Structure and Dynamics of the Inner and Outer Core

Project description

Motivation (background)
Of all the Earth’s main layers, (oceanic/continental) crust, (upper and lower) mantle and the (inner and outer) core the structure, dynamics and history of the core is least well understood. This is not very surprising as the core is ’hidden from view’ by the crust and mantle. An important part of the dynamics of the core that is reasonably well understood is the inner core’s growth caused by precipitation of iron from the fluid outer core. Lighter elements (such as hydrogen, nitrogen, oxygen, magnesium and sulphur) stay in the outer core and this remaining lighter fluid, together with the latent heat release due to the solidification, drives convection in the outer core. This convection generates the Earth’s magnetic field and facilitates heat transfer from the core into the mantle.

Hypothesis (scientific problem):
However, many issues remain. For example, the viscosity of the outer core is not well constrained, the inner core rotates with variable degree with respect to the mantle/crust, there probably is convection in the inner core and there could be mass transfer from the core into the mantle. In terms of structure, questions regarding the structure of the core-mantle boundary and inner core boundary as well as the internal structure of both the inner and outer core remain. For example, quite different types of anisotropy have been reported for the inner core, which also contains isotropic scatterers. In order to better understand the dynamics and history of the core, it is important to get more reliable and more detailed estimates of the core’s structure. This can be done by using accurate waveform modeling and inversion of the multiple body wave arrivals that traverse the core.

Test (work):
Most of the analysis of the core’s body wave arrivals (such as PKP, PKiKP and there multiples as well as corresponding S arrivals) is done using 1D velocity models and a strong focus on the travel times. In this project 3D elastic waveform modeling techniques will be developed and applied to study certain aspects of the core’s structure. These waveform modeling techniques will mainly be ray based and will be general in the sense that they are valid for 3D heterogeneous anisotropic and attenuative core structures. If there is time the modeling technique will be combined with real data observations to invert for core structure.

Proposed course plan during the master's degree (60 ECTS):
GEOV274 (10 sp)
GEOV276 (10 sp)
GEOV277 (10 sp)
GEO-DEEP course on Earth dynamics in UiO (5 sp)
GEOV300 (5 sp)
Geophysics field course (5 sp)
GEOV302 (5 sp) 
MAT160 (10sp)

Prerequisites
Bachelor degree in Geophysics