Santorini Earthquake Update 22.2.25 – Spring Tides
The fall in the number of earthquakes seems to be leveling out far above the normal level. The rate of fall in earthquake intensity is also leveling out and this level is around double the norm. In this Santorini earthquake update we’ll take our standard look at earthquake frequency and intensity over the past 90 days and past seven days, we’ll take our usual look at the seismographs from Anydros island and then we’ll revisit the tide connection theory and dig in to some actual scientific research on seismicity in general, the results of which surprised me, which is why I think it is very important for people to see, especially people in the South Aegean.
Links to live data here plus general information sources for the Santorini earthquake swarm.
Cumulative & Frequency Earthquake Data
First a quick look at the 90 day trend to illustrate the trends I just highlighted.
Ninety Days
The blue line for cumulative energy released is levelling out at a point which is about double the normal energy released in the South Aegean sea. Earthquake frequency is also showing the same trend ie levelling out.
Seven Days
Moving on to the part seven days data we get better resolution. The axis is broken down into hours. On the cumulative energy front we see that the data is not being skewed by a big event (the green blocks illustrating magnitude are pretty evenly spaced through time). And likewise with earthquake frequency, we are not seeing a big spike in activity followed by a lull. All in all I think we can say we are looking at constant underlying activity, which I think is fair to say, may not be being driven by fault movement.
Seismograph Data – Anydros Island
Our favourite seismograph station Anydros. The image on the left is yesterday the 21st, the right image is the 22nd. I would say both graphs are very, very similar both for line roughness (underlying ongoing seismic activity) and for the frequency of the spikes in intensity. This I think confirms exactly what we saw above in the cumulative data. Constant activity, low intensity.
Island Movement
Let’s take a quick look at the GNSS data for the islands and see if there is anything unusual.
Ios
North movement still constant, westward and upward movement both seem to be slowing.
Santorini
North movement continuing to slow. East movement appears to be constant. Downward movement still accelerating
Amorgos
Southern movement speed looks to be stabilising, as does western and uplift speeds.
Tide Data
Are we still seeing a potential connection between the tide coefficient (difference between high and low tide) and earthquake activity?
Below is an overlay of tide times, over the 7 day cumulative graph we featured above. Tides have a low coefficient at the moment and the earthquake data, as we have said, is also stable at the moment ie not increasing or decreasing. In short, we could still, potentially be seeing a connection.
IF
I’m prefacing the next section with the biggest possible “IF”.
IF there is a connection between the tides (pull of the moon and the sun) what can we expect to see in the coming days?
Perhaps starting as early as the 24th but probably from the 25th onwards, earthquake activity starting to increase again. By how much, if it even happens, is anyone’s guess. I can’t say there will be any correlation between the earthquake intensity and the tide coefficient.
Nevertheless I think it is worth keeping an eye on the tides, we have nothing to lose by doing so.
Friendly Recommendation
A preface to what I’m about to say, I think the chances of anything happening are extremely low. Having said that if I was in a position to maximise my insurance I would say the following.
If I were a resident in the area of the earthquakes, and I had already evacuated, and I was thinking about coming back in the next day or so, I think personally, and if I was in the position to do so, I would delay my return until at least the 26th of Feb. The cost would be potentially very little and it could add an extra 0.000001% layer of insurance. If I was already away, I’d delay my return. I mean, why not?
And if I hadn’t evacuated, and bear in mind I am not in the area, I think personally, I would just be cautious.
Research On Tide-Earthquake Connection
When I did that first video on tides, I presumed that the general consensus among experts was that tides play no role in seismic activity. Having looked into it in a bit more detail, I think I may have made a mistake.
Research Papers – Links
Starting with…
Earthquake-Tide Relationship
Below I am going to give a list of links to articles I thought were interesting. These are articles which deal with the effect of tides on earthquakes and volcanos. I want to stress I haven’t read each article all the way through, but if the first few paragraphs were interesting and easy to read, I include them below.
A review of tidal triggering of global earthquakes
Easy to read an explores the research that has be done on the subject. I think the authors lean towards there being a connection but they also highlight that there is also research showing that there is no connection. I have said there may be connection to tides and the Santorini earthquake swarm. I have also looked at the Campi Flegrei earthquakes are saw no sign of a pattern between the quakes in Naples, Italy at the moment and the tides. In short, I think sometimes tides may be an indicator, sometimes they are not. We have to look at the data for each situation and location.
