Joint inversion of subduction zone velocity structure of central Chile by body wave arrival times and surface wave dispersion data

In this study, we assemble body wave arrival times from earthquakes occurring in the central Chile between 2014 and 2019, and Rayleigh wave phase velocity maps at periods of 5-80 s from ambient noise Empirical Green's functions in Chile. By jointly using body wave arrival times and surface wave dispersion data, we refine the Vs model and improve earthquake locations in central Chile. Compared to other velocity models in the region that are determined by individual data type, our joint inversion Vs model shows better consistency with the intraslab seismicity distribution as well as the Moho and slab interfaces. Our Vs model clearly images an eastward dipping high velocity band of 40-50 km thick, corresponding well to the thickness of the Nazca plate estimated by receiver function imaging and thermal modelling.

Overall, the intraslab seismicity distribution spatially correlates well with the slab high velocity anomalies except for along the subduction paths of the Copiapó Ridge and Juan Fernández Ridge. Additionally, parallel low-velocity stripes are imaged beneath the subducting plate, which are likely associated with the accumulated melts. The joint inversion velocity model also resolves widespread low-velocity anomalies in the crust beneath the Central Volcanic Zone of the central Andes, likely representing crustal magma chambers for various volcanoes.