All posts by Keren_F

An amateur volcanology enthusiast with an interest in volcanic and seismic activities, viewed from the comfort and safety of my armchair. Meandered into this from using publicly available earthquake data to improve my Excel modelling skills. Then had to research the results both to understand and verify them. :)

Iceland, Reykjanes Peninsula

Intense Earthquake Swarm Near Grindavík. Aviation Code for the Reykjanes – Svartsengi Volcanic System Orange_Updated 17/11/2023, 17:30

November 10, 2023 Keren_F

Good evening

Update 17/11/2023 17:30

The earthquake swarm is continuing as we write, although he magnitude of earthquakes has reduced. As the uncertainty continues, our thoughts are with those required to evacuate Grindavík, those supporting them, the Department of Civil Defence, and the scientists and others monitoring the activity.

According to IMO, ground deformation is continuing at a slower rate. It is thought that if an eruption occurs, it is most likely to be in the region of Hagafell. Yesterday, sulphur dioxide was detected in a borehole at Svartsengi located north of Mt Þorbjörn. The borehole extends eastwards towards the Sundhnúkur crater row, close to the where the magma intrusion is. This is considered evidence of magma north of Hagafell. The possibility of an eruption is still considered high.

If we ccompare the locations to our geodensity plots (ref. Fig 31 below), the areas of most seismic activity are located at the Sundhnúkur crater row, Hagafell and northwest Grindavík. The geodensity plots are often good predictors of where an eruption will occur. However, with three current seismic hot spots, the situation is not clear at the moment. If an eruption occurs, the precise location(s) will depend on where weak spots allow magma through.

Our updated earthquake plots are below. The data source is as below.

Seismic activity is occurring along the dike and also at Krýsuvík.

Reykjanes Peninsula

Area 63.746°N, 22.631°W to 63.996°N, 22.211°W

These show the activity near the dike in more detail.

Fig 31: Earthquake geodensity plot of earthquakes for area 63.746°N, 22.631°W to 63.996°N, 22.211°W between 10^th November 2023 to 17^th November 17:30. There are three seismic hot spots: northwest Grindavík, Hagafell and the Sundhnúkur crater row. © Copyright remains with the author; all rights reserved, 2023.

Fig 32: Earthquake scatter plot of the earthquakes for area 63.746°N, 22.631°W to 63.996°N, 22.211°W between 10^th November 2023 to 17^th November 17:30. Red denotes earliest earthquakes; yellow denotes latest earthquakes. G denotes Grindavík, Þ, Þorbjörn and S, the power plant. © Copyright remains with the author; all rights reserved, 2023.

For more recent updates, please consult the relevant authorities, such as IMO.

Armchair Volcanologist

Sources as below.

Update 15/11/2023 18:50

The earthquake swarm continues as we write. The intensity has lessened, and the size of the earthquakes decreased. The probability of an eruption is still considered high.

According to IMO, most monitoring is focussing on the dike formation and Grindavík. Ground deformation is consistent with magma flowing into the dike. Part of the magma may be solidifying at the edges of the dike. Magma inflow is thought to be near Sundhnúk. SO2 measurements show fluctuating degassing associated with the dike. Magma may have come within 500m of the surface. The sink hole which opened in Grindavík continues to widen.

We have updated our earthquake plots to 18:50 today.

The most recent earthquakes occur along the dike, and at Krýsuvík. We do not understand the relationship between Fagradalsfjall and activity further west, other we have observed than activity at Krýsuvík usually precedes activity west of it. Frustrating not to be a geologist!

Plots for the Reykjanes Peninsula

Fig 23: Earthquake geoscatter plot by the author of earthquakes recorded between 10^th November 2023 and 15^th November 2023 18:50 on the Reykjanes Peninsula (source: Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is) using earthquakes with a quality over 90%). © Copyright remains with the author; all rights reserved.

Fig 24: Earthquake geodensity plot by the author of earthquakes between 10^th November 2023 and 15^th November 2023 18:50 recorded on the Reykjanes Peninsula (source: Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is) using earthquakes with a quality over 90%). © Copyright remains with the author; all rights reserved.

Plots for the area 63.746°N, 22.631°W to 63.996°N, -22.211°W

These show the activity near the dike in more detail.

Fig 25: Earthquake geoscatter plot by the author of earthquakes recorded between 10^th November 2023 and 15^th November 2023 18:50 on the Reykjanes Peninsula (source: Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is) for the area 63.746°N, 22.631°W to 63.996°N, -22.211°W using earthquakes with a quality over 90%). © Copyright remains with the author; all rights reserved.

Fig 26: Earthquake geodensity plot by the author of earthquakes recorded between 10^th November 2023 and 15^th November 2023 18:50 on the Reykjanes Peninsula (source: Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is) for the area 63.746°N, 22.631°W to 63.996°N, -22.211°W using earthquakes with a quality over 90%). © Copyright remains with the author; all rights reserved.

Fig 27: Earthquake scatter plot by the author of earthquakes recorded between 10^th November 2023 and 15^th November 2023 18:50 on the Reykjanes Peninsula (source: Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is) for the area 63.746°N, 22.631°W to 63.996°N, -22.211°W using earthquakes with a quality over 90%). G denotes Grindavík, Þ denotes Mt Þorbjörn and S denotes the power plant. © Copyright remains with the author; all rights reserved.

For more recent updates, please consult the Icelandic authorities, such as IMO (link below).

Armchair Volcanologist.

Sources: information and raw earthquake data, Home-page – Icelandic Meteorological Office | Icelandic Meteorological office (vedur.is)

Update 13th November 2023, 14:49

Correction: Fig 20 is for the period 10th November to 13th November (Error was in the image title, not the caption. The plot, itself, is unchanged). Apologies for any inconvenience.

