VIBRATION OF ROCK ARCHES AND TOWERS STIMULATED BY ANTHROPOGENIC TRANSIT ACTIVITY

Over the past few decades, dozens of rock arches and towers have collapsed, including many notable landforms: Wall Arch (2008, Arches National Park, UT), The Cobra (2014, Moab, UT), Azure Window (2017, Malta), and Punta Ventana (2020, Puerto Rico). As human activity increasingly alters the vibration wavefield of the Earth, the impacts of this added energy on culturally valuable rock landforms poses a growing concern. We assess the effects of various anthropogenic vibration sources—helicopters, semi-trucks, and trains—on the stability of arches and towers. Our results from helicopter flights at the sites of eleven rock arches and towers indicate the size, geometry, material properties, and alignment of the landform’s natural frequency with incoming helicopter infrasound determine the level of induced vibration in each landform. We find a broader range of landforms are sensitive to ground-borne vibrations from nearby trucks and trains. We compare the vibrations of arches located in environments with minimal anthropogenic vibration sources with those of arches situated in areas experiencing high levels of man-made energy. Our data show arch vibrations in anthropogenically-active areas reach high velocities (>0.1 mm/s) nearly 100 times more frequently than arches located in quiet areas. While we have not measured vibration levels in rock arches or towers that are considered instantaneously damaging, we explore implications of these landforms’ repeated exposure to anthropogenic vibration sources over time.