- © 2015 by the Seismological Society of America
Online Material: Table of Mercalli–Cancani–Sieberg (MCS) intensities, onset times and associated phases, complete parameter sets for each 1951 location and computation of the isostatic stress variation due to unloading in the upper crust.
On the night of 15–16 May 1951, two moderate earthquakes with estimated magnitudes of Mw 5.4 and 4.5 occurred in northern Italy, about 40 km southeast of Milan, close to the small town of Caviaga. They were recorded by several observatories worldwide, as reported by the International Seismological Summary (ISS) On‐Line Bulletin (ISS, 1951; International Seismological Centre [ISC], 2011). Despite the moderate magnitudes, these two events caught the attention of seismologists and have been studied in detail, in particular by Caloi et al. (1956), because they were close to Caviaga in an area that was assumed to be aseismic. Moreover, their shallow hypocenters (∼5 km in Caloi et al., 1956) indicated a possible anthropogenic source, related to wells for gas withdrawal (Fig. 1; see Data and Resources).