Crustal S-wave velocity structure in the western and central North China Craton and its geological significance

作者：Hou, Jue; Pan, JiaTie; Li, YongHua^*; Wu, ZhenBo; Yu, GuiPing; Xu, Tao

来源：CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2023, 66(5): 1960-1975.

DOI：10.6038/cjg2022Q0287

• North China Craton
• Crustal structure
• Central orogenic belt
• Ambient noise
• Seismogenic background

The North China Craton (NCC) is one of the oldest cratons in the world. In order to study the deep structure in the central and western parts of the NCC and its control on magma and earthquakes, we derive a new high-resolution 3-D shear wave velocity model of the central and western NCC crust and uppermost mantle using ambient noise tomography. The crosscorrelation of vertical -component continuous noise recordings from 461 temporary seismic stations belonging to the ChinArray project provides Rayleigh wave group velocity dispersions in the period range 5-45 s. These dispersion data at each model grid are inverted to obtain 1D shearwave velocity models, and then construct a pseudo-3-D model of crustal and uppermost mantle. The dense path coverage allows us to examine lateral variations of shear wave velocity structure in unprecedented detail, shedding new light on the deep structure and its impacts on magma activities and earthquakes. Our velocity model at depth of 8 km show that surface basins and mountains are characterized with low-velocity and high -velocity anomalies, respectively. The Swave velocity profiles in different longitude and latitude directions show that the crust of the western craton can be roughly divided into upper, middle and lower crust. The S-wave velocity in the lower crust of the Ordos block ranges between 3. 7 and 3. 8 km " s, suggesting that the lower crust is dominated by felsic rocks. The low S wave velocity anomaly below the Datong volcanic area extends from the middle crust to the uppermost mantle, implying that the upwelling mantle provides a near-vertical channel and controls the formation and development of Cenozoic magmatism in this area. The strong earthquakes are concentrated in the interior of the highvelocity bodies, or alternating regions of high and low velocities in the upper crust, and the middle-to-lower crust is characterized with low velocity, implying that creep rupture and stress release of stressed rigid blocks associated with the deep heat flow of the uppermost mantle/lower crust are the deep causes of large earthquakes.

• 单位
  中国科学院; 桂林理工大学; 中国科学院研究生院