Earthquake kills two in the Italian island of Ischia.

The United States Geological Survey recorded a Magnitude 4.2 Earthquake at a depth of 9.3 km, roughly 4 km to the north of the island of Ischia, in the Gulf of Naples, Italy, slightly before 7.00 pm local time (slightly before 10.00 pm GMT) on Monday 21 August 2017. Surprisingly for such a small event the Earthquake caused a large number of buildings to collapse on the island, leading to two confirmed deaths and many being injured. Around 2500 people are thought to have been made homeless by this event.

A young victim of the 21 August 2017 Ischia Earthquake being evacuated to hospital after being dug from rubble the day after the event. Yahoo News.

Historically Italy has suffered a significant number of devastating Earthquakes that lead to large numbers of casualties, though in recent decades the country has made serious attempts to prevent this, with better warning systems and tighter building regulations, though the large number of historic buildings in Italy, which cannot easily be replaced (and any attempt to do so would be unlikely to succeed due to their high cultural value), meaning that the country is unlikely to be completely risk free any time soon.

The approximate location of the 21 August 2017 Ischia Earthquake, USGS.

However the large number of building collapses and casualties on Ischia this week has raised concerns about building safety there, as a Magnitude 4.2 Earthquake would not be expected to cause much damage to buildings in areas where Earthquakes are rare, and is alarming in an Earthquake-prone developed country such as Italy. The problems are being blamed on lax enforcement of planning regulations on the island, with many properties being built without any formal permission or reference to planning regulations, predominantly by landlords who typically then let out the buildings as holiday accommodation.

A damaged building on the island of Ischia folowing the 21 August 2917 Earthquake. Ciro De Luca/Reuters.

Italy is in an unusual tectonic setting, with the west of the country lying on the Eurasian Plate, but the east of the country lying on the Adriatic Plate, a microplate which broke away from North Africa some time in the past and which is now wedged into the southern margin of Europe, underlying eastern Italy, the Adriatic Sea and the west of the Balkan Peninsula. This, combined with the northward movement of the African Plate into Italy from the south, leads to uplift in the Apennine Mountains that run the length of the country, and makes Italy extremely prone to Earthquakes.

 Map showing the tectonic plates underlying Italy and southern Europe, and the location of the l'Aquila Earthquake. Napoli Unplugged.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

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