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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Articles avec #tectonics catégorie

Publié le par Bernard Duyck
Publié dans : #volcanic activity, #Tectonics

In Chile, four volcanoes have their volcanic alert in Amarilla level today: the Nevados de Chillan complex, the Villarica, the Copahue and the Laguna del Maule complex.

All are monitored 24/7 by professionals from the South Andes Volcanic Observatory, OVDAS.

Activity of the Copahue, the Laguna del Maule complex, the Veniaminof and earthquakes off Raoul island.

Over the past few days, Copahue's volcanic activity has evolved to show visible signs on the surface. It is important to mention that very low frequency (very long period VLP) seismicity has been recorded in the previous months, generally linked to the rise of the magmatic material to more superficial levels. Likewise, on May 20, a series of volcanic seismological events located south-southwest near the volcanic building were recorded.

On June 16, there was an increase in energy from the seismic tremor with subsequent stabilization and decrease in the following hours. At the same time as this decrease, the incandescence and the emission of particles were detected from cameras installed by OVDAS. The latest sulfur dioxide recordings obtained by the equipment installed for its detection indicate average flows of 592 tonnes / day for June 15, considered as usual values ​​for this activity.

On the other hand, the monitoring stations which measure the deformation in the volcanic sectors do not show changes related to this activity. In addition, the images available on the Planet satellite platform indicate a decrease in the volume of the lake housed in the active crater.

In summary, the changes in seismological behavior, the anomalies in the surface assessments and the decrease in the volume of the crater lake suggest the presence of a volume of magma at superficial levels.

 

Sources: Sernageomin & Onemi

Copahue - photo Valentina Sepulveda @Valecaviahue 14.06.2020 in the evening - un clic pour agrandir

Copahue - photo Valentina Sepulveda @Valecaviahue 14.06.2020 in the evening - un clic pour agrandir

The Sernageomin through a special report of volcanic activity (REAV) reported the change of alert from GREEN to YELLOW in the volcanic complex of Laguna del Maule

The above responds to the increase in volcano-tectonic (VT) type seismic activity, associated with rock fracturing, through seismic swarms on June 11, 13 and 15-16. These events were characterized by their small scale and by their location in the southwest of the lagoon (Las Nieblas sector)

In addition, in this same area during the previous months, diffuse carbon dioxide (CO2) anomalies were detected through the ground.

Therefore, due to the persistent presence of seismic swarms in the same area, added to the gas anomaly and the constant deformation that has characterized the volcanic complex over the past decade, it is considered to be at above its basic level.

A potential allocation area is set at a radius of 2,000 meters around the passive carbon dioxide degassing center

 

Source: Sernageomin

The Laguna del Maule volcanic complex - photo Sernageomin / Rayen Gho

The Laguna del Maule volcanic complex - photo Sernageomin / Rayen Gho

In the past few days, there have been periods of earthquakes and occasional earthquakes in Veniaminof. This represents a deviation from the background activity. Thus, the aviation color code and the alert level of the volcano are increased to YELLOW / ADVISORY.

This type of seismic activity generally precedes the eruptive activity with Veniaminof, but does not mean that an eruption will occur. Eruptive activity generally consists of emissions of minor ash, lava fountains and lava flows from the small cone of the summit caldera. Ash emissions are generally confined to the summit crater, but larger events can cause ash to fall in nearby communities and drift of airborne ash.

 

The Veniaminof volcano is an andesitic stratovolcano with a summit caldera 10 km in diameter located on the Alaskan Peninsula, 775 km (480 mi) southwest of Anchorage and 35 km (22 mi) north of Perryville . It is monitored by local seismic sensors, satellite data, web cameras, and infrared and lightning networks remotely.

 

Source: AVO

Veniaminof - the summit cone and the lava flows 2018 - photo Matt Loewen / AVO taken during the field visit in June 2019

Veniaminof - the summit cone and the lava flows 2018 - photo Matt Loewen / AVO taken during the field visit in June 2019

An earthquake of M7.4, 470 km south of Raoul island, in the north of New Zealand, on 19.06.2020 at 12:49 local time occurred in the Tonga-Kermadec subduction zone, where the Pacific plate plunges towards west under the Australian plate, causing tension events at shallower depths and compression tremor at greater depths.

This earthquake was felt widely along the east coast of New Zealand.

 

Source: GeoNet

 Location of Raoul Island in the Kermadec Islands and earthquakes over M5.0 in the last month (20 May – 20 June 2019). The subduction zone north of New Zealand is visible in red. - Doc. GNS

Location of Raoul Island in the Kermadec Islands and earthquakes over M5.0 in the last month (20 May – 20 June 2019). The subduction zone north of New Zealand is visible in red. - Doc. GNS

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Publié le par Bernard Duyck
Publié dans : #Sismologia, #Tectonics

If I tell you about the Michoacán-Guanajuato volcanic field, that doesn't mean much to you ... but if I say that it shelters the Parícutin, you can see better.

This extensive volcanic field in central Mexico, 250 km by 200 km, contains more than 400 vents. The predominant volcanic form is cinder cone, but small shield volcanoes, lava domes, maars and tuff rings, lava flows without cones are also present.

The two best representatives known are the Jorullo, which was built in the 18th century and the Parícutin, which formed in a grain field between 1943 and 1952.

Seismic swarm at Michoacán - Doc. SSN / UNAM 04.02.2020 - one click to enlarge

Seismic swarm at Michoacán - Doc. SSN / UNAM 04.02.2020 - one click to enlarge

 Seismic swarm at Michoacán - Doc. SSN / UNAM on 27.01.2020

Seismic swarm at Michoacán - Doc. SSN / UNAM on 27.01.2020

Why come back today ... because from January 5 to February 3, 2020 (in progress), the National Seismology Service (SSN) reported a seismic sequence with 1,824 earthquakes located near Uruapan, in the State of Michoacán, and more generally in the Mexican Neovolcanic Axis.

The largest earthquakes in the sequence were magnitude 4.1, one of them occurred at 2:49 a.m. on January 23, 2020, two others on February 2 at 7:47 p.m. and 10:58 p.m. respectively.

Uruapan / Michoacan - epicenter of the M3.9 earthquake / depth 12 km from 02.02.2020 / 22:48 - Doc. EMSC - EMSC

Uruapan / Michoacan - epicenter of the M3.9 earthquake / depth 12 km from 02.02.2020 / 22:48 - Doc. EMSC - EMSC

This region is characterized by intense seismic activity, related to the subduction of the Cocos plate under the North American plate. Under this part of the North American plate, the Cocos plate plunges with a very small angle almost horizontally, then after about 250 km, almost under Mexico, the diving is done abruptly.

Regional tectonics  &  Diving of the Cocos plate in 2 stages / © Perez-Campos et al., GRL 2008 - one click to enlargeRegional tectonics  &  Diving of the Cocos plate in 2 stages / © Perez-Campos et al., GRL 2008 - one click to enlarge

Regional tectonics & Diving of the Cocos plate in 2 stages / © Perez-Campos et al., GRL 2008 - one click to enlarge

For the moment, and pending the results of sampling, there is no indication of a link between earthquakes and magmatic intrusion activity.

More news is expected from Cenapred and the SSN / National Seismology Service.

 

Sources:

- National seismology service / UNAM - Special report / seismic sequence from January 5 to February 3, 2020.-  http://www.ssn.unam.mx/sismicidad/reportes-especiales/2020/SSNMX_rep_esp_20200113_secuenciaMichoacan_M39.pdf

- Global Volcanism Program - Michoacán-Guanajuato - http://volcano.si.edu/volcano.cfm?vn=341060

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