地震研究

利用2003年7月21日、10月16日大姚6.2、6.1 级地震余震序列的震源机制解资料,采用滑动方向拟合法反演出大姚两次强震的构造应力,定量给出其构造应力变化量。以反演得到的2003年大姚6.2、6.1级地震构造应力为基础,分别计算两次强震后产生的静态库仑破裂应力变化,研究大姚6.2级地震引起的应力变化是否触发了6.1级地震。结果显示:两次地震发生后震源区构造应力场最大主压应力S₁作用由北东向近水平作用为主转为北东东向水平作用,6.2 级地震对6.1 级地震有明显的触发作用。

Using the focal mechanism solutions of aftershock sequence of Dayao M6.2,M6.1 earthquakes occurred on Jul.21 and Oct.16 in 2003,we inversed the tectonic stress of these two strong earthquakes by slips direction fitting method and obtained their tectonic stress variation. Basing on the tectonic stress of these two earthquakes,we calculated static coulomb failure stress variation after these two strong earthquakes and studied whether the tectonic stress of Dayao M6.2 earthquake triggered the Dayao M6.1 earthquake. The results showed that the maximum principal stress S₁ of tectonic stress field which was nearly horizontal action with NE turned to NEE direction in the focal zone after two strong earthquakes. The Dayao M6.2 earthquake on Jul.21 apparently triggered the Dayao M6.1 earthquake on Oct.16 in 2003.

引言
1 震源区构造应力场反演
3 最优取向断层面投影的库仑破裂应力变化计算
4 结论与讨论

图1 断层面上应力示意图<br/>(n为断层面单位法向矢量,f '为断层面上应力,τ'为断层面上剪应力,σ'n为断层面上正应力,S为断层面滑动方向,α为断层面上剪应力与滑动方向间的夹角; f,σn和τ分别是偏应力张量作用于断层面上的应力、正应力和剪应力)<br/>Fig.1 Schematic diagram of stress on the fault plane(n is unit normal vector,f ' is stress,τ' is shear stress,σ'n is the normal stress,S is the sliding direction,α is angle between shear stress and slip direction on the fault plane; f,σn and τ is the stress,normal stress and shear stress which are deviator stress tensor acting on the fault plane)

图1 断层面上应力示意图
(n为断层面单位法向矢量,f '为断层面上应力,τ'为断层面上剪应力,σ'n为断层面上正应力,S为断层面滑动方向,α为断层面上剪应力与滑动方向间的夹角; f,σn和τ分别是偏应力张量作用于断层面上的应力、正应力和剪应力)
Fig.1 Schematic diagram of stress on the fault plane(n is unit normal vector,f ' is stress,τ' is shear stress,σ'n is the normal stress,S is the sliding direction,α is angle between shear stress and slip direction on the fault plane; f,σn and τ is the stress,normal stress and shear stress which are deviator stress tensor acting on the fault plane)

图2 大姚地区地震构造图<br/>Fig.2 Seismotectonic map of Dayao area

图2 大姚地区地震构造图
Fig.2 Seismotectonic map of Dayao area

表1 大姚M6.2、M6.1地震震源机制解<br/>Tab.1 Focal mechanism solution of Dayao M6.2,M6.1 earthquakes

表1 大姚M6.2、M6.1地震震源机制解
Tab.1 Focal mechanism solution of Dayao M6.2,M6.1 earthquakes

表2 2003年7月21日、10月16日大姚6.2、6.1级地震序列余震震源机制解<br/>Tab.2 Focal mechanisms of aftershocks of Dayou Ms6.2 earthquake on Jul.21 and Ms6.1 earthquake on Oct.16 in 2003

表2 2003年7月21日、10月16日大姚6.2、6.1级地震序列余震震源机制解
Tab.2 Focal mechanisms of aftershocks of Dayou Ms6.2 earthquake on Jul.21 and Ms6.1 earthquake on Oct.16 in 2003

表3 大姚6.2、6.1级地震构造应力场反演结果<br/>Tab.3 Inversion results of tectonic stress field of Dayao MS6.2,MS6.1 earthquakes

表3 大姚6.2、6.1级地震构造应力场反演结果
Tab.3 Inversion results of tectonic stress field of Dayao MS6.2,MS6.1 earthquakes

图3 反演得到的大姚6.2级(a)、6.1级(b)地震区域构造应力场<br/>Fig.3 Regional tectonic stress field of Dayao MS6.2(a),MS6.1(b)earthquakes obtained in inversion

图3 反演得到的大姚6.2级(a)、6.1级(b)地震区域构造应力场
Fig.3 Regional tectonic stress field of Dayao MS6.2(a),MS6.1(b)earthquakes obtained in inversion

表4 滇西南地区D区构造应力场(崔效锋,谢富仁,1999)<br/>Tab.4 Tectonic stress field of D-area in Southwestern

表4 滇西南地区D区构造应力场(崔效锋,谢富仁,1999)
Tab.4 Tectonic stress field of D-area in Southwestern

图4 最优取向断层面上应力的坐标系示意图<br/>Fig.4 Sketch map of coordinate system on the fault plane stress in optimal orientation

图4 最优取向断层面上应力的坐标系示意图
Fig.4 Sketch map of coordinate system on the fault plane stress in optimal orientation

表5 大姚地区的地壳模型<br/>Tab.5 The crustal model in Dayao area

表5 大姚地区的地壳模型
Tab.5 The crustal model in Dayao area

表6 大姚主震断层参数<br/>Tab.6 Fault parameters of Dayao MS6.2、MS6.1 earthquakes

表6 大姚主震断层参数
Tab.6 Fault parameters of Dayao MS6.2、MS6.1 earthquakes

图5 地震库仑破裂静应力变化计算结果<br/>(a)大姚MS6.2地震;(b)大姚MS6.1地震<br/>Fig.5 Calculation results of variation of seismic coulomb static stress(a)Dayao MS6.2 earthquake;(b)Dayao MS6.1 earthquake

图5 地震库仑破裂静应力变化计算结果
(a)大姚MS6.2地震;(b)大姚MS6.1地震
Fig.5 Calculation results of variation of seismic coulomb static stress(a)Dayao MS6.2 earthquake;(b)Dayao MS6.1 earthquake

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备注

引言

1 震源区构造应力场反演

3 最优取向断层面投影的库仑破裂应力变化计算

4 结论与讨论

期刊信息