大别-苏鲁及其邻近地区基于背景噪声的瑞雷波和勒夫波相速度层析成像

Phase velocity tomography of Rayleigh and Love waves in Dabie-Sulu and its adjacent areas from ambient seismic noise

采用与作者2014年发表的"大别-苏鲁及其邻近地区基于背景噪声的勒夫波群速度成像"文章相同的资料,用频时分析提取5000余条瑞雷波和4000余条勒夫波相速度频散曲线,反演得到了8-32 s的瑞雷波和勒夫波相速度分布图像.结果显示,瑞雷波与勒夫波相速度分布具有很好的一致性.8s的相速度分布与地表构造特征相吻合,造山带与隆起区均表现为高速,盆地因其规模不同而显示不同程度的低速.随着周期的增大,大别-苏鲁的高速带由强变弱,但始终存在.16-24 s的高速可能主要受到中地壳高速的控制,而32 s的高速则可能与上地幔顶部的高速有关.比较大别造山带与苏鲁造山带的平均频散曲线,发现大别造山带和苏鲁造山带的勒夫波频散曲线均高于AK135模型计算的理论频散曲线,而瑞雷波则没有这一现象.这可能意味着两个地区有比较强烈的径向各向异性.

We used the same seismic data as the published paper ＂Love wave group velocity tomography in Dabie-Sulu and its adjacent areas from ambient seismic noise＂ by the author in 2014 and obtained more than 5000 Rayleigh wave velocity dispersion curves and 4000 Love wave phase velocity dispersion curves by frequency-time analysis （FTAN）. Then, we constructed the Rayleigh and Love wave phase velocity maps at the period of 8--32 s. The results of Rayleigh wave is consistent with those of Love wave. The phase velocity maps at 8 s are well correlated with surface geological features. Orogenic belts and uplifts reveal high velocity anomaly, and the basins exhibit different levels of low velocity anomaly due to the different scales of deep sediments. The high ve- locity feature in the Dabie and Sulu regions becomes successively less prominent from 16 s to 32 s, but always exists. The high velocity anomaly from 16 s to 24 s may be controlled by the high velocity in the middle crust, while high velocity at 32 s may be influenced by the high velocity structure of uppermost mantle. The average dispersion curves of Love waves in Dabie and Sulu orogenic belts are all higher than the theoretical dispersion curves of AK135 model, whereas the dispersions of Rayleigh waves are not, possibly suggesting strong radial ani- sotropy in Dabie and Sulu orogenic belts.