The role of accurate earthquake locations in the mapping of the volcanic plumbing system at Soufrière Hills Volcano, Montserrat

Eyles, Jade (2021) The role of accurate earthquake locations in the mapping of the volcanic plumbing system at Soufrière Hills Volcano, Montserrat. Doctoral thesis, University of East Anglia.

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Abstract

Volcanic seismicity is used to monitor volcanic activity worldwide, with seismic monitoring the main method used to monitor Soufrière Hills Volcano, Montserrat. Soufrière Hills began erupting on the 18th July 1995 and has undergone five phases of activity, which were preceded by an increase in seismicity. Earthquake location is a complex problem, with several unknowns; computed hypocenters represent the optimal solution given the information available. Synthetic earthquakes allow the testing of velocity models and location methods to be compared with known earthquake locations. The current location method used at Montserrat Volcano Observatory produced large hypocenter errors, with poor constraints on hypocenters at particular depths. Comparison with other velocity models and location methods shows the Rowe et al. (2004) velocity model with NonLinLoc produces locations that more accurately represent synthetic earthquake locations. This new location method was used to relocate the seismic catalogue at Montserrat from 1995 to 2018, to understand how changes in hypocenters influence interpretations. Relocations show a migration of hypocenters towards St Georges Hill on the 12th-14th August 1995; this alongside computed focal mechanisms, suggests dyke propagation and inflation, differing from previous interpretations. Prior to a Vulcanian Explosion on the 29th July 2008, relocated hypocenters are located in SE Montserrat. The majority were located using four P phases; this has been shown to produce large hypocenter errors with synthetic testing. Therefore, earthquakes were repicked for additional P and S phases to improve locations during this period. This resulted in reduced hypocenter errors, with the majority of earthquakes relocated beneath Soufrière Hills with minimal SE locations. This project highlights the importance of using a robust location method suitable for the region to ensure that outputted hypocenters are trustworthy and accurate. Use of unsuitable methods can influence earthquake patterns and thus interpretations. This impacts understanding of volcanic systems, and ultimately
hazard assessment.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Chris White
Date Deposited:	14 Jun 2022 14:18
Last Modified:	14 Jun 2022 14:18
URI:	https://ueaeprints.uea.ac.uk/id/eprint/85612
DOI:

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