THE 26 NOVEMBER 1920 VERGIATE EXPLOSION: A GEOPHYSICAL PERSPECTIVE ON SOUND AND SEISMIC WAVES

On 26 November 1920, a massive explosion at an electrochemical plant in Vergiate, northern Italy, generated strong acoustic and seismic waves that were recorded across a wide area. This event became a case study for early investigations into wave propagation, led by geophysicist Emilio Oddone, who documented both observational reports and seismographic data. In this study, we revisit Oddone’s original analysis in light of modern atmospheric and geophysical knowledge, comparing early 20th-century interpretations of sound propagation with contemporary models incorporating the role of atmospheric stratification, such as the ozone layer and thermosphere. We also re-examine the seismic data collected by Oddone from six stations and provide the first quantitative estimate of the event’s local magnitude, yielding ML = 3.45 ± 0.30. Our work recovers a historically significant case in seismology and illustrates how scientific interpretations evolve with advances in theory and instrumentation.