Campi Flegrei

[bjdeming]

Since the last post there has been at least one more typical swarm, which had a fine sciame called.

Earlier today Cronaca Flegrea reported a house in Pozzuoli was evacuated and closed due to high CO2.

A couple of hours ago, a 4-pointer hit in the same general area as all the swarms. Napoli Today reports (Italian) damage but no known injuries -- one person had to be helped out after their attic collapsed and several had to leave their homes via the window because the door stuck (which could be from construction issues and/or ground deformation, in this layperson's opinion).

An hour ago, INGV reported a swarm, which started off with the 4-pointer and is ongoing.

The people are in the street and official meetings are underway.

 

[bjdeming]

Two blog posts in one -- on a crowded weather day, too. Sorry! -- but mine is necessary for the situation update, to translate the INGV's science talk a little more closely to how we see things, because of the high risk and high international interest in Campi Flegrei, and also, at the end, some sobering expert words to put that risk into perspective.

March 14, 2025, 1:06 p.m., Pacific: Twelve hours ago, INGV declared the end of the swarm, and included a note about the rules they use to define swarms (it’s a matter of elapsed time).

Despite its location, Campi Flegrei has displayed a total disregard for impeccable Latin logic and, an hour ago, had a M3.5.

The volcano is stronger than us, and ultimately always wins, but logic and rapid response and learning are how to save the most lives in these crises.

The browser translation of their recent post (Italian) about the swarm doesn't fit in post size limits here, but it's on my blog.


Some things in it that drew my attention are (my emphasis):

• “…in the last 10 years an increase in the number and energy of the recorded events has been observed…”
• “…in the previous months, since August 2024, the same area, at the centre of the caldera, had shown an average uplift rate of ~ 10 mm/month; b) only during the second half of February 2025 this value had risen to ~15±5 mm/month (Figure 3).”
• “…yesterday’s Md 4.4 earthquake fits into a context of a rapidly increasing rate of uplift that had not been detected during the event of the same magnitude on May 20, 2024. “
• “…very high acceleration values are observed , between 0.6 and 1 g (where g is the gravitational acceleration), especially towards the edge of the Solfatara and Pozzuoli, towards the sea and towards the east, in the direction of the Posillipo hill and the city of Naples.”
• “Although for many months we have continued to record fluctuating and variable, but sustained, variations in some parameters such as the speed of ground deformation and CO2 emissions, the other parameters detected by the Vesuvius Observatory-INGV monitoring system as a whole do not currently show evidence of an imminent volcanic eruption…”
• The scenarios that we can expect in the short term must therefore be inserted into the geophysical framework that the Campi Flegrei caldera has been highlighting for some time: seismicity will continue as long as the ground uplift is underway and earthquakes of energy comparable to that of today’s earthquake, or slightly higher, will still be possible. An intensification of the bradyseismic crisis remains possible, as well as a decrease, with a transition from uplift to subsidence (as occurred in the crises of the last century.”

There is no point in a layperson speculating on all that. From the little bit I know, however, it sounds reassuring in the doom-gloom-padded room sensationalism aspect — no eruption of any sort (most likely one, eventually, is a Monte Nuovo style “normal” eruption) in the foreseeable future. That said, this layperson thinks the change in behavior recently is significant enough to warrant keeping a close eye on this situation.

By the way, did you know that Campi Flegrei is not technically a supervolcano?

I’m willing to give total respect to a volcano whose eruptions have sent pyroclastic flows up and over the nearest range of the Appenine Mountains, but it's not, according to the source I’m using in the supervolcanoes series:

Frontiers in Earth Science
Front. Earth Sci. , 04 May 2022
Sec. Volcanology
Volume 10 – 2022 | https://doi.org/10.3389/feart.2022.859237
…
What should not be called a supervolcano?
This goes to the crux of the abuse and misuse of supervolcano due to a lack of attention or awareness of the formal definition established by Miller and Wark in 2008 and the conflation of the volume and magnitude measures. There are some caldera volcanoes that over their lifetime have exceeded 450 km3 in cumulative output of felsic magma, but have never had a supereruption, per se. These are not supervolcanoes. One of the most common misrepresentations is Campi Flegrei, the famous European or Italian “supervolcano” or “Europe’s Yellowstone” (a Google Search brings up many of such comparisons from Newsweek, National Geographic, Wired, and the BBC), which does not fit its’ proposed status. The so-called Campanian “supereruption” is currently estimated at 181–265 km3 DRE, a mass of 4.7–6.9 × 1014 kg, a magnitude (M) of 7.7–7.8 and a VEI of 7 (Silleni et al., 2020). It is possible that when more work is done, Campi Flegrei may rise to the status of a supervolcano, but at present it does not fit the bill as defined above. However, we do note that given its location, a future eruption with a magnitude comparable to the Campanian Ignimbrite would be even more catastrophic than a true supereruption in a remote region like the Altiplano/Puna of the Andes, for instance.

