Study on crustal deformation characteristics before Xinjiang Yutian MS7.3 earthquake in 2014
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摘要: 利用1999—2007年和2009—2013年两期GPS速度场资料， 采用最小二乘配置方法分别计算了2008年和2014年新疆两次于田MS7.3地震前新疆及周边地区的主应变率、 面应变率及最大剪应变率， 分析了该区域的变形动态特征， 并结合速度剖面分析方法给出了震源区的构造变形特征. 速度场及应变率场动态结果表明： 新疆天山地区的地壳变形特征整体表现为由南向北缩短， 相对运动速率表现为由南向北、 由西向东逐渐减小； 震源区东侧的左旋剪切变形明显大于西侧； 2008年与2014年两次于田MS7.3地震的震源区均处于拉张与挤压变形的过渡地带， 易于强地震的发生； 2008年于田MS7.3地震的张性兼有少量剪性破裂的发生使得阿尔金断裂的左旋剪切变形增强. GPS速度场剖面分析结果表明， 2014年于田MS7.3地震前震源区西侧的变形宽度大于东侧， 剪切应变积累程度西侧高于东侧. 综合分析认为， 震源周边构造区应变积累的差异性有利于强震的孕育， 2008年于田MS7.3地震对2014年于田MS7.3地震可能有促进作用.Abstract: This paper calculates the principal strain rate, plane strain rate and maximum shear strain rate in Xinjiang and its vicinity by using the least squares method with GPS data set during 1999—2007 and 2009—2013. The crustal tectonic deformation characteristics in this area before 2008 and 2014 Yutian MS7.3 earthquakes are also analyzed comprehensively. The dynamic results of velocity field and strain rate field indicate that the crust shortening decreases gradually from south to north and from west to east, suggesting that the sinistral shear deformation in the eastern side is significantly greater than that in the western side around focal area. The source areas of 2008 and 2014 MS7.3 Yutian earthquakes are located in the transitional zone of the tensile and compressive deformation, which is prone to occurrence of a great earthquake. The surface rupture in 2008 Yutian earthquake, which is mainly tensile with little shear component, strengthened the sinistral shear deformation of Altyn Tagh fault. The GPS velocity profiles show that the deformation width of western side is greater than that of the east in the hypocentral region before 2014 Yutian MS7.3 earthquake, consistent with the degree of shear strain accumulation. In conclusion, this difference between two sides in strain accumulation are easy for the nucleation process of 2014 Yutian earthquake. And it is inferred that the 2008 Yutian MS7.3 earthquake may play a role in promoting the 2014 Yutian MS7.3 earthquake.
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Keywords:
- GPS /
- crustal deformation /
- GPS profile /
- strain accumulation
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图 1 新疆及周边地区1999—2007年(a)与2009—2013年(b)GPS速度场结果
Figure 1. GPS velocity fields in Xinjiang and its adjacent areas during 1999—2007 (a) and 2009—2013 (b)
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图 2 1999—2007年(a)与2009—2013年(b)区域面应变率和主应变率结果
Figure 2. Plane strain rate and principal strain rate results in Xinjiang and its adjacent areas during 1999—2007 (a) and 2009—2013 (b)
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图 3 1999—2007年(a)与2009—2013年(b)区域最大剪应变率和主应变率结果
Figure 3. Maximum shear strain rate and principal strain rate results in Xinjiang and its adjacent areas during 1999—2007 (a) and 2009—2013 (b)
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图 4 横跨断裂带的2009—2013年GPS站速度剖面和拟合结果(a)剖面A平行断裂带结果；(b)剖面A垂直断裂带结果；(c)剖面B平行断裂带结果；(d)剖面B垂直断裂带结果
Figure 4. GPS velocity profiles cross fault during 2009—2013， and model fitting results(a)Results of profile A(parallel component);(b)Results of profile A(vertical component);(c)Results of profile B(parallel component);(d)Results of profile B(vertical component)
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