THE EARTHQUAKE SEQUENCE IN CENTRAL ITALY (AUGUST – OCTOBER 2016)
The earthquake that HAS had the most disastrous consequences on buildings ever recorded in Italy
The scientific report on the seismological and engineering characteristics of the most harmful events in the earthquake sequence is now online (by ITC-CNR, ReLUIS consortium, University of Naples Federico II and INGV).
The tragic earthquake of August 24 was only the onset of a far more energetic and destructive earthquake sequence. Apart from the human aspect, which remains the most sensitive and important issue to take care of, the news published by the press is generally unclear when not completely wrong. Too many illogical concepts are presented that have no technical grounds (e.g. sand/cement ratio in masonry constructions, purportedly dangerous reinforced concrete floors, constructive typologies seemingly safer than others, never applied “miracle” measures, etc.).
The researchers from ITC-CNR, along with the ReLUIS consortium, the University of Naples Federico II and ANV, have unceasingly worked on seismic data collected day after day and compiled a report comparing four of the strongest events recorded: Mw 6.0 on 24/08/2016, Mw 5.4 and Mw 5.9 on 26/10/2016, and Mw 6.5 on 30/10/2016. The report is subject to updating and revision in the coming days and is available at this link.
The objective is to provide a general overview of the main features of the events and ground accelerations recorded in the most affected areas. Simple indicators of the structural response associated with these signals are also given.
In case of high-magnitude earthquake events, epicentral areas are the ones with the highest concentration of structural damage. In the specific case, the magnitude 6.5 event of 30/10/2016, though not the most energetic occurred in Italy, was characterized by acceleration values, which, if confirmed, are the highest ever recorded in our country. Admittedly, unlike the past, the Italian accelerometric network is now much denser and, probably, previous measurements could not record the highest values of soil shake. The peak horizontal ground acceleration value recorded on October 30 was 0.96g: about as strong as the force of gravity!
It is also known that stiffer constructions are generally the most damaged in epicentral areas because of soil motion. This phenomenon, which occurred during the sequence concerned, added to the poor resistance of part of the affected built heritage structures. From this point of view, the occurrence of the magnitude 6.5 event following previous destructive events resulted in the collapse of many structures, also due to damage accumulation mechanisms, that “fortunately” occurred in areas that had already been evacuated, which helped to significantly reduce the loss of human lives.
ITC-CNR – Researcher
Prof. ing. Antonio Occhiuzzi
ITC-CNR – Head of Institute