MEASURING INFLATION AND DEFLATION OF ACTIVE VOLCANOES WITHIN THE AFAR DEPRESSION USING InSAR

Volcanic inflation and deflation of silicic and basaltic volcanoes in the Afar Depression of Ethiopia and Eritrea was measured using Envisat satellite, Advanced Synthetic Aperture Radar (ASAR), C-Band data. The Afar is a diffuse tripe junction and is the only location in the world where two oceanic rifts step onto and form an overlapping rift system represented by the SE-propagating Red Sea propagator (RSP) and the Gulf of Aden propagator (GAP). Volcanic activity along the RSP has been well studied at Erte Ale, which contains the world largest lava lake and the Dabbahu volcanic region, which is the location of the 2005 volcano-seismo crisis. The Afar Depression hosts 30 + volcanoes as identified by the Global Volcanism Program and published literature, but only the Dabbahu spreading segment has been extensively studied using InSAR. This study examined select ASAR data collected over 8 years from 2002-2010 in three domains: (1) the RSP, which has been extending generally southward from the Gulf of Zula to the southern Tendaho Graben for the past ~13 Ma (2) the GAP, which has been extending from the Gulf Tadjoura to the ~northwest for the past ~0.8 Ma and 3) the Nabro traverse range, a marginal volcanic center likely related to crustal thinning due to the clockwise rotation of the Danakil Microplate. Ascending and descending interferograms and phase displacement maps were generated. Along axis rift volcanic deformation between 2002-2010 is shown by inflation and deflation of select volcanoes along both propagators, however no deformation was detected in the Nabro range. Along the RSP, the basaltic Erte Ale volcano deflated ~20 cm between June 28, 2004 and February 17, 2010 and the silicic Gablaytu volcano deflated ~ 6 cm. The theorized termination point of the Red Sea Propagator at Dama Ali, inflated ~ 3 cm between October 30, 2007 and November 18, 2008. Along the GAP, the silicic Oyma and Dibolli volcanoes, which formed at the termination of the Manda Inakir rift, both inflated (~2 and 1.5 cm respectively) between November 18, 2008 and August 10, 2008. This study detected 5 volcanoes that exhibited significant deformation between 2002 and 2010. Also, this study contributes to the understanding of along axis rift volcanism and for identification of volcanic hazards in a region that has shown a ~27.5 % population increase between 1997 and 2007.