Regional rumble: a seismological study of glacial earthquakes in Greenland

Glacial earthquakes occur primarily in Greenland, in connection with major outlet glaciers. They were first discovered by Ekstrom et al in 2003 using teleseismic data and a global detection algorithm based on surface waves. Seismograms recorded in Greenland reveal a much richer frequency content in the glacial earthquakes than observed in the teleseimic data. Thus the regional data have the potential to provide more accurate locations of the events as well as a better understanding of this peculiar phenomenon. Since 2000 a total of 30 broadband (BB) seismographs have been deployed in Greenland for periods ranging from 3 months to currently 7 years. While the seismographs were installed for structural studies, the data are equally useful for analyzing glacial earthquakes. One of the most productive glaciers in Greenland with respect to glacial earthquakes is Helheim Glacier in East Greenland. A BB seismograph has operated continuously in the nearby town of Tasiilaq since January 2000. In July and August 2007 two additional BB seismographs were installed in the vicinity of Helheim Glacier, where they will operate for at least a year. The first data have already been retrieved and will be presented. This study of glacial earthquakes is part of a large multidisciplinary effort involving seismology, geodesy, glaciology and climatology. Major field work has been carried out on Helheim Glacier during the summers of 2006 and 2007. In this presentation we will focus on the seismological results based on recordings from Greenland.