Q&A on Guadeloupe tsunami scenario

SRC Director, Dr. Richard Robertson, provides answers to some popular questions on the Guadeloupe tsunami scenario as written in the document Large Coastal Landslides and Tsunami Hazard in the Caribbean (EOS, Transactions, American Geophysical Union).

Q: How likely is it that a landslide from Dominica’s Morne aux Diables could trigger a tsunami?
A: This is really difficult to quantify given the large number of variables involved but it is certainly less likely than the possibility
of a large and potentially damaging earthquake occurring near to the north coast of Dominica. In the context of day to day life, this is much less likely than being killed in a traffic accident in any normal day anywhere in the Caribbean.

Q: What could cause the landslide?
A: A large enough landslide to generate a tsunami off the north coast of Dominica could be triggered by a large earthquake on-land or near to the coast or by the eruption of the volcano itself. It is possible that excessive rainfall combined with a large earthquake could also result in a large landslide.

Q: Should a tsunami be triggered would there be sufficient time to issue warnings?
A: No, there is likely to be insufficient time since the impact of such a landslide generated tsunami is likely to be very local i.e. close to the source and therefore will provide little time to issue a warning. It is possible with careful study and monitoring to determine which slopes are more likely to fail but determining exactly when the failure will occur will always be difficult.

Q: If a tsunami were to be triggered would it also impact other Caribbean islands? Why or why not?
A: If a tsunami were to be triggered by a large landslide off the coast of northern Dominica or any of the other islands, the impact is most likely to be local or only affecting nearby islands. This is largely because of the lower energy involved compared to earthquake generated tsunami and also to the more directional nature of the event. Essentially the landslide will ‘push’ the ocean in a particular fashion that will not allow the ocean waves to go very far.

Q: How concerned should we be about this scenario?
A: We should be concerned about this kind of scenario but it should be kept in the context of the multi-hazard environment of the Caribbean. This means that other kinds of hazards such as hurricanes, flooding, storm surges, earthquakes and volcanic eruptions are also possible and more likely to happen than the kind of landslide generated tsunami dealt with in this scenario. It is more likely for a tsunami to be generated by a large earthquake in the region than for there to be a landslide generated tsunami.

Q: What can be done to mitigate the possible effects of this scenario?
A: Further research needs to be done to verify if this kind of scenario is a real possibility. The study done so far has really been preliminary and based on remote sensing techniques – there needs to be some ‘ground truthing’ of what has been observed. The key mitigation effort is public education since these kinds of events are likely to provide insufficient time for warnings to be issued so the public will need to know how to recognize tsunami waves and be aware of what to do to reduce their risk when these occur.

Q: What plans are there for future study of this area?
A: There is a significant amount of additional research that needs to be done to essentially verify that this potential for landslide generated tsunami from the north coast of Dominica is possible. This could include airborne surveys to get a better image of the ground surveys supported by ground-based surveys of the land to determine the kind of topography and materials that make up the area. This will help to determine the severity of north Dominica to landslide hazard and enable improved estimates of the tsunami hazard.

For more information visit the Tsunami pages of our Web site.