Santorini Earthquake Update 25.4.25 – Next 80 Days
Generally things are still quiet but after the earthquake in Istanbul I’d thought I do a summary of how things are today in the South Aegean and detail what I’ll be looking for over the coming couple of months. In this Santorini earthquake update we’ll look at activity over the past couple of weeks, look at what is happening as of today and then look at some ground movement patterns and see what they might tell us with regards to what could happen in 80 days.
General Activity – April 2025 vs All of 2024
Looking at VolcanoDiscovery.com and their data for the South Aegean for the year to date and the last 30 days.
Over the last 30 days activity looks pretty stable but is this normal for the region?
Looking at the year-to-date data we can see it isn’t. The number of earthquakes still look to be around 10 times higher than what would be expected so I’d say something is still going on but with much much less severity than during the main swarm we saw in February.
And if we look briefly at the 2024 data to confirm what is normal. There were 1527 quakes of all magnitudes, or around 4 a day.
In April 2025 we have had 2333 quakes of all magnitudes which equates to around 77 quakes a day.
So confirmed, the number of quakes (ignoring magnitude and energy released) is around 20 times more in April 2025 than we would expect (if 2024 number are normal).
Seismic Data
Does the seismic data back up the VolcanoDiscovery numbers?
Normally you know I’d look at the Anydros seismograph but unfortunately that only has data from the end of January 2025 (when the Santorini earthquake swarm started).
But the “SANT” seismograph station on Santorini does have data from last year.
Looking at the data from this year and last, I think we can say there is more activity this year. We can’t read too much into these graphs because the scales used, (10,000 HZZ) is too large in my opinion and creates too much noise. Nevertheless I think it’s possible to compare the same scale at different times and activity is up but again we can’t really tell by how much because of the scale.
Anydros
While we are looking at Seismographs, let’s take a quick look at Anydros.
And we can see it’s picking up activity. The scale of this graph is much better at 500 HZ and this cuts out the noise. But we don’t know what it would have looked like last year.
Earthquake Locations
Looking quickly at where the epicentres of the earthquakes are occurring.
The earthquake activity is the same as it’s been throughout the swarm ie centred around Anydros island but the number of quakes is much less versus February.
Ground Movements
This I think is the most interesting one.
I said in the previous update that we had lost data from two key stations. I’ve gone back and found links direct to the web pages of these stations and they are still up so it’s possible data is still being collected but it looks like there is a week or two lag. I’ll put the links here if you want to see them. Amorgos & Ios.
With regards to stations still being updated regularly, we still have the main one on Santorini SNT2.
And this station is giving some very interesting data and is why I am focusing on the next 80 days.
Santorini
Just to go over what we can see in the above image.
First of all Northerly movement. We can see Santorini was moving North since around mid/autumn 2024. A change from the normally southerly direction. And we can see an acceleration in Northerly movement around the same time as the Santorini earthquake swarm started. There could be some correlation here between rate of Northerly movements and the seismic activity we saw and are seeing.
Easterly movement has been consistent throughout the earthquake swarm so no obvious correlation here.
Vertical Movement
Vertical movement accelerated around the same time as the ground changed direction and started to move North.
But the vertical movement could be telling us a bit more because it reversed to a downward movement when the quakes started at the end of January and when the number of quakes dropped this coincided with the resumption of the land rising again.
Let’s dig into that in more detail.
Apologies for the child like “graphic”. The blue dots show roughly when the Santorini earthquake swarm started, the green dots when the number of quakes dropped off noticeably from their peak.
The red line is tracking the movement of the station vertically.
It looks like the quakes precede the movement of the land rise change in direction, which I suppose makes sense. Earthquakes hint that there has been some movement in the crust, we get the quakes first and we measure the movements caused by the quakes after.
And likewise when the number of quakes started to drop off the ground movement downwards also reduced in speed. Less quakes, less ground movement to measure.
Next 80 Days – Santorini Earthquake Update 25.4.25
So why am I talking about 80 days?
Going back to the big view .
The acceleration of the upward movement didn’t appear to cause a noticeable increase earthquake activity.
However when the quakes started in earnest we saw ground movement turn downwards.
The relative height of the ground was around +40mm when it changed direction. Was there something stopping the ground from rising higher? And did this blockage/resistance trigger the earthquakes. At +40mm, did pressure build up to a point that triggered the quakes?
Dyke Theory
There is the dyke theory which proposed that magma was moving away from Santorini towards Anydros. Is this why the ground started to move downward? And did this magma moving north east cause the quakes?
And then towards the end of February the number of quakes dropped off and at this point we see the ground moving upwards again.
At the point where the quakes dropped off, is this when the dyke became full? And if the dyke is full, has the Santorini volcano lost this pressure relief mechanism and is this why we see ground rising again at about the same rate it was prior to the quake storm and perhaps a bit faster?
If we assume that at +40mm there is some sort of resistance under Santorini, what is going to happen this time? (If the ground movement continues upward to this height).
Are we going to see resistance again and if so, what will happen to the pressure build up if the proposed dyke is now full?
Rate of Rise
Looking at the image above, the ground has risen by around 10mm over the last 20 days. If this rate continues we will be back at the +40mm level in around 80 days.
When the earthquake swarm started previously we were at +40mm vertical movement. If we get back to +40mm, can we expect the same result as before? Will it be a trigger point for earthquakes again? Over the next 80 days I’ll be looking at the vertical movement of Santorini to see if it continues on it’s present course. Subscribe if you want to get more Santorini earthquake updates.