I’m a big fan of impeccable logic.

 

[bjdeming]

INGV reported a M3.9 eight hours ago. They aren't mentioning swarms any more.

Cronaca Flegrea did some live streaming of the resulting public move into the streets on their Facebook page. They also report that an important traffic overpass was briefly closed but reopened after checks revealed its stability. A total of 242 people in the Naples, Pozzuoli, and Bacoli area have been ordered out of unsafe buildings thus far.

Among the shelters is an abandoned NATO base in Bacoli that I believe, from news reports, is close to recent epicenters. News photographs I've seen show empty beds and staff in welcoming poses, but I don't know how many people actually are using it and other shelters. In the last crisis, media reports sounded as though most of Pozzuoli simply left the area.

They may do so again and it might become official if this keeps up and the powers that be call an evacuation, which they said, after the 4-pointer, they would be ready to do if needed.

Dr. Di Vito of INGV in the past has said a couple times that the maximum expected quake intensity would be in the M5 range. That would do much damage, given the old and occasionally illegal construction -- reportedly, especially in the Solfatara area where, this layperson supposes, the likelihood of a hydrothermal explosion also remains high.

 

[bjdeming]

Volcano Discovery on the quakes.

A paper published in Nature this year on the quakes, with mention of phreatic events (hydrothermal explosions).

 

[bjdeming]

There are no new big quakes noted, but latest news is that the 4-pointer, which has been upgraded to a 4.6, the strongest yet, was actually a doublet and it activated a 1-km fault. This probably explains the insane acceleration values and at least some of the damage.

 

[bjdeming]

INGV has a post (Italian) up on that paper. Among other things, and some good graphics, they note (browser translation):

...The volcanic area of Campi Flegrei is going through a long period of gradual intensification of activity that began in 2005. During this period, an increase in general seismicity, an intensification of gas emission and an acceleration of ground deformation have been observed” ...

...

The zone of maximum deformation coincides with the central part of the caldera, which has risen by about 140 cm since 2005 (Figure 1d). The amount of uplift gradually decreases from the centre of the caldera outwards, giving the deformation field a general bell shape (Figure 2).

Figure – 2 Map of the uplift (in mm) recorded in the Phlegraean area from January 2023 to January 2025 (from the INGV-OV surveillance bulletin ).
A recent study, conducted by a large group of researchers from the INGV, Vesuvius Observatory and INGV-Pisa Section , in collaboration with the Institute for Electromagnetic Sensing of the Environment (CNR) in Naples, has allowed the identification of Volcano-Tectonic seismic sequences, characterized by very short time intervals between one seismic event and another, which have become increasingly frequent since the beginning of 2021. In particular, peculiar seismic swarms known in the literature as “ burst-like swarms ” have been recognized among these sequences. These sequences, whose name could be translated as “burst swarms” , are characterized by intervals between one event and another so short that the individual earthquakes are often difficult to recognize in the seismogram (Figure 3).

Figure – 3 Examples of “burst” swarms recorded at Campi Flegrei.

...

an increase in rock permeability. This would further favor gas emission and the rapid circulation of hot fluids in the upper crustal layers. In this scenario, the accelerated circulation of hot fluids could predispose the system to phreatic activity, and the presence of “burst” swarms could represent a signal of this possible evolution in the Solfatara-Pisciarelli area. However, this consideration remains a hypothesis, as other factors also influence the probability of triggering phreatic explosions. Therefore, to evaluate this hypothesis, further research and insights will be needed...

Phreatic explosion is another term for hydrothermal explosions.

 

[bjdeming]

From INGV's latest update (via Online Doc Translator):

...2) DEFORMATIONS: After the seismic events of Md=4.6 (13/03) and Md=3.9 (15/03) a decrease in the ground uplift velocity was recorded, the value of which can be defined with the acquisition of further data, which will be available in the coming weeks.

3) GEOCHEMISTRY: No significant changes in the geochemical parameters monitored in the reference week were reported compared to the already known trends of increased flows and heating of the hydrothermal system. The temperature sensor installed in a fumarolic emission 5 meters from the main fumarole of Pisciarelli in the last week showed an average value of ~97°C.

