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Title: Modelling shallow earthquakes with seismic and InSAR data : uncertainty and robustness analysis
Author: Frietsch, Michael
ISNI:       0000 0004 7660 6535
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available