The earthquake swarm continues as we write. The intensity has lessened, and the size of the earthquakes decreased, most probably reflecting the fact that magma has reached less brittle rock layers nearer the surface. Scientists have said the magma inflow has lessened, seismic activity is between depths of 2km and 5km but there is no change in the assessment of the likelihood of an eruption.

The InSAR image showing the formation of the possible graben running through part of Grindavík has been published on IMO’s site today. The sudden formation of the graben on Friday night led to the evacuation of Grindavík. Local news sources have images of the damage done to roads and property.

Fig 15: InSAR image showing ground displacement caused by seismic activity between 3^rd November 2023 and 11^th November 2023. Source: IMO

Fig 16: Estimate of the vertical displacements caused by the dike during its initial propagation from Friday afternoon to Saturday morning. The displacements were estimated by combining ICEYE and COSMO-SkyMed pixel offset tracking results. Source: IMO.

We have updated our earthquake plots for the swarm from 10^thNovember 2023 to 13^th November 2023 14:49. We used the earthquakes published on Whole Country (vedur.is) for the Reykjanes Peninsula with a quality of over 90%., a total of 3,560 earthquakes. We may have picked up some ghosts and other errors (confirmed earthquakes have a quality of 99%) but we believe that this will give a rough idea of what is going on.

Fig 17: Earthquake geoscatter plot of the earthquakes on the Reykjanes Peninsula between 10^th November 2023 and 13^th November 2023. Red denotes the earliest earthquakes; yellow denotes the latest. © copyright remains with the author; all rights reserved, 2023.

Fig 18: Earthquake geodensity plot of the earthquakes on the Reykjanes Peninsula between 10^th November 2023 and 13^th November 2023. © copyright remains with the author; all rights reserved, 2023

Our 3D scatter plots for the above seismic activity covered too big an area to look at the formation. We extracted earthquakes between 63.746°N, 22.211°W and 63.996°N, 22.631°W, a total of 2,974 earthquakes. For the 3D scatter plots only we removed a small earthquake with a depth of more than 40 km from the data set as it distorted the scale of the plots too much.

Fig 19: Earthquake geoscatter plot of the earthquakes between 63.746°N, 22.211°W and 63.996°N, 22.631°W between 10^th November 2023 and 13^th November 2023. Red denotes the earliest earthquakes; yellow denotes the latest. The map is greater than the area plotted; the earthquakes on the edges show the borders of the area. © copyright remains with the author; all rights reserved, 2023.

Fig 20: Earthquake geodensity plot of the earthquakes between 63.746°N, 22.211°W and 63.996°N, 22.631°W between 10^th November 2023 and 13^th November 2023. We have focussed on the area with highest density. © copyright remains with the author; all rights reserved, 2023.

Fig 21: 3D scatter plot of earthquakes of the earthquakes between 63.746°N, 22.211°W and 63.996°N, 22.631°W between 10^th November 2023 and 13^th November 2023. This view looks along the formation. © copyright remains with the author; all rights reserved, 2023.

Fig 22: 3D scatter plot of earthquakes of the earthquakes between 63.746°N, 22.211°W and 63.996°N, 22.631°W between 10^th November 2023 and 13^th November 2023. This view looks at the side of the formation. © copyright remains with the author; all rights reserved, 2023.

For more recent updates, please consult the Icelandic authorities, such as IMO (link below).

Armchair Volcanolgoist

Source for inform,ation and raw earthquake data: Icelandic Meteorological office (vedur.is)

Update 11th November 2023 ,18:01

IMO reported this evening that there is a significant likelihood of a volcanic eruption in the coming days.

Modelling based on ground deformation and seismicity by scientists at IMO and the University of Iceland shows that there is a 15km long magma intrusion located northwest of Grindavík. The intrusion stretches from Kálffellsheiði, northeast of Grindavík, to offshore southwest of Grindavík.

Magma has ascended to 800m below the surface. Where and when an eruption will occur cannot be predicted now – other than to say that it would most likely be in the vicinity of the intrusion, if it occurs.

Fig 12 *Map showing the location of the dike intrusion based on combined satellite radar imagery, GPS measurements, and geophysical modelling. Source: IMO*

We have updated our earthquake plots for the swarm to 18:01, this time using those with more than 90% quality from IMO’s Reykjanes peninsula – earthquakes during the last 48 hours (Preliminary results) | Reykjanes peninsula | Icelandic Meteorological office (vedur.is). The reduced quality may mean that we have picked up a few ghosts and other errors in the plots but it is reasonable enough to give an idea of what’s going on. A total of 2,334 earthquakes were recorded at the time of our download.

Fig 13 Earthquake geoscatter plot by the author of the swarm occurring on the Reykjanes Peninsula from 10^th November to 11^th November 18:01. Red denotes the earliest quakes; yellow denotes the latest quakes. © Copyright remains with the author; all rights reserved, 2023.

The geoscatter plot has picked up the magma intrusion and faults moving to accommodate the intrusion.

Fig 14 Earthquake geodensity plot by the author of the swarm occurring on the Reykjanes Peninsula from 10^th November to 11^th November 18:01. © Copyright remains with the author; all rights reserved, 2023.

The geodensity plot shows that most earthquake activity occurring is from the magma instrusion.

Armchair Volcanologist

Source for the update and raw earthquake data as before: Icelandic Meteorological office (vedur.is)

Good morning

Update 11^th November 2023 , 05:58

Since our original post below, events have moved on. The town of Grindavík was evacuated overnight when it became apparent that a dike could be forming under the town. The Svartsengi Power Plant will be operated remotely.

