Modeling the Jiyang Depression, Northern China, Using a Wave-Field Extrapolation Finite-Difference Method and Waveform Inversion

We study the 2D seismic velocity structure of the south edge of the Jiyang depression, in the Bohai Bay Basin, northern China, using recordings from 28 broadband seismic stations and a method combining an shear horizontal (SH) forward synthetic calculation and waveform inversion. The forward synthetic calculations are performed by a finite-difference (FD) method, with its computational domain localized in the basin area and input motions at the base of the model extrapolated from the displacement recorded at a nearby hardrock station. In waveform inversion, the shapes of the strata are varied to search for a best-fitting model based on the fit of relative timing, amplitude, and phase of the synthetics to the seismic data. Numerical experiments using synthetic data and test models demonstrate the validity, resolution, and sensitivity of our technique. With this technique, we obtain two cross sections of the south edge of the Jiyang depression, the Bohai Bay Basin, northern China. The waveform inversions using the seismic data from four teleseismic events show consistent results for both cross sections. Those inversion results are also in agreement with a geological cross section available in the region. Our models estimate that the south edge of the Jiyang depression is juxtaposed against the Luxi uplift and its structures. Our inversion results also reveal a blind fault in the region and features suggesting major extensions in Paleogene.