In-Situ Ambient Vibration Modal Analysis of Saguaro Cacti (Carnegiea Gigantea)

Each saguaro was temporarily instrumented with a Raspberry Shake 3D seismometer. The Raspberry Shake 3D is a low-cost and light-weight three-component seismometer that has been extensively benchmarked against other instruments (e.g., Arosio et al., 2023). It records three mutually-orthogonal components of motion (two horizontal and one vertical) using 4.5 Hz geophones with range electronically extended down to at least 0.5 Hz, at a sampling rate of 100 Hz, and internal data storage. I devised a custom mounting bracket for this study consisting of a 3D-printed platform that could be strapped to a saguaro stem and leveled about 1.5 m above ground level. The mounting height was arbitrary, being as high as feasible without requiring a ladder, and the method ensured that no damage was caused to the cactus. A small portable battery provided power.