The seismic swarm of recent days has stopped, the surveys of the Ingv continue on the Bassano-Valdobbiadene-Vittorio fault
TREVISO. It seems that the seismic swarm that affected the Valdobbiadenese in recent days has stopped, but a “big one” cannot be excluded.
“We do not know if the seismic events of this sequence are foreshocks, that is, they precede a stronger event,” writes an October 3 report from the National Institute of Geophysics and Volcanology. “According to some statistical models there is an increase in the probability of a strong earthquake when an event, even as small as those that have been recorded, occurs, but the calculated probabilities are still low.”
No alarm, however, attention, for an area that has been monitored by the institution for over a decade and classified as having a high seismic risk. “It is well established that the vast majority of these sequences (between 95% and 99%) – let the Ingv know – end after a few days or weeks without a strong earthquake”. The institute carried out an in-depth analysis of the series of tremors that occurred in late September.
“The sequence is located in a region with a high seismic hazard – recalls Ingv – In addition, the seismic risk of the area is also high not only for the high seismic hazard, but also for the high exposure, due to both the population density and in the presence of one of the major industrial districts of the Northeast ».
Since 2009 Ingv has installed GPS stations to accurately measure the deformation levels. The detection systems are present on Mount Cesen near Malga Garda and Malga Mariech. “In the region affected by the sequence of the last few days, the convergence rates between these two plates are estimated between 1.5 and 2 mm / year – observe from the Institute of Geophysics – The rear chain is made up of a range of thrusts, the most recent of which they run under the Veneto-Friuli pre-Alpine front. The overthrust of Bassano-Valdobbiadene-Vittorio Veneto, or the more external and deeper one of Montello, could be responsible for the events of this sequence ».
A “big one” of magnitude 6.4 occurred in the area on February 16, 1695, the largest earthquake in the known history of Veneto. It is estimated to have caused 150 deaths. «From the analysis of GPS signals together with geological and seismological information – establishes a research by Ingv – it was possible to verify that the Bassano-Valdobbiadene and Montello faults are accumulating elastic deformation. The data are compatible with the ability to generate an earthquake of Mw 6.5 in about a millennium, apparently higher for the Bassano-Valdobbiadene fault than for the Montello fault ».
For the calculation of probabilities, therefore, residents can sleep peacefully. But always remembering the rules to be implemented in the event of an earthquake.
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