Scientific Report for NERC Geophysical Equipment Facility Loan 914
This loan comprised 40 SEIS-UK seismometers operating alongside 10 Cambridge-owned seismometers to provide coverage of 150 km of the Northern Volcanic Zone (NVZ) active spreading centre in Iceland, with denser local arrays around Askja and Krafla volcanoes, during July 2010 – September 2011 (Fig. 1). The loan of 30 SEIS-UK seismometers was extended to September 2012 to enable monitoring of increased seismic activity under Vatnajökull at the south end of the NVZ. We purchased a further 15 seismometers using NERC funding, thus maintaining a network of 55 instruments during the extension period. The work was supported by a NERC research grant and NERC post-doc and Ph.D studentships as well as several M.Sci. research projects. Preliminary results include: mapping of several thousand earthquakes along the rift zone in both the lower and upper crust; tomographic evidence for the magma chamber under Askja; detailed analysis of how strike-slip faulting accommodates shear in the transfer zone between rift segments; evidence for strongly non-double-couple source mechanisms at Krafla; demonstration of faulting in the brittle layer at extremely low stress drops of 1‒3 bars, probably caused by migration of carbon dioxide from an underlying magmatic intrusion.
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