A Natural Seismic Isolating System: The Buried Mangrove Effects

TL;DR

This study investigates how a buried mangrove layer at a Caribbean seismic site acts as a natural isolating system, reducing seismic stress and liquefaction potential through its flexibility and damping effects.

Contribution

It demonstrates that natural mangrove layers can serve as effective seismic isolators, providing insights into natural mitigation mechanisms in coastal regions.

Findings

The mangrove layer reduces seismic shear forces.

Flexibility of mangrove decreases soil distortion.

Potential liquefaction is significantly lowered.

Abstract

The Belleplaine test site, located in the island of Guadeloupe (French Lesser Antilles) includes a three-accelerometer vertical array, designed for liquefac- tion studies. The seismic response of the soil column at the test site is computed using three methods: the spectral ratio method using the vertical array data, a numerical method using the geotechnical properties of the soil column, and an operative fre- quency domain decomposition (FDD) modal analysis method. The Belleplaine test site is characterized by a mangrove layer overlaid by a stiff sandy deposit. This con- figuration is widely found at the border coast of the Caribbean region, which is exposed to high seismic hazard. We show that the buried mangrove layer plays the role of an isolation system equivalent to those usually employed in earthquake engineering aimed at reducing the seismic shear forces by reducing the internal stress within the structure. In our case, the flexibility of the mangrove layer reduces the distortion and the stress in the sandy upper layer, and consequently reduces the potential of liquefaction of the site.