Giuseppe Mercalli

On this day in history: Giuseppe Mercalli – seismologist – died

History of Italy

Giuseppe Mercalli was one of Europe’s leading authorities on earthquakes and volcanic activity. He died on 19th March 1914 in a fire at home.

The seismologist and volcanologist Giuseppe Mercalli died in a fire at his home in Naples on this day in 1914. At the time he was director of the Vesuvius Observatory. He developed a scale for determining the strength of earthquakes according to the intensity of shaking.

Initially considered an accident, it was later suggested he may have been strangled after disturbing an intruder, who then soaked his clothes in petrol before setting light to them.

Best remembered for the intensity scale for measuring earthquakes named after him, Mercalli was initially an ordained priest. He left the priesthood and the Italian government appointed him a professor at Domodossola in Piedmont. Later he had a post at Reggio di Calabria.

Mercalli was professor of geology at the University of Catania in the late 1880s, with a post at the Naples University in 1892. He became director of the Vesuvius Observatory in 1911.

The Mercalli Scale

While studying seismic activity in Italy, Mercalli had limited access to seismic instrumentation. Most of his information came from personal accounts and observations of damage. To provide consistency in his analyses, he created a measurement of the relative effects of each event.

He first developed a scale with six degrees, with the most disastrous earthquakes given an intensity of six. However, he felt there was not enough precision in this scale.  Another intensity scale called the deRossi-Forel scale was gaining in prominence at the same time. That had the advantage of 10 degrees of intensity, although Mercalli felt it lacked meaningful description.

In 1902, Mercalli modified this 10-degree scale to include the detail he desired. His new scale caught on among European scientists, and is still used in a modified form today – known as the Modified Mercalli Intensity Scale.

Mercalli observed eruptions of the volcanoes Stromboli and Vulcano in the Aeolian Islands. It was his descriptions of these eruptions that became the basis for two indices in the Volcanic Explosivity Index: 1 – Strombolian eruption, 2 – Vulcanian eruption.

He also catalogued Italian earthquakes, producing the book – I vulcani e fénomeni vulcanici en Italia.

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