Measurement Of Rayleigh Wave Ellipticity And Its Application To The Joint Inversion Of High-resolution S-wave Velocity Structure

We present a new 3-D S-wave velocity model of the northeast(NE)China from the joint inversion of the Rayleigh-wave ellipticity and phase velocity at 8~40 s periods.Rayleigh wave ellipticity,or Rayleigh-wave Z/H(vertical to horizontal)amplitude ratio,is extracted from both earthquake(10~40 s)and ambient noise data(8~25 s)recorded by the NECESSArray array with 127 stations.The estimated Z/H ratios from earthquake and ambient noise data show good consistency within the overlapped periods.The observed Z/H ratio shows a good spatial correlation with surface geology and is systematically low within the basins.We jointly invert the measured Z/H ratio and phase velocity dispersion data to obtain a refined 3-D S-wave velocity model beneath the NE China.At shallow depth,the 3-D model is featured by strong low velocity anomalies that are spatially well correlated with the Songliao,Sanjiang and Erlian basins.The low velocity anomaly beneath the Songliao basin extends to 2~3 km deep in the south and 5~6 km in the north.At lower crustal depths,we find a significant low velocity anomaly beneath the Great Xing'an range that extends to the upper mantle in the south.Overall,the deep structures of the 3-D model are consistent with previous models,but the shallow structures show a much better spatial correlation with tectonic terranes.The difference in sedimentary structure between the southern and northern Songliao basin is likely caused by a mantle upwelling associated with the Pacific subduction.