基于GPS数据分析渭河盆地现今地壳形变特征

基于2001—2015年流动及连续GPS观测资料,借助多面函数拟合法建立渭河盆地水平速度场模型,并计算球面坐标下的应变特征参数。结合陕西地区地质构造背景,分析渭河盆地水平速度场及应变场分布特征。结果表明:(1)渭河盆地西部GPS速度场受青藏块体及鄂尔多斯块体共同作用明显,西部GPS速度场大于中东部,且GPS速度场有顺时针旋转的运动特征。(2)渭河盆地西部主应力场变化复杂,中部的西安地区主应变差异变化明显,与2009年11月5日高陵M_S4.4地震对应;渭河盆地西部出现最大剪应变及面应变高值区及差异变化高梯度带,在西安附近出现最大剪应变及面应变差异变化梯度带,高陵地震震中位于零值线附近。(3)2001—2010年的主应变、最大剪应变、面应变变化比2011—2015年显著,表明高陵地震发生后,应力场进行了释放调整,近期渭河盆地地震紧迫性相对较低。

Characteristics of Present-day Crustal Deformation of Weihe Basin Based on GPS Data

Based on 2001-2015 flow and continuous GPS observation data, the horizontal velocity field model of Weihe basin is established in this study using the Hardy function interpolation method, and the strain characteristic parameters in spherical coordinates were calculated. Based on the geological tectonic background of the Shaanxi area, the distribution characteristics of horizontal velocity field and strain field in the Weihe basin are analyzed. The results show the following:(1) The GPS velocity field in the Western Weihe basin was obviously affected by the combined action of Qinghai-Tibet block and Erdos block, and the GPS velocity field in the western region is larger than that in central and eastern regions, which the GPS velocity field rotates clockwise. (2) The change of main stress field in the Western Weihe basin is complicated, while the change of the main strain in the Xi''an area is obvious, corresponding to the Gaoling M_S4.4 earthquake on November 05, 2009. (3) The changes of principal strain, maximum shear strain, and plain strain during 2001-2010 are more obvious than those during 2011-2015, indicating the stress field in the whole Weihe basin has been released and adjusted after the Gaoling M_S4.4 earthquake, and the earthquake urgency has been relatively low in the Weihe basin.