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The Azores Fault Zone
by Frank Hoogerbeets

4 November 2016

Since 26 October no less than 28 M4+ quakes have accompanied the three main tremors in Central Italy, plus an additional M4.3 in Southern Italy 261km deep on the 29th. This is not counting the numerous smaller aftershocks below M4.

It is a lot of continuous shaking along the Apennines fault in a relatively small area. No doubt the fault to the North and South is affected, which means seismic shifts in other parts of Italy will occur sooner or later.

In the last 12 months we have seen some strong earthquakes in the Mediterranean from Greece to Gibraltar. Since November 2015 there have been 9 earthquakes with magnitudes between 5.5 and 6.6.

If we consider this activity in the Mediterranean, plus the M7.8 earthquake in Ecuador last April, which put more pressure on the Mid and North Atlantic Ridge as well, one area in between stands out because of its silence and sub-ducting nature. It is part of the Azores fault zone, a fault line running from Southern Spain/Portugal to the Azores.

The most recent large earthquake in the Azores fault zone had magnitude 8.0 and occurred on 25 November 1941. A much more powerful earthquake occurred on 1 November 1755 with an estimated magnitude between 8.5 and 8.7. It is often referred to as the Great Lisbon Earthquake.

Like the Cascadia subduction zone, which had its last great one in 1700, the Azores fault zone seems due as well, but it is much less mentioned by scientists.

There is no way to know when an area is going to crack, but we can be aware of the potential hazard where we live and prepare ourselves accordingly.

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