巴颜喀拉块体东北缘GPS应变率空间分布特征及其与2017年九寨沟MS7.0地震的关系

巴颜喀拉块体东北缘是构造变形和地震活动较强的区域, 2017年九寨沟M_S7.0地震就发生在该区域内。 利用多尺度球面小波方法解算GPS应变率场, 分析巴颜喀拉块体东北缘2009年至2017年的应变率场分布特征, 该方法的优点是可以将GPS应变率场按照不同的空间尺度进行小波分解, 给出不同空间尺度的应变率场。 结果表明在2017年九寨沟地震之前, 震中附近应变积累显著, 虎牙断裂北延断裂的左旋走滑速率为3.0 mm/a, 拉张速率为3.1 mm/a, 表明该条断裂以左旋走滑为主兼有拉张特征, 与九寨沟地震的震源机制解一致。 除九寨沟震中附近外, 在岷县与漳县交界处、 理县和汶川、 青川等地区主应变率、 面应变率、 最大剪应变率也较大, 这可能与2013岷县漳县(M_S6.6)、 2008年汶川(M_S8.0)、 2014年理县(M_S4.8)以及2014青川县(M_S4.8)地震有关。

Heterogeneous Strain Rate Field in the Northeast Margin of Bayan Har Block from GPS Observations and its Relationship with the 2017 Jiuzhaigou MS7.0 Earthquake

The northeast margin of Balyan Har block is a region of strong tectonic deformation and active seismicity. The 2017 Jiuzhaigou M_S7.0 earthquake occurred in this zone. We use the method of multi-scale sphere wavelet to estimate GPS strain filed and analyse strain field in the northeast margin of Balyan Har block from 2009 to 2017. The advantage of this method is that the GPS strain rate field can be decomposed according to different spatial scales, and can give the strain rate field of different space scales. The results show that the before the 2017 Jiuzhaigou earthquake, the strain accumulation near the epicenter zone has been significant. Strike-slip rate in the extension of the north Huya fault is 3.0 mm/a, tensile rate is 3.1 mm/a. It indicates that the fault is dominated by left-lateral slip accompanied by tensile, which is consistent with the focal mechanism of the Jiuzhaigou earthquake. Besides, in the junction of Minxian and Zhangxian, Lixian, Wenchuan and Qingchuan areas, There also exists large principal strain rate, the dilatation rate, and maximum shear strain rate, which may relate with the 2013 Minxian-Zhangxian M_S6.6, the 2008 Wenchuan M_S8.0 and the 2014 Lixian M_S4.8, Qingchuan M_S4.8 Earthquakes.