Innocent Ezenwa, Carnegie Earth and Planets Laboratory
Electrical Resistivity, Thermal Conductivity and Melting of Fe Alloys at Planetary Core Conditions
February 3, 2023 at 3:00 pm (PLS 1140)
The global magnetic field of the terrestrial planets is generated by the action of the dynamo, with motions thought to be due to convection. For the Earth, compositional convection from the release of light alloying elements at the inner core boundary has been known to be the leading driver of the present-day geodynamo. The onset of the nucleation of the inner core has been estimated to be about 1.5 billion years ago whereas the magnetic field has been in existence for over 4.5 billion years, evidenced in paleomagnetic rock record. The early dynamo has been assumed to be powered thermally before the birth of the inner core. However, literature data from the past decade have raised skepticism in the generation and sustainability of a thermally driven early geodynamo. To closely access this phenomenon, the understanding of the transport properties of Fe and its alloys at core conditions are needed. In this talk, I will present the electrical resistivity, thermal conductivity and the melting processes of Fe and its alloys with light elements (e.g., Si, C, S etc.) at extreme pressure and temperature conditions.
Sean Peters, Middlebury College
February 17, 2023 at 3:00 pm (PLS 1140)
Lucien Nana-Yobo, Texas A&M University
March 10, 2023 at 3:00 pm (PLS 1140)
Rasheed Ajala, Columbia University
Multiscale Earth models: Wavefield verification and space exploration
March 31, 2023 at 3:00 pm (PLS 1140)
Accurate Earth models are fundamental to the study of the composition, structure, and evolution of our planet. Over four decades have passed since the introduction of seismic waveform inversion, yet regional- and global-scale Earth models rarely exceed 0.2 Hz in frequency content. A primary impedance to progress is the computational demand for optimization on a large spatial domain. Urban seismology offers a paradigm shift through advancements in field instrumentation using dense local seismograph arrays and telecommunication cables to provide wavefield records with unprecedented detail. Artificial intelligence also shows promise in accelerating wavefield simulations. One tractable strategy then uses these datasets to develop high-frequency models, possibly exceeding 1 Hz in perceived regions of interest, and incorporate them into longer-wavelength reference Earth models. To illustrate some elements of these research ideas and implementation challenges, we employ a case study in southern California, where earthquake hazard assessment is paramount to the seismological community. Local Earth models with a better characterization of sedimentary basins and fault zones are assimilated into the most popular regional models of the area to enhance them. We further investigate the accuracy of the multiscale models by measuring the errors in their wavefield predictions using complete three-component broadband seismograms. Some of the improvements in the reference models indicate that the approach represents a suitable path forward pending the next technological leap in computing.
Rodney Tollerson II, Caltech
April 7, 2023 at 3:00 pm (PLS 1140)
Lindy Elkins-Tanton, School Of Earth and Space Exploration, ASU
April 21, 2023 at 3:00 pm (PLS 1140)
The coordinator for the Colloquium Series is Dr. Megan Newcombe. You can contact her at newcombe [at] umd [dot] edu.