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Dike intrusion now north of Dyngjujokull

24.08.2014 - 18:36
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More than 1200 earthquakes have been detected in the Bardarbunga area since midnight, most of them at the northern tip of the dike intrusion in the Dyngjujokull outlet glacier. Seismic activity has now been detected about 4 km outside the glacier. 270 million m³ of magma are thought to have flowed.

Martin Hensch, a geophysicist at the Icelandic Met Office says the dike intrusion seems to be propagating at a slower rate than yesterday. „Overnight, the intrusion migrated outside the margin of the Dyngjujokull outlet glacier, and the northernmost tip of the seismic activity is now about 4 kilometers north of the margin of the glacier. The propagation seems to have slowed, but is still continuing. Several strong earthquakes larger than magnitude 3 have occurred at the tip of the intrusion today. One interpretation could be that the magma is hitting colder and more resistive rock as it migrates further away from the volcano, but this is only an idea so far.“

Continuous seismic activity has been detected today, mostly at the northern tip of the dike intrusion. „The activity there seems to go in steps,“ says Martin. „Yesterday, the propagation was relatively quick, but today the activity seems to be more stop-and-go.“

0,27 cubic kilometers of magma. 

GPS measurements of land deformation around the Bardarbunga region indicate that magma is still flowing into the dike intrusion under Dyngjujokull. This observation is supported by the intense current seismic activity at the northern tip of the intrusion. Model calculations suggest a total volume um 270 million cubic meters ( 0,27 km³ ) of magma have intruded into the crust since seismic activity started on August 16. This volume of magma is similar to the total output of volcanic material in the Heimaey eruption in 1973. 

No eruption yesterday. 

The Met Office´s status report states that observations show that no eruption occurred yesterday and the intense low frequency seismic signal therefore had other explanations. Accordingly, the IMO downgraded today the aviation alert from red to orange. The Civil Protection Agency also downgraded its level of preparedness from emergency to danger. Road closures and area restrictions north of Vatnajokull are however still in effect, as an eruption can not be ruled out. 

Excerpt from the IMO status report today:

„More than 1000 earthquakes have been automatically detected in the area of Bárðarbunga calderaand along the propagating dike intrusion since midnight today (24 August). By far most of themwere located at the northern tip of the dike. Dike region NE of Bárðarbunga caldera: The seismicactivity has increased in number and intensity of the events since around 06:00 UTC and is still high at the moment. The northern-most front of the seismicity is already located outside the glaciermargin, but appears to be migrating at smaller rates than yesterday. Along the dike more than 20earthquakes were larger than M3 and three larger than M4. Event depths remain unchanged atabout 5-10 km.

Bárðarbunga caldera: Two earthquakes larger than M5 occurred along the calderarim (M5.3 at 00:09 UTC and M5.1 at 05:33 UTC). Same as for recent strong events in the caldera,they were located at about 2-5 km depth. These events mark the largest earthquakes recorded at the Bárðarbunga caldera since 1996. Joint interpretation of seismic and gps data suggest that the caldera might be responding to stress changes caused by the intruding dike.“

This story, by the Icelandic National Broadcasting Service (RUV), was updated on 24 August 2014, at 18.30 GMT.

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