NABRO volcano eruption


Since May 2011, The Arta observatory has detected isolated earthquakes of low magnitude (M ~ 2.5) in the Nabro-Dubbi area of the Alps Danakil (see fig. 1). Before that date, the historical instrumental seismicity (1964-2011) display very few events near these volcanoes.

On june 12, the Arta Geophysical observatory (OGA) has detected and localized an important seismic crisis beginning at 15:37 (UTC) followed by numerous events among them one magnitude 6.0 (Mw=5.7 USGS) at 20:32. All the epicenter are near the NABRO volcano and the focal depths are low (<10 km). (see fig. 2 and 3).


           
                                          Fig. 1    May, 2011                                                                                      Fig. 2    June, 12


                                                                                     Fig. 3   USGS focal mechanism


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At 21:00 appears a volcanic tremor which is the typical signature of an eruption (see fig. 4). The 6 hours crisis is interpreted as the fracturation by the intrusion (dyke) migration from down (magma chamber ??) toward surface.




                                               Fig. 4    helicorder of DAMY, GEOFON Dhamar, Yemen station.

From the sky satellite image of NASA (see fig. 5) confirm a large plume is emitted by the NABRO volcano in Eritrea, and the website like Earthquake-report was among the first to relay the information on this awakening of the NABRO after probably last 10.000 years. For additional information see IPGP webpage .




                                                 Fig. 5    The asches spread over a wide area in the WNW direction, covering Ethiopia end Sudan.

The VAAC in Toulouse (France) gives advisories concerning ashes at different flight level. For instance, on june 15, "Ash from Nabro eruption has no longer been detected over the Middle East since June 14th. The eruption still on-going and appears stronger from june 15th. 09h (UTC) but mainly producing SO2. The latest concentration charts and VAA/VAG take into account this situation" (see fig. 6 )



                     Fig. 6    Ash advisory bulletin of VAAC