July 06 , 2017. EN. San Miguel , Bogoslof , Aira , Campi Flegrei .

Home / aira / July 06 , 2017. EN. San Miguel , Bogoslof , Aira , Campi Flegrei .

July 06 , 2017. EN. San Miguel , Bogoslof , Aira , Campi Flegrei .

July 06 , 2017.


San Miguel , ( Chaparrastique ) , El Salvador :

Monthly Volcanic Monitoring Report June 2017.

The activity of the San Miguel volcano remained stable, with a level of seismic vibrations fluctuating between 61 and 88 units of RSAM / day on average. There was no trace of earthquakes related to the fracturing of rocks on the volcano. The occurrence of micro – earthquakes associated with fluid dynamics in the volcanic system on 12 June persisted until the end of the month. Because of their small size, none of them was perceived by the population.



As regards emissions of sulfur dioxide (SO2) values, these varied between 54 and 826 tonnes per day. Basic data typical of an open volcanic conduit system. At the end of the month the activity of the volcano was normal. However, the strengthening of the monitoring of the MARN in real time on the volcano is maintained.

Visual Surveillance:
The images captured daily showed gas plumes, which is usual for this volcano (Figure 1). Although most of the time the volcano remained cloudy.
Seismic monitoring:
During the month of June, the seismic vibration of the volcano remained at the reference level between 54 and 88 RSAM / day units on average, with frequency ranges between 5.3 and 7.5 Hz. Had no trace of earthquakes related to the fracturing of rocks on the volcano. It should be noted that from Monday 12 June until the end of the month, the increase in the number of volcanic earthquakes has presented high frequencies. This indicates the movement of fluids (magma and gas) inside the volcanic conduit.



Gas monitoring:
The flow of sulfur dioxide (SO2) emitted by the volcano remained between 54 and 826 tons per day. These values are considered as reference and typical of a degassing process of the volcanic system through an open duct. From May 21 to June 30, a clear downward trend in these parameters, consistent with the normal level of activity of the volcano, was recorded.

Source : Snet.


Bogoslof , Alaska :



53°55’38 » N 168°2’4″ W,
Summit Elevation 492 ft (150 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE


During the past 24 hours Bogoslof experienced two explosive eruptions. The first occurred at 16:51 AKDT July 4 (00:51 UTC, July 5), lasted 13 minutes, and was detected in seismic, infrasound, and satellite data. A small cloud was produced that was carried to the southeast. This event prompted AVO to raise the Aviation Color Code/Alert Level to RED/WARNING.


Following the event seismicity decreased for several hours before a second explosive event occurred at 19:07 AKDT (03:07 UTC, July 5). This event lasted about 11 minutes and was also detected in seismic, infrasound, and satellite data. A similar small cloud was again carried to the southeast.




Seismicity on neighboring networks has remained low since the last eruption and no further emissions have occurred at the volcano. AVO reduced the Aviation Color Code/Alert Level to ORANGE/WATCH this morning.


Source : AVO.


Aira ( Sakurajima ) , Japan :

31.593°N, 130.657°E
Elevation 1117 m

JMA reported that events at Showa Crater (at Aira Caldera’s Sakurajima volcano) at 1811 and 1904 on 27 June generated ash plumes that rose 1 km above the crater rim. Weak incandescence from the crater was noted on 30 June. During 30 June-3 July there were five events, one of which was explosive. Material was ejected as far away as 500 m from the crater. The Alert Level remained at 3 (on a 5-level scale).


The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan’s most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu’s largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Source : GVP.

Photo : Sakurajima volcano photography


Campi Flegrei , Naples , Italy :

The seismicity background, a new parameter to monitor Campi Flegrei.

Predicting the evolution of the activity of a volcano requires a joint interpretation of the seismicity, the deformation of the soil and the variations affecting the fluids emitted (composition of fumaroles, volume of flows, etc.). A group of researchers from the National Institute of Geophysics and Volcanology in Italy (INGV), the University of Granada (Spain), the University of Aberdeen (United Kingdom), the Institute of Volcanology of the Islands Canaries (Involcan) and CNRS (France), have identified a parameter defined by authors as background seismicity, which makes it possible to monitor, quickly and easily, the status of the Campi Flegrei caldera.


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The researchers studied the causes of earthquakes after 2000 in the Campi Flegrei caldera. With a statistical model, they found that there is a strong correlation between micro – earthquakes (with a maximum amplitude of 2.5), vertical deformation and increasing concentration of temperature – sensitive gases in the composition of fumaroles in vents in the zone of the Solfatara, the most active in the area of ​​the caldera.

These simultaneous changes point to a process of increasing the temperature and pressure of the hydrothermal system due to an increase in the injection of deep magmatic fluids.

In particular, they found that since 2008, the seismicity and soil elevation curves are practically confused.
Since 2005, the activity has been interpreted by studying two variable activities, soil deformation and hydrothermal activity. The evolution of these variables can be due either to magmatic intrusions or to injections of magmatic fluids.


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By studying seismicity, the authors have estimated that the cause is magma injections, because micro – earthquakes occur at very shallow depth, within 2 km. Most micro – earthquakes are volcano – tectonic and their epicentres are located within a radius of 2500 meters centered on the crater of the Solfatara.

Researchers believe that interpretations of signals associated with volcanic phenomena are particularly complex in the case of a caldera. A seismic swarm and an increase in emissions do not always provide for an eruption. But the opposite can also happen, « an eruption is preceded only by small variations of geophysical and geochemical signals, » says Giovanni Chiodini, lead author of the study. For this reason, and because of their high explosiveness, caldeiras are considered one of the most dangerous types of volcanoes.
However, he explains, background microseismicity is easier to monitor than other parameters and the discovery of the strong relationship between these three variables is necessary for monitoring and will be taken into account in monitoring the volcano.

Since December 2012, the Campi Flegrei are in a state of alert yellow, in an area where live three million people.


Sources : nature.com , Ingv , Olga Rodriguez.

Photo : voce di Napoli

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