2008年于田MW7.2地震滑动分布反演及三维同震形变场解算

基于ENVISAT ASAR升降轨数据, 利用InSAR获取2008年于田M_W7.2地震同震形变场; 采用SDM反演本次地震断层滑动分布; 使用PSCMP正演获取于田M_W7.2地震南北向模拟形变量, 并结合升降轨同震形变场, 解算三维同震形变场。 同震形变场分析表明, 2008年于田M_W7.2地震以正断为主, 且带有走滑运动特征, 破裂带走向为NNE向。 同震滑动分布反演结果显示, 断层沿走向被分为4段F1、 F2、 F3、 F4, 其滑动分布集中在0~14 km区间, 以F2、 F3段为主, 最大滑动量约5.31 m, 位于F2段深部2.76 km处; 沿破裂带走向, 左旋走滑位移与垂直位移比值有增大的趋势; 反演获得的地震矩M₀=5.58×10¹⁹N·m, 相当于矩震级M_W7.1。 三维同震形变场解算结果显示, 断层上盘整体表现为沉降, 断层下盘整体表现为隆升, 且沉降量明显大于隆升量, 表明地震以正断破裂为主; 除靠近断裂带中上部表现为向东南运动外, 上盘整体上表现为向西南运动; 断层下盘则整体表现为向东北运动, 证明破裂兼有左旋走滑运动。 滑动分布反演、 正演与三维同震形变场解算结果皆表明, 于田M_W7.2地震破裂以正断为主, 且带有一定的左旋走滑。

Slip Distribution Inversion and 3D Co-seismic Deformation Field Calculation of the 2008 Yutian MW7.2 Earthquake

We obtained the co-seismic deformation fields of the 2008 Yutian M_W7.2 earthquake using InSAR based on ascending and descending orbits of ENVISAT ASAR data. SDM is used to invert the fault slip distribution. Using PSCMP to forward and obtain the simulated NS direction deformation, then combining with the co-seismic deformation fields of ascending and descending orbits to calculate the 3D co-seismic deformation field. The analysis of the co-seismic deformation fields shows that the 2008 Yutian M_W7.2 earthquake is mainly rupturing along the NNE-trending normal fault with a slight strike-slip component. The inversion of the co-seismic slip distribution shows that the fault is divided into four segments along strike, and slip distribution mainly concentrates in 0 to 14 km depth and fault plane of F2 and F3, the largest slip is about 5.31m located in depth of 2.76 km along the fault plane of F2, the ratio of left-lateral strike-slip deformation to vertical deformation along the rapture tends to increase, the inverted seismic moment is about M₀=5.58×10¹⁹ N·m, which is equal to a moment magnitude of M_W7.10. The result of three-dimensional co-seismic deformation field calculation shows that the hanging wall of fault is subsidence deformation, the footwall of fault is uplift deformation, and the subsidence is obviously larger than the uplift, which proves that the earthquake is mainly normal fault. Except that the mid-upper part of the hanging wall near the fault zone moved to ES direction, the hanging wall moved to WS direction, however, the footwall moved EN direction on the whole, which demonstrates that the rupture has left-lateral strike-slip. Forward and inversion of the slip distribution and calculation of three-dimensional deformation field show that the 2008 Yutian M_W7.2 earthquake is mainly normal fault with a significant left-lateral strike-slip.