辽宁地区上地幔各向异性研究

Seismic anisotropy of upper mantle in Liaoning region

利用辽宁数字地震台网2013-2017年间15个宽频带地震台站记录到的震中距在85°到140°之间的且Mw≥5.5的远震SKS波形数据,基于SplitLab软件,使用旋转相关法、最小切向能量法和最小特征值法,计算每一个台站的SKS快波偏振方向和快、慢波的延迟时间,获得辽宁地区上地幔各向异性参数共398对。结果显示,辽宁地区存在比较明显的上地幔各向异性,快波偏振方向大部分呈NWW方向,与中生代晚期岩石圈伸展形变方向一致;各向异性快慢波延迟时间在0.4~1.2s之间,可以推测软流圈对各向异性的影响比较小,主要是由残留在岩石圈的古老形变所导致。

Using the SplitLab software package,the teleseismic SKS waveform data,of which the epicentral distance is between 85°and 140°with Mw≥5.5 recorded by 15 broadband seismic stations from the Liaoning Digital Seismic Network during 2013~2017 is used to calculate the polarization direction of the SKS fast wave and the delay time between the fast and slow waves of each waveform.The rotation correlation method,minimum transverse energy method and minimum eigenvalue method were used in the calculation.A total of 398 pairs of splitting parameters of the upper mantle in Liaoning Province are obtained.The results show that there is obvious seismic anisotropy in the upper mantle in Liaoning region,and the polarization direction of fast wave is mostly NWW,which is consistent with the extensional deformation direction of lithosphere in late Mesozoic.The delay time of anisotropic fast and slow waves is between 0.4 s and 1.2 s.It can be inferred that the anisotropy is mainly caused by the deformation in the lithosphere,while the effect of the asthenosphere on the anisotropy is relatively small.