Tidal sea level fluctuations trigger earthquakes
This paper looks at quakes around the Sea of Marmara. A quote for the article
” For first time in this region, they documented a strong effect of the Sea of Marmara water level changes on the local seismicity.”
One thing I would pick out from their initial introduction is their focus on sea levels being a driver. I would say it’s not the sea level change that is the driver but the pull of the moon and the sun. The change in the sea level is just a symptom of the moon and sun’s position. The tides in Santorini are low but that does not mean the force of the moon and the sun is any less there than it is in the Bay of Fundy.
Earthquake forecast models based on earth tidal correlation
An article that says there is no correlation, at least in the area they sampled, at the times they sampled.
Monitoring tides could predict major earthquakes
Tidal quakes happened more frequently in the run-up to bigger quakes, suggesting stress had built up year-on-year.
Another article that focuses on sea movement and not the driver of the sea movement. And one that stresses that tides are not a primary driver.
Can Astronomical Tidal Forces Trigger Earthquakes?
But in the past 20 years some studies have suggested that this long-suspected phenomenon might actually be real. The most recent of these was published in February by researchers at the Aristotle University of Thessaloniki in Greece who analyzed records from more than 17,000 earthquakes that struck the south of that country between 1964 and 2012. Rather than occurring at random intervals, the quakes seemed to be related to oceanic tidal effects, the team found.
Evidence of tidal triggering on the earthquakes of the Hellenic Arc, Greece (the paper referred to above)
These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level.
Extremely relevant to Santorini
A review of tidal triggering of global earthquakes
In this study, publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes, which were classified into three main types: tectonic, volcanic, and slow earthquakes. The results reveal a high correlation between tectonic earthquakes and tides (mainly for semidiurnal and diurnal tides; 14-day tides) before and after the occurrence of significant earthquakes. For volcanic earthquakes, observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces, mostly those with semidiurnal and diurnal periods.
Our analysis provides new insights about the features of impending mainshocks, which are proposed to emerge from a large-scale crustal-weakening preparation process whose duration depends on their seismic moments
This sentence is a potential worry for the Aegean issue we see at the moment. I think it could be fair to say over the last few weeks we may have seen “large-scale crustal weakening”
Can the position of the moon or the planets affect seismicity?
Earthquakes are equally as likely to occur in the morning or the evening. Many studies in the past have shown no significant correlations between the rate of earthquake occurrence and the semi-diurnal tides when using large earthquake catalogs.
Several recent studies, however, have found a correlation between earth tides (caused by the position of the moon relative to the earth) and some types of earthquakes. One study, for example, concludes that during times of higher earth and ocean tides, such as during times of full or new moon, earthquakes are more likely on shallow thrust faults near the edges of continents and in (underwater) subduction zones.
This USGS article also covers something key but which needs to be reiterated. The vast majority of the time, tides have no affect on seismicity, I think it’s fair to say something else also needs be be happening, tides on their own are not a main driver.
Analysis of Solid Earth Tides…Implications for Earthquake Precursors
A spatio-temporal analysis from 1995 to 2004 reveals distinct patterns preceding higher magnitude earthquakes, offering valuable insights for long-term forecasting. It has been correlated with foreshocks that occur to the same spatiotemporal extent. In a nutshell, singular spectrum analysis SSA of Solid Earth Tides emerges as a promising precursor for long-term earthquake magnitude prediction.
Tidal Triggering of Earthquakes
Research work has shown a robust correlation between small tidally induced forces and non-volcanic tremor activity.
Tidal modulation of plate motions
We review the data and show that lithospheric plates retain a non-zero horizontal component of the solid Earth tidal waves and their speed correlates with tidal harmonics. High-frequency semidiurnal Earth’s tides are likely contributing to plate motions, but their residuals are still within the error of the present accuracy of GNSS data.
Tidal interplate Lithospheric Deformation of Earth
Recent analysis has identified a statistical relationship between tidal forces originating from the Moon and Sun and the incidence of earthquakes. However, existing GNSS (Global Navigation Satellite System) geodetic models do not adequately account for local factors that significantly impact how the Earth’s crust responds to tidal stress, thereby impeding accurate hazard forecasting.
