical rupture mechanism of dextral strike slip along the NW strike joint plane revealed by focal mechanism solution. This area had no faults, but dominated by many NW strike Mesozoic fold structures. Abundant field investigations attested that plenty of longitudinal joints and transverse joints associated with folds have been developed intensively in this area, the former were more development than the latter. These joints become concentrated belts which array in unequal space, with a width of 30m to 50m and 20m to 30m per miter. On the joint plane, there are calcites and gabbro dykes developed as well as squeezed schistosition belt, fresh striations and soft fault gouge, all these phenomenas suggest that these joints are not only related to deep crust, but also active recently. It is inferred that:under the SSE movement of central Yunan block, these earthquakes produced, with the NW strike longitudinal joints structure strengthening, liking-up and rupturing under the present NNW orientation pressed stress fields. The active joints, just like active faults and active folds, are one of the most widespread active structures on Earth. Joint structures may become structure strengthening or activity belts and then become particular seismogenic structures under particular tectonic circumstance and special tectonic stress field.
keywords:earthquake  joint generated by fold  conferted joint belt  structure strengthening belt
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