In July 1883, a destructive earthquake struck the small island of Ischia, west of Napoli in southern Italy. After the earthquake, the famous seismologist Giuseppe Mercalli reported on huge destructions in Casamicciola village, on geological effects of the earthquake, and produced one of the first macroseismic map, which is shown below. Mercalli accurately located the epicenter south of Casamicciola.
Find an illustrated poster (PDF) on the 1833 earthquake, by Napoli Osservatorio Vesuviano (INGV), and an overview of Giuseppe Mercalli biography and work by Andrea Tertulliani also from INGV (PDF of Tertulliani keynote). Giuseppe Mercalli is so famous as he eventually invented the first intensity scale called Mercalli intensity scale to describe and rate the sensible and destructive effects of earthquakes.
Maximum macroseismic intensities for the 1833 event are now reported to have reached IX-X level on the most recent scale used in Italy, as shown on the map below from INGV database of Italian past earthquakes.
This last summer, on August 21st, an earthquake of low-moderate magnitude (Mw~3.8) struck Ischia, making destruction nearly at the same place than in 1833. Though less destructive, and reaching intensities VIII only, this recent event made important damages in Casamicciola and nearby and killed two. You may read INGV report on this earthquake there.
The earthquakes affecting Ischia are of low-moderate magnitudes (typically Magnitude 4). But they are very shallow (few kilometers) for they are related to the island volcanic edifice and processes. Their shallowness and the amplification of seismic shaking at some sites explain their damaging effects. As well, the bad-quality of the houses, often illegally built, bear important responsibility. On this last issue read this piece quoting the president of Italian National Council of Geologists F. Peduto saying it's “allucinante morire di magnitudo 4”, you may also read this by Reuters.
