地震研究

2013年广西平果地区发生浅源震群活动,目前对于该震群活动的触发机制还存在争议。通过研究区构造裂隙渗透性调查,发现NW向和近EW向断层或节理是深浅流体交换的主要通道,浅表流体沿通道下渗形成深部地下流体带,震前排泥库附近30 m高的壅水使地下流体的温压条件发生变化,从而加速流体向右江断层带NW向次级断层和近EW向断层内部渗透。结合地震波形初动记录、ETAS模型μ值检验、震源机制解等,推断平果震群是构造因素以及流体参与并触发断层浅部活动的结果,其中震源深度大于3 km的地震主要是由于右江断裂带上盘构造背景应力较高且应力集中等原因引起,而小于3 km的浅部震群活动则主要是由以下2个因素共同作用所触发:①深部流体渗透作用改变了断层结构面上的原有应力状态,降低了断层面的有效正应力和断层的有效强度,增强了断层深部流体压力,加速了浅部断层局部解锁滑动; ②浅表流体与深部承压流体的水力联系、沟通和交换,改变了断层内部的温压条件和应力环境。

In 2013,an earthquake swarm with shallow depth occurred in Guangxi Pingguo,and its triggering mechanism is still discussed. According to the survey on the permeability of structural fissures in the study area,we found that the faults or joints in NW and EW were the main paths for exchanging between the deep and the shallow fluids,and the shallow fluid infiltrated along the paths to forming the underground fluid zone. The 30 m high tailing pond retained water around sludge drainage before the earthquake changed the temperature and press of original underground fluid,which hastening the fluid flow to the secondary fault in NW of Youjiang fault zone and faults in EW. Combined with initial motions of seismic wave,μ-value test of the ETAS model and focal-mechanism solutions,we induced that the 2013 Pingguo earthquake swarm was caused by tectonic factor and the fluid participated in and triggered shallow faults. The earthquakes whose focal depth is above 3 km were caused by the high stress and stress concentration on the hanging wall of the Youjiang fracture zone. The other earthquakes whose focal depth is under 3 km triggered by following factors:①The osmosis of deep fluid changed the original stress system and reduced the available normal stress and effective strengthened of faults surface. Also it improved the press of deep fluid in the fault zone and hastened the local unlocking and slipping of shallow faults. ②The hydraulic contact,communication and exchanging between the shallow and deep fluids changed the temperature,press and stress environment.

引言
1 地震构造背景和水文地质条件
2 构造裂隙渗透性与地下流体的形成
3 流体触发浅层断层活动
4 讨论与分析
5 结论

图1 2013年广西平果震群地震构造图(小震精定位资料来源:李细光,周斌,2014)<br/>Fig.1 Seismotectonics map of Guangxi Pingguo earthquake swarm in 2013(pricise location of small earthquake based on Li and Zhou,2014)

图1 2013年广西平果震群地震构造图(小震精定位资料来源:李细光,周斌,2014)
Fig.1 Seismotectonics map of Guangxi Pingguo earthquake swarm in 2013(pricise location of small earthquake based on Li and Zhou,2014)

表1 震群附近岩溶发育优势方位统计<br/>Tab.1 Preferred orientation of karst in earthquake swarm zone

表1 震群附近岩溶发育优势方位统计
Tab.1 Preferred orientation of karst in earthquake swarm zone

图2 震群附近岩溶发育优势方位玫瑰花图<br/>Fig.2 Rosette diagram of preferred orientation of karst in earthquake swarm zone

图2 震群附近岩溶发育优势方位玫瑰花图
Fig.2 Rosette diagram of preferred orientation of karst in earthquake swarm zone

图3 2013年6月16日至7月21日平果震群μ值随时间的变化(李细光,周斌,2014)<br/>Fig.3 The variation of μ value of Pingguo earthquake swarm with time from Jun.16 to Jul.21,2013(Li,Zhou,2014)

图3 2013年6月16日至7月21日平果震群μ值随时间的变化(李细光,周斌,2014)
Fig.3 The variation of μ value of Pingguo earthquake swarm with time from Jun.16 to Jul.21,2013(Li,Zhou,2014)

图4 小震精定位后的震源深度与断层关系的横切剖面图
Fig.4 Cross section profile of the relationship between focal depth of earthquake swarms after precision location and faults

图5 ML≥2.3地震震源机制解(据郭培兰等,2016)<br/>Fig.5 Focal mechanism of the ML≥2.3 earthquakes(based on Guo et al,2016)

图5 ML≥2.3地震震源机制解(据郭培兰等,2016)
Fig.5 Focal mechanism of the ML≥2.3 earthquakes(based on Guo et al,2016)

图6 断层内流体孔隙压力触发断层滑动的应力模型(据李志勇等,2015)<br/>Fig.6 Stress model showing fault slip triggered by pore-fluid pressure(based on Li et al,2015)

图6 断层内流体孔隙压力触发断层滑动的应力模型(据李志勇等,2015)
Fig.6 Stress model showing fault slip triggered by pore-fluid pressure(based on Li et al,2015)

杜运连,王洪涛,袁丽文.2008.我国水库诱发地震研究[J].地震,28(4):39-51.
郭培兰,龙政强,何嘉幸,等.2016.2013年6月广西平果3级震群地震活动特征分析[J].华南地震,36(1):87-96.
胡小静,付虹,毕青.2016.基于年降水干扰排除的云南地区地下水位群体异常研究[J].地震研究,39(4):545-552.
李志勇,李细光,严小敏,等.2015.广西凌云—凤山“6.28”震群:岩溶发育区流体触发断层浅层活动机理[J].地球科学,40(10):1667-1676.
刘锡大,侯建军,游象照.1987.右江断裂带的新构造活动[J].地震研究,10(2):47-55.
龙政强,姚宏,阎春恒,等.2015.2013年6月广西平果震群特征及成因分析[J].华南地震,35(2):89-95.
陆丽娟,史水平,周斌.2014.广西平果2013年震群震源参数特征[J].地震地磁观测与研究,35(5/6):21-28.
宋方敏,李传友,陈献程,等.2004.右江断层带晚更新世活动的若干地质地貌证据及位移速率[J].地震地质,26(4):611-621.
吴建超,陈蜀俊,陈俊华,等.2016.三峡水库蓄水后仙女山断裂北段数值模拟及其孕震机理研究[J].地震研究,39(2):218-223.
张华,蒋海昆,姚宏,等.2014.2013-06广西平果小震群及发震机理探讨[J].大地测量与地球动力学,34(4):88-95.
Bollinger L,Nicolas M,Marin S.2010.Hydrological Triggering of the Seismicity around a Salt Diapir in Castellane,France[J].Earth and Planetary Science Letters,290(1-2):20-29.doi 10.1016/j.tifl.2009.11.051.
Grunthal G.2013.Induced Seismicity Related to Geothermal Projects Versus Natural Tectonic Earthquakes and Other Types of Induced Seismic Events in Central Europe[J].Geothermics,52(9):22-35.doi:10.1016/j.geothermucs.2013.09.009.
Hunt J M.1990.Generation and Migration of Petroleum from Abnormally Pressured Fluid Compartments[J].AAPG Bulletin,74(1):1-12.
Jiang H K,Yang M L,Sun X J,et al.2011.A Typical Example of Locally Triggered Seismicity in the Boundary Area of Lingyun and Fengshan Following the Large Rainfall Event of June 2010[J].Chinese Journal of Geophysics-Chinese Edition,54(10):2606-2619.
Li Z Y,Li X G,Mohammed A S,et al.2016.A Secondary Sludge Flow Hazard Induced by Shallow-source Seismic Activity in Karst Mining Area,Guangxi,South China:Localized Karstification in Anticline[J].Natural Hazards,83(1):75-95.
Orlecka S B,Papadimitriou E E,Kwiatek G.2009.A Study of the Interaction among Mining-induced Seismic Events in the Legnica-G ogów Copper District,Poland[J].Acta Geophys.Special Section:Triggered and Induced Seismicity,57(2):413-434.

备注

引言

1 地震构造背景和水文地质条件

2 构造裂隙渗透性与地下流体的形成

3 流体触发浅层断层活动

4 讨论与分析

5 结论

期刊信息