Earthquakes: a study on the role of water accumulated in karst aquifers offers new insights for analyzing seismic activity

29.11.2024

A recently published study in the scientific journal 'Nature Communications', titled "Non-linear elasticity, earthquake triggering and seasonal hydrological forcing along the Irpinia fault, Southern Italy" provides innovative insights into the processes connecting the seasonal variation of water masses, the elasticity of crustal rocks, and seismic activity in Irpinia.

The research, conducted within the multidisciplinary project Dynamic Planet-MYBURP (Modulation of Hydrology on Stress Build-up on the Irpinia Fault), was carried out by a research team from the University of Padua, the National Institute of Geophysics and Volcanology (INGV), the University of Naples Federico II, and the Acquedotto Pugliese company.

"Our study revealed how hydrological effects influence the mechanical characteristics of the fault system in Irpinia and the temporal distribution of its seismicity" explains Nicola D'Agostino, INGV researcher and coordinator of the research team. "To discover this, we analyzed the seasonal variations in the speed of seismic waves in the Earth's crust and the time series of deformation from an advanced network of seismic and GNSS stations of the Irpinia Near Fault Observatory and the GNSS RING Network."

It was found that the hydrological recharge of the karst aquifers in the Apennines generates natural deformations that modulate the speed of seismic waves and local seismicity. Through an innovative technique of analyzing ambient seismic noise, it was possible to measure the seasonal variations in the speed of seismic waves passing through the Earth's crust and compare them with measurements of crustal deformation induced by hydrological effects.

"These two pieces of information allowed us to measure the variations in the speed of seismic waves as a function of crustal deformation, an important parameter for quantifying the non-linearity of the elastic properties of rocks," emphasizes Stefania Tarantino, INGV research fellow and first author of the article.

Piero Poli, professor at the University of Padua and co-author of the article, adds, "Laboratory observations show how the elastic properties vary based on the deformation state of the materials (non-linear elasticity), with significant implications for the mechanical characteristics with which fault rocks respond to the accumulation of deformation preceding earthquakes. The observed sensitivity was similar to the values measured in the laboratory, confirming the validity of the scientific approach adopted."

"Our observations also show an increase in low-magnitude seismic events (M < 3.7) in spring-summer, when the hydrological load is greater, suggesting that non-linear elasticity may play a key role not only in minor seismic phenomena but also in the preparation of large-magnitude earthquakes, such as the one that struck Irpinia in 1980," emphasizes Aldo Zollo, professor at the University of Naples Federico II and co-author of the article.

Gaetano Festa, Professor at the University of Naples Federico II and co-author of the article, adds that "the geographical area studied is now monitored by an advanced multiparametric infrastructure called the 'Irpinia Near Fault Observatory,' consisting of seismic, geodetic, and geochemical stations, as well as a seismic detection system using fiber optics (DAS), managed by INGV and the University Federico II."
An important aspect of the work was the synergy with the Acquedotto Pugliese company, an important public infrastructure for water supply in the Puglia region and manager of the Sanità Spring in Caposele, which provided essential data for understanding the relationship between hydrological effects and crustal processes.
The results of this study offer new perspectives for better understanding and monitoring the processes of seismic deformation accumulation and release, with the aim of improving seismic risk mitigation techniques.