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

• Main Author: M. Mucciarelli
• Format: Article
• Language: English
• Published: Istituto Nazionale di Geofisica e Vulcanologia (INGV) 2005-06-01
• Series: Annals of Geophysics
• Subjects: earthquake statistics; Molise earthquake
• Online Access: http://www.annalsofgeophysics.eu/index.php/annals/article/view/3200

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%.