Asia, Japan

Shallow 6.8 magnitude Earthquake South of Kumamoto, Japan, 28th July 2026

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On 28th July 2026 a 7.1 magnitude (USGS 6.8 magnitude) earthquake struck Uto, south of Kumamoto, Kyushu.  At the time of writing, 34 fatalities had been reported, with 123 injured and 9,000 people displaced.  The earthquake was widely felt, including as far afield as China. In 2016 the area was hit by three large earthquakes: a 6.2 and 6.0, followed by a 7.0 the following day. Our thoughts are with the victims, their families and friends, and everyone else impacted.

Fig 1: Inside Aeon Mall, 警察庁, CC BY 4.0, via Wikimedia Commons

Shinichi Sakai, from the Earthquake Research Institute, University of Tokyo, has said that the earthquake may have been caused by slip on the southern portion of the Hinagu Fault. During the 2016 Kumamoto earthquakes, only the northern extent of the Hinagu Fault slipped. The Hinagu Fault is located in the southern section of  Futagawa-Hinagu fault zone, the Futugawa Fault to the north.  This fault zone lies at the southern end of the Japan Median Tectonic Line, Japan’s longest fault system, which begins near Ibaraki Prefecture on the Pacific coast of Honshu and  runs parallel to Japan’s volcanic arc to Kyūshū.

Fig 2  Shake map  for  2026 6.8  Kumamoto Earthquake  by USGS, Published in the public domain, via Wikimedia Commons.

The Geospatial Information Authority of Japan reported ground deformation: in Yatsushiro, the Sencho geographic reference point was displaced 0.84 m (2 ft 9 in) northeast, and the Izumi station recorded a 0.17 m (6.7 in) movement southward; in Kumamoto, the Jonan station recorded 0.4 m (1 ft 4 in) of displacement to the north.   Surface ruptures along the Hinagu Fault damaged roads, bridges, and buildings. 

Some of the fatalities and injuries were caused by the collapse of the second floor of Aeon Mall Kumamoto, followed by an explosion; a factory chimney, part of the 19th century Yatsushiro-gūshrine and part of bridge collapsed in Yatsushiro; fires were also reported in Yatsushiro.  Damage to rail infrastructure occurred; a freight train derailed near Yatsushiro Station;  there were more than 200 reports of snapped rails and collapsed sound barriers; bent rails were reported at a train depot in Kumamoto and between Matsubashi and Ogawa stations on the Kagoshima Main Line. Landslides occurred on Mount Mayuyama.  48,300 homes lost power in Kumamoto Prefecture; businesses were also impacted. Kumamoto Castle, which was undergoing restoration work following the 2016 Kumamoto earthquakes, was extensively damaged.

Tectonic Setting

The Japanese Archipelago comprises 5 main islands, Hokkaido, Honshu, Shikoku, Kyushu and Okinawa. and c.14,000 smaller islands. Its geology is dominated by the subduction of the Pacific Plate in the north and the subduction of the Philippine Sea Plate in the south.  Japan is seismically very active and home to  c.100 active volcanoes.

Fig 3:  Amur Plate by Alataristarion, CC BY-SA 4.0 , via Wikimedia Commons.  The Okinawa Plate is the small plate between the Philippine Sea Plate and the Yangtze Plate.

Kyushu Island, itself, lies on the rift boundary between the Amur and Okinawa Plate to the west of the subduction of the Philippine Sea Place under these plates.   

The Amur Plate is a small tectonic plate located on the eastern edge of the Eurasian Plate.  It has clearly defined boundaries on the the south by the Qinling suture zone in central China and the Baikal Rift Zone and Stanovoy Mountains on the north. The eastern boundary is with the Okhotsk Plate. The plate is moving anti-clockwise, according to GPS measurements.

The Okinawa Plate is another small continental tectonic plate. To its north is the Amur Plate.  On its eastern margin the Philippine Sea Plate subducts at the Ryuku Trench.  On its western edge there a divergent boundary with the Yangstze Plate.

The Philippine Sea Plate, comprising oceanic lithosphere, lies beneath the Philippine Sea, to the east of the Philippines.  The Philippine Sea plate, the Amur Plate, and the Okhotsk plate meet near Mount Fuji in Japan.

Seismicity

We plotted earthquakes occurring from 1st January 2006 to 30th July 2026 10:00am between 39.63°N, 153.14°E to 28.60°N, 124.75°E.  Our download from USGS contained 17,396 events. The plots clearly show the subduction zones.

Fig 4: Geoscatter plot by the author of earthquakes occurring from 1st January 2006 to 30th July 2026 10:00am between 39.63°N, 153.14°E to 28.60°N, 124.75°E.  For earthquakes of magnitude less than 6.5, colour denotes depth:  purple, 0-33km, blue 33-70km, green 70-150km, yellow, 150-300km. orange, 300-500km, red ≥500km. © remains with the author, all rights reserved, 2026. Yellow stars are earthquakes between 6.5 and 6.8 magnitude.  Orange stars are earthquakes with magnitude ≥ 6.8. © Copyright remains with the author, all rights reserved, 2026.
Fig 5: 3D scatter plot by the author of earthquakes occurring from 1st January 2006 to 30th July 2026 10:00am between 39.63°N, 153.14°E to 28.60°N, 124.75°E.  For earthquakes of magnitude less than 6.5, colour denotes depth:  purple, 0-33km, blue 33-70km, green 70-150km, yellow, 150-300km. orange, 300-500km, red ≥500km. © Copyright remains with the author, all rights reserved, 2026.

