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Modelling shallow earthquakes with seismic and InSAR data: uncertainty and robustness analysis

Frietsch, Michael; (2019) Modelling shallow earthquakes with seismic and InSAR data: uncertainty and robustness analysis. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis uses advanced seismo-geodesy modelling tools for enhanced characterisation of earthquake sources, with a special emphasis on robustness and error quantification. InSAR, local seismic and teleseismic waveforms are used to investigate seismic events in two distinct regions: (i) the intraplate Nevada region (USA), within the Basin and Range tectonic province, which has good instrumental coverage; and, (ii) the Azores archipelago, an oceanic triple junction area with limited data coverage. A new multiple fault inversion technique using 3-D Earth models is developed to estimate fault geometry and dimensions, the average slip vector and the centroid for each sub-event. Synthetic inversion tests accounting for data noise highlight the strengths of each data type and help quantify the expected parameter uncertainties and trade-offs in real data inversions. It is also found that iterative inversions as often performed in the literature can lead to erroneous solutions. The simultaneous modelling of multiple subfaults is necessary to successfully recover the source parameters. In the case of the Mw 6.0, Wells, Nevada earthquake, the local seismic data require a two-fault source solution suggesting a listric normal fault consistent with the aftershocks’ distribution. While the lowest magnitude sub-event in the two-fault solution cannot be constrained by the InSAR or the teleseismic data alone, the joint data modelling helps reduce parameter uncertainties and trade-offs. Earth models from a previous receiver function study help modelling five earthquakes in the Azores. The accurate source location obtained from local seismic data helps stabilise moment tensor inversions based on local and teleseismic waveforms. The solutions for the Mw 5.9, 2013 Povoac¸ ˜ao basin earthquake show a lower variability than in existing seismic catalogues and exhibit a persistent non-double-couple component of 40–60 per cent. This is potentially due to geometrically complex faulting in the region, notably curved faults.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Modelling shallow earthquakes with seismic and InSAR data: uncertainty and robustness analysis
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10067200
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