High-resolution imaging beneath the Santorini volcano
File(s)
Author(s)
Chrapkiewicz, Kajetan Marcin
Type
Thesis
Abstract
Volcanoes are surface expressions of much deeper magmatic systems, inaccessible to direct observation. Constraining the geometry and physical properties of these systems, in particular detecting high melt fraction (magma) reservoirs, is key to managing a volcanic hazard and understanding fundamental processes that lead to the formation of continents. Unfortunately, unambiguous evidence of magma reservoirs has not yet been provided due to the limited resolving power of the geophysical methods used so far.
Here, a high-resolution imaging technique called full-waveform inversion was applied to study the magmatic system beneath the Santorini volcanic field, one of the most volcanically and seismically active regions of Europe. Quality-controlled inversion of 3d wide-angle, multi-azimuth ocean-bottom seismic data revealed a previously undetected high melt fraction reservoir 3 km beneath the Kolumbo volcano, a centre of microseismic and hydrothermal activity of the field.
To enable the above method to handle land data, two major algorithmic improvements were added to the high-performance inversion code. First, to simulate instrument response of land seismometers, a pressure-velocity conversion has been implemented in a way that ensures reciprocity of the discretised 2nd-order acoustic wave equation. Second, the immersed-boundary method, originally developed for computational fluid dynamics, was implemented to simulate the wave-scattering off the irregular topography of the Santorini caldera. These advancements can be readily used to provide a higher-resolution image of the melt reservoir beneath the Santorini caldera already detected by means of travel-time tomography.
Here, a high-resolution imaging technique called full-waveform inversion was applied to study the magmatic system beneath the Santorini volcanic field, one of the most volcanically and seismically active regions of Europe. Quality-controlled inversion of 3d wide-angle, multi-azimuth ocean-bottom seismic data revealed a previously undetected high melt fraction reservoir 3 km beneath the Kolumbo volcano, a centre of microseismic and hydrothermal activity of the field.
To enable the above method to handle land data, two major algorithmic improvements were added to the high-performance inversion code. First, to simulate instrument response of land seismometers, a pressure-velocity conversion has been implemented in a way that ensures reciprocity of the discretised 2nd-order acoustic wave equation. Second, the immersed-boundary method, originally developed for computational fluid dynamics, was implemented to simulate the wave-scattering off the irregular topography of the Santorini caldera. These advancements can be readily used to provide a higher-resolution image of the melt reservoir beneath the Santorini caldera already detected by means of travel-time tomography.
Version
Open Access
Date Issued
2021-08
Date Awarded
2022-03
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Morgan, Joanna
Paulatto, Michele
Sponsor
Leverhulme Trust
Publisher Department
Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)