Mapping 3D Sedimentary Structures with Joint Inversion of H/V Spectral Ratios and Multimode Dispersion Curves Derived from Ambient Noise—Application to the Xiong‘an New Area, China

ABSTRACT We present a procedure to use ambient noise recordings to derive high-resolution 3D S-wave velocity models for sedimentary structures by joint inversion of phase velocity dispersion curves (DCs) and horizontal-to-vertical spectral ratios (HVSRs). This procedure is applied to seismological data from a network of 894 stations with a spacing of about 1 km located in the Xiong’an New Area (China), close to Beijing. To obtain the DCs, a Modified Correlation BeamForming method is used to process the noise at subarrays, which enables us to map directly the lateral variations of the phase velocity of the Rayleigh-wave fundamental mode, first overtone, as well as fundamental Love wave, in the total frequency range of 0.3–3 Hz. HVSRs are derived in the frequency range 0.1–10 Hz from the computation of the directional energy density of the three components at each station based on the diffuse field assumption. By combining the DCs obtained by the array-based method and the single-station HVSR curves in a joint inversion, a high-resolution 3D S-wave velocity model of the study area is established down to 2 km depth. The model brings useful information for seismic hazard assessment as well as geothermal energy exploration. It reveals that the thickness of the sediments is highly correlated with the distribution of geologic structures such as highs and lows.