Thank you for visiting.

Armchair Volcanologist

© Copyright remains with the author, all rights reserved, 2026.

Sources:

USGS for raw earthquake data: Earthquake Hazards Program | U.S. Geological Survey

Wikipedia: 2026 Kumamoto earthquake – Wikipedia

Venezuela

Venezuela: Very Large Damaging Shallow Doublet Earthquakes, 24th June 2026

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On 24th June 2026, two large shallow doublet earthquakes with magnitudes of 7.2 and 7.5 and depths of 20 km and 11.1 km, resp., struck northern Venezuela within 39 seconds of each other.   The death toll at the time of writing is 3,811 with 16,740 injured, tens of thousands reported missing and 17,854 who have lost their homes.  Roughly, 60,000 buildings were destroyed.  USGS modelling for each shock predicts higher numbers of fatalities and significant economic loss of between 4 to 20% of Venezuela’s GDP.  Our thoughts are with all those who have lost their lives, livelihoods, friends or homes, and also with those involved with the relief effort.

Fig 1: Photo of  rescuers in La Guaira, Venezuela, June 28, 2026.  Attribution: U.S. Marines 24MEU by Cpl. Daniel Garcia, Public domain, via Wikimedia Commons

The first shock occurred 21 km ENE of San Felipe at 23:04:34 and the second occurred 20 km ESE of Yumare at 23:05:11.  Because the earthquakes occurred such a short time period apart the deformation from each is hard to distinguish. Some organisations report them as a single event, e.g. INGV reports the earthquakes as a single event of magnitude 7.6 with two bursts of high energy release, having analysed the deformation from satellite data (Sentinel – 1).  In the first burst, slip occurred along a 210 km by 30 km section of the fault ,moving with a velocity of 3 – 3.5km per second to north east of Caracus; it started with 2.5 m of slip t a depth of 20km near Morón.  The second burst had a maximum slip of 3.6m north of Catia La Mar at a depth of 11.1km.

The earthquakes occurred on or near the San Sebastián fault system which is part of the larger Boconó– San Sebastián – El Pilar fault system.  The Bonocó Fault is 500 km long strike slip fault located in the Eastern Ranges of northeastern Colombia and the Mérida Andes of northwestern Venezuela; it has been active since the Early Holocene. It is part of the boundary between the North Andes Plate and the South American Plate. The San Sebastián Fault Zone is 500 km long, located mostly offshore in the Caribbean Sea north of Venezuela. It is right-lateral strike-slip, forming part of the boundary between the Caribbean and South American tectonic plates. The El Pilar Fault System is 700 km long, located in state of Sucre in northern Venezuela. The fault system is of right-lateral strike-slip type with an east–west orientation and also forms part of the transform plate boundary between the Caribbean and South American plates.

The South American Plate is moving west at a rate of 32 mm  per year, the North Andes Plate north west at a rate of 23 mm  per year and the Caribbean Plate north west at a rate of 11 mm  per year.  Because movement the Caribbean Plate is slower than the North Andes Plate, it subducts under the northwest margin of North Andes Plate; the North East margin is extensional.  The boundary between the Caribbean Plate and South American Plate comprises transform faults.

Fig 2:  Caribbean (brown shaded area) and surrounding plates by Alataristarion, published under CC BY-SA 4.0, via Wikimedia Commons.

The San Sebastian  fault system has produced large earthquakes in the past. In 1812 the Caracas earthquake with magnitude 7.7 caused 15,000 to 20,000 fatalities.  It is thought to have involved two sub-events, the first on the Boconó Fault and the second on the western part of the San Sebastián Fault.  In 1900 San Narciso earthquake with magnitude 7.7 is thought to have been caused by rupture along the San Sebastián Fault to the east of Caracas.  Before the recent earthquakes geophysicists had calculated that the accumulated slip deficit on the Bonocó fault could produce a 7.0 – 7.6 magnitude earthquake and likewise the San Sebastián fault might  produce a 7.1 magnitude earthquake.

We have plotted the earthquakes between in the region between 15.0°N, 73.0 ° W and 7 ° N, 62.5 ° W from 1st January 2006 to 10th July 2026. In addition to the area of interest, this picks up part of the subduction of the Caribbean Plate under the North Andes Plate to the west of the plots and also the subduction of the South American Plate under the Caribbean Plate to the east of the plot. The latter includes a 7.3 magnitude earthquake at depth. Seismic activity in the area where the recent 7.2 and 7.5 earthquakes occurred tends to comparatively shallow, consistent with a transform plate margin.

Our first plot is a geoscatter plot. In this plot we can see that the doublet earthquakes occur near the junction of the three plates: Caribbean Plate, North Andes Plate and South American Plate.

Fig 3: Geoscatter plot of earthquakes between 15.0°N, 73.0 ° W and 7 ° N, 62.5 ° W from 1st January 2006 to 10th July 2026 by the author. Colour denotes depth for earthquakes with magnitude less than 7.0: 0-33km: purple; 33-70km: blue; 70-150km: green; 150-300km: yellow. Yellow stars are earthquakes with magnitude 7.2 in the centre of the plot and 7.3 in the east of the plot; the orange star is the 7.5 magnitude earthquake. © Copyright remains with the author; all rights reserved, 2026.
Fig 4: 3D rotating plot of earthquakes between 15.0°N, 73.0 ° W and 7 ° N, 62.5 ° W from 1st January 2006 to 10th July 2026 by the author. Colour denotes depth for earthquakes with magnitude less than 7.0: 0-33km: purple; 33-70km: blue; 70-150km: green; 150-300km: yellow. Yellow stars are earthquakes with magnitude 7.2 in the centre of the plot and 7.3 in the east of the plot; the orange star is the 7.5 magnitude earthquake. © Copyright remains with the author; all rights reserved, 2026.

