Hi Kyle, I completely agree with this interpretation. The NE-trending Ios Fault Zone appears to be a key factor in this seismic swarm. The concentration of seismicity at 10–15 km depth aligns well with the fault’s downward extension. One possible explanation is that fluids—potentially hot—are migrating along trough faults, parallel to the maximum horizontal stress axis (NE). These fluids could be altering the effective stress conditions on the faults, bringing them closer to failure and triggering seismic activity.
Hi Leonidas! It's great to hear from you. I fondly recall a trip we made together in Greece - were you showing me the Itea-Amfissa Detachment? We stayed with an old man who made the best croquettes with local honey for breakfast. I also saw your recent paper on the Northern Giona Fault Zone, which I recall seeing from the floor of the valley below. Your pictures of the fault in outcrop take me straight back to Greece. I hope things are well with you. Anyway, thanks for the comment on the Ios Fault Zone. I always like writing about Greece, but I want to be sure that the views of the local experts are respected. So please do comment anytime. It will be interesting to see how this seismic crisis resolves, and I'm sure that there will be a lot of interest in tying the recorded events to the real faults in the subsurface. Cheers - Kyle
Thanks again for the update on this swarm! Question: Often people have the misconception that small or moderate earthquakes “relieve stress” on major faults to the extent that they prevent major earthquakes from happening. They’re told by seismologists that it would take thousands of such earthquakes to relieve enough stress to theoretically prevent a larger quake…So, the question is, if there have been over 8,000 earthquakes of all magnitudes in this swarm over a certain area, is it possible that stress has been reduced, perhaps in the Amorgos fault zone?
Hi Nancy, that is indeed a common thought process. It is true that small earthquakes do release a small amount of stress on their faults, possibly reducing the size of later earthquakes - maybe. However, for this to have an effect on the actually big earthquakes, there would have to be a huge number of events across the lower magnitudes. I quickly calculated that all of the earthquakes in the swarm to date (as reported by EMSC, who has a pretty good database of events) only add up to an equivalent single earthquake of Mw=6.02. So, if a Mw7.0 earthquake were to eventually happen (and this isn't saying that it will), then the energy released thus far would only be about 3.4% of that earthquake's energy release. So maybe the effect of the swarm will be to delay a large earthquake by a few decades. However, it is also not at all clear to me whether stress is actually being relieved on the big faults that might rupture with a big earthquake, or is being transferred onto those big faults by rupture of nearby faults. We tend to think that having more earthquakes in general leads to a higher probability of triggering a larger event. In the end, we don't know the real stress states of these faults, and I think we will only find out what is happening down there by seeing what really ultimately occurs! Sorry if it's not a very conclusive answer...
Kyle, Thank you for the response. So, I guess there are no definitive answers yet until whatever happens, happens…I’m wondering if there has been any historical precedence for a swarm scenario very similar to this with moderate spaced out quakes etc.. What type of likely scenarios is AI modeling in the Aegean? Might continue or it may stop; there could be a large earthquake or, less likely, volcanic activity…
Disregard my previous idiotic comment :) What an awesome article!
Haha, no worries! We do sometimes make mistakes and are grateful to readers who make the effort to check our work. And, thanks! :)
Hi Kyle, I completely agree with this interpretation. The NE-trending Ios Fault Zone appears to be a key factor in this seismic swarm. The concentration of seismicity at 10–15 km depth aligns well with the fault’s downward extension. One possible explanation is that fluids—potentially hot—are migrating along trough faults, parallel to the maximum horizontal stress axis (NE). These fluids could be altering the effective stress conditions on the faults, bringing them closer to failure and triggering seismic activity.
Hi Leonidas! It's great to hear from you. I fondly recall a trip we made together in Greece - were you showing me the Itea-Amfissa Detachment? We stayed with an old man who made the best croquettes with local honey for breakfast. I also saw your recent paper on the Northern Giona Fault Zone, which I recall seeing from the floor of the valley below. Your pictures of the fault in outcrop take me straight back to Greece. I hope things are well with you. Anyway, thanks for the comment on the Ios Fault Zone. I always like writing about Greece, but I want to be sure that the views of the local experts are respected. So please do comment anytime. It will be interesting to see how this seismic crisis resolves, and I'm sure that there will be a lot of interest in tying the recorded events to the real faults in the subsurface. Cheers - Kyle
Thanks again for the update on this swarm! Question: Often people have the misconception that small or moderate earthquakes “relieve stress” on major faults to the extent that they prevent major earthquakes from happening. They’re told by seismologists that it would take thousands of such earthquakes to relieve enough stress to theoretically prevent a larger quake…So, the question is, if there have been over 8,000 earthquakes of all magnitudes in this swarm over a certain area, is it possible that stress has been reduced, perhaps in the Amorgos fault zone?
Hi Nancy, that is indeed a common thought process. It is true that small earthquakes do release a small amount of stress on their faults, possibly reducing the size of later earthquakes - maybe. However, for this to have an effect on the actually big earthquakes, there would have to be a huge number of events across the lower magnitudes. I quickly calculated that all of the earthquakes in the swarm to date (as reported by EMSC, who has a pretty good database of events) only add up to an equivalent single earthquake of Mw=6.02. So, if a Mw7.0 earthquake were to eventually happen (and this isn't saying that it will), then the energy released thus far would only be about 3.4% of that earthquake's energy release. So maybe the effect of the swarm will be to delay a large earthquake by a few decades. However, it is also not at all clear to me whether stress is actually being relieved on the big faults that might rupture with a big earthquake, or is being transferred onto those big faults by rupture of nearby faults. We tend to think that having more earthquakes in general leads to a higher probability of triggering a larger event. In the end, we don't know the real stress states of these faults, and I think we will only find out what is happening down there by seeing what really ultimately occurs! Sorry if it's not a very conclusive answer...
Kyle, Thank you for the response. So, I guess there are no definitive answers yet until whatever happens, happens…I’m wondering if there has been any historical precedence for a swarm scenario very similar to this with moderate spaced out quakes etc.. What type of likely scenarios is AI modeling in the Aegean? Might continue or it may stop; there could be a large earthquake or, less likely, volcanic activity…
Hi Manos, I don't believe that is the case. What makes you think it is backwards?
Forgot to say, thanks for an awesome article!