Seismic Analysis in Arctic Environments (COMPLETED 03.12.2020)

Tor Arne Johansen (UiB), Bent Ole Ruud (UiB), Leiv-Jacob Gelius (UiO)

2017 - 2020

The PhD project aims to explore some challenges related to seismic surveying in arctic environments, with special emphasis on the following subjects:

• Impacts of seismic surveying in the Arctic on marine mammals: Concerns about the effects seismic shooting may have on animals life have been raised (e.g. Harris et al. 2001, Gordon et al. 2003, Southall et al. 2007, Hermannsen et al. 2015). We want to study seismic sound levels occurring for various acquisition set-ups, and how these may affect marine mammals in this region. 
• Seismic processing of data acquired on floating ice: Separation of wave modes on multi-component seismic data: Seismic data acquired on floating ice contains a suite of various wave modes, including surface waves (flexural ice waves and Scholte waves), longitudinal waves, guided wave modes, along with primary and multiple reflections and refractions from the subsurface, (Press and Ewing 1951, Del Molino et al. 2008, Boiero et al. 2013). To increase the signal-to-noise ratio it is important to be able to separate various wave modes. A method referred to as vector valued deconvolution (Claerbout & Wang 2017) will particularly be implemented and tested for this purpose.
• Rock physics and seismic modelling of thawing ice and frozen sediments: In the Arctic, shallow sediments are usually frozen. Understanding the rock physics properties of these sediments and how they may vary with thawing is important in order to be able to provide a best possible seismic model of the overburden, which is vital for seismic imaging of deeper geological horizons. This is also crucial information for monitoring the state of the permafrozen layers. The viscoelastic properties of melting frozen sediments are not well understood, and one focus will be to study this experimentally and theoretically. 

OBJECTIVES

From the previous paragraphs, it should be clear that work is needed to improve the knowledge about these subjects. The main objectives of the PhD project are to:

1. Study processing techniques for improved separation of wave modes in seismic records acquired on floating ice.
2. Study how the elastic properties of sediments change with degree of freezing, with focus on rock physics modelling. Also, to study the propagation of seismic waves in such sediments by seismic modelling. 
3. Study possible impacts of seismic surveying on marine life, especially focusing on seals.

We expect to increase the knowledge about all of these subjects.