The causes and activation methods of earthquakes that periodically affect the island of Ischia revealed by an international team of researchers
After the seismic events that affected the Casamicciola area of the island of Ischia in the summer of 2017, the scientific community deemed it necessary to focus its attention on the natural phenomenon which, in reality, had already occurred several times in the past centuries with sometimes dramatic consequences, such as the 1883 earthquake which caused over 2300 victims.
However, the understanding of seismic activity on Ischia has always been hindered by the volcanic nature of the island which, with extremely diversified characteristics, greatly complicates the factors to be considered. Ischia is, in fact, one of the most complex Italian volcanoes, characterized among other things by an impressive uplift of about a thousand meters, starting from 55 years ago, and by dozens of more recent eruptions, the last of which occurred in 1302.
Taking up the challenge of understanding this seismicity in such a complex environment, also at the instigation of the National Civil Protection, an international team of volcanologists from the National Institute of Geophysics and Volcanology (INGV), the University of Roma Tre (UniRoma3) and the Université de Genève in Switzerland (UNIGE) combined diversified expertise in monitoring, modeling and understanding magmatic processes in the study 'Magma Degassing as a Source of Long-Term Seismicity at Volcanoes: The Ischia Island Case', just published in the magazine Geophysical Research Letters.
Volcanologists have thus understood that, paradoxically, it is precisely the complex volcanic nature of the island that explains its seismicity, but in a relatively simple way. In fact, monitoring data collected over decades show that the strong uplift that in the past led to the emergence of the highest peak of the island, Mount Epomeo, is currently replaced by a slow and continuous lowering.
Therefore, the earthquakes observed in Casamicciola constitute episodes of acceleration of this lowering, triggered by the same seismic structures that had caused the previous uplift of the island.
The cause of the lowering of Ischia, and therefore of the Casamicciola earthquakes, is attributable to the emission of gas from the same magma which for about 6000 years has produced at least 45 eruptions, up to the last one in 1302. This degassing, in fact, decreases the pressure in the superficial magma system, effectively lowering the island.
The results of the research not only allow us to finally understand the origin of the disastrous seismicity of Ischia, but also to predict, through model extrapolations, that the prolongation of the degassing of the magma can continue for at least several hundred years.
According to the authors, the lowering in progress in Ischia will therefore be able to continue to generate seismicity in the Casamicciola area with similar characteristics to what has been observed in recent centuries
#ingv #uniroma3 #unige #ischia #casamicciola #earthquake #volcano
Link to the article: