Quantifying surfcam imagery to measure the 2022 Hunga Tonga-Hunga Ha'apai tsunami along the California coast

On January 15, 2022, the eruption of the Hunga Tonga-Hunga Ha'apai volcano created a tsunami that reached a height of 20.5 m in the near field. The tsunami impacted the entire Pacific Ocean basin and was the largest tsunami to impact California since the 2011 To over bar hoku tsunami. Videos recorded on surfcams during the event were downloaded from three sites along the California coast (Santa Cruz, Pismo Beach, and Santa Barbara Harbor). Airborne Lidar data, shadow projections, and vessel traffic information was used to rectify imagery instead of traditional field methods. Water level was extracted at 2 Hz based on the change in brightness relative to a fixed background object and filtered to remove swell and tidal influences. Tsunami inundation was captured at all three sites, with image extracted maximum tsunami heights measuring 1.42 m at Santa Cruz, 1.07 m at Pismo Beach, and 0.49 m at Santa Barbara Harbor. Comparisons to nearby in-situ water level measurements were made to calculate the accuracy, with a RMSE of 0.41 m, 0.52 m, and 0.17 m at each site, respectively. Analysis of surfcam extracted water levels measurements show promising results, and in combination with providing holistic monitoring of the scene, suggests an alternative platform for future tsunami events.