Deep seismicity revealing magma dynamics of the Askja volcano, north Iceland

Janet Key, Heidi Soosalu, Robert S. White
2008
Deep seismicity revealing magma dynamics of the Askja volcano, north Iceland
This is a Full Scientific Report resulting from NERC Geophysical Equipment Facility Loan 842, principal investigator Prof Robert White.

Abstract

The Askja region is located on the mid-Atlantic spreading boundary in central Iceland. The study area includes the Askja caldera and the mountains Herðubreið and Herðubreiðartögl which are part of the larger Askja volcanic system. During a two month deployment in summer 2006 over 1800 earthquakes were detected in the region including 100 previously unwitnessed lower-crustal earthquakes. A new deployment of 22 Güralp 6TDs was conducted during July and August 2007 specifically designed to target these deeper events. Over 250 lower-crustal Askja events were recorded, more than double the number seen in 2006. Shallow earthquakes in the 2 – 5 km depth range within the caldera appear to delineate the upper edge of a magma chamber. In February 2007 a new region of lower-crustal seismic activity began below Upptyppingar mountain in the Kverkfjöll volcanic system, just 20 km E of Askja. One of our stations was directly above much of this activity and detailed relocations have been performed combining data from our network and the permanent Icelandic network; revealing short term clusters of ~10-100 events that are grouped very tightly horizontally and migrate vertically.