Increased earthquake activity

Over the past days, seismic activity under the large ice-covered volcano has increased. It seems likely that at least some of this activity is caused by injections of new magma into the volcano's system, as some earthquakes were detected at depths between 10 and up to 25 km where no normal tectonic activity that could be triggering the earthquakes is expected.
Most earthquakes in the recent swarms were tiny, with only 5 quakes during the past week above magnitude 3 (the largest being a 3.6 event on Tuesday).
For the time being, the observed activity seems small and probably does not mean that a new eruption of Katla is imminent.

Magnitude 4.3 earthquake, increased seismic activity

Seismic activity has increased at the volcano. A magnitude 4.3 earthquake occurred under the volcano on 26 Jan at shallow depth beneath the summit caldera covered by the Mýrdalsjökull glacier.
Scientists now believe that the increased seismic activity indicates that the volcano is more likely to erupt in the near to medium term future compared to some years ago, but it is impossible to make any precise predictions.
Icelandic authorities are increasing their surveillance of the volcano, which is one of the country's largest and most active, with potentially devastating eruptions due to the hazard of catastrophic glacial floods.

Earthquakes under SE part of caldera

An increased number of earthquakes has been occurring at shallow depths (few km) under the SW part of the ice-covered volcano's caldera.
The largest event was a near-surface magnitude 3.5 event 3.9 km ESE of Goðabunga at 07:09 local time this morning. Whether the quakes are volcanic in origin (a swarm caused by magma intrusion) or caused by adjustments of the glacier's weight (or likely both) is unknown.

Katla has been on elevated alert since Oct 2016 when an intense seismic swarm occurred that triggered fears the volcano might erupt again soon (its last eruption dating back to 1918 and it is thought to be statistically "overdue").
The seismic swarm in Sep / Oct 2016 had been the largest in recent decades. It began on 29 Sep 2016, increased on 30 Sep with several quakes of magnitudes of 3 and higher, and lasted until early October.
Volcanic tremor was also detected, suggesting that it had been caused by intruding magma inside the volcano.

Volcano remains restless; increased melt water and H2S concentrations

Following Monday's large earthquakes, the volcano remains relatively calm seismically, with only small swarms of deep to shallow earthquakes occurring under the northern flank. According to experts, there is currently no sign of an eruption being imminent.
Icelandic authorities are aware of the potential danger the next eruption of Katla represents (whether it occurs in the next months or only decades from now). A delegation of the volcanologists from the Icelandic Met Office was invited to discuss with a committee of the Icelandic Parliament about how to respond in case of an eruption.
The biggest hazard are large-scale, potentially catastrophic glacial floods when an eruption occurs, which is likely going to be subglacial, as a result of rapid melting of ice by magma. A fast and wide-spread evacuation of all river beds draining from the Katla massif and alternative routes are likely a major topic in such plans.

During the past days, an increase in glacial water into the Múlakvísl river, south of Mýrdalsjökull, has been detected. The river water has a strongly elevated content in hydrogen sulfide (H2S) and people are advised not to travel near the river due to gas pollution.
Such events are not uncommon, especially at the end of the summer and not necessarily related to magma movements inside the volcano.

Small earhquakes

An increased number of small earthquakes, up to magnitude 2.7, has been occurring near the surface or at very shallow depths under Katla's ice cap since yesterday.
These quakes are most likely related to weight adjustments of the thick ice cap during the ongoing seasonal melting and unlikely to represent a true seismic swarm caused by (internal) volcanic activity.
In the meanwhile, the alert (uncertainty level) for the areas around rivers from the Mýrdalsjökull glacier has been cancelled by Iceland authorities.

Increased earthquake activity, uncertainty level declared

Earthquakes have been more frequent recently under the volcano recently. Most of them were small (below mag. 3) and shallow events. It is unknown whether these relate to magmatic movements inside the volcano, increased hydrothermal activity or are adjustments of the ice cap due to increased melting.
The government has declared "Uncertainty level" for Katla volcano yesterday. The largest hazard comes in the form of melt-water floods and sulfurous volcanic gasses dissolved in and released from glacial rivers.
People are advised not to stop at Múlakvísl and Jökulsá and other glacier river valleys and keep cell phones turned on in order to be able to receive potential SMS alerts.
Currently, there are no signs of an impending eruption at Katla.

Increasing number of earthquakes at Katla ?

As can be seen from our new plots of recent nearby quakes, the number of earthquakes near Katla appears to have been gradually increasing during August. However, most quakes are very shallow and probably NOT caused by magmatic movements, but adjustments of the shallow hydrothermal system. A possibility is that this is a seasonal pattern caused by the warming and increased melting of ice during summer.
To watch out for, when trying to anticipate a new eruption, would be earthquake swarms at some depth (5-20 km) that become shallower.

Small earthquake swarm at Katla

A small swarm of quakes has been going on at Katla since yesterday. So far, 10 quakes have occurred today, including a M2.8 quake at 1.8 km depth 6.8 km E of Goðabunga.

Slightly elevated number of quakes under Katla

In recent days, the number of quakes has been slightly elevated at Katla.

Weak seismic swarm on 25 June

Another swarm of very weak and shallow (around 1 km) quakes took place under the Katla volcano caldera on Sunday 24 June.

New seismic swarm under Katla volcano caldera on 21 June

Another seismic swarm has occurred at Katla volcano yesterday. About 30 small quakes at shallow depths mostly between 1 and 6 km in the central part of the caldera were recorded and could indicate another intrusion or changes in the hydrothermal system.

Shallow earthquake swarm under Katla's southern caldera continues

The earthquake swarm under the southern part of the icecap of Katla volcano that had started on 5 June continues with 30 more quakes recorded during the past 48 hours.
The quakes are mostly very small, but a few were between magnitude 2 and 3, and most are located at shallow depths of less than 5 km.
For the list of latest quakes go to the Icelandic Met Office website.