The swarm has continued relentlessly since yesterday.

Fig 8: Earthquakes on the Reykjanes Peninsula. Note the activity is concentrated near Mount Þorbjörn; most of the outliers are ghost in the auto system. Source: IMO.

We have plotted the activity from 10^th November 2023 to 11^th November 2023 05:58 using the confirmed earthquakes reported on Skjálfta-Lísa (vedur.is), a total of 134 earthquakes. Our plots show the possible dike formation.

Fig 9: Earthquake geoscatter plot by the author of confirmed earthquakes occurring on the Reykjanes Peninsula from 10/11/2023 to 11/11/2023 05:58. Colour denotes age (red earliest, yellow latest). © Copyright remains with the author; all rights reserved, 2023.

Fig 10: Earthquake scatter plot by the author of confirmed earthquakes occurring on the Reykjanes Peninsula from 10/11/2023 to 11/11/2023 05:58. Colour denotes age (red earliest, yellow latest). Here we are looking sideways at the dike. © Copyright remains with the author; all rights reserved, 2023

Fig 11: Earthquake geodensity plot by the author of confirmed earthquakes occurring on the Reykjanes Peninsula from 10/11/2023 to 11/11/2023 05:58. © Copyright remains with the author; all rights reserved, 2023.

It is not possible to predict when and where an eruption may occur. For updates, please consult the Icelandic Authorities, for example, IMO.

Armchair Volcanologist

Source for raw earthquake data as before: Icelandic Meteorological office (vedur.is)

Original Post 10/11/2023

Good evening,

Fig 1: Image cropped from one by Arian Zwegers of the Blue Lagoon with Mt Þorbjörn. Published under CC BY 2.0

A large earthquake swarm started north of Grindavík, Iceland, on 24^th October 2023 in the vicinity of the Svartsengi Geothermal Plant and Mount Þorbjörn. This is the fifth time such a swarm has occurred during the volcano-tectonic episode which started on the Reykjanes Peninsula in December 2019, including the three eruptions of Fagradalsfjall. Earlier today (10^th November 2023), the swarm intensified. The aviation code for the Reykjanes – Svartsengi system has been raised to orange.

Fig 2: ongoing earthquake swarm near Svartsengi by IMO. (Note: many of the earthquakes in the image are ghosts in the auto system; most activity is confined to the Svartsengi area). Source: Reykjanes peninsula – earthquakes during the last 48 hours (Preliminary results) | Reykjanes peninsula | Icelandic Meteorological office (vedur.is)

Because this activity started near Fagradalsfjall, it was initially thought that the swarm was caused by magma movement associated with Fagradalsfjall and the earthquakes to the west were triggered earthquakes (faults moving to accommodate the magma). This was born out by initial ground deformation showing at station FEFC, southwest of Fagradalsfjall. However, this has been followed by consistent uplift at the stations near Mt Þorbjörn, raising concerns that there is magmatic activity there. It is believed that magma is accumulating in a sill at a depth of 5km. Since then, there have been seven earthquakes with a magnitude greater than 4.0M in the area (as of 9th November 2023).

Fig 3: Time series for GPS stations FEFC and Thorbjörn to 9^th November 2023. Source: IMO.

Fig 4: Interferogram (InSAR) for the period 28th of October – 6th of November showing around 7cm ground deformation. The green indent SW of Mt. Þorbjörn is an offset in the deformation signal caused by fault movements by earthquakes. Source: IMO

We have plotted the earthquakes reported on Skjálfta-Lísa (vedur.is) for the Reykjanes Peninsula for the period 24^th October 2023 to 10^th November 2023 (16:07) to see what is going on. 3,239 earthquakes have been recorded, although many more have occurred.

The geoscatter plot shows the initial seismic activity southwest of Fagradalsfjall, followed by its migration westward.

Fig 5: Earthquake geoscatter plot by the author for the earthquakes reported between 24^th October 2023 and 10^th November 2023 16:07. © Copyright remains with the author; all rights reserved, 2023.

The earthquake density plot shows most activity in the vicinity of Mt Þorbjörn

Fig 6: Earthquake density plot by the author for the earthquakes reported between 24^th October 2023 and 10^th November 2023 16:07. © Copyright remains with the author; all rights reserved, 2023.

Fig 7: Close up of the earthquake geodensity plot by the author for the earthquakes reported between 24^th October 2023 and 10^th November 2023 13:10. The plume of steam comes from the Svartsengi Power Station, which provides electricity and hot water to the Peninsula. Mt Þorbjörn is east of the power station. The town of Grindavík is south of the swarm. © Copyright remains with the author; all rights reserved, 2023.

Time will tell whether an eruption ensues. But as a precautionary measure the Blue Lagoon is now closed to visitors and the residents of Grindavík have been advised of evacuation plans.

Our plot do not include the larger recent earthquakes, including the 5M. When we get more data, we will update our plots.

Armchair Volcanologist

Source: Raw earthquake data: Icelandic Meteorological office (vedur.is)

Iceland, Reykjanes Peninsula

Update on the Eruption at Litli Hrútur, 13th July 2023

July 14, 2023 Keren_F

Fig 1: Screenshot from Bein streymi frá eldgosinu við Litla-Hrút – RÚV.is (ruv.is) Lava flowing south from the crater today. Smoke from the moss fires is visible at the edge of the lava field.

