Speaker：Dr. Kai-Xun Chen(Department of Earth Environmental and Planetary Sciences, Brown University)
Title: Imaging the upper mantle structure of Pacific seafloor using surface wave and scattered body wave data: Case studies of the PLATE and PLUME OBS arrays
Venue：2nd Floor Lecture Hall
Host：Frédéric Deschamps / Research Fellow
The seismic structure of the oceanic lithosphere-asthenosphere system is key to deciphering the creation and evolution of tectonic plates and to resolving fundamental issues of mantle dynamics, for example, whether partial melt has ponded beneath oceanic plates of wide-ranging ages. To better constrain the physical properties of oceanic lithosphere and asthenosphere, an integrated result of regional shear velocity profiles derived from seismic data recorded by multiple ocean bottom seismometer (OBS) arrays is required.
In global shear wave tomography inverted from surface wave data, some properties are not entirely consistent with regional studies, for example the depth and velocity gradient of lithosphere-asthenosphere boundary (LAB), perhaps due to the large depth extent of the sensitivity kernels of long-period surface waves. A solution to obtain better vertical and horizontal resolutions is via regional studies that sample seafloor of different ages. To achieve a detailed understanding of oceanic mantle structure, I constrained the properties of velocity gradients beneath 155 Ma western Pacific seafloor by analyzing converted body wave data recorded by the PLATE deployment. Additionally, I inverted surface wave data recorded by the PLUME array for the absolute shear velocity of the upper mantle structure beneath the Hawaii islands using two-plane wave method.