Magmatic Plumbing at an Incipient Oceanic Spreading Centre: Evidence From Local Earthquake Data in Northern Afar

Posted by pkm at Mar 31, 2015 10:18 PM |
Finnigan Illsley-Kemp (1), Derek Keir (1), Jonathan Bull (1), Thomas Gernon (1), James Hammond (2), J-Michael Kendall (3), Berhe Goitom (3), Atalay Ayele (4) - (1) National Oceanography Centre, University of Southampton, Southampton, UK, (2) Department of Earth Science and Engineering, Imperial College London, London, UK (3) School of Earth Sciences, University of Bristol, Bristol, UK, (4) Institute of Geophysics, Space Science and Astronomy, Addis Ababa University, Addis Ababa, Ethiopia

The transition from continental breakup to seafloor spreading is characterised by voluminous intrusive and extrusive magmatic activity, focused along narrow rift segments. The exact manner in which this magma is stored and transported within the crust is poorly constrained. It is difficult to answer these questions by studying previously rifted continental margins, as the area of transition is buried deep beneath volcanic and sedimentary sequences. Northern Afar presents a unique opportunity to resolve this problem, as it exposes subaerially a volcanically accommodated transition from continental rifting to an oceanic spreading centre. The region therefore acts as a laboratory in which the geological signatures of continental breakup can be investigated unambiguously. For two years, between 2011 and 2013, a seismic network comprised of 12 broadband instruments was deployed in the area. Presented here are the hypocentre locations of over 4500 earthquakes. I discuss the implications that the data may have on our understanding of stress accommodation and volcanic activity during late stage continental rifting.

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