Tjörnes Fracture Zone - news & activity updates
Tjörnes Fracture Zone (north of Iceland): ongoing earthquake swarm update
Sunday Apr 07, 2013 06:24 AM | BY: T
Earthquakes in the TFZ during the past 48 hours (Icelandic Met Office)
Map of tectonic faults and rift zones in northern Iceland (Icelandic Met Office)
The powerful earthquake swarm that started a week ago continues, but at reduced intensity compared to 2 April when the large magnitude 5.4 quake struck. Each day, hundreds of earthquakes have been occurring (more than 200 > magnitude 2 during the past 2 days).
Time and depth of recent quakes at the TFZ
The earthquake swarm is the result of release of tectonic stress that has accumulated in the crust and is being released at the moment. The area is one of the main so-called transform zones,- regions where the separating Eurasian and North-American tectonic plates move sideways along strike-slip faults rather than spreading apart directly as is the case in the main rift zones, where also the main volcanoes are located, because the opening movment here allows large batches of magma to rise easily.
The transform zones separate the rift zones at spreading plate boundaries at regular intervals in order to accommodate differential movements that are a result of the earth's curved surface where rigid plates move apart. In the transform zones, the sideways movement can produce much more strain in the rocks and has therefore the potential of larger earthquakes.
Recent GPS and seismic studies of the TFZ suggest that the plates at depth have been "locked" for a while and accumulated large stress, which is why the recent and present earthquake swarms are no a surprise. It seems that this stress has started to be released right now. However, the possibility of a larger earthquake (up to magnitude 7) remains in place.
The TFZ (as most transform zones) are not particularly prone to volcanic activity, although from time to time, (usually smaller amounts of) magma still can reach the surface in such areas as well. This happens much less so than in the rift zones, where most volcanic activity takes place. For the case of the TFZ, there has probably been an eruption in 1868 following an earthquake swarm, and little else is known about this event.
Whether the current activity is related to magmatic activity, or could lead to a submarine eruption in the TFZ is unknown, but unlikely. So far there are no signs that suggest that there IS an eruption going on at the sea floor.
Links / Sources:
Links / Sources:
- Measuring the present-day crustal displacements in the Tjörnes fracture zone and adjacent areas (Icelandic Met Office)
- How rifting occurs in Iceland, explanations regarding the recent earthquake swarm (VolcanoCafe)
- Update on the TFZ earthquake swarm at 01:01 UTC (Iceland geology blog)
Tuesday, Apr 02, 2013
A strong earthquake swarm including a widely felt magnitude 5.4 earthquake at 15 km depth this morning and hundreds of pre- and aftershocks is occurring in the Tjörnes Fracture Zone in a N-S elongated area about 15 km east of the island of Grimsey. [more]
Friday, Mar 01, 2013
An earthquake swarm is in progress east of Grímsey Island. So far, the largest quakes are below magnitude 3. [more]
Wednesday, Jan 30, 2013
Earthquakes continue with typically 10-20 quakes recorded in the TFZ. The swarm that had started 20 Oct last year has now been going on for over 3 months and shows no signs of stopping. [more]
Tuesday, Dec 11, 2012
The earthquake swarm in the Tjörnes Fracture Zone north off Iceland still continues at reduced intensity and there seems no end in sight. Most quakes are very small, but there are still occasional quakes at around magnitude 3, and the area remains at risk for a larger quake. [more]
Tuesday, Nov 20, 2012
The earthquake swarm still continues at much reduced pace. [more]