How come the strike-slip 7.6 M earthquake, occurring January 9th, 2018, produced no tsunami? Has there ever been any produced in this region?


2 Answers 2


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This is the centroid moment tensor published by the USGS as of 01/10/18 (it will likely be updated in the future). As you can see this was an almost pure strike-slip mechanism on a near vertical plane.

Tsunamis are generated when the ocean floor is displaced upwards by an earthquake, displacing the water above it in the same pattern. This displaced water then spread out laterally to form the tsunami. Thrust faults tend to produce large seafloor uplifts and so most (maybe all?) tsunamis are associated with thrust faulting earthquakes.

There was no tsunami in this case because a strike slip fault like this does not produce a significant uplift of the seafloor. Instead the seafloor slides past each other.

With regard to the second part of the question; yes there have been tsunamis in the Caribbean before. This website provides a good list of known ones.

  • 3
    $\begingroup$ Tsunamis can also be generated by underwater landslides, which if I recall correctly are more commonly associated with continental outflows. That is, coastal sediment builds up offshore of a river outlet and a quake can cause the slope to collapse. (Land-side landslides, like avalanches in fjords, can also generate waves.) $\endgroup$ Commented Jan 10, 2018 at 22:56

The reason why there was no large tsunami is due to the reason above, no significant uplift of the sea floor.

However, a small tsunami was produced. This was due to vertical features such as trenches and seamounts (basically, undulating bathymetry) moving laterally, in a strike-slip earthquake acting as paddles within the overlying water column.

Graphic from Trinidad and Tobago Weather Center

They have a pretty good overview of the situation here: The M7.6 Great Swan Island Earthquake & Tsunami


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