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

巨大的破坏性地震是由近地表岩石中断层的突然移位(即滑动)引起的。然而，并不是所有跨越断层的滑动都是突然的。事实上，对于一些断层，可能会在不震动地面的情况下发生明显的滑动，这使得使用传统地震仪仪器很难检测到它们。了解这两种类型的断层滑动行为之间的差异，对于我们评估全球活动断裂带(包括美国众多危险断裂带)构成的潜在地震威胁至关重要。位于意大利中部的Alto Tiberina断层似乎经常在发生或没有引发大地震时滑动，这是一个最好的例子之一。这条断层不同寻常的几何形状，使其成为世界上最容易使用近地表观测进行研究的断层之一，这为研究在剧烈震动地面和不剧烈震动的情况下滑动的断层的物理特征提供了独特的机会。它是记录断层对破坏性地震构成最大威胁的条件的理想目标。在国家科学基金会催化新的国际合作(CNIC)计划的支持下，这项新的合作将为部署现代应变计仪器网络奠定基础，该网络专为探测Alto Tiberina断层上非常广泛的断层行为的微小但诊断滑动事件而设计。当与意大利合作伙伴已经部署的现有地震仪和大地测量技术相结合时，新的应变仪网络将首次能够测量滑动事件的频率、持续时间和震级，以及它们与地面运动和地震的关系。理解断层滑动行为的第一项任务是建立一份谅解备忘录，概述国际合作的所有方面，包括：资金、选址、许可、遥测、数据流和存档、日常现场维护、数据处理和科学合作的作用和责任。将建立的正式合作将(1)为来自美国机构的职业生涯早期和中期的研究人员增加未来的研究机会，(2)为美国的下一代地震断层研究人员做好准备，(3)为未来几代美国科学家提供在其职业生涯早期超越政治边界的重要专业经验，以及(4)产生丰富的新信息，为全美的地震危险评估提供参考。

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.