The eruption site is closed to the public right now due to the danger from volcanic gasses and smoke from moss fires; some visitors have been affected. Also, some visitors have been taking insane risks (e.g., attempting to climb the crater wall). High winds yesterday also caused issues.

The Institute of Earth Sciences, Iceland, have provided an update on the eruption here: Volcanic eruption at Litli-Hrút, measurement results 13 July | Institute of Earth Sciences (hi.is) . This is summarised below.

As we know the eruption started on 10^th July 2023 at 16:40 with the opening of four fissures with a combined length of c.800m in a north easterly direction from Litli Hrútur towards Keilir. The eruption peaked at c.21:00, diminishing to form a single crater c. 400m northeast of Litli Hrútur.
Lava is flowing south with an average flow rate of 13m³/s (similar to the 2021 eruption) for the period 11 July to 13 July. As of 13 July 13:38, the lava volume is c. 3.4 million cubic metres covering an area of 0.4km². Calculations were performed by NLSI from Pleiades satellite images.
The lava composed of vesicular glass, microphenocrysts and microlites of plagioclase, olivine, clinopyroxene and spinel, similar to the 2022 lava. Lava is estimated to have a temperature of c.1190°C. The chemical composition is similar to that of the 2021 and 2022 eruptions: MgO wt.% = 8.5, and, K₂O/Ti₂O = 0.26.
The gas composition is similar to that of the 2022 eruption, with a high concentration of CO2. The CO₂ may have accumulated prior to the eruption. SO₂ gas emissions range from 5.4-11.5 ktonnes / day and CO₂ is 7.1 – 15 5 ktonnes / day.

If lava continues to flow southwards, it may reach the 2022 lavas in Meradalir.

We have updated our earthquake plots to 13^th July 2023 02:06, focussing more on the area between Fagradalsfjall, Keilir and Krýsuvík.

The earthquake density plot is still showing most activity southwest of Keilir and close to the eruption site, which we determined from eyeballing the location of the crater. The area southeast of Keilir is also showing more activity. Whether the activity close to Keilir is triggered quakes, the result of faults moving to accommodate the magma intrusion, or magma-related (or, indeed, both) remains to be seen.

Fig 2: Geodensity plots by the author. The blue star shows the approximate location of the crater. In the image to the right, we have removed the satellite image background so that the earthquakes are more visible. © Copyright remains with the author; all rights reserved, 2023.

Armchair Volcanologist

Sources

Raw earthquake data: Skjálfta-Lísa (vedur.is)

Other sources are included in the text.

Iceland, Reykjanes Peninsula

Eruption Started Near Litli Hrútur, Iceland

July 10, 2023 Keren_F

Updated for earthquake plots from 28th June 2023 to 10th July 15:04 (pre eruption) for the Reykjanes Peninsula

*Fig 1: Screenshot from RUV.is webcam on Litli Hrutur. The eruption site is behind the hill. Source: https://www.ruv.is/frettir/innlent/2023-07-06-beint-streymi-fra-fagradalsfjalli-387091*

The Icelandic Met Office has confirmed the onset of an eruption on the eastern and northeastern flanks of Litli Hrútur, Iceland. The eruption started around 16:40 today with the opening of three small fissures on a 200m fault. Lava is collecting in a depression then flowing southwards, with gas and steam emissions going northwestwards.

Fig 2: Image by Benedikt Ófeigsson from IMO’s facebook page showing the two fissures. Image appears to have been taken from Lilti Hrútur. Source: https://www.facebook.com/photo/?fbid=701454135343917&set=a.312131834276151

Images taken by Jakob Vegerfors, which he posted onto Facebook, show two initial fissures. The images can be found here: https://www.facebook.com/photo?fbid=10159116738742038&set=pcb.1442657949904754 The hill in the left foreground is Litli Hrutur and the larger hill to the right in the background is Kelir.

IMO reported noticing a disturbance on the earthquake station at Fagradaslfjall last night and again at 14:00 today similar to those preceding the 2021 and 2022 eruptions.

*Fig 3: Helicorder plot for Fagradalsfjall today. Source: IMO*

The eruption site appears to be a little east of the southern end of the calculated position of the dyke intrusion.

Fig 4: Calculated position of the dyke instrusion (red line) from IMO. Red stars show the position of earlier eruptions (2021 and 2022). The blue line is the location of surface deformation from ICEYE wave interference images taken 7-8 July. Location of surface fracture and insert model determined by Michelle M. Parks and Vincent Droin, Icelandic Meteorological Office. Photo: Ásta Rut Hjartardóttir, University of Iceland

We have updated our earthquake plots from 28th June 2023 to 10th July 2023 15:04 for the Reykjanes Peninsula. We used the 764 confirmed earthquakes published by IMO on https://skjalftalisa.vedur.is/#/page/map. The total number of earthquakes in the swarm was c.12,000 as of 9th July 2023.

Fig 5: Geoscatter plots by the author for 28th June 2023 to 10th July 2023 15:04. Colour denotes age: red is the oldest, yellow the youngest. © Copyright remains with the author; all rights reserved, 2023

Fig 6: Scatter plots by the author for 28th June 2023 to 10th July 2023 15:04. Colour denotes age: red is the oldest, yellow the youngest. © Copyright remains with the author; all rights reserved, 2023

*Fig 7: Scatter plots by the author of quake v depth for 28th June 2023 to 10th July 2023 15:04. Size denotes* magnitude. © Copyright remains with the author; all rights reserved, 2023

*Fig 8: Geodensity plots by the author for 28th June 2023 to 10th July 2023 15:04. © Copyright remains with the author; all rights reserved, 2023*

*Fig 9: Zoomed in geodensity plot by the author for 28th June 2023 to 10th July 2023 15:04. © Copyright remains with the author; all rights reserved, 2023*

Apparently the eruption site is difficult to get to. If you intend to visit, please follow the advice of the local authorities and stay safe.

