The level of activity of the volcanic complex of Nevados de Chillán is at level : YELLOW: changes in the behavior of the volcanic activity. Time for an eruption: Weeks / month.
Based on the analysis of information obtained from monitoring equipment and surveillance of the volcanic complex, the National Service of Geology and Mining (SERNAGEOMIN) through the Volcanological Observatory of Southern Andes (OVDAS) communicates :
It was recorded nine hundred and twenty four (924) seismic events, including:
Sixty-three (63) were associated with the fracturing process of rigid materials (called volcano-tectonic earthquakes, VT) with a maximum local magnitude (ML) of M3.2. It was ranked 858 earthquakes associated with fluid dynamics inside the volcano (called long-period events, LP) with maximum local magnitude (ML) of M2,8 and a reduced displacement value (RDC) less than 75cm2.
Finally, during this period, three (3) Tornillos type of events were recorded (TO), processes involving resonance in volcanic conduits with magnitudes equal or below 1.4 and reduced displacement values (DRC ) less than 1cm2.
During the period analyzed, it was also noted 175 episodes of discrete tremor, signal associated with the fluid dynamics inside volcanic conduits, and the emission of particulate matter to the surface (explosions), which were recorded by IP cameras installed in the volcano area. These tremor episodes had reduced displacement values (DRC) of less than 30 cm2, values considered to be high.
The images obtained by the camera network installed in the region, showed surface activity, especially characterized by the appearance of occasional explosions from issuing centers near the the crater Arrau and the “New” crater as was observed during the last flyby.
The data provided by two (2) electronic inclinometers and five stations (5) GNSS that monitor the deformation of the volcanic complex, showed no change due to the internal activity of the volcano during this period.
Sulphur dioxide (SO2) recorded on the Nevados de Chillan volcanic complex by the team DOAS (differential optical absorption spectrometry) of Chillán Station , installed 3 km to the North East (NE) of the active crater showed a mean value of 2051 ± 279 t / day and a maximum value observed during the first two weeks, with 3113 t / day, registered on 13 February, seen as an intermediate value.
In collaboration with the ONEMI of the Bío Bío region, a survey was held on February 11, which has managed to identify a third crater, at a location that suggests a linear trend of about 150 m in total length from the two other craters on a North-east axis (NNE). A decrease of activity of fumaroles is also highlighted, consistent with a drop in temperature of these ones (about 50 ° C lower) compared to the overflight conducted on January 30. The lowest temperature (125 ° C) indicates a decrease in the heat transfer from the magma to the hydrothermal system, which increases the proportion of the water vapor in the degassing process.
The images published by the OMI Group (The Ozone Monitoring Instrument), Sulfur Dioxide Group (http://so2.gsfc.nasa.gov/) and NESDIS (National Environmental Satellite, data and information (http // satepsanone. Nesdis.noaa .gov) not report any anomaly in the sulfur dioxide (SO2) into the atmosphere in the volcanic complex sector.
Thermal radiation released by the MODVOLC (Moderate Resolution Imaging Spectroradiometer) MODIS on its website (http://modis.higp.hawaii.edu/) and Mirova (Middle InfraRed Observation of volcanic activity) on its website (http: / /www.mirovaweb.it/), surveillance systems that indicate major changes in surface temperature, reported no thermal alerts in the area associated with the volcanic complex.
Monitoring parameters during the last 15 days showed a trend suggesting the release of the pressure on the the hydrothermal system near the surface of the active cone may be related to a decrease in heat flow from the underlying magma, characterized by lower explosive events and ash emissions in recent days. However the levels of sulfur dioxide flows and the recording of seismic events VT type suggest movement in depth of new masses of igneous materials. This implies the emergence of new impulses for surface activity with the possibility of generating phreatic explosions equal and / or greater than those recorded so far, and with phreatomagmatic eruptions or an evolution towards a purely magmatic stage represented by lava effusions from the currently active craters.
Therefore, the level of volcanic alert level remains at YELLOW, focusing on areas considered as high risk, including an area of 2 km around the active craters. It is recommended to limit access to this area.
February 19 , 2016. Nevados De Chillan , Chile :
Source : Sernageomin.
Photos : Sernageomin, Patricio Arias .