M6.1 Earthquake off Cayman Islands Follows M7.7 Jamaica Earthquake

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Are strong and shallow quakes becoming the new normal in the Caribbean?

M6.1 strikes off Cayman Islands just hours after major M7.7 off Jamaica.

M6.1 earthquake hits off the Cayman islands on January 28 2020
M6.1 earthquake hits off the Cayman islands on January 28 2020. Earthquake map via USGS

A M6.1 earthquake struck 57km SE of East End, Cayman Islands about three hours after the strongest quake in the Caribbean since 1900, a M7.7, struck between Cuba and Jamaica on January 28, 2020.

As shown on the map below, the two strong quakes hit directly on the plate boundary (red line).

M7.7 earthquake Jamaica and M6.1 earthquake Cayman Islands, M7.7 earthquake Jamaica and M6.1 earthquake Cayman Islands january 28 2020
M7.7 earthquake Jamaica and M6.1 earthquake Cayman Islands hit on the plate boundary (red line) on January 28, 2020. Earthquake map via USGS

Seismic activity in the Caribbean

The Caribbean Sea lies over the Caribbean Plate, a section of the earth’s crust bounded by active faults separating it from other tectonic plates.

These other plates include the North American Plate to the north and east and the Pacific Plate to the west.

Relative motions between these plates cause earthquakes at their boundaries. The video below shows the earthquakes that hit the Caribbean between 1918-2019.

Most of the east-west trending boundaries are “strike-slip” or transform faults such that the plates move past each other horizontally. Since they move sideways they do not generally cause earthquakes that move the ocean water above them, though they can trigger landslides that generate tsunamis, such as in Haiti in 2010.

But the boundaries of the Caribbean Plate that run northwest-southeast in Central America and the Leeward Islands are subduction zones, a type of plate boundary that can produce megathrust earthquakes with large vertical motions that can cause devastating tsunamis, such as the pair of devastating Dominican Republic earthquakes in 1946.

Some earthquakes in this region that produced significant tsunamis include:

  • Oct 11, 1919 – M7.1 – Puerto Rico (tsunami killed 140)
  • Aug 5, 1946 – M7.5- Dominican Republic (tsunami killed 1790)
  • Aug 8, 1946 – M7.0 – Dominican Republic (tsunami killed 75)
  • Apr 22, 1991 – M 7.6 – Costa Rica (tsunami killed 3)
  • Sep 2, 1992 – M7.7 – Nicragua (tsunami killed 170 on the Pacific coast)
  • Jan 12, 2010 – M7.0 – Haiti (tsunami killed 7)
  • Aug 27, 2012 – M7.3 – El Salvador (Pacific Coast, no deaths)

Videos showing the consequences and cracks triggered by the M7.7 earthquake are available here. Find similar catastrophe headlines on Strange Sounds or Steve Quayle. [USGS]

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