Mapping detailed seismic structure near the transition zone discontinuities
Transition zone seismic discontinuities (TZSDs) at depths of about 410 and 660 km are generally attributed to phase transitions in the olivine system. They offer great insights into the temperature, composition, and dynamics of Earth’s interior. A detailed characterization of the seismic structure near the discontinuity, such as shear velocity and density jump, and the transition width, is essential for inferring the thermos-chemical properties near the transition zone and understanding the tectonic processes. While numerous studies have investigated TZSDs with diverse datasets, few have simultaneously obtained robust observations of these properties.
Converted waves (Pds) from the discontinuities are sensitive to shear velocity structure near the discontinuity and top-side reflections (PpPds) are more sensitive to the density. A joint analysis of the two waves allows us to independently constrain the seismic features near the TZSDs. We propose a simultaneous inversion of the shear velocity and density jump, as well as transition width and velocity gradient near the TZSDs using multiband (15 sec ~ 1 Hz) amplitudes and traveltimes of Pds and PpPds waves.
We apply joint analysis of converted waves and topside reflected waves in the context of teleseismic P-wave receiver function technique at several large seismic arrays (USArray, China Array, Australian National Network, African Array, etc.) and compare the discontinuity structures across continents. These new descriptions will serve as the basis for exploring compositional models of the transition zone and understanding its relationship with prior and ongoing tectonic processes.