We hope you find the above plots interesting. In our earlier post: Mt. Pelée, La Soufrière St. Vincent And A Quick Tour Of The Plates Surrounding The Caribbean Plate, we also looked at seismicity in a wider area.

Armchair Volcanologist

Sources:

USGS: Earthquakes | U.S. Geological Survey

Wikipedia: 2026 Venezuela earthquakes – Wikipedia

© Copyright remains with the author; all rights reserved, 2026.

Asia, Philippines

Philippine Earthquake, Magnitude 7.8 08/06/2026

On 8th June 2026 at 07:37 (local time) a 7.8 magitude earthquake occurred 32 km south west of Maasim in Sarangi Province, off the coast of Mindanao Island, Philippines, with a depth of 33 km.  Tragically, at the time of writing reports suggest that at least 55  people were killed, 38 missing, 1,120 injured, with 390,000 people impacted.  Severe infrastructure damage has impacted rescue and recovery services.  A tsunami, with waves ranging from a few centimetres to 1.4 metres, was recorded.  Our thoughts are with all those affected now and in the coming months.

Fig 1: Location of the 7.8 Philppines earthquake.  Source PhiVolcs: PRIMER ON THE 08 JUNE 2026 MAGNITUDE (MW) 7.8 OFFSHORE SARANGANI EARTHQUAKE | PHIVOLCS

Tectonic Setting

The Philippines  is an archipelago made up of c.7,641 islands.  It lies on the Philippine Mobile Belt, a zone lying above two opposing subduction zones: the Sunda Plate along the western edge at the Manila, Negros and Cotabato Trenches ; and, the Philippine Sea Plate on the eastern edge along the Philippine Trench and the East Luzon Trough. The Philippine Mobile Belt, itself, is the result of oblique collision between the westward-moving Philippine Sea Plate and the eastern margin of the Sunda Plate. It is rapidly deforming, made up of fragments of continental and oceanic crust.

Fig 2:  Map of Philippine Faults by Gubernatoria, published under CC BY 2.5 AU <https://creativecommons.org/licenses/by/2.5/au/deed.en&gt;, via Wikimedia Commons

The 7.8 earthquake was reverse thrust and attributed to movement at the Cotabato Trench.

The archipelago has three main geological features:

  • The 1,200-kilometer-long Philippine Fault Zone; a  strike-slip fault system which accommodates much of the shearing force caused by the colliding plates.  It is seismically active producing large earthquakes, including the destructive M7.6 Luzon earthquake of 1990.
  • Volcanism from the subduction. The Philippines is home to numerous active volcanoes, e.g., Taal, Mayon and Mount Pinatubo
  • A complex structure containing a mixture of ancient metamorphic rocks (dating back to the Jurassic and Cretaceous periods), early volcanic arcs, and microcontinental blocks.
  • The 7.8 earthquake is attributed to movement at the Cotabato Trench.

All in all, an interesting are to study seismicity.

Our Plots

We looked at the area 4.4150°N, 116.16°E  to  21.1218°N, 137.90°E for the period 1st January 2016 to 11th June 2026 (07:33 am).  Our raw data was downloaded publicly available earthquake data from USGS, a total of 7,357 earthquakes with a  minimum magnitude of 3.7 and maximum depth of c.668 km. 

Fig 3: Geoscatter plot of earthquakes occurring between 4.4150°N, 116.16°E  to  21.1218°N, 137.90°E for the period 1st January 2016 to 11th June 2026 (07:33 am).  Earthquakes with magnitude ≥ 7.0 are shown as yellow stars; the magnitude 7.8 earthquake is shown as an orange star.  Smaller earthquakes are coloured by depth as per the legend; their transparency has been increased so we can see the land. © copyright remains with the author; all rights reserved, 2026.

In our Geoscatter plot, we can clearly see the seismicity on the Manila Trench, west of Luzon, the Philippine Trench east of the Philippines, the Philippine Fault Zone to the west of the Philippine Trench and other trenches. Activity along the Philippine Trench dominates the plot.  Most of the earthquakes with magnitude greater than 7.0 are associated with subduction at the Philippine Trench.

We can also see some deeper activity  in the southern part of the plot.  We think that this is related to the fully subducted Molucca Sea Plate which lies to the south of the Philippine Mobile Belt.  The Molucca Sea Plate lies between the southeastward subducting Sangihe Plate and the northwestward subducting Halmahera Plate; the collision zone is thought to be arc to arc collision rather than the more usual arc to continent collision.    This shows better in our scatter plot below.

Fig  4:  Video of 3D scatter plot of of earthquakes occurring between 4.4150°N, 116.16°E  to  21.1218°N, 137.90°E for the period 1st January 2016 to 11th June 2026 (07:33 am).  Earthquakes with magnitude ≥ 7.0 are shown as yellow stars; the magnitude 7.8 earthquake is shown as a black star.  Smaller earthquakes are coloured by depth as per the legend. © copyright remains with the author; all rights reserved, 2026.

