Richter mortis

With the death toll from the Italian earthquake likely to exceed 300, the aftershocks continue. More than 1,000 have been detected since the quake struck the epicentre, the town of Accumoli.

Bad as it was, the final tally is far from being the worst.

In recent times that dubious record goes to the quake which struck Haiti in January 2012, where official estimates were that 316,000 people died.

The Accumoli quake had a magnitude of 6.2 as measured by the Richter scale. A comparably powerful quake, 6.0, struck the city of Skopje, in the former Yugoslavia, in July 1963, which destroyed 75% of the buildings and killed 1,100 people. The Haiti quake had a magnitude of 7.0.

The Richter scale was created in 1935 by two seismologists, Charles Francis Richter and Beno Gutenberg, who were staff at the California Institute of Technology. It was superseded in the 1970s by the ‘moment magnitude scale’ or MMS, which measures earthquakes with a magnitude greater than 8, beyond the Richter scale capacity. There are millions of small quakes across the world every year, with magnitudes less than 2.0. While the mass media persists in referring to the Richter scale it’s more accurate to refer to the MMS.

The Accumoli quake is more common than might be imagined – about 100 such events happen each year. But it is categorised as strong and was felt hundreds of miles from the epicentre.

With magnitudes of 9.0 and above complete destruction is to be expected across a wide area. Fortunately such events rarely happen – perhaps every 50 years.

The Chicxulub crater in Mexico, 110 miles wide and 12 miles deep, created by the impact of a 6 mile wide meteor around 66 million years ago, caused an earthquake estimated to have a magnitude of 13.0 MMS. Many think this caused the mass extinction that destroyed dinosaurs.

A magnitude 15.0 earthquake would be likely to completely destroy the Earth.

It’s no comfort to those in Accumoli – but maybe the rest of us got off lightly, this time.


Picture source: Mario Fornasari from Ferrara via Wikimedia