Crustal azimuthal anisotropy in the trans-North China orogen and adjacent regions from receiver functions

Crustal Azimuthal Anisotropy Beneath the Central North China Craton Revealed by Receiver Functions

“…Yang et al () used the P m s phase to map crustal anisotropy in the CNCC beneath 23 stations and obtained an average δt of 0.23 s. Comparison between our measurements and those by Yang et al () is shown in Figure . While some differences exist at some stations in the Datong Basin, the δt and ϕ measurements in the whole Yanshan Uplift from the two studies are generally consistent.…”

“…Reverberation removal was applied to 28 of the 112 stations. Figure 6 shows all the 112 crustal anisotropy measurements and the comparison between the P m s moveout results from this study and the results of Yang et al (2018b). The observed t measurements at the stations vary from 0.06 to 0.54 s with an average of 0.25 ± 0.08 s. For stations located in the Zhangjiakou-Penglai Fault Zone, the mean t is 0.40 ± 0.07 s, which is about twice as large as that observed at stations in the other areas (0.23 ± 0.08 s; Figure 7).…”

“…The final data set consists of 57,431 RFs, and the number of RFs per station varies from 17 to 620. While some of the previous crustal anisotropy studies also used the transverse RFs (e.g., Liu & Niu, ; Yang et al, ), a visual inspection of the transverse RFs suggests that the arrival corresponding to the Moho on the transverse RFs has a SNR that is much lower than that on the radial RFs (Figure ). Therefore, only radial RFs are used in the study.…”

“…While upper crustal anisotropy can be characterized using splitting of direct S waves from local earthquakes, one of approaches for the characterization of anisotropy for the entire crust is to utilize source‐normalized P to S converted waves from the Moho ( P m s ), which are termed as receiver functions (RFs; Kong et al, ; Levin & Park, ; Liu & Niu, ; McNamara & Owens, ; Park & Levin, ; Rumpker et al, ). In the CNCC, Yang et al () used a joint analysis (Liu & Niu, ) of P m s waves from RFs to obtain crustal anisotropy measurements at 23 out of 198 stations. They suggested that the observed crustal anisotropy on the margin of the Bohai Bay Basin is related to horizontal principal compressive stress and that in the Yanshan Uplift indicates an effect of multiple‐phase N‐S shortening from the early‐to‐middle Jurassic to the Early Cretaceous.…”

“…Lateral variations between the two sides of the NSGL in surface wave phase velocities (Chen et al, ), depth of the lithosphere‐asthenosphere boundary (Chen et al, ), and radial anisotropy (Fu et al, ) are also reported. These sharp contrasts in tectonic setting and crustal characteristics, together with the recent availability of a broadband seismic data set recorded by 200 densely spaced stations, make the CNCC an ideal locale for investigating crustal deformation and its relationship with mantle deformation (e.g., Chen et al, ; Gao et al, ; Yang et al, ; Zhu et al, ).…”