Lithosphere structure and thickness beneath the north china craton from joint inversion of ambient noise and surface wave tomography

Abstract

We imaged detailed 3-D crustal and uppermost mantle seismic structures in the North China Craton from inversion of Rayleigh wave phase velocity at periods of 6 to 143 s. The phase velocities were obtained from a combination of ambient noise and teleseismic surface wave tomography, and then the phase velocities were inverted to S-wave velocities. The results show that both the Huabei Basin and Ordos Block have markedly rapid variations in both crustal velocities and the Moho depth. Huabei Basin has a thin (31-34 km) crust with low velocities while Ordos Block has a thick (~40 km) crust with high velocities. We also estimated the lithospheric thickness from the inverted S-wave velocities using a simple S-wave velocity/temperature relationship. Huabei Basin was imaged as a low S-wave-velocity anomaly in the uppermost mantle with very thin lithosphere (~65 km), while Ordos Block was revealed as a high S-wave-velocity anomaly with rather thick lithosphere (>120 km). These results indicated that Huabei Basin and Ordos Block have different thermal and/or chemical properties and had experienced different mantle processes and evolution histories since the Cenozoic. Furthermore, slow S-wave velocities and very thin lithosphere (~65 km) were also found beneath Hetao and Weihe rifts bounding Ordos Block at north and south, respectively. However, Shanxi Rift-the boundary between Huabei Basin and Ordos Block-had a much thicker and higher velocity lithosphere than Hetao and Weihe rifts. © 2013. American Geophysical Union. All Rights Reserved.