CHAPTER 6

 
 
 
 
 
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GEO ON

DISASTER RISK REDUCTION

 
 
 
 
 
 
 
 
 
 

CHAPTER 6

 
 
 
 

GEO-GSNL

 
 
 
 
 
 
 
 
 
 
 
 
 

GEO-GSNL Ecuador Supersite supports emergency response during the 2020 Sangay volcano eruption

GEO’s GSNL Initiative maintains a network of 12 Geohazard Supersites spread over six continents. For each Supersite a large number of EO datasets is made openly available by local monitoring institutions and by the CEOS space agencies, to support scientific research and hazard assessment for risk prevention and emergency response.

The Instituto Geofísico of the Escuela Politécnica Nacional (IGEPN) in Quito, coordinator of the Ecuador Supersite, receives hundreds of satellite images per year by which, together with ground data, it monitors the activity of over 10 active volcanoes.

The most recent eruption of the Sangay volcano started on 20 September 2020 at 04h20LT with pulses of seismic tremor and explosions that hoisted an eruption cloud to over 14 km.  Conditions were cloudy, but GOES-16 satellite imagery allowed observation in near real time of the propagating ash cloud, so that an early warning of impending ashfall could be given to provincial governments downwind. Interferometric processing of Sentinel-1 and TerraSarX imagery starting in January 2019 shows that an inflationary zone (3-7 cm/yr) on the NE summit area has notably increased in the past 8 months, while the W flank has a gradual sinking, perhaps from magma migration.  Two weeks before the 20 September eruption, a deflationary signal was registered on the NE summit zone.

Fig. 1: Velocity map and NE time series from Sentinel 1 data (Descending track) between January 22nd, 2019 and September 25th, 2020. Software processing: ISCE and Mintpy.  Red broken lines represent eruptions on 08 June (smaller) and 20 September (larger) of 2020.

The mostly positive InSAR values and their correlations with upticks in seismicity and gas emissions (SO2) allowed the IGEPN staff to indicate to local and national authorities that Sangay was in a very active state and that a stronger eruption was likely.  The information was communicated via Webpage reports, press releases, radio and television interviews and tweets to the IG´s 1.3 M followers.

To firmly establish that important deformation is occurring on Sangay´s summit and also on the middle flanks, the Supersite-provided data is invaluable, since it picks up a signal in very inaccessible areas.  Additionally, other Supersite volcanologists are also contributing with their expertise in a joint evaluation of the InSAR results seen before and post eruption.

Fig. 2:  TerrasarX Interferograms on the Sangay Volcano Area, showing the deformation before the eruption (left) and during the eruption (right), especially in the NE part of Sangay´s summit. Each interferogram fringe is equivalent to 3.2 cm in line of sight.  These values are similar to those shown for LOS change in cm in Fig. 1B.   Processed with ISCE.

Globally, GSNL Supersites serve as paradigms of how open EO data and focused international collaboration can effectively support volcano and seismic monitoring and generate actionable information for disaster risk management.

During the short-lived crisis, more than 80,000 hectares of crop lands were covered in ash, including banana plantations and the airport in Guayaquil had to close down for half a day (see figure 3).

Fig. 3: Photos taken by members of IGEPN of secondary lahars which threaten a main bridge to the provincial capital of Macas; and ash-covered areas to the west and ash covering vegetation, 21 September, 2020.

After the eruption the volcano displayed sporadic tremor intermixed with explosions, and ash columns rising a km or so above the 5200 m summit ( See Fig. 4).

Fig. 4: Photos of Sangay´s NE flank taken on 26 September, 2020.  The ash column emanates from a deep crater whose E side is blown out by eruptive activity and erosion of lava collapse flows. Photos used with permission given by Jaime  Arteaga.

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