NSFGEO-NERC: The central Apennines earthquake cascade under a new microscope

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Three strongly felt earthquakes of magnitude M>5.9 occurred within a 50 km source zone along the Central Apennines mountain chain in a period of just over 2 months. The first, on the 24th August M=6.0 earthquake killed 297 people, leaving the medieval villages of Amatrice, Accumoli and Pescara di Tronto devastated. On 26th October two large shocks of M=5.4 and M=5.9 (32 minutes after) struck ~30 km further north in the same region as the 1997 M=6.0 Colfiorito earthquake. The largest (M=6.5) event to date that occurred only four days later, on 30th October, caused severe damage to buildings at Norcia, including the historical cathedral of San Benedetto. The area has been struck by destructive earthquakes of significant magnitude in historical and modern times. This is the third catastrophic sequence to occur in the Central Apennines, with preceding sequences to the north (M=6.0 Colfiorito) and south (M=6.1 L'Aquila) in 1997 and 2009, respectively. Cultural heritage sites including word-famous medieval churches near Amatrice village, have suffered severe damage and total collapse in many cases.Within this post-disaster environment there is a clear need to improve our understanding behind the evolution of such sequences and to develop tools that can support informed decision-making in the future. Our research will be based on a unique high quality dataset that is a product of on-going UK-Italian collaboration involving the deployment of more than 85 seismic sensors at the affected area since last fall. This unprecedented observational capability enables us to capture the "breadth and depth" of seismicity leading to the large events within the sequence. Based on this dataset we will develop innovative methods to translate measurements into testable physical models for the underlying processes. We aim at developing a comprehensive earthquake catalog that includes precise locations, source parameters and focal mechanisms derived from algorithms that are able detect, locate and characterize even the smallest events. This new 'microscope' provides information that is crucial for unravelling the physical processes that underlie sequences such as the extended 2016 Amatrice/Norcia earthquakes in Italy. We will then use the high-accuracy catalog to formulate and test alternative earthquake triggering hypotheses and integrate those in the development and validation of testable forecast models using empirical and physics based models to ensure high predictability. The project brings together world-experts on earthquake detection, seismic source characterization, earthquake triggering and forecasting from US, UK and Italy in an effort to develop breakthrough approaches to address current challenges that not only impede our understanding behind earthquake processes but also weaken our scientific response in any post-earthquake disaster environment. In the course of our research we will involve further international initiatives such as CSEP (Collaboratory for the Study of Earthquake Predictability) to ensure transparent testing of our forecast models, and EPOS (European Plate Observation System) to maximize knowledge exchange and the scientific impact of the project in other countries. The new observational capability to detect, locate and characterize even the smallest magnitude events within few hours will find application to induced, geothermal and volcanic activity areas in US and Europe. We anticipate that the application of our research framework especially in high seismic hazard sites worldwide will enable future decision making with the same scientific standards across different operational and cultural environments.