For local news sources, try

IMO: https://en.vedur.is/ and their Facebook page, https://www.facebook.com/Vedurstofan

RUV.is: https://www.ruv.is/frettir

MBL.is: https://www.mbl.is/frettir/

For local webcams, try

https://www.ruv.is/frettir/innlent/2023-07-06-beint-streymi-fra-fagradalsfjalli-387091

Armchair Volcanologist

Iceland, Reykjanes Peninsula

Update on July 2023 Earthquake Swarm Fagradalsfjall to Kelir as at 7th July 2023 18:23

July 7, 2023 Keren_F

The earthquake swarm which started on 4^th July 2023 is continuing vigorously as we write, with 7,000 earthquakes detected. InSAR has confirmed that there is a dike intrusion between Fagradalsfjall and Kelir. IMO have said that magma is likely to have reached a depth of around 1 km by 6th July, causing a fracture of a 2.8 km length between Fagradalsfjall and Keilir, centred a little north of Litli-Hrútur. The expectation is that, if an eruption occurs, it will be in hours or days. The eruption may be short but bigger in its initial stages than the 2021 and 2022 eruptions. The alert level remains at orange.

A smaller swarm is also ongoing southwest of the peninsula on the Reykjanes ridge, near the island of Eldey. This may be due to crustal accommodation of the magma intrusion between Fagradalsfjall and Kelir and/or it may be independent activity. The alert level has been raised to yellow. We will look at this in later posts.

Fig 1: Earthquake map and plot of earthquake magnitude v time from IMO (preliminary results only). Magnitude is decreasing, following the pattern of the 2021 and 2022 eruptions. Many of the “quakes” scattered over the peninsula and environs are ghosts. Source: Reykjanes peninsula – earthquakes during the last 48 hours (Preliminary results) | Reykjanes peninsula | Icelandic Meteorological office (vedur.is)

*Fig 2: InSAR image confirming dike intrusion. See main text for attribution and description.*

From IMO, Earthquake activity in Fagradalsfjall area | News | Icelandic Meteorological office (vedur.is), “COSMO-SkyMed interferogram covering the period 28 June to 6 July 2023.

The wrapped image (Fig 2) clearly shows a series of multicolored fringes centered bewtween Fagradalsfjall and Keilir. These fringes show ground deformation caused by the new dike intrusion which commenced on 4 July 2023. The maximum observed deformation related to the dike intrusion is up to 18 cm in the satellite‘s line-of-sight (los) in the NW direction.

Although the deformation signal extends over a large area of the western Reykjanes Peninsula, this does not mean there is magma beneath this entire region. The magma intrusion is situated bewteen Fagradalsfjall and Keilir. There is no indication of additional magma movements outside this area.

Several small lineaments are also visible in the interferogram which cut across the fringes. These represent fault movements/earthquakes that were triggered during the dike propagation.”

We have updated our earthquake plots to this morning, 7^th July 2023 09:37 using the published earthquakes from https://skjalftalisa.vedur.is .

Fig 5: *Geodensity plot by the author of earthquakes occurring in the current swarm on the Reykjanes Peninsula. © Copyright remains with the author; all rights reserved, 2023.*

Time will tell whether and where lava emerges with the current swarm.

Our thanks go again to the Icelandic Met Office, IMO, https://www.vedur.is/, for the raw earthquake data. For updates, please visit IMO.

Armchair Volcanologist

Iceland, Reykjanes Peninsula

Earthquake Swarm on the Reykjanes Peninsula, 4th July 2023 to 5th July 2023.

July 5, 2023 Keren_F

An earthquake swarm started on the Reykjanes Peninsula, Iceland, on 4th July 2023. It is still on progress at the time of writing.

*Fig 1: Earthquake swarm on the Reykjanes Peninsula. Source: https://www.vedur.is/skjalftar-og-eldgos/jardskjalftar/reykjanesskagi/*

Local volcanologist have said that the likelihood of an eruption in a matter of hours or days has increased. The aviation alert level has been increased to orange.

So we have plotted the published earthquakes from https://skjalftalisa.vedur.is from 28th June 2023 to 5th July 2023 20:16 to see what is going on.

*Fig 4: Geodensity plot by the author of earthquakes occurring in the current swarm on the Reykjanes Peninsula. © Copyright remains with the author; all rights reserved, 2023*

It certainly looks like a magma intrusion close to the sites of the recent Fagradalsfjall eruptions. Time will tell whether or not and where lava emerges with the current swarm.

Our thanks go again to the Icelandic Met Office, IMO, https://www.vedur.is/, for the raw earthquake data. For updates, please visit IMO.

Armchair Volcanologist

Iceland, Mýrdalsjökull Region

Katla – Further Unrest; an examination of seismicity from 1st January 1995 to 25th June 2023

July 3, 2023 Keren_F

Good afternoon,

Fig 1: Katla: photo 3 of 6. Retrieved from http://icelandicvolcanoes.is/?volcano=KAT. Jökulhlaup from underneath Mýrdalsjökull glacier in 1999. It remains controversial whether it was caused by a subglacial eruption. Photographer: Oddur Sigurðsson. Date: 18 July 1999

In recent weeks Katla has been showing a heightened level of unrest. Just last month there was an earthquake swarm which led to the temporary raising of the aviation alert level to yellow. Yesterday, the Iceland Met Office reported a risk of ongoing earthquakes at Mýrdalsjökull, gas pollution near Kötlujökull and higher than usual water levels at Múlakvisl; this may be indicative of geothermal activity or magma movement. The alert level is green at the time of writing.