In the video we can see that most of the magnitude seven and over earthquakes occur in the region between 0 to 100 km in the southern part of the region and a few are occurring at a depth of over 600 km.  The former are mostly associated with the Philippine Fault Zone and the Philippine Trench.

We hope you find the earthquake plots useful. 

Once again, our thoughts are with all those impacted by the earthquake.

Armchair Volcanologist

© copyright remains with the author; all rights reserved, 2026.

Sources:

USGS:  https://earthquake.usgs.gov/earthquakes

China Daily Asia: Philippine quake death toll reaches 55, search on for 38 missing

PhiVolcs: PRIMER ON THE 08 JUNE 2026 MAGNITUDE (MW) 7.8 OFFSHORE SARANGANI EARTHQUAKE | PHIVOLCS

Iceland, Reykjanes Peninsula

Svartsengi: Will It, Won’t It or, most likely, When Will It… ?

Good Evening,

Today, we are looking at the earthquake plots for the Reykjanes Peninsula since the 16th July 2025 eruption on the Sundhnúkur crater row.

The Icelandic Met Office (IMO) are reporting that ground deformation and magma accumulation has continued under Svartsengi on the Reykjanes Peninsula, Iceland, since the 16th July 2025 eruption on the Sundhnúkur crater row. To date the cumulative uplift is just over 25cm and the estimated volume of magma accumulated is in the region of 26 million cubic metres.  IMO conclude that the most likely outcome is another eruption on the Sundhnúkur crater row. Their updates can be found here: Ground uplift and magma accumulation continue beneath Svartsengi | News | Icelandic Meteorological office .

We started by plotting the earthquakes for the Reykjanes Peninsula from 16th July 2025 to 10th May 2026 for the area between 63.7°N, 23.0°W to 64.4°N, 21.0°W.  This is followed by a closer look at the area covering Svartsengi and Krýsuvík.

Reykjanes Peninsula, 17th July 2025 to 10th May 2026

We downloaded publicly available earthquake data from Skjálftalísa for the area above; a total of 6,186 earthquakes. Our data set includes automatically recorded earthquakes which have not been reviewed so there is less certainty about their location, especially where have been earthquake swarms.

Fig 1: Geoscatter plot of earthquakes occurring in the area 63.7°N, 23.0°W to 64.4°N, 21.0°W for the period 17th July 2025 to 10th May 2026 15:00. Colour denotes age: yellow are the most recent, red are the oldest in the sequence.  © Copyright remains with the author; all rights reserved.

We have created a video of the sequence.  Frames are captured in steps of 100 earthquakes.

Fig 2: Video of geoscatter plots of earthquakes occurring in the area 63.7°N, 23.0°W to 64.4°N, 21.0°W for the period 17th July 2025 to 10th May 2026 15:00 in buckets of 100 earthquakes. Colour denotes age: yellow are the most recent, red are the oldest in the sequence.  © Copyright remains with the author; all rights reserved.

A geodensity plot of the same data set shows that activity is focussed on Eldey out on the Reykjanes Ridge, an area to the west of Hveragerdi near Raufarhólshellir, Krýsuvík and, harder to see, Svartsengi and an area to the west of Grindavík. We had to change the background to improve visibility.

Fig 3: Geodensity plot of earthquakes occurring in the area 63.7°N, 23.0°W to 64.4°N, 21.0°W for the period 17th July 2025 to 10th May 2026 15:00. Colour denotes density: yellow is the densest are, red is less dense.   © Copyright remains with the author; all rights reserved.

To see what is going on below the surface, we plotted the earthquakes latitude v depth, count per day and depth v longitude; the geoscatter plot is shown for reference.

Fig 4: Depth plots of earthquakes occurring in the area 63.7°N, 23.0°W to 64.4°N, 21.0°W for the period 17th July 2025 to 10th May 2026 15:00. Key: bright green circles are earthquakes occurring on that day, magnitude  < 3.0 mag; bright yellow stars are earthquakes occurring on that day, magnitude  ≥ 3.0 mag; teal circles are cumulative earthquakes occurring on previous days, magnitude  < 3.0 mag; and, dull yellow starts are cumulative earthquakes occurring on previous days, magnitude  ≥ 3.0 mag. © Copyright remains with the author; all rights reserved.

We have created a video of above plots covering the whole 298 day period by day.

Fig 5: Video of depth plots of earthquakes occurring in the area 63.7°N, 23.0°W to 64.4°N, 21.0°W for the period 17th July 2025 to 10th May 2026 15:00. Key: as for Fig 4. © Copyright remains with the author; all rights reserved.

Most earthquake activity is occurring in the crust. There would appear to magma doming under the western end of the Reykjanes Peninsula. It is less clear what is going on to the east of this and also further west, but, as most activity is in the crust, we feel that this most likely faults moving to accommodate the uplift under Svartsengi. Whether the activity at Krýsuvík or Eldey is enough to permit magma ascent in the future remains to be seen, but, at the time of writing, they are showing little ground deformation.

Svartsengi, 17th July 2025 to 10th May 2026

We plotted the area 63.746°N, 22.631°W to 63.996°N, 21.864°W; this covers both the Svartsengi and Krýsuvík regions from the above data set; a total of 3,174 earthquakes.

Fig 6: Geoscatter plot of earthquakes occurring in the area 63.746°N, 22.631°W to 63.996°N, 21.864°W for the period 17th July 2025 to 10th May 2026 15:00. Colour denotes age: yellow are the most recent, red are the oldest in the sequence.  © Copyright remains with the author; all rights reserved.

