Extended sources of the main events of the Umbria-Marche (1997) seismic sequence inverted from geophysical data

M. E. Belardinelli


The three largest events of the 1997 Umbria-Marche (Italy) sequence occurred on September 26, 1997 at 00:33
GMT (Event 1, MW=5.7) and 09:40 GMT (Event 2, MW=6.0) in the Colfiorito area and on the October 14, 1997
at 15:23 (Event 3, MW=5.6) in the Sellano area. The availability of different sets of geodetic and seismological
data allowed several studies to characterize the extended sources of events 1-3. In this work, I review some of
the studies that obtain the properties of the seismic sources by inversion of available data. Generally these studies
assume the seismic sources as dislocations or distributions of equivalent point sources in elastic half-spaces.
Following their chronological order, they model increasing complexities of the sources by using an increasing
number of data. Some of the differences between results obtained, such as the top edge depth estimates, are
shown to be due to the different approaches used. Commonly a 1-D crustal model is used in inverting strongmotion
data. Instead homogeneous elastic half-spaces are mainly assumed in inverting geodetic data to obtain
the three main sources of the 1997 Umbria-Marche sequence. Assuming the same crustal structure is important
to make comparable results obtained analyzing seismological data or geodetic data separately, as it has been
done till now for this sequence.


DInSAR;GPS;strong-motion;teleseismic data;seismic source

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DOI: https://doi.org/10.4401/ag-3030
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X