* Astronomy

In the Shadow of Vesuvius (1987)

Since the days of the Roman Empire, Italy's Mount Vesuvius has erupted more than 50 times, devastating whole cities and towns. In A.D. 79 it destroyed Pompeii and Herculaneum, burying people alive as they ran to escape the volcano's fury. Lost and forgotten for more than 1,600 years, the once-thriving trade center of Pompeii has been successfully uncovered by archaeologists. At Herculaneum, human skeletons were found in a fatal embrace. Although Vesuvius is sleeping now, this active volcano is never far from the minds of the two million people who live in its shadow.

In the year of AD 79, Mount Vesuvius erupted in one of the most catastrophic and famous eruptions of all time.
Small earthquakes started taking place on 20 August, 79 becoming more frequent over the next four days, but the warnings were not recognised.
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Title: Two-way coupling between Vesuvius eruptions and southern Apennine earthquakes, Italy, by elastic stress transfer
Authors: Concetta Nostro, Ross S. Stein, Massimo Cocco, Maria Elina Belardinelli, and Warner Marzocchi

During the past 1000 years, eruptions of Vesuvius have often been accompanied by large earthquakes in the Apennines 50-60 km to the northeast. Statistical investigations had shown that earthquakes often preceded eruptions, typically by less than a decade, but did not provide a physical explanation for the correlation. Here, we explore elastic stress interaction between earthquakes and eruptions under the hypothesis that small stress changes can promote events when the Apennine normal faults and the Vesuvius magma body are close to failure. We show that earthquakes can promote eruptions by compressing the magma body at depth and opening suitably oriented near-surface conduits. Voiding the magma body in turns brings these same normal faults closer to Coulomb failure, promoting earthquakes. Such a coupling is strongest if the magma reservoir is a dike oriented normal to the regional extension axis, parallel to the Apennines, and the near-surface conduits and fissures are oriented normal to the Apennines. This preferred orientation suggests that the eruptions issuing from such fissures should be most closely linked in time to Apennine earthquakes. Large Apennine earthquakes since 1400 are calculated to have transferred more stress to Vesuvius than all but the largest eruptions have transferred to Apennine faults, which may explain why earthquakes more commonly lead than follow eruptions. A two-way coupling may thus link earthquakes and Vesuvius eruptions along a 100-km-long set of faults. We test the statistical significance of the earthquake-eruption correlation in the two-way coupling zone, and find a correlation significant at the 95% confidence level.

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