We have created a video of the sequence.  Frames are captured in steps of 100 earthquakes.

Fig 7: Video of geoscatter plots of earthquakes occurring in the area 63.746°N, 22.631°W to 63.996°N, 21.864°W for the period 17th July 2025 to 10th May 2026 15:00 in buckets of 100 earthquakes. Colour denotes age: yellow are the most recent, red are the oldest in the sequence.  © Copyright remains with the author; all rights reserved.

A geodensity plot of the same data set shows that activity is focussed on Krýsuvík, Svartsengi and an area to the west of Grindavík.

Fig 8: Geodensity plot of earthquakes occurring in the area 63.746°N, 22.631°W to 63.996°N, 21.864°W for the period 17th July 2025 to 10th May 2026 15:00. Colour denotes density: yellow is the densest are, red is less dense.   © Copyright remains with the author; all rights reserved.

To see what is going on below the surface again, we plotted the earthquakes latitude v depth, count per day and depth v longitude; the geoscatter plot is shown for reference.

Fig 9: Depth plots of earthquakes occurring in the area 63.746°N, 22.631°W to 63.996°N, 21.864°W for the period 17th July 2025 to 10th May 2026 15:00. Key: bright green circles are earthquakes occurring on that day, magnitude  < 3.0 mag; bright yellow stars are earthquakes occurring on that day, magnitude  ≥ 3.0 mag; teal circles are cumulative earthquakes occurring on previous days, magnitude  < 3.0 mag; and, dull yellow starts are cumulative earthquakes occurring on previous days, magnitude  ≥ 3.0 mag. © Copyright remains with the author; all rights reserved.

We have created a video of above plots covering the whole 298 day period by day.

Fig 10: Video of depth plots Depth plots of earthquakes occurring in the area 63.746°N, 22.631°W to 63.996°N, 21.864°W for the period 17th July 2025 to 10th May 2026 15:00. Key: as for Fig 9. © Copyright remains with the author; all rights reserved.

Due to the low level of seismic activity in the Svartsengi area, our plots do not add much more than the plots of the Reykjanes Peninsula at the moment in terms of predicting what will happen next. Time will tell when and where the next eruption occurs.

We hope you find the plots useful.

For up to date information and advice, please visit the Icelandic Met Office site: https://en.vedur.is/

An Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2026.

Sources are credited in the text.

Iceland, Reykjanes Peninsula

We’re Back!

Hello!

After a long period of absence to care for a sick relative, we are back.

A lot has happened in the interim in terms of volcanic and seismic activity globally. So a lot of catching up to do.

We are starting by looking at Iceland. The Icelandic Met Office (IMO) (https://en.vedur.is/) has changed its earthquake monitoring system from its SIL system to SeisComP to make monitoring easier. In the process they have updated Skjálftalísa (https://skjalftalisa.vedur.is/) which we use to download earthquake data. This makes it easier to select data. It also has a 3D plotting capability for those who do not have the time or software to be able to do it themselves. Our thanks to IMO.

Our new post on the seismic activity on the Reykjanes Peninsula will be up shortly.

Armchair Volcanologist

12/05/2026

© Copyright remains with the author; all rights reserved, 2026.

Reykjanes Peninsula

Updated Earthquake Plots for Svartsengi and Krýsuvík, 24th October 2023 to 9th March 2024

While waiting to see where and when the next eruption on the Reykjanes Peninsula occurs, we have updated our earthquake plots for the area between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024 – a total of 12,988 earthquakes.  We have extended the area plotted to include Krýsuvík.

First, we start with the geodensity plot for the period 24th October 2023 to 9th March 2024.  Most activity is still occurring on the magma intrusion / graben between Hagafell and Stóra-Skógafell.  The earthquake density plots for the entire period also picks up some activity southwest of Grindavík, west of Fagradalsfjall and at Mount Þorbjörn.  This shows best on a topographic map with a lighter background.

Fig 1: Earthquake density plot by the author of earthquakes occurring between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024. © copyright remains with the author; all rights reserved, 2024.

Next, we look at the geoscatter plot for the same area and period.  This shows the activity along the magma intrusion / graben, that west of Fagradalsfjall, and, also, an upkick in activity in the Krýsuvík area.  The last may be local faults accommodating the uplift at Svartsengi.  Whether or not this lets magma ascend in the Krýsuvík volcanic system, itself, remains to be seen.  At the time of writing, the alert level for Krýsuvík is unchanged at green. 

Fig 2: Geoscatter plot by the author of earthquakes occurring between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024. © copyright remains with the author; all rights reserved, 2024

We have complied a video of the earthquake sequence in increments of 50 quakes.

Fig 3: Video of geoscatter plots by the author of earthquakes occurring between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024. © copyright remains with the author; all rights reserved, 2024.

We have also looked at the sequence by the various events (inflation, intrusion / graben formation and eruption).  The events are:

Fig 4: Table by the author of events in the earthquake sequence (inflation, intrusion / reactivation of the graben and eruption).  © copyright remains with the author; all rights reserved, 2024.

For each event we have done the geodensity and geoscatter plots.  These can be found in the video below.

Fig 5: Video of geodensity and geoscatter plots for events by the author of earthquakes occurring between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024. © copyright remains with the author; all rights reserved, 2024.

Other plots

Fig: 6 Combined geoscatter and scatter plots by the author of earthquakes occurring between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024. © copyright remains with the author; all rights reserved, 2024
Fig 7: Scatter plots by the author of earthquakes occurring between 63.746°N, 22.631°W and 63.996°N, 21.864°W from 24th October 2023 to 9th March 2024. © copyright remains with the author; all rights reserved, 2024.

We hope you find the above plots useful.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2024.

Source:

Our thanks go to IMO for the raw earthquake data.  IMO:  Icelandic Meteorological Office

Iceland, Reykjanes Peninsula

A New Eruption Started on 8th February 2024 Northeast of Sýlingarfell, Iceland

The eruption start early this morning at 6am with a 3km long fissure near to the location of the 18th December 2023 eruption. Lava is flowing westwards. 

Fig 1: screenshot from local webcam of the fissure this morning. Source: https://www.livefromiceland.is/webcams/langihryggur

At the time of writing there is no immediate threat to Grindavík the Blue Lagoon or Svartsengi Power Plant. No-one is thought to have been in Grindavík when the eruption started; the Blue Lagoon was evacuated successfully. It will be some time before lava may reach the protective walls round Grindavík.

The eruption started with little notice. The precursors were an earthquake swarm which started 30 minutes before at 5:30 am and around ten minutes later pressure changes in bore holes at the power plant were noted.

Fig 2: Earthquake swarm heralding the onset of the eruption (red dots). Source: https://en.vedur.is/earthquakes-and-volcanism/earthquakes/reykjanespeninsula/

The eruptive mechanism is similar to the two previous eruptions. Magma flows into the channel and then erupts with jets of lava. Lava fountains are currently reaching 80m height and the plume rises to 3km.

Inflation has been continuous at Svarsengi since the December 18th eruption. It is too soon to see what effect thus eruption has had on local ground deformation. 

Fig 3: another screenshot of the eruptive fissure this morning. Source: https://www.livefromiceland.is/webcams/fagradalsfjall

For updates, please refer to local news sources (we use https://www.ruv.is/english/2024-02-08-eruption-started-on-reykjanes-peninsula-404272), or the local authorities, Department of Civil Protection and Emergency Management (https://www.almannavarnir.is ), the Icelandic Meteorological Office (https://vedur.is ).

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2024.

Sources are referred to in the text.

Iceland, Reykjanes Peninsula

Fissure Eruption Started Near Grindavík, Iceland, 07:57 UTC 14th January 2024 (updated 19th January 2024)

Fig 1:  Screengrab of the eruption from Sundhnúkar – Live from Iceland – Webcams around Iceland

Update, 19th January 2024

There are no signs of eruptive activity, however, inflation still continues at Svartsengi.

We have updated our earthquake plots to 17th January 15:49. The geodensity plot shows an increase in density south westwards from the hotspot. The geoscatter plots (latitude v longitude) show the development of seismic activity near Fagradalsfjall after the December eruption in addition to activity at Svartsengi / Grindavík.

We recommend that you watch the videos on YouTube rather than here; you can adjust the size and speed more easily there.

Fig 7: Plot by the author of confirmed earthquakes from 24th October 2023 to 17th January 2024 15:49 at Svartsengi / Grindavík. © Copyright remains with the author; all rights reserved, 2024.
Fig 8: Geodensity plot by the author of the swarms from 24th October 2023 to 17th January 2024 15:49 at Svartsengi / Grindavík. © Copyright remains with the author; all rights reserved, 2024.
Fig 9: Earthquake plots by the author of the swarms from 24th October 2023 to 17th January 2024 15:49 at Svartsengi / Grindavík. The plots show by day latitude v depth, latitude v longitude and depth v longitude for the earthquakes. © Copyright remains with the author; all rights reserved, 2024.
Fig 10: Earthquake geoscatter plots by the  author of the swarms from 24th October 2023 to 17th January 2024 15:49 at Svartsengi / Grindavík. The plots show by day latitude v longitude for the earthquakes. © Copyright remains with the author; all rights reserved, 2024.
Fig 10: Earthquake scatter plots by the  author of the swarms from 24th October 2023 to 17th January 2024 15:49 at Svartsengi / Grindavík. The plots show by day depth plots the swarm from the side and then the southern end. © Copyright remains with the author; all rights reserved, 2024.

Update, 17th January 2024

IMO are reporting that a new graben has formed to the east of the graben which formed in November 2023. The new graben is between 800m and 1,000m wide with a depth of up to 30cm, whereas the older graben is 2km with with depths of up to 1.3m. The new graben is widening and deepening. Unfortunately, this increases the risk of new fissures in and around Grindavík.

Because a new graben has formed the magma intrusion which supplied the 14th January 2024 eruption is thought to be further east than that which supplied the 2023 eruptions.

Fig 6: Map published by IMO showing the location of the graben which formed in November 2023 and the new graben which formed in January 2024. The graben are outlined by red lines; the new graben is coloured in blue. The grey areas are the lava flows from the January 2024 eruption. Warm colours denote land which rose and blues denote land which dropped (note some is due to the creation of the defensive walls). Source: https://vedur.is/um-vi/frettir/jardskjalftahrina-nordan-vid-grindavik-hofst-i-nott

Meanwhile, inflation at Svartsengi continues. This is thought to be due to more magma entering the system.

Update, 16th January 2024

From what we can see on the webcams, the eruptive activity (or this phase of the eruption) seems to have ended on the northern fissure at around midnight last night. Activity on the southern fissure ended yesterday.