2. EXPECTED SCENARIOS
________________________________________________________________________
Based on the current picture of volcanic activity outlined above, there are no elements that suggest significant short-term developments.

NB Any changes in the monitored parameters, which may lead to a different evolution of the phenomena described above, will be the subject of in-depth analyses communicated promptly.

 

[bjdeming]

No bad news -- the rate of uplift might be slowing further, per today's INGV update (emphasis added; Google translated):

In light of the monitoring data, the following is highlighted:

1) SEISMOLOGY: In the week from April 21 to April 27, 2025, in the Campi Flegrei area, 57 earthquakes with magnitude Md≥0.0 (Mdmax=2.7 ± 0.3) were located.

2) DEFORMATIONS: After the seismic events of Md=4.6 (13/03) and Md=3.9 (15/03), a decrease in the ground uplift velocity was recorded, with an average monthly velocity value of approximately 20±5 mm/month. The values of the last 15 days highlight a possible further decrease in the average monthly uplift velocity, which will be verified and quantified with the data of the next few weeks.

3) GEOCHEMISTRY: No significant variations were reported in the geochemical parameters monitored in the reference week compared to the already known trends of increased flows and heating of the hydrothermal system. The temperature sensor installed in a fumarolic emission 5 meters from the main fumarole of Pisciarelli in the last week has shown an average value of ~96 °C and a range of variation from ~94 °C to ~98 °C, with the lowest values recorded in conjunction with rain events.

2. EXPECTED SCENARIOS __________________________________________________________________________
Based on the current picture of volcanic activity outlined above, there are no elements that suggest significant short-term evolutions.

N.B. Any changes in the monitored parameters, which may lead to a different evolution of the phenomena described above, will be the subject of in-depth analyses promptly communicated.

It isn't always good news when deformation decreases at a restless volcano, but given the Campi Flegrei bradyseism history AND the lack of change in other parameters, this is pretty cool to hear.

 

[bjdeming]

Ongoing swarm at Campi Flegrei, with the strongest shock thus far 4.4, which caused some landslides and much barking in the video included in this article (Italian, and ad intensive -- sorry!)

INGV addressed it in their weekly bulletin (via Online Doc Translator):

Weekly Bulletin
05/05/2025 – 13/05/2025
(Issuance date 05/13/2025)
1. SUMMARY OF ACTIVITY STATUS ________________________________________________________________________
In light of the monitoring data, it is highlighted:

1) SEISMOLOGY: In the week from 5 to 11 May 2025, in the Campi Flegrei area, 46 earthquakes with magnitude Md≥0.0 (Mdmax=2.3 ± 0.3) were located.
Since 12:06 local time on 13/05/2025, a seismic swarm has been underway which, at the time of issuance of this press release (16:00), has been characterized by 32 earthquakes of magnitude ≥0.0 and Mdmax equal to 4.4 ± 0.3, located in the coastal area of Pozzuoli. During the swarm, the other major events were of magnitude 3.5 ± 0.3 and 3.3 ± 0.3.

2) DEFORMATIONS: Since the beginning of April 2025, ground uplift has continued to be recorded, with a monthly mean value of approximately 15±5 mm/month.

3) GEOCHEMISTRY: No significant changes in the geochemical parameters monitored in the reference week were reported compared to the already known trends of increased flows and heating of the hydrothermal system. The temperature sensor installed in a fumarolic emission 5 meters from the main fumarole of Pisciarelli in the last week showed an average value of ~97 °C.

2. EXPECTED SCENARIOS ________________________________________________________________________
Based on the current picture of volcanic activity outlined above, there are no elements that suggest significant short-term developments.

NB Any changes in the monitored parameters, which may lead to a different evolution of the phenomena described above, will be the subject of in-depth analyses communicated promptly.

 

[bjdeming]

No major changes, but per INGV via GT:

"
#CAMPIFLEGREI #SEISMIC EVENT AND #SWARM ANNOUNCEMENT
Since 1:00 on 21/06/2025, a seismic swarm has been underway at Campi Flegrei, preliminarily consisting of about 20 events with M≥0.0 and max magnitude Md=3.2±0.3 (attached figure)
Info terremoti.ov.ingv.it/gossip/flegr...
#INGV #OsservatorioVesuviano"



The 3-pointer was reportedly widely felt but I've seen no news of damage. (Triangles are their stations.)

 

[bjdeming]

And it was a fine attivita -- the 3-pointer was the strongest quake in the swarm