US-Italy planning visit to develop a new international collaboration to improve understanding of fault mechanics and earthquake hazards

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Large and damaging earthquakes are caused by abrupt displacement (i.e., slip) across faults in the rocks near Earth's surface. However, not all slip across faults is abrupt. Indeed, for some faults, appreciable slip may occur without shaking the ground making them difficult to detect using traditional seismograph instruments. Understanding the difference between these two types of fault slip behavior is critical to our ability to gauge potential earthquake threats posed by active fault zones worldwide, including numerous hazardous fault zones in the United States. One of the best examples of a fault that appears to frequently slip with and without creating large earthquakes is the Alto Tiberina fault located in central Italy. The unusual geometry of this fault, which makes it among the most accessible faults in the world to studies using near surface observations, provides a unique opportunity to investigate the physical characteristics of faults that slide with and without violently shaking the ground. It is an ideal target for documenting the conditions under which faults pose the greatest threat of damaging earthquakes. The new collaboration that will be forged with support from the National Science Foundation Catalyzing New International Collaborations (CNIC) program sets the stage for the deployment of a network of modern strainmeter instruments designed specifically to detect small but diagnostic slip events on the Alto Tiberina fault across a very broad spectrum of fault behaviors. When combined with existing seismograph and geodetic technologies that have already been deployed by Italian partners, the new strainmeter network will allow for the first time measurements of the frequency, duration, and magnitude of sliding events, and their relationship to ground motion and earthquakes. The first task toward understanding fault slip behavior is the establishment of a Memorandum of Understanding outlining all aspects of the international collaboration, including: the roles and responsibilities for funding, siting, permitting, telemetry, data flow and archiving, routine site maintenance, data processing, and scientific collaboration. The formal collaboration that will be established will (1) enhance future research opportunities for early- and mid-career researchers from US-based institutions, (2) prepare the next generation of earthquake fault researchers in the United States, (3) provide future generations of United States scientists with significant professional experience beyond political borders early in their careers, and (4) generate a wealth of new information that will inform earthquake hazards assessments throughout the United States.