It is too early for the eruption to be declared over. Inflation continues at Svartsengi and has resumed at the stations which recorded initial inflation. New fissures may open with little to no warning.

Three properties were lost to lava. The defensive walls were effective in diverting most of the lava flow from the town, itself, despite not being completed. We do not know whether or not livestock and pets trapped in the town have been rescued. The full damage to the town has yet to be assessed. However, due to ground deformation with displacement of up to 1.4m spread over existing and new fissures, new surface cracks can appear without warning.

IMO has published an updated hazard map:

Fig 3: Updated hazard map. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

IMO has also published maps showing the extent of the lava flow as of yesterday and thickness of the lava flow. The se also show how the defensive walls diverted lava and lava pooling by the defensive wall.

Fig 4: Map published by IMO showing the extent of the lava flows. The dark purple area is the extent of the lava as at 1:50 pm on January 14; the light purple shape shows the extent as of 4:15 pm. The eruptive fissures are denoted by red lines and the defensive walls are represented by orange dotted lines. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night
Fig 5: Map published by IMO showing lava thicknesses as at 15h January 1:50pm. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

Original Post, 14th January 2024

Two eruptive fissures have opened north of Grindavík today. The summary below is   sourced from IMO’s updates and RUV’s live English blog.

Inflation at Svartsengi had continued uninterrupted since the 18th December 2023 eruption at the Sundhnúksgígar crater row.  A new earthquake swarm started before 03:00 UTC today (14th January 2024) at the  the Sundhnúksgígar crater row migrating south westwards towards Grindavík. By 05:30am both seismicity and ground deformation indicated that the magma intrusion had propagated under the town.

Fig 2: Inflation at Svartsengi.  Source: IMO
Fig 3: Earthquake swarm today.  Source: IMO

A fissure opened east of Þorbjön and southeast of Hagafell, the southern most part of which was 900m from Grindavík.  By 10:44, the fissure was around 1 km in length.  A second fissure opened at 12:10 just north of the town.  Lava has now entered the town.

Grindavík was evacuated at c.03:00 this morning.  However, some sheep and other animals kept in the town were trapped.

The defensive walls built to protect the town from lava were working well, despite not being completed, until the second fissure opened; the fissure’s southern most end was south of the defensive walls.

The authorities are asking that sight seers keep away from the site at the moment.  We have given links to some webcams where you can view the eruption live.

Armchair Volcanologist

© copyright remains with the author; all rights reserved, 2024.

Sources:

IMO: An eruption has started | News | Icelandic Meteorological office (vedur.is)

RUV.is:  Eruption north of Grindavík – RÚV.is (ruv.is)

Webcams:  Bein streymi frá gosstöðvum – RÚV.is (ruv.is) and Webcams – Live from Iceland – Webcams around Iceland

Iceland, Reykjanes Peninsula

Eruption Started to the North East of Grindavík, 18th December 2023

Update 23rd December 2023

IMO have confirmed that the eruption has ended. However, since uplift resumed immediately at Svartsengi after the onset of the eruption and is at a higher rate than that which preceded the eruption, magma is still accumulating under Svartsengi and the risk of further eruptions increases daily. The rate of uplift decreased prior to the eruption; this process is thought likely to be repeated. The most likely site for another eruption is thought to be between Stóra-Skógfell and Hagafell.

A new hazard assessment has been issued by IMO. It can be found here: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night . The purple zones (very high risk) over the magma intrusion have been lowered to red (high risk); all other zones remain the same. The hazard level for Grindavík remains considerable. Conditions can change rapidly and adverse weather can hinder detection, reducing warning time.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

Update 21st December 2023

At risk of jinxing it, the eruption appears to be over. Activity decreased late last night / early this morning. Scientists who viewed the site from the air today report that there is no visible activity in the craters and the lava flow appears to have ceased. It is, however, feasible that lava is flowing in closed channels. It would be premature to declare the eruption over. Scientists continue to monitor the area. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Update 20th December 2023

IMO are reporting that the eruption remains steady today. The authorities are concerned that the eruption started with considerable force after only an hour from the start of the latest episode in the seismic swarm. Magma is most likely sourced from Svartsengi, which has had several periods of inflation since 2020, although the eruption started on the magma intrusion which formed on 10th November 2023. The current level of activity is comparable to recent eruptions at Fagradalsfjall.

A new risk assessment has been carried out. Seismic activity has remained fairly steady, following the initially intense swarm, and ground deformation has not changed significantly to date (or not as much as during the formation of the November magma intrusion). The risk of a new eruptive site forming near Grindavík is thought to have decreased but the risk still remains substantial. Magma can reach the surface quickly, not giving the authorities much time to issue warmings. The most likely sites for new activity remain over the November magma intrusion. A new hazard map has been created.

Fig 6: Ground deformation at Svartsengi. Source: IMO
Fig 7: New hazard map from IMO for the current eruption, effective 21st December 2023 to 28 December 2023. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

Scientists collected lava samples on 19th December 2023. Their analysis shows a composition of c.6% Mg2O, c.2.29% TiO2 with a K2O/TiO2 ration of 0.23. The lava is thought to be more evolved than the lavas erupted at Fagradalsfjall, having spent more time in the crust. It may have the same source as the recent Fagradalsfjall eruptions. (Source: https://jardvis.hi.is/is/eldgos-vid-sundhnuksgiga-nidurstodur-maelinga-18-desember).

