Title: Video cameras as a new world of looking to disasters

Abstract

In a recent paper, Oliveira et al. (2021) presented a large selection of video and personal camera footage of various earthquakes and tsunamis. As the use of video surveillance cameras is increasing in recent years due to the monitoring of spaces in either the urban setting, building´s interior, etc., and the number of occurrences is keeping its trend, if not increasing, much more information is getting available in the Internet or assembled in earthquake agencies. Video cameras are becoming essential tools to obtain real-time information on the mechanical performance of structures during seismic events, as well as on wave propagation properties causing tsunamis, landslides, water sloshing, etc. Their recorded images also provide essential clues on human behavior during shaking. It is like solving the inverse problem during its entire duration, not only by inspecting the final stage of its trajectory (animated versus fixed image). We will be looking at cases created by earthquakes but not described. In many instances, we could estimate motion associated with the movement in analysis, and we accompanied the presentation with analytical formulations to explain the real-time information qualitatively. For example, video images were a fundamental tool in investigating the collapse of two structures during the 2015 Nepal earthquake: the Dharahara Tower and the Tetrastyle Canopy. We can understand their time evolution from the onset of shaking to total collapse by accessing the video footage. Video footage does not replace laboratory static tests or tests on shaking table, pseudodynamic walls, etc., and instrumental networks to monitor Earth and buildings. Still, as long as well-used, the information collected over time is of great value as it shows the “reality” and complements other sources of information. They can serve as an "inspiration" and a random visual health monitoring system.