Home-page - Icelandic Meteorological Office | Icelandic Meteorological office
Specialist remark
An earthquake swarm began yesterday evening located near the SW-ern tip of the Reykjanes Peninsula. The swarm began with an M3.9 earthquake and six other earthquakes with magnitude above 3.0 have been detected. Nearly 600 earthquakes have been detected since the swarm began. The swarm is still ongoing though the intensity of it has decreased. The IMO has received felt reports for the largest earthquakes from the Reykjanes peninsula and the Capital area. Last time an earthquake of similar magnitude was recorded in this area was in November 2021 when an M3.5 earthquake occurred there.
Written by a specialist at 13 Apr 09:18 GMT
Week overview 4 April - 10 April
Just under 600 earthquakes were detected by the IMO¿s SIL-seismic network last week, a similar number as the previus week when 630 earthquakes were located. All earthquakes on land were below a magnitude 3 and most of the activity was located in the Reykjanes peninsula where around 300 earthquakes were located, other activity was distributed in traditional locations. Twenty earthquakes were located around 150 km north of Iceland at Kolbeinsey ridge where the largest earthquakes were roughly a 3 in magnitude.
Biggest earthquakes during the last 48 hours
Size Time Quality Location 3.9 12 Apr 21:21:53 Checked 7.3 km NE of Reykjanestá 3.6 13 Apr 00:28:33 34.5 31.6 km WSW of Eldeyjarboði 3.5 12 Apr 22:53:28 81.5 97.6 km S of Eldeyjarboði
Last week saw just one M6, that being a M6.1 in PNGLast week saw two M6, both in Vanuatu, with the highest being a M6.3.
In the usual area, there were 0 out of 100 earthquakes worldwide equal to or greater than 4.5 and 1485 out of 1881 quakes of all sizes.
Percentage: 78.9%
Deep earthquakes were discovered in the 1920s, but they remain a subject of contention today. The reason is simple: they aren't supposed to happen. Yet they account for more than 20 percent of all earthquakes.
Shallow earthquakes require solid rocks to occur, more specifically, cold, brittle rocks. Only these can store up elastic strain along a geologic fault, held in check by friction until the strain lets loose in a violent rupture.
The Earth gets hotter by about 1 degree C with every 100 meters of depth on average. Combine that with high pressure underground and it's clear that by about 50 kilometers down, on average the rocks should be too hot and squeezed too tight to crack and grind the way they do at the surface. Thus deep-focus quakes, those below 70 km, demand an explanation.
Subduction gives us a way around this. As the lithospheric plates making up Earth's outer shell interact, some are plunged downward into the underlying mantle. As they exit the plate-tectonic game they get a new name: slabs. At first, the slabs, rubbing against the overlying plate and bending under the stress, produce shallow-type subduction earthquakes. These are well explained. But as a slab goes deeper than 70 km, the shocks continue.