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Near-field recordings of large earthquakes and volcano-induced events using traditional seismological instrumentation often suffer from unaccounted effects of local tilt and saturation of signals. Recent hardware advances have led to the development of the blueSeis-3A, a very broadband, highly sensitive rotational motion sensor. We installed this sensor in close proximity to permanently deployed classical instrumentation (i.e., translational seismometer, accelerometer, and tiltmeter) at the Hawaiian Volcano Observatory (USGS). There, we were able to record three similar to Mw 5 earthquakes associated with large collapse events during the later phase of the 2018 Kilauea summit eruption. Located less than 2 km from the origins of these sources, the combined six-axis translational and rotational measurements revealed clear static rotations around all three coordinate axes. With these six component recordings, we have been able to reconstruct the complete time history of ground motion of a fixed point during an earthquake for the first time.

Plain Language Summary By combining a traditional seismometer with a fiber optic gyroscope adapted from navigation technology we record for the first time the complete dynamic history of a point motion during strong shaking close to the source of seismic signals. The collapsing crater of Kilauea leads to static displacements and rotations that help characterizing the geometry of the associated source processes.