Revising macroseismic data in Switzerland: The December 20, 1720 earthquake in the region of Lake Constance
Authors: Gisler, Monika; Fäh, Donat; Schibler, Reto
Source: Journal of Seismology, Volume 8, Number 2, April 2004 , pp. 179-192(14)
Abstract:Upgrading the Earthquake Catalog of Switzerland (ECOS) included revising the earthquake of 1720. This change has major importance for history and seismology.Although that quake has been the subject of several publications, none was based on critical methods. This re-evaluation of the event is built upon a new and more reliable database established after investigating archives and libraries. Using data from such historical sources, we assigned new site intensities, adopting the criteria established by the European macroseismic scale EMS 98 (Grünthal, 1998).We discovered that the event had been assigned an overestimated intensity, due to interpretation errors in former earthquake catalogs and compilations. We recommend reducing the intensity from I0= VIII to I0= VI (EMS 98). The moment magnitude is given as MW= 4.6. Since the event had been considered the largest for its respective area, downgrading it now will influence the seismic hazard assessment for this region.
Document Type: Research Article
Publication date: April 1, 2004