The National Secretariat for Risk Management said yellow alert remains in surrounding communities of Tungurahua volcano in Ecuador.
On April 27, 2013 two small earthquakes associated with fracturing of rocks within the volcano (volcano-tectonic earthquakes) were recorded. According to a preliminary assessment, these volcano-tectonic earthquakes started a new increase in seismic activity at the volcano Tungurahua surface.
Seismic signal from Tungurahua (RETU station, IG) on April 29 ,2013
On April 27, 2013 an emission occurred and reached 2 km in height with a load of medium to low ash. Throughout the day the volcano continued producing short pulses of vapor emissions, which eventually had a moderate to low ash content. During this episode there was only one report of ash fall during the morning in the area of Juive Grande. Since April 27, 2013 more than 70 signals of long period events have been recorded, and 13 tremor emission periods, marking a clear shift to the values obtained in the previous days, where on average there were 12 earthquakes per day.
Steam and ash emission from Tungurahua on April 27, 2013.(left) and on April 28, 2013 (right) (Source: C. Viracucha – OVT / IGEPN)
Early on April 28, 2013 an explosion created a column of steam with average content of ash that rose about 4 km above the crater, then decreased and remained more or less sustained at 2.5 km height above the crater for 30 minutes. The column began scattering on all sides of the volcano, and drifted W and SW for more than 100 km and caused light ash falls in areas close and around the volcano, in Banos, Chacauco, Bilbao, Cusúa, Juive Grande, Pondoa and Pillate.
Later on April 28, 2013 several explosions happened, the largest of which created shock waves and a thunderous roar, ejected huge blocks and created an eruption column that rose 3.5 km above the crater.
Graphs show ash emission at altitude of 5023 m (Source: VAAC Washington)
Featured image: Steam and ash emission on April 27, 2013. (Credit: C. Viracucha – OVT / IGEPN)