1. Earth and Mineral Sciences; Pennsylvania State University; University Park; Pennsylvania; USA
2. Department of Terrestrial Magnetism; Carnegie Institute of Washington; Washington; D. C.; USA
3. Montserrat Volcano Observatory; Flemmings, Montserrat; West Indies
4. School of Earth and Space Exploration; Arizona State University; Tempe; Arizona; USA
5. Department of Geosciences; University of Arkansas; Fayetteville; Arizona; USA
6. Department of Earth Sciences; Bristol University; Bristol; UK
7. Earth Observatory of Singapore; Singapore