14 comments on ““And Fire Exploded from Seven Places…” – SÃO JORGE – Azores Part 6

  1. Kilauea summit earthquake ciycles in June so far. Average recurrence time for the daily large quake (~M5) is 24.84 hours (24 hours and 51 minutes).

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    • You know, that 24h 51′ change in large earthquake is very close to the tidal timing. Tides lag a bit and take around 12h 25′ for a single cycle. Interesting coincidence? Cheers –

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      • Yes, I had thought of this too; it sure looks weird. But, if you look at the plot, you see that the time spans have decreased over time. If they decrease further (or increase again) that average will change. And, thinking logically, a strong EQ occurs when enough internal gas pressure has built up from the degassing magma to break through the blocked surface. I believe it would make no sense to connect it to tides. You never know, though; this eruption will bring about a wealth of new research results, I look forward to seeing the ones about the EQ cycles.

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  2. Sierra Negra volcano, Isla Isabela, Galápagos: IGEPN Special Rep. No. 7: New swarm of earthquakes began. Depths vary between 3 & 5 km and max. magnitude was 4.6. Although IGEPN say it “could be the precursor of an eruption”, they may not declare an eruption before someone had actually seen it erupt. To my squinting eyes it looks like an eruption has already started… 😉 could be wrong, though.
    https://www.igepn.edu.ec/servicios/noticias/1596-informe-especial-volcan-sierra-negra-n-7-2018

    Edit:
    Reports state that people begun to hear noise from the volcano after an EQ at 13:40 GT. The above seismogram ends at 13:05 GT. So, unless the eruption started quietly, what we see is not the beginning of it. Therefor my squinting eye was wrong. 🙂

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    • Something interesting happening on the lower right hand corner of the plot? Lots of earthquakes centered around there 38 30′ – 38 00′ and 27 00′ – 26 30′. Need to review how the islands grew (west to east? / north to south? / something else?). Cheers –

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      • The MAR is in the west, so the oldest islands are E. But we know this area IS active. S. Miguel is ~150 km SE of the quakes and it has active volcanoes. You’d have to look up a fault map. The main rifts and faults go NW-SE. Find one that cuts in an angle, and if the quakes are where the two faults cross there might be volcanic action. If there are no crossing faults near, they’re probably just the usual rifting events.

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      • You know, I think it’s at or near the Castro Bank. Has not one of the VC guys written a post about that as a place to watch out for?

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        • Which would make it about a third of the way SE along the main rift from Terciera to Sao Miguel. I did a post on Azores tectonics. Completely missed the Castro Bank, though. Looks like generally, the farther east you get, the older the island. The closer you get to the MAR the younger. For some reason, seismicity since 1900 does not necessarily correspond with island age or volcanic activity. Lots of quakes along the North Azores Fracture Zone as it approaches the junction with the East Azores Fracture Zone. Something interesting is clearly going on. Cheers –

          https://volcanohotspot.wordpress.com/2016/03/19/azores-part-2-tectonics/

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