Tidal drag and westward drift of the lithosphere
Mathematical modeling suggests a role for tidal drag in polarizing plate motion
Volcano Research
I’m reluctant to use the “V” word around the Santorini earthquake swarm because I think the consensus is, there is nowhere near enough data to support a hypothesis saying that something can erupt. I use these links below in the name of completeness and to highlight that seismicity in general can be affected by the tides (moon & sun)
Triggering of volcanic eruptions
A recent study of Kilauea and Mauna Loa volcanoes in Hawaii (D. Dzurisin Geophysical Research Letters 7, 925; 1980) shows a weak but significant correlation of the Earth tide maxima with eruptions of Kilauea. No correlation at all was seen with the activity of Mauna Loa – a result which serves to emphasize how individual the behaviour pattern of very similar volcanoes can be.
Can tides influence volcanic eruptions?
To understand this preference for erupting far away from neap tides, we have developed a new lumped-parameter model that accounts for the deformation of magma reservoirs, a partially open conduit, and a gas layer where bubbles accumulate beneath volcanic craters before being released. We demonstrate that this system reservoir-conduit-gas layer acts as an amplifier of the tidal stresses, such that, when a volcano approaches to a critical state, the gas overpressure beneath the crater can reach up to several MPa more during a spring tide (full and new moon) than during a neap tide. This amplification mechanism can explain why active volcanoes are sensitive to the moon cycles.
Unfortunately this link is to a very brief abstract only. Having said that, it did cause me to research “reservoir conduit gas layer” in Google but the results were well over my head.
Moon’s weird pull could help predict deadly volcanic eruptions
The current state of the field can best be summed up by an eye-catching paper published in January by Susan Hough. A seismologist with the United States Geological Survey, she had set out to answer an age-old question: does the timing of powerful earthquakes coincide with the phases of the moon? The abstract ran to one word: No.
Behind a pay wall unfortunately, I add it for balance.
Tidal cycles could help predict volcanic eruptions
Just before a surprise eruption of New Zealand’s Ruapehu volcano in 2007, seismic tremor near its crater became tightly correlated with twice-monthly changes in the strength of tidal forces, a new study has found. The research, published in the journal Scientific Reports, suggests that signals associated with tidal cycles could potentially provide advanced warning of certain types of volcanic eruptions.
Tides and Volcanoes: A Historical Perspective
The idea of an influence of the Moon and Sun on magmatic processes dates back to the Hellenistic world. However, it was only since the late 19th century, with the establishment of volcano observatories at Mt. Etna and Vesuvius allowing a systematic collection of observations with modern methods, that the “tidal controversy” opened one of the longest and most important debates in Earth Science.
More than 25 years ago, a pair of earth scientists compared the records for 680 eruptions that occurred since 1900 and found that “the probability of an eruption is greatest at times of maximum tidal amplitude.” In plainer language, volcanoes are more likely to erupt at the fortnightly (or 14-day) “high” tide.
Since 1800, 48% (23 of 48) of Fuego’s eruptions occurred within ±2 days of the fortnightly maximum amplitude of vertical tidal gravity acceleration. The probability of 23 successes out of 48 events being random is 0.1%.
Research Papers – The Takeaways
The vast majority of the time, tides have no effect.
For tides to have an effect I think the consensus is that there also has to be something else happening first.
And some areas of the world show a correlation, others don’t. Again, Campi Flegrei is not showing any correlation at the moment whereas I think the Aegean is.
Santorini Earthquake Update 22.2.25 – Summary
Some of the links above suggest that the conditions we have been through over the past few weeks, may cause the upcoming tides to have a greater effect than normal.
On this basis I don’t think it would be bad advice to recommend people to take precautions.
I didn’t included the links to cause alarm, I just think it is important to be aware of what has been said, and for people to make the most informed decision for their personal circumstances.
And finally, let’s not forget the facts
As the facts stand today, things are much better than they were over the past three weeks and I don’t think there are any concrete reasons to say things will not continue to improve.
That’s it for today’s installment, subscribe to the YouTube channel for more updates, look after yourself, stay safe and I’ll see you in the next video!
