[S07P-06] Shear Wave Tomography Beneath the Ontong Java Plateau Region Using a Joint Inversion of Body Wave and Surface Wave Data
Seismic tomography has become an essential tool for mapping the Earth's interior, providing constraints on temperature, composition, mineralogy, tectonic history, and dynamic behavior. Travel-time tomography using body waves provides high-resolution images in regions where a number of rays intersect, but is susceptible to vertical smearing in the upper mantle because the teleseismic waves propagate dominantly in the vertical direction. On the contrary, the fundamental mode dispersion characteristics of surface wave data, while providing good vertical resolution in the crust and the upper mantle, are less sensitive to deep perturbations at typically used frequencies. Besides, full waveform inversion has attracted much attention in recent years, but it requires a lot of computational resources and does not take full advantage of the large amount of seismic data available.We performed a joint inversion of body wave and surface wave data to obtain the three-dimensional shear wave structure by taking advantage of the complementary sensitivity of each dataset. The inversion algorithm for surface wave data is based on Fang et al. (2015), which is a one-step inversion of surface wave traveltimes at different frequencies for Vs models without constructing the phase velocity maps. The body wave data set consists absolute traveltimes picking and multiband differential traveltimes between each two stations, and was inverted following Obayashi et al. (2013) that use hybrid kernel of finite frequency and ray-theoretical kernels. The combination of these methods, similar to Golos et al. (2018), allows all data sets to be solved simultaneously. To demonstrate its usefulness, we applied the method to determine the 3-D shear wave velocity structure beneath the Ontong Java Plateau (OJP) using multi-frequency differential traveltime between two stations, Rayleigh and Love wave phase velocity dispersion measurements (Isse et al., 2021), and global traveltime data catalog (International Seismology Centre, 2023). We will present the results in comparison with previous tomographic studies in the OJP region, both multi-frequency tomography using P-wave wave arrival times (Obayashi et al., 2021) and radially anisotropic shear wave tomography using surface wave dispersion measurements (Isse et al., 2021).