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Update 19th December 2023, 16:30 (video issues corrected)

The lava flow has decreased and is now about 25% of the initial output.

The Coast Guard reports that the eruption is now mainly in two places on the fissure and a small vent in the south. The larger sites are each c. 300 metres to 500 metres long. The southernmost site is c. 2 kilometres north of Sundhnúk. There is also a very small site north east of Stóra-Skógsfell.

Magma plumes are also smaller, reaching about 30 meters at their highest point. Lava is currently flowing eastwards towards Fagradalsfjall, with two smaller flows heading westward, both north of Stóra-Skógfell.

The eruption is currently following a similar pattern to recent volcanic eruptions at Fagradalsfjall, where the fissures have started to contract and form single vents.

Fig 4: Location of the fissures. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night

We have updated our earthquake plots. These are in the video below. 

Fig 5: earthquake plots by the author of the swarms from 24th October 2023 to 19th December 2023. © Copyright remains with the author; all rights reserved, 2023.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Original Post, 19th December 2023

This evening an intense earthquake swarm started c. 20:40 local time, north of Grindavík, following the path of the recent magma intrusion.  This heralded the eruption which started just after 10:00pm. The eruption is located close to Sundhnúkagígar, about four kilometres northeast of Grindavík. At the time of writing, the aviation code is orange.

Fig 1: Eruption north of Grindavik. Source: https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night
Fig 2: earthquake swarm on the Reykjanes Peninsula. Source: https://en.vedur.is/earthquakes-and-volcanism/earthquakes/reykjanespeninsula/#view=map

The local authorities are evacuating Grindavík and Reykjanesbraut (the road which connects Reykjavik to the airport). A civil defence emergency has been declared. This is not a tourist eruption.

The eruption is powerful, with jets reaching hundreds of metres high. The initial fissure was 200m to 300m long, with a lava flow of 100 to 200 cubic metres per second. The fissure has now reached c. 3.5km length. There is a risk that lava may reach Grindavík.

Prior to the eruption, inflation at Svartsengi had reached 10th November 2023 levels prior to the formation of the graben and magma intrusion.

Fig 3: inflation at Svartsengi. Source: IMO.

For updates, please consult the relevant authorities, for example, IMO and Department of Civil Protection and Emergency Management

We will update our earthquake plots as soon as we get a chance.

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Sources are referred to in the text and also https://www.ruv.is/english/2023-12-18-eruption-on-reykjanes-peninsula-399922

Reykjanes Peninsula

The Calm Before the Storm? Update on the earthquake swarm near Grindavík

At the time of writing, the eruption has not materialised.  The swarm continues, albeit the magnitude and number of the earthquakes has decreased. 

The status of Grindavík has been downgraded from “emergency” to “danger”. The aviation code has been reduced to yellow.  If an eruption does ensue from this swarm, the most likely location is between Hagafell and Sýlingarfell.

On 21st November 2023, IMO reported significant uplift in the vicinity of Svartsengi.  While an eruption may follow here, it is thought that it would be preceded by an increase in seismic activity.  There is still a likelihood of an eruption near the magma intrusion.  Since then, uplift has continued.

Fig 33:  COSMO-Skymed interferogram spanning 24-hours between 18−19 November at 06:41. The broad uplift signal visible in orange/red around Svartsengi is indicative of inflation occurring at a depth of > 5km.  Source: IMO
Fig 34: GPS from IMO showing ground deformation at Svartsengi.  There was initial uplift at the start of the swarm, followed by large drop when the graben was reactivated / dike formed, which, in turn, is followed by resumed uplift.  Source: IMO.

We have updated our earthquake plots from 24th October 2023 to 26th November 2023 13:27. Most activity is occurring along the magma intrusion, although it is focussed more on the area to the east of Sýlingarfell on Sundhnúksgigar.

Fig 35:  Earthquake geoscatter plot by the author of earthquakes occurring for area 63.746°N, 22.631°W to 63.996°N, 22.211°W between 24th October 2023 to 26th November 2023 13:27.  Red denotes earliest earthquakes; yellow denotes latest earthquakes.  © Copyright remains with the author; all rights reserved, 2023.
Fig 36: Earthquake geodensity plot by the author of earthquakes occurring for area 63.746°N, 22.631°W to 63.996°N, 22.211°W between 24th October 2023 to 26th November 13:27 on the left and 10th November 2023 to 26th November 13:27 on the right.  © Copyright remains with the author; all rights reserved, 2023.

We have summarised earthquake activity by day in the following video.

Fig 37: Video of earthquake plots by the author for the area 63.746°N, 22.631°W to 63.996°N, 22.211°W between 24th October 2023 to 26th November 13:27.  © Copyright remains with the author; all rights reserved, 2023.

Our plots show faults responding to magma, with decreasing seismic activity along the possible dyke formation since the reactivation of the graben.  This may reflect the fact that magma has reached less brittle layers or most of the seismicity associated with the magma intrusion was in fact due to tearing of the crust in response to the inflation at Svartseni and environs, which, in turn, may or may not have allowed magma to flow into the formation.  Time will tell.

Since our earthquake plots were compiled, there has been another small swarm to the east of Sýlingarfell.

We believe that this is the calm before the storm (an eruption) but when will the storm break?

For updates, please consult the relevant authorities, e.g IMO (link below).

Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2023.

Source for raw earthquake data: IMO, https://en.vedur.is/