CNR and INGV researchers have identified the source fault of the Amatrice earthquake by analyzing the permanent movements of the ground identified with the Japanese satellite ALOS 2. A spoon-shaped lowering of the ground has been highlighted, with a maximum value of about 20 centimeters in the area of Accumoli. The source fault of the Amatrice earthquake is located a few kilometers deep in the area between Amatrice and Norcia
In the post-earthquake emergency, the Civil Protection Department, from the very first hours after the earthquake, has activated its centers of expertise in the sectors of seismology and radar data processing satellites – National Research Council (Institute for Electromagnetic Sensing of the Environment, CNR-IREA of Naples) and of the National Institute of Geophysics and Volcanology (INGV) - for a data analysis satellites aimed at measuring the movements of the ground triggered by the tremors and at studying the sources seismic.
"Using data from the Japanese satellite ALOS 2, obtained through scientific projects, a team of researchers from CNR and INGV measured with high precision the permanent movements of the ground originating during the earthquake, using the Differential Interferometry technique", explains Riccardo Lanari , director of the CNR-IREA. “It allows, by comparing radar images acquired before the event with images after the earthquake, to detect deformations of the ground surface with centimeter accuracy. In particular, a spoon-shaped lowering of the ground was highlighted which extends for about 20 km in a northerly direction and has a maximum value of about 20 centimeters in correspondence with the Accumoli area”.
Deformation map obtained by processing, with the Differential Interferometry technique, the radar images of the ALOS 2 satellite acquired on 09/09/2015 (pre-event) and 24/8/2016 (post-event); the red area highlights the area affected by the lowering (removal from the radar) due to seismic events, which reaches about 20 centimeters in correspondence with Accumoli.
The ground movement map was then used to develop physical-mathematical models of the fault that originated the earthquake. The faults can be visualized as fracture planes along which the two blocks of the earth's crust slide: when the movement is very rapid, an earthquake is generated. “The source fault of the Amatrice earthquake is located a few kilometers deep in the area between Amatrice and Norcia, passing under Accumuli. It is a fracture plane approx
25 km that plunges towards the southwest (towards Rieti) with an inclination of 50°. This plane corresponds to a fault already partly known from surface geological studies”, explains Stefano Salvi of INGV. "Detailed knowledge of the position and characteristics of seismic sources is a fundamental element for emergency management and is also important for drawing up increasingly reliable seismic hazard maps".
Preliminary localization of the fault plane that generated the Amatrice earthquake. The rectangle represents the surface projection of the fracture plane, the colors indicate the amount of sliding that occurred during the fracture (values in metres). Also shown are the two major events of the sequence on 25/8 (red pentagons) and all reruns up to 25/8 (white circles).
The objective of the Civil Protection Department, during a seismic emergency, is to quickly obtain a synoptic picture of the deformations and displacements of the ground caused by the earthquake in the epicentral area. These results are the result of the long and consolidated collaboration promoted by the Department between its Centers of Competence - in this case CNR-IREA and INGV. Based on their expertise, these centers support the DPC in using satellite data and information and integrating it with in situ data; this activity has allowed the development of products, methods and procedures that have improved the capabilities of the national emergency alert and response system. The results from this first interferometric monitoring are available for the entire National Civil Protection System through the Civil Protection Department, engaged in the coordination of emergency management.