The Intergovernmental Oceanographic Commission (IOC) of UNESCO supported a Group of Experts meeting on Lesser Antilles tsunami sources to better understand the uncertainties associated with the Lesser Antilles Trench and the nearby volcanic activity.
The 3-day experts meeting was held from 18 to 20 March 2019 on the French Lesser Antilles island of Martinique, France. The purpose of the experts meeting was to identify and quantify tsunami sources of both tectonic and volcanic origins, and related hazards and risks to support holistic risk management for the Lesser Antilles (preparedness, mitigation, response, and recovery).
Tsunamis from seismic and volcanic sources could have widespread impacts on the population health and economy of the Lesser Antilles. There are historical precedents for tsunamis generated by earthquakes associated with the Lesser Antilles Trench and volcanic activity. A very large tsunami associated with the Lesser Antilles Trench has the potential to cause widespread loss of life, damage and disruption to the region. Similarly, volcanic activity along the Lesser Antilles volcanic arc could potentially generate locally devastating tsunamis that would compound the volcanic crisis. The Lesser Antilles are made up of small islands with an increasing dependency on coastal-based tourism. Moreover, the population of these island nations and their infrastructure are concentrated in areas particularly prone to tsunami effects, low-lying coastal areas.
The meeting in Martinique aimed to focus on the uncertainties in tsunami hazard assessment for the Lesser Antilles and identify possible tsunami sources. The outcomes of the meeting can be used for Lesser Antilles hazard and risk assessment studies. The invited experts analysed credible tsunami sources, for which they identified the following groups of sources related to the subduction of North and South America plates beneath the Caribbean plate with potential to impact the Lesser Antilles:
1. Subduction Zone related sources consist of tsunami sources stemming from the interaction of North and South America plates with the Caribbean producing shallow thrust events capable of inducing near-field catastrophic tsunamis. Events in this category include sources tentatively similar to the 8 February 1843 earthquake (M7.5-8.0; Bernard and Lambert, 1988).
2. Island Arc Normal sources consist of crustal faults within the arc itself and thus not directly related to the subduction process. Tsunamigenic sources in this category are smaller events with smaller shallow rupture areas that are oriented perpendicular to the arc. An example of such a source is the M7.4 October 8, 1974 event that ruptured a normal fault oriented perpendicular to the arc between Antigua and Barbuda.
3. Island Arc Parallel sources consist of crustal faults within the arc itself and thus not related directly to the subduction process. Tsunamigenic sources in this category are smaller events with smaller shallow rupture areas that are oriented parallel to the arc. An example of such a source is the M6.3 November 21, 2004 earthquake along the Roseau fault between Guadeloupe and Dominica, an oblique fault oriented parallel to the arc axis.
4. Volcanic-induced sources consist of tsunamis generated by the explosive nature of volcanic islands either by volcanic eruption of underwater volcanoes, debris flows, or lateral collapse of volcanic islands. An example of such a source is the tsunami generated by debris flows at the volcano crisis of Mont Pelée in Saint Pierre, Martinique, on 4 May 1902.