Nevados de Chillan volcanic complex (16 to 31 March).
The level of activity of the volcanic complex is at: Yellow level, changes in the behavior of volcanic activity -Time For a probable eruption weeks / months.
Based on the analysis of information obtained from monitoring equipment and monitoring of the volcanic complex, the National Geology and Mining Service (SERNAGEOMIN) -Observatorio Volcanológico of los Andes del Sur (OVDAS) announces:
1590 seismic events were recorded, of which 151 were related to rock fracturing process, called volcano-tectonic earthquakes (VT). The biggest event was recorded with a local magnitude (ML) of m2,1 and located 5km to the South East (SE) of the active crater at a depth of 1.5 km. In addition, 1439 earthquakes associated with fluid dynamics inside the volcano have been recorded, 1348 of whom were long-term events (LP), the largest with a local magnitude (ML) of 2.6 M and a reduced displacement value (DRC) of 41,3cm2. Four ninety one were classified as tremor type events (TR), which reached a reduced displacement value equal to or less 2,5cm2.
Note that the 18 saw a change in seismic activity with the recording of repetitive events (REAV March 18, 1:50 p.m. HL), with low power, but significant from a qualitative point of view.
The LP type of seismicity and the tremor was associated with ash emissions. The most notorious was registered on 30, accompanied by a LP type event with a displacement reduced equal to 25 cm 2 and a low-energy tremor (DRC = 1 cm2) which continued for hours.
Sulphur dioxide (SO2) recorded on the Nevados de Chillan volcanic complex, by the team DOAS (Differential Optical Absorption Spectrometry), Chillan Station, located 3 km to the east-northeast (ENE) of active crater, presented an average value of 1292 ± 730T / day and a maximum value observed during the first two weeks at 2743t / day, registered on 20 March. In particular, due to the pulsating nature of the eruption process, the values of SO2, have high variability. The intermittent degassing in the process, was tested by evaluating the SO2 emissions with the infrared camera (IR), which recorded SO2 rate values close to the detection limit, measurements made during the months of January and February .
The images obtained through the network of cameras installed in the area showed surface activity mainly characterized by the emission of a white plume associated with the water vapor. Sporadically emissions were accompanied by ash, often with a long period seismicity (LP) and tremors (TR), the largest on March 30 with the explosion mentioned above, in which the height of the ash column reaches 200 m. about.
Although the height of the column was low, it was characterized by a high concentration of ash.
According to the analysis of data provided by two (2) electronic inclinometers and five (5) GNSS stations that monitor the deformation of the surface of the volcanic complex, small variations were observed in the morphology of the volcano.
In particular, the GNSS signals indicate variations, mainly horizontal components, resulting in an increase of the distance between two stations that make up a control line passing through the volcano, suggesting moderate inflation.
The images published by the OMI Group (Ozone Monitoring Instrument) Sulfur Dioxide Group (http://so2.gsfc.nasa.gov/) and NESDIS (National Environmental Satellite, Data and information- http: // satepsanone. nesdis.noaa.gov) reported no abnormality in sulfur dioxide (SO2) in the area near the volcanic complex.
Thermal radiation released by the MODVOLC (Moderate Resolution Imaging Spectroradiometer – http://modis.higp.hawaii.edu MODIS) and Mirova (Middle InfraRed, Observation of volcanic activity) on its website (http: // www. mirovaweb.it /), surveillance systems that indicate significant changes in surface temperature, reported no heat alert in the area associated with the volcanic complex.
Monitoring of the parameters during the last fortnight has shown that the activity continues in a process of interaction between hydrothermal system and the magmatic system, with signs indicating greater dynamic heat flow from the magmatic body underlying .
In this scenario the possibility of generating new phreatic explosions and / or phreatomagmatic eruptions of currently active craters continues.
Therefore, the volcanic alert level remains at yellow.
April 04 , 2016. Nevados de Chillan , Chile :
Source : Sernageomin .