Tuesday November 16th, 2021 @ 6:30pm Virtually

Dr. Dayanthie S. Weeraratne, CSUN, will be presenting:
"Investigating the role of relative sea-level change in the retreat of a marine based ice stream in northwest Scotland."

Dr. Dayanthie S. Weeraratne/ November Speaker


Continental and oceanic lithosphere, which form in different tectonic environments, are studied in a single amphibious seismic array across the Southern California continental margin. This provides a unique opportunity to directly compare oceanic and continental lithosphere, asthenosphere, and the LAB (Lithosphere-Asthenosphere Boundary) in a single data set. The complex history of the region, including spreading center subduction, block rotation, and Borderland extension and translation, allows us to study limits in the rigidity and strength of the lithosphere. We study Rayleigh wave phase velocities obtained from the ALBACORE (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) offshore seismic array project and invert for shear wave velocity structure as a function of depth. We divide the study area into several regions: continent, inner Borderland, outer Borderland, and oceanic seafloor. A unique starting Vs model is used for each case including appropriate crust and other layer thicknesses, densities, and P and S velocities which predicts Rayleigh phase velocities and are compared to observed phase velocities in each region. We solve for shear wave velocities with the best fit between observed and predicted phase velocity data in a least square sense. Preliminary results indicate that lithospheric velocities in the oceanic mantle are higher than the continental region by at least 2%. The LAB is observed at 50 ± 20 km beneath 15-35 Ma oceanic seafloor. Asthenospheric low velocities reach a minimum of 4.2 km/s in all regions, but have a steeper positive velocity gradient at the base of the oceanic asthenosphere compared to the continent. Preliminary results from seismic tomography images in two and three dimensions will be presented.

Dr. Dayanthie S. Weeraratne/ November Speaker

Speaker Biography

Currently Full Professor of Geophysics at California State University, Northridge (CSUN) in the Dept of Geological Sciences where the female/male faculty ratio is 50/50.

Undergrad and MS degree at University of Oregon
Ph.D. from Brown University
Postdoc at Carnegie Institution of Washington

Director of the GEMS program (Geological Experience for Minority Students) which has been supporting underrepresented minority (URM) students at CSUN for past 12 years. (https://csun.edu/science-mathematics/geology/gems-program)

Third Tuesday of Every Month: 6PM – 9PM
Poinsettia Pavilion
    3451 Foothill Rd Ventura, CA 93003
Have Questions? Email: coastgeologicalsociety@gmail.com
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