*Fig 2: Earthquakes in the Katla caldera 30^th June 2023. Source:* *Mýrdalsjökull (vedur.is)*

So we took a moment to update our Iceland earthquake database to 25^th June 2023 (the earthquake list for week ending 2nd July 2023 is not yet available, although they can be viewed on Skjálfta-Lísa (vedur.is)) and plot the earthquakes at Myrdalsjökull, 63.1°N,18.5°W to 64.2°N,20.00°W, and then the caldera area, 63.45°N,18.98°W to 63.72°N, 19.24°W from 1^st January 1995 to 25^th June 2023.

Fig 3: Mýrdalsjökull earthquake statistics from 01/01/1995 to 25/06/2023. 2002 to 2004 are associated with a possible intrusion at the Godabunga cryptodome. 2011 to 2012 and 2016 to 2017are associated with jokulhlaups and possible subglacial activity. © Copyright remains with the author; all rights reserved, 2023.

Our earthquake density plots show that most activity is close to Godabunga, Katla’s cryptodome.

*Fig 4: Geodensity plot by the author of earthquakes occurring in Mýrdalsjökull from 01/01/1995 to 25/062023. © copyright remains with the author; all rights reserved, 2023.*

Given that activity near Godabunga has dominated the above plot, we plotted a smaller area for the caldera.

*Fig 5: Geodensity plot of earthquakes in the Katla caldera from 01/01/1995 to 25/06/2023 by the author. © Copyright remains with the author; all rights reserved, 2023.*

This plot shows most seismic activity in the NE of the caldera, near the site of the source of the 1955 jökulhlaup, some in the S of the caldera near the source of the 1918 eruption and 2011 jökulhlaup and another swarm on the volcano’s flank, south of the caldera. The swarm to the south of the caldera occurred in 2011 at the Gvendarfell Ridge. Later study of the Gvendarfell Ridge found sources of recent flank eruptions, including rhyolitic domes and Surtseyan craters.

We have also plotted monthly geoscatter plots for Myrdalsjökull from January 1995 to June 2023 (25 June 2023) and created a 3D rotating scatter plot for the same time period and area.

Fig 6: Geoscatter plots by the author for Mýrdalsjökull, January 1995 to June 2023 (25 June 2023). Key: Current Month Green dots denote earthquakes <3.0M, Yellow stars denote earthquakes ≥ 3.0M and <4.0M and Red stars denote earthquakes ≥4.0M; and, Prior Months Grey/aqua dots denote earthquakes <3.0M, Old gold stars denote earthquakes ≥ 3.0M and <4.0M, and, Dull red stars denote earthquakes ≥4.0M. Blue triangles denote GPS stations. © Copyright remains with the author; all rights reserved, 2023.

Fig 7: Scatter plots by the author for Mýrdalsjökull, January 1995 to June 2023 (25 June 2023). Key: Red denotes older earthquakes and yellow the most recent. © Copyright remains with the author; all rights reserved, 2023.

We make no predictions. For updates, please refer to the Icelandic authorities. IMO is a good starting point.

Armchair Volcanologist

Sources:

Raw earthquake data: Icelandic Meteorological office (vedur.is)

Giulisa Sgattoni, Federico Lucchi, Páll Einarsson, Ólafur Gudmundsson, Gianfilippo De Astis, and Claudio Antonio Tranne, “The 2011 unrest at Katla volcano: seismicity and geological context”, JÖKULL. No 69, 2019. https://jokull.jorfi.is/wp-content/uploads/2021/12/J69-53-70

Also see our earlier article for background information: The Katla Volcanic System, Mýrdalsjökull – the not so cuddly Katla

Africa, Europe

Türkiye-Syria Earthquakes, 6th February 2023

Video March 7, 2023 Keren_F

Fig 1: Rescue workers in in Osmaniye, Turkey. Cropped from image by Onur Erdoğan, Public Domain, Wiki Commons

It’s approximately one month on from 6^th February 2023 when a 7.8 magnitude earthquake struck on the south western end of the East Anatolian Fault Zone at 01:18 UTC (04:18 local time) 32.4km west northwest of the town of Gaziantep. This, followed by large aftershocks, including a very shallow 7.5 magnitude earthquake to the north of the first quake, caused catastrophic damage in central and southern Turkey, and northern and western Syria. The 7.5 earthquake signalled the rupturing of a second fault zone, the Sürgü-Misis Fault. The final fatality number is not yet available but, at the time of writing, fatalities exceeded 50,000, with hundreds of thousands injured and millions displaced. Our thoughts are with the victims, including those facing a long road to recovery.

We have taken a look at the earthquakes surrounding the Anatolian Plate from the start of January 2023 to 1^st March 2023.

Tectonic Settings

The Anatolian Plate lies between the Eurasian Plate, Arabian Plate and African Plate. The African Plate is moving at a rate of 2.15cm per year in a north easterly direction, the Eurasian Plate is moving south, relative to the African Plate, at a rate of 7-14mm per year, the Arabian Plate is moving northward at a rate of 15-20mm per year and the Anatolian Plate is moving south west at the rate of 21mm per year. The relative motions are accommodated by the North Anatolian Fault, East Anatolian Fault, Bitlis – Zagros Fold and Thrust Belt and Dead Sea Transform Fault System.

