1. School of Geography, Geology and the Environment, Keele University, Keele ST5 5BG, UK
2. Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA
3. Centro de Informação e Vigilância Sismovulcânica dos Açores, 9501-801 Ponta Delgada, Azores, Portugal
4. Instituto de Investigação em Vulcanologia e Avaliação de Riscos, University of the Azores, 9501-801 Ponta Delgada, Azores, Portugal
5. School of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK