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

Umbria-Marche region (Central Italy) has been interested by a seismic sequence, which caused a large amount of damage within an extensive area (around 5000 km²). The sequence produced eight shocks with magnitude higher than 5.0, the largest of them occurring on September 26, UTC 09:40, M₁ = 5.8. The 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 month. Such seismic behavior motivated field operators to perform a real-time macroseismic survey to update the data set. One of the major objectives was to differentiate the effects pertaining to each of the largest shocks. In this paper we present the macroseismic survey performed during the sequence, along with some preliminary results inferred. Intensity points of seven of the main shocks are shown, together with the filtered macroseismic fields produced following the application of specific statistical methods. Finally, consideration is given to the comparison of these study results with corresponding tectonic and geological data.