Since its first version (1995) the Catalogue of Strong Earthquakes in Italy (CFTI) has always paid great attention to the evolution of the shocks that occurred before (generally referred to as “foreshocks”) and after (“afteshocks”) the events that are considered as “principal” in the sequence. This was accomplished by dedicating a specific descriptive summary commentary to these secondary shocks. After the publication of the second version of the Catalog (1997), the SGA Working Group developed several specific analyses on the pattern of some of the strongest Italian historical earthquake sequences, such as those of 1693 in eastern Sicily, 1743 in Salento, 1783 in central and Southern Calabria. All the results were then made available to the INGV, thus highlighting the importance of knowing the chronological sequence of major earthquakes, of observing the multiplicity of earthquakes occurring in a limited area, and of evaluating the contribution of each individual shock to the overall picture of the effects.
Since the importance and abundance of this type of information has grown over the years, we decided to make this data more understandable and immediately usable for comparisons and for further processing. In 2018 we carried out a feasibility study by developing a method that, by extending the experiences described above, made it possible to transpose the available qualitative data into chronologies organized in tabular form, so as to allow a graphic representation of each single CFTI sequence.
By putting into play the multidisciplinary skills of the CFTI Working Group, and thanks to the triennial nature of the project currently being implemented as part of the activities envisaged by the INGV-DPC Agreement, annex B2 (2019-2021), Work Package 1, Task 1, we have set ourselves an ambitious but achievable goal: that of displaying all the earthquake sequences present in the CFTI with interactive graphs and maps, offering the possibility to consult them both for single shocks and for single locations while keeping the descriptive text comments visible. The need to include the effects suffered by individual locations that are currently not present in the Catalogue, for all shocks of each sequence including minor ones, made it necessary to develop a further structure of the CFTI database, which now allows for a more effective storage and use of such data.
An advanced consultation web interface that allows the simultaneous and interactive display of a time-line and a history map for the sequence being considered is currently being tested. A test version of this comparison tool, giving the possibility of consulting two earthquake sequences as a test of its capabilities, is available at the link: http://storing.ingv.it/cfti/cftilab/seq/
Interface of the seismic sequence analysis tool of the Catalogue of Strong Earthquakes in Italy. The example shows the 1929 Bolognese earthquake sequence.