Variations of lithospheric structures around the Mt. Baekdu (Changbaishan) volcano from Bayesian joint inversions with receiver functions and surface wave dispersions

The distribution of magmatic structures within lithosphere beneath Mt. Baekdu is important to understand the origin, evolution history, and current status of the volcano. A previous study using ambient noise surface wave dispersions (Kim et al., 2017) suggested a feature of magma fractionation and cooling with layering of mafic and felsic structures in deeper crust. However, the existence of melt directly beneath the Mt. Baekdu and corresponding modification of lithosphere are still unclear. In this study, we additionally calculate P-wave receiver functions for stations in Mt. Baekdu and surrounding regions to confirm the previously defined structures and to check the existence of partial melting. We obtain data from three temporary arrays distributed over areas in Northeast China and DPRK. A harmonic decomposition approach is used to account for anisotropy and to obtain isotropic receiver functions. A series of joint inversions is performed for isotropic receiver functions and surface wave dispersion data using a hierarchical transdimensional Bayesian method. Retrieved isotropic radial receiver functions from stations near (<50 km) the Mt. Baekdu show a consistent negative signal between P and Ps conversion, which indicates low velocity layers in the crust. In addition, relatively high energy of tangential receiver functions with two- and four-lobe patterns indicate that effects of azimuthal anisotropy and/or tilted interfaces are also significant beneath the volcano. On the other hand, stations away from the volcano show features of more isotropic and homogeneous crustal structures. Inverted models show a clear pattern of thicker crust (35-40 km) with slower S-wave velocities (3.2-3.4 km/s in the crust and 4.0-4.2 km/s in the upper mantle) beneath the Mt. Baekdu compared to other regions with relatively shallow Moho (33-35 km) and high velocities (>3.4 km/s in the crust and >4.2 km/s in the upper mantle). The result indicates that a localized structure with elevated temperature and potentially partial melting is exist directly beneath the volcano. With further analysis, more detailed variations of whole lithosphere structures will be presented.