Fig 2: Image by Roxy – Own work, CC BY-SA 3.0, Wiki Commons

The East Anatolian Fault is a 500km long fault zone which marks the plate boundary between the Anatolian and Arabian Plates; the boundary is a transform one with left lateral strike slip seismic activity and a slip rate of 10mm per year. The Anatolian Plate is pushed westward by the Arabian Plate moving northwards towards the Eurasian Plate.

The East Anatolian Fault is a single fault between Karliova and Çelikhan. After Çelikhan the fault zone splits into north and south strand, both of which include multiple faults. The Sürgü-Misis Fault makes up the northern strand; it is a 380km long stretching between Çelikhan and Karataş; the eastern parts of the east-west section are made up of the Çardak and Sürgü faults; the sytem changes direction at the Göksun bend dividing into seven north east trending fault systems – the Karataş, Yumurtalık, Toprakkale, Savrun, Misis, Çokak and Düziçi-İskenderun faults. The Sürgü-Misis Fault system connects to the Cyprus Arc via the Misis-Kyrenia fault system. The southern strand of the East Anatolian Fault is less certain; the East Anatolian Fault may extend to the north of Cyprus; and, the NNE trending Türkoğlu-Amik section (the Karasu Fault Zone) may be a separate fault, linking the Dead Sea Transform to the East Anatolian Fault. The Karasu Rift has had Quaternary volcanic activity on northern part and sides of the rift between Kirikhan, Reyhanli and Fevzipaşa in an area 94km long and 12-25km wide.

The North Anatolian Fault, another strike slip fault, accommodates the relative motion between the Anatolian Plate and the Eurasian Plate. The North Anatolian Fault and the East Anatolian Fault meet the Bitlis – Zagros Fold and Thrust Belt, where the Arabian Plate subducts under the Eurasian Plate, at the Karliova Triple Junction.

Not very far to the west, the African Plate is subducting under the Anatolian Plate at the Cyrpus Arc. The Dead Sea Transform Fault System to the south marks the transform boundary between the Arabian and African Plates. The East Anatolian Fault meets the Dead Sea Transform Fault System at the Maras Triple Junction.

Earthquake Plots

We initially plotted the earthquakes from 1 January 2023 to 25 February 2023 for the area 34.47361°N, 25.22222°E to 42.25833°N, 44.45056°E. We then looked at 35.3122°N, 32.50944°E to 41.21667°N, 42.70056°E, focussing on the East Anatolian Fault. The results are shown in the following videos and earthquake density plot.

Fig 3: Video by the author of earthquake plots from 1 January 2023 to 1^st March 2023, latitude v depth, Geoscatter, earthquake count and longitude v depth. Key: cyan circles denote current earthquakes <4.5M, green stars, current earthquakes between 4.5M and 5.5K, yellow stars, current earthquakes between 5.5M and 6.5M and red stars, current earthquakes over 6.5M; and, grey circles denote previous earthquakes <4.5M, green stars, previous earthquakes between 4.5M and 5.5K, yellow stars, previous earthquakes between 5.5M and 6.5M ,and red stars, previous earthquakes over 6.5M. © copyright remains with the author, 2023; all rights reserved.

Fig 4. Video by the author of the Geoscatter plot of the East Anatolian Fault and by earthquakes in groups of 10 from 6 February 2023 to 1^st March 2023. Key: red circles denote current earthquakes <7.0M and red stars denote current earthquakes >7.0M, and dark red circles, previous earthquakes <7.0M and black stars, previous earthquakes >7.0M. © copyright remains with the author, 2023; all rights reserved.

Fig 5: Video of a rotating 3D scatter plot of the earthquakes in the East Anatolian Fault for the period 6 February 2023 to 1^st March 2023. Colour denotes age: red, the oldest, and yellow, the newest. © copyright remains with the author, 2023; all rights reserved

The geodensity plot shows that most activity occurred on the Sürgü-Misis Fault to the west and east of the 7.5M earthquake.

*Fig 6: Geodensity plot by the author of earthquakes occurring between 35.3122°N, 32.50944°E to 41.21667°N, 42.70056°E, from 6^th February 2023 and 1^st March 2023.* Red triangles denote volcanoes with dated activity in the Holocene and blue triangles denote volcanoes with activity in the Holocene of unknown date. *© copyright remains with the author, 2023; all rights reserved.*

Fig 7: Surface rupture from the two earthquakes as shown by analysing before and after satellite images. The first rupture on the East Anatolian Fault was 190km long and the second on the Sürgü-Misis Fault was 38km long (Image credit: Copernicus/NERC/COMET)

Most of the faults within the East Anatolian Fault Zone seem to have moved in the period we looked at. However, the scale of our plots may be misleading. Our plots do show a tenuous link between the East Anatolian Fault and the Cyprus Arc. There was some activity on the Arc preceding the 7.8 earthquake. After shocks have migrated through the fault system towards the Arc. There is no obvious link with the Dead Sea Transform Fault in the time period selected but geologically-speaking that is a very short period.

Armchair Volcanologist

Sources & Further Reading

Raw earthquake data was downloaded from EMSC, https://www.emsc-csem.org

“Paleoseismology of the western Sürgü–Misis fault system: East Anatolian Fault, Turkey”, Tamer Y. Duman, Hasan Elmacı, Selim Özalp, Akın Kürçer, Meryem Kara, Ersin Özdemir, Ayhan Yavuzoğlu & Çağıl Uygun Güldoğan, Mediterranean Geoscience Reviews volume 2, pages411–437 (2020) https://link.springer.com/article/10.1007/s42990-020-00041-6

Iceland

Merry Christmas & A Happy New Year

December 25, 2022 Keren_F

Apologies for not posting for a while now. Illness in the family has made more demands on our time than anticipated.

