INGV research has revealed differentiated seismic behavior in the Alto Tiberina faults. The results represent an important contribution to the understanding of regional seismicity
A new study conducted mainly by a team of researchers from the National Institute of Geophysics and Volcanology (INGV) has led to interesting discoveries on the seismic behavior of the Alto Tiberina fault system, i.e. the complex system of faults existing in the Upper Tiber Valley Tiber, in the territory between the sources of the river on Mount Fumaiolo up to the municipality of Umbertide (PG), between Tuscany, Umbria and Marche. Research “Statistically significant difference between earthquake size distributions of independent and triggered seismicity” has just been published in a renowned scientific portfolio journal Nature.
“The objective of the research was to examine in detail the seismic behavior of the different faults of the Alto Tiberina system in order to identify any differences between the main fault and the secondary faults", explains Matteo Taroni, first author of the study.
"Two different zones of the Alto Tiberina fault system exhibit significantly different seismic behaviors. The main fault, which reaches deeper, shows seismicity characterized by solitary events, and a higher percentage of small magnitude events. On the other hand, shallower secondary faults exhibit seismicity with events occurring in swarms and a lower percentage of small magnitude events”, continues the researcher.
The team conducted the investigation using a high-definition seismic catalog covering the period between 2010 and 2015. Thanks to INGV's TABOO project, which installed numerous seismic stations in the study area, it was also possible to record earthquakes of very low magnitude, allowing a detailed analysis of seismic behavior.
"Sophisticated statistical methods, including an algorithm, were applied to analyze seismic data and obtain significant information on fault characteristics", added Rodolfo Console, member of the research team and developer of the algorithm.
The absolutely novel element of this research lies in the connection between two aspects of seismicity: the temporal one, which concerns solitary events and "clustered" ones (i.e. which occur in swarms), and that relating to the distribution of earthquake magnitudes, note as the Gutenberg-Richter law. These two aspects are closely related in the Alto Tiberina fault system.
"Our results provide a more in-depth view of the seismic behavior of faults in the Alto Tiberina area and represent an important contribution to the understanding of regional seismicity", underlined the researcher Matteo Taroni.
Given that the study was conducted on earthquakes of relatively low magnitude, between 0.5 and 3.9, the authors underline that further research will be necessary to evaluate whether the same properties are also present in events of higher magnitude, potentially damaging to structures.
"The next steps of our research will include studying seismic zones with higher magnitude earthquakes, such as oceanic subduction zones in South America, Japan and Indonesia", concludes Rodolfo Console.
Link to the study: .
Quote: Taroni, M., Console, R., Montuori, C. et al. Statistically significant difference between earthquake size distributions of independent and triggered seismicity. Commun Earth Environ 5 (193).
figure. Section of the Alto Tiberina fault system; the main fault is indicated by the dashed blue line, the secondary ones are in the most superficial part. On the horizontal axis there is the distance from the beginning of the section, on the vertical one the depth (both in kilometers). The points are the hypocenters of the earthquakes. Top: solitary (yellow) and clustered (blue) events. Bottom: areas where there is a higher (yellow) and lower (blue) percentage of small events. From the figure you can appreciate how the two aspects are connected to each other.