Santorini Earthquake Update 17.2.25 – The BIG Picture
This is a big picture Santorini earthquake update. We are going to look at overall earthquake activity, which parts of the crust are moving in which direction and what the seismographs in the area are showing us.
All the data in this update are from the links on this page
General Situation – Santorini Earthquake Update
Earthquake activity has been gradually declining back to the norm over the past few days but today that decline has stopped and we are seeing an increase in activity
Plate Movement from GNSS Stations
Vertical – Amorgos and Ios are rising slightly, Santorini seems to be going back down.
Santorini – Plate Movement GPS Data
There are two stations which give what looks like reliable data on Santorini, 048A and SNT2.
North-South Movement
Generally the normal movement is southerly for both of these stations. However since the start of the earthquake swarm both stations are showing northerly movement.
East-West Movement
Generally both these stations see easterly movement. Since the swarm started this easterly movement has accelerated.
Vertical Movement
The trend is for the stations to rise. When the swarm started this upward movement had accelerated but over the last week the movement is down.
Amorgos – Plate Movement
The island of Amorgos has one station called 047A. The trend for this station prior to the swarm was quite stable
North-South Movement
Southerly movement of the plate is the norm. The speed at which is moves south may be accelerating slightly.
East-West Movement
Easterly movement in the long term trend for this station. But this trend has been reversed since the swarm started. The station has moved around 10mm west.
Vertical Movement
Vertical trend for Amorgos is around 1mm increase in height per year over the past 12 years. In the last 15 days the height of the station has increased by 6mm.
Plate Movement – Ios
There is one station on Ios called 049A.
North-South Movement
Normally around 13mm a year southerly movement. This has reversed to a 14mm northerly movement over the past 14 days.
East-West Movement
Normally east, reversed to a 40mm westerly over past 14 days.
Vertical Movement
Very slight uplift, less than a mm a year is the trend for this station. In the last 14 days uplift has been around 5mm.
Plate Movement – Other Stations in South Aegean
Looking at other stations in the area, the ones I have looked at all seem to be registering normal movement, ie they are behaving inline with their long term trends. It is only the stations above that are showing unusual movement.
Seismograph Data
There are many seismograph stations in the South Aegean, unfortunately many of them either do not work or their scales are unusual making it impossible to compare their data against other stations using the standard seismograph updates.
Having said that, the key stations in the area do all use the same(/similar) scale on their seismographs.
Santorini – THR8 Station
Unfortunately the stations of Santorini use unsuitable scales for their graph output making analysis next to impossible. THR8 is the best of a bad bunch, it uses 3000 HHZ scale. Even small events will show big on this graph but it’s something. It is showing some ongoing activity all the time by I am almost positive that the movements are so tiny that they are completely unfelt by people on Santorini. In short, apart from the occasional quake, it is quiet on Santorini (according to this station).
Anafi Island – ANAF Station
This station has a good seismograph axis scale and is comparable to the other key stations. Seismograph uses 500HHZ scale.
This station is picking up slight ongoing seismic activity. It’s graph shows ongoing activity to the same level as THR8 on Santorini except the scale on ANAF’s graph is 6 times less sensitive than THR8. In short, the activity in ANAF station is more than on Santorini and I would say by quite a bit.
Anydros – ANYD Station
The station at the centre of the earthquake swarm. This use the 500HHZ scale on it’s seismograph, same as ANAF but it is picking up much more activity. Activity is being picked up every 30 seconds of less.
Amorogos – AMGA Station
Uses same 500 HHZ scale as Anydros but activity is what looks like 90% less than Anydros.
Big Picture Summary – Santorini Earthquakes
It would be really nice to have lateral and vertical movement for Anydros island given that is at the centre of the swarm and it’s seismograph is showing the most activity. Unfortunately we don’t have movement data, at least from what I can see.
Given that the seismic activity is almost constant at Anydros station I’d guess either the crust in the area is very weak there ie it can’t build up a lot of stress to create a larger quake, or we are looking at magma movement close to the surface as many of the quakes are stated as being at 2km depth.
Generally I lean toward Anydros being at the centre of anything that may happen. At the moment it seems the general trend is for things to be calming down but we have had a 5.1 and a 4.2 earthquake within four minutes of each other this morning (directly under Anydros) so obviously, things still need to be monitored.