We have missed the eruptions of Mauna Loa and Kilauea, to name but two, and two catastrophic earthquakes: one in West Java in Indonesia and the other in Khost, Afghanistan.

Even when we are not posting, our thoughts remain with all those impacted by volcanic and seismic hazards.

Christmas Candles from: https://www.myfreetextures.com/

Greetings of the season,

Armchair Volcanologist

Iceland, Reykjanes Peninsula

Eruption at Meradalir, Iceland, Stalled 21st August 2022

August 23, 2022 Keren_F

Eruptive activity at the new fissure in Meradalir stalled on 21^st August 2022 at around 6:00 am. The seismic tremor ceased following the emission of a blue grey plume. Lava was seen on webcams to be still flowing from the crater just before then. We await to see whether or not this is the end of this eruptive episode.

*Fig 1: Tremor plot for Fagradalsfjall. Source: Tremor (vedur.is)*

To quote IMO, “A new chapter is about to begin in the Fagradalsfjall fires, but whether the seismic activity will recur and it will erupt again in the near future or not, time will tell.”

What do we know of the eruption so far? The eruption started on 3^rd August 2022. The initial discharge rate was c. 32 cubic metres per second, dwindling to 2 cubic metres per second by 16th August 2022. The total volume of lava emitted by 16^th August 2022 was 12 million cubic metres, c. 8% of that emitted by the Geldingadalir eruption last year. At the crater the lava is 20 to 30 metres deep and 40 metres deep by the crater rims, themselves. Over the rest of the lava field the lava is between 5 and 15 metres deep. The new lava has displaced cooling older lava causing it to rise by 3 to 5 metres in places.

The lava composition is similar to the basalt emitted by Geldingadalir in September 2021. The K₂O / TiO₂ ratio ranges from 9.3 to 9.4 and the MgO is around 8.4 wt(%).

Armchair Volcanologist

Sources: in the text

Iceland, Reykjanes Peninsula

A New Eruption Near Fagradalsfjall, Iceland, Started 3rd August 2022

August 4, 2022 Keren_F 1 Comment

So, it was hours, not days! The eruption started near Fagradalsfjall / Meradalir yesterday at around 13:18 about 1.5 km north of Stóra-Hrut on a north-easterly southwest fissure. The onset was detected by a local webcam and later confirmed by scientists. The alert level is currently orange (Volcanic eruption is underway with no or minor ash emission.)

Fig 1: Image of the new fissure taken by Halldór Björnsson at the Icelandic Meteorological Office on a flight over the eruption site on 03.08.2022. Source: Volcanic eruption resumed on the Reykjanes Peninsula | News | The Icelandic Meteorological Office (vedur.is)

Like the previous eruption, lava is contained by the local geography so no infrastructure is currently threatened. Gas emissions are, however, a hazard. The lava flow is estimated to be 5 – 10 times that of Geldingadalir at 32 cubic meters per second in the first 24 hours; gas emissions may well be similarly larger.

Fig 2: The red line shows the location of the new fissure on the northern edge of the lava flow from the 2021 eruption. The 2021 eruption was located near “Fagradalshraun” on the map. Source: Volcanic eruption resumed on the Reykjanes Peninsula | News | The Icelandic Meteorological Office (vedur.is)

Visitors are advised not to approach the site at the moment. When the site is open, bear in mind that it is not an easy walk, so for the fit only, and visitors should be properly prepared, including having gas masks and metres.

A video made by Reykjanes Grapevine shows the eruption site yesterday: RVK Newscast #203: New Volcanic Eruption In Iceland – YouTube

Seismic activity has decreased since the onset of the eruption. We have now updated our earthquake plots to 4th August 2022 10:27- see below.

Fig 3: IMO’s earthquake map. Source: Reykjanes peninsula – earthquakes during the last 48 hours (Preliminary results) | Reykjanes peninsula | Icelandic Meteorological office (vedur.is)

Updated earthquake plots

At the time of updating, we did not have confirmation of the coordinates of the eruption site, so we have guessed based on maps of the fissure. The plots will be updated when more up to date information becomes available.

Fig 4: Earthquake density plot of the swarm from 29th July 2022 to 4th August 2022 10:27 by the author showing how close the eruption site is to the densest parts of the current swarm. © Copyright remains with the author; all rights reserved, 2022

Fig 5: Scatter plot depth v earthquake number in the swarm *from 29th July 2022 to 4th August 2022 10:27* *by the author. © Copyright remains with the author; all rights reserved, 2022*

Happy volcano watching and stay safe.

Armchair Volcanologist

Sources: within the text

An Armchair Volcanologist

All posts by Keren_F

Intense Earthquake Swarm Near Grindavík. Aviation Code for the Reykjanes – Svartsengi Volcanic System Orange_Updated 17/11/2023, 17:30

Update on the Eruption at Litli Hrútur, 13th July 2023

Eruption Started Near Litli Hrútur, Iceland

Update on July 2023 Earthquake Swarm Fagradalsfjall to Kelir as at 7th July 2023 18:23

Earthquake Swarm on the Reykjanes Peninsula, 4th July 2023 to 5th July 2023.

Katla – Further Unrest; an examination of seismicity from 1st January 1995 to 25th June 2023

Türkiye-Syria Earthquakes, 6th February 2023

Merry Christmas & A Happy New Year

Eruption at Meradalir, Iceland, Stalled 21st August 2022

A New Eruption Near Fagradalsfjall, Iceland, Started 3rd August 2022

An amateur's observations on volcanoes and earthquakes

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An amateur's observations on volcanoes and earthquakes