Revealing geomorphic changes after the occurrence of a seismic event on the south coast of Puerto Rico (2020)

Abstract

A coastal geomorphological study was conducted to assess the impact of seismic events on the southern coast of Puerto Rico (PR). The goal of this study was to provide new information related to the state of the coast and its geomorphic changes associated with the seismic sequence of 28 December 2019 and the 6.4-magnitude earthquake of 7 January 2020. Coastal geomorphic changes and damage to infrastructure were documented using a combination of a geographic information system (GIS), remote sensing techniques (e.g. unmanned aircraft system [UAS] images), ground-penetrating radar (GPR), high-resolution aerial photos, and field inspection techniques. A geospatial analysis was performed to evaluate the effect of the earthquake events and understand its associated effect on coastal communities’ exposure to this hazard. The findings indicate that the 6.4-magnitude earthquake caused remarkable geomorphic changes, generating a new shape for the southern coast of PR. Coastal changes were characterized by localized coastal subsidence, coastal landslides (e.g. rockslides and rockfalls), the collapse of natural arch-forming sea stacks, changes in cliff profiles, lateral spreading, the destruction of coastal infrastructure, inland shoreline migration, and coastal flooding. This information will be useful for designing new management tools and recontextualizing existing coastal planning instruments in post-earthquake scenarios. These findings clarify the importance of seismic events and their influence on coasts within active tectonic settings.