What is a surprise earthquake? The example of the 2002, San Giuliano (Italy) event

M. Mucciarelli


Both in scientific literature and in the mass media, some earthquakes are defined as «surprise earthquakes».
Based on his own judgment, probably any geologist, seismologist or engineer may have his own list of past «surprise
earthquakes». This paper tries to quantify the underlying individual perception that may lead a scientist to
apply such a definition to a seismic event. The meaning is different, depending on the disciplinary approach. For
geologists, the Italian database of seismogenic sources is still too incomplete to allow for a quantitative estimate
of the subjective degree of belief. For seismologists, quantification is possible defining the distance between an
earthquake and its closest previous neighbor. Finally, for engineers, the San Giuliano quake could not be considered
a surprise, since probabilistic site hazard estimates reveal that the change before and after the earthquake
is just 4%.


earthquake statistics;Molise earthquake

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DOI: https://doi.org/10.4401/ag-3200

Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X