Preliminary results of a macroseismic survey of the Colfiorito sequence (Central Italy)

Umbria-Marche region (Central Italy) has been interested by a seismic seque nce, which caused a large amount of damage within an extensive area (around 5000 km(2)). The sequence produced eight shocks with magnitude higher than 5.0, the largest of them occurring on September 26, UTC 09:40, Ml = 5.8. T he incidence of many shocks with a magnitude higher than 4.0 contributed to the creation of a damage pattern that was in evolution for more than one m onth. Such seismic behavior motivated field operators to perform a real-tim e macroseismic survey to update the data set. One of the major objectives w as to differentiate the effects pertaining to each of the largest shocks. I n this paper we present the macroseismic survey performed during the sequen ce, along with some preliminary results inferred. Intensity points of seven of the main shocks are shown, together with the filtered macroseismic fiel ds produced following the application of specific statistical methods. Fina lly, consideration is given to the comparison of these study results with c orresponding tectonic and geological data. (C) 1999 Elsevier Science Ltd. A ll rights reserved.