Sea-level fluctuations control the distribution of highly liquefaction-prone layers on volcanic-carbonate slopes

Understanding and quantifying the hazards related to earthquake-induced submarine liquefaction and landslides are particularly significant offshore of tropical volcanic-carbonate islands, where carbonate production competes with volcanism to create highly contrasted lithological successions. To improve the detection of liquefaction-prone layers, we analyzed physical properties and mineralogy and performed 70 dynamic triaxial tests on 25 sediment cores offshore of the eastern side of Mayotte (Comoros archipelago in the western Indian Ocean) in an area that has experienced significant seismicity since 2018. We found that the main parameter controlling the liquefaction potential offshore of Mayotte is the presence of low-density layers with high calcite content accumulating along the slope during lowstands. This phasing with sea-level fluctuations implies a significant recurrent geohazard for tropical volcanic-carbonate islands worldwide. Furthermore, the relationship we found between the cyclic resistance of sediment and its density and magnetic susceptibility represents a time -effective approach for identifying the hazards related to earthquake-induced liquefaction.

Automated summary

Understanding and quantifying the hazards related to earthquake-induced submarine liquefaction and landslides is crucial for tropical volcanic-carbonate islands. This study focused on the eastern side of Mayotte and found that low-density layers with high calcite content are the main control on liquefaction potential. The relationship between the cyclic resistance of sediment and its density and magnetic susceptibility provides a time-effective approach for identifying liquefaction hazards.