A Quick Survey of Local Amplifications and Their Correlation With Damage Observed During the Umbro-Marchesan (Italy) Earthquake of September 26, 1997

The seismic sequence that struck Central Italy during September and October 1997 caused severe damage (up to IX degree MCS). The most affected area is populated by several sparse, small-sized villages (some hundred inhabitants each). The damage pattern shows spot-like features, with strong variations on a short-scale range. Localised changes in the buildings' vulnerability may account for some of the effects observed, but it is likely that most of the variation may be attributed to site amplification effects. In any case, local amplification has to be estimated in order to allow engineers' to sort effects according to either cause. A series of field measurements were undertaken in the aftermath of the main event. Local geology appears to be the dominant factor in most of the damage observed, which can be linked to empirical amplification functions obtained with the Nakamura's technique. A tentative correlation is established between damage enhancement and amplification in selected frequency bands. Additional informationNotes on contributorsMARCO MUCCIARELLI∗ ∗e-mail: mmucciarelli@ismes.it GIANCARLO MONACHESI† †e-mail: geo@wmt.it