Cuba, already reeling from hurricane and power outage, struck by powerful M6.8 earthquake

Shaking also reported in Jamaica and Florida

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A magnitude 6.8 earthquake struck southern Cuba on November 10th, 2024 at 11:49 local time. The earthquake was preceded about an hour earlier by a M5.9 earthquake, which can now be termed a foreshock. The earthquake compounds an already challenging situation in the country: it occurred just four days after a Category 3 hurricane (Rafael) made landfall, causing not only strong winds and flooding, but also a national electrical blackout. The earthquake occurred ~200 km away from the track of the hurricane, which made landfall further to the west. In the image below, the area of strong winds was much wider than the track itself.

Figure 1: Track of Hurricane Rafael. Size of dots indicates hurricane strength. Basemap from https://data.usatoday.com/storm/rafael/al182024/; yellow star added by us.

This coincidence of a hurricane and earthquake is reminiscent of the 2021 M7.2 earthquake in Haiti, which was followed two days later by the arrival of Tropical Depression Grace. In that case, the storm made rescue and recovery efforts more difficult due to rainfall, flooding, and mudslides.

We note that there is no strong reason to believe that Hurricane Rafael caused the earthquakes, although that is a common question and is an area of actual research.

The USGS estimates that the earthquake caused up to intensity VII shaking (very strong) near the epicenter. Shaking at this level is expected to cause considerable damage in poorly built structures. Many of the buildings in this region are indeed expected to be vulnerable: mud structures, or informal buildings constructed out of metal or timber.

Figure 2: Map of the M6.8 earthquake and its M5.9 foreshocks, below Cuba’s southern coast. Colored lines are contours of shaking estimated by the USGS for the mainshock.

Based on the severity of shaking and associated impacts, the USGS PAGER system estimates that some fatalities are likely.

Figure 3: USGS PAGER estimates for fatalities and economic losses, as of 2024-11-10 16:49:50 UTC. Source: https://earthquake.usgs.gov/earthquakes/eventpage/us7000nr0v/pager

Fortunately, so far, news reports do not indicate damage at this level. While there has been structural damage to a number of buildings, footage and reports shows cracks and fallen bricks rather than structural collapse, and no fatalities have been reported.

According to the USGS, the M6.8 earthquake may have also caused minor landsliding and significant liquefaction. Rainfall and saturated soils have the potential to make both issues worse. While Cuba is a fairly flat country in general, the Sierra Maestra mountain range along the southern coast does have steep slopes susceptible to landslides.

Figure 4: Liquefaction probability map by the USGS, estimated for the 2024-11-10 M6.8 earthquake. Source: https://earthquake.usgs.gov/earthquakes/eventpage/us7000nr0v/map?shakeMapIntensity=false&ground-failure-liquefaction=true

Although the earthquake did not trigger a tsunami, footage posted to X indicates that local residents evacuated to higher ground when they felt the shaking, only returning after official sources indicated that it was safe to do so.

Cuba operates a seismic network, operated by the Centro Nacional Investigaciones Sismológicas (CENAIS). In a statement soon after the earthquake, CENAIS indicated that no reports of damage or injury had been received at that time.

Tectonic setting

What causes earthquakes along Cuba’s southern coast? To answer that, we need to look at the big picture tectonic motions.

The Greater Antilles is a chain of islands that includes Cuba, Jamaica, Hispaniola (comprising Haiti and the Dominican Republic), and Puerto Rico. Of these islands, Cuba is the largest but least mountainous. These islands all owe their existence in some way to the motion of the Caribbean Plate, which remains one of the more perplexing tectonic puzzles on Earth.

We can’t get too involved with the details, but for the purposes of this post, want to explain why there is a big fault next to Cuba. So, we have modified some figures from a recent paper on the Caribbean from Braszus et al. (2021), with the goal of telling only one small part of the story.

Our story starts 50 million years ago. At that time, the Caribbean Plate was caught between North and South America, and was moving eastward relative to North America. The northern edge — where Cuba is today — collided with a piece of continental crust that is currently sitting under some very nice beaches in the Bahamas.

Figure 5: The state of affairs in the Caribbean region circa 50 million years ago. Cuba is about to collide with the Bahama Bank. Modified from Figure 4 of Brazsus et al. (2021).

Exactly why the Caribbean Plate originally formed, and why it has moved eastward relative to its neighboring continental plates, is a matter of continuing debate. To the east of the Caribbean, the seafloor of the Atlantic Ocean has subducted westward-and-downward into the mantle, with the Caribbean Plate riding out over the top to fill in the gap. To the west of the Caribbean, the great oceanic plates beneath the Pacific Ocean have shouldered their way eastward and downward, colliding with and subducting beneath the Caribbean Plate. Other factors might also be at play. Somehow, the balance of all forces required eastward motion of the Caribbean Plate relative to both North and South America.

The next time slice is 30 million years ago. The collision with the Bahamas Bank smushed Cuba upward. Met with stiff resistance, something apparently had to give. Continuing its eastward journey, the Caribbean Plate broke off its northern edge, leaving Cuba behind much like a lizard sheds its tail to escape a hungry fox. This breaking-away required the formation of an entirely new plate boundary fault, cutting straight across the previously solid Caribbean Plate. That fault was the left-lateral Septentrionale-Orientale Fault Zone.

Figure 6: The state of affairs in the Caribbean region circa 30 million years ago. The Septentrionale-Orientale Fault Zone has formed as Cuba has sheared off. Modified from Figure 4 of Braszus et al. (2021).

The Septentrionale-Oriente Fault Zone marks the southern edge of North America (in sensu tectonico), and was the source of today’s earthquakes. This great fault lurks below the deep water just offshore, paralleling the east-west, unusually mountainous coast of southern Cuba.

Let’s fast-forward to the present day.

Figure 7: The state of affairs in the Caribbean region today. The Septentrionale-Orientale Fault Zone has been joined by a new strike-slip fault zone cutting through southern Hispaniola and Jamaica, due to ongoing collision with the Bahama Bank. Modified from Figure 1 of Braszus et al. (2021).

Today, the Septentrionale-Orientale Fault Zone slips at about 1 centimeter per year, taking up half of the motion of the Caribbean Plate relative to North America. This is enough to generate a lot of seismic trouble.

Since is founding in 1515, the city of Santiago de Cuba has experienced many notable local earthquakes. The earliest events were in 1578, 1678, and 1770 (each about M~6.7), followed by a much larger event in 1766 (M~7.6). Two separate earthquakes occurred in 1852 (M~7.2 in August, ~7.0 in November), preceded in July by another 1852 event (M~7.5) farther to the west. More recently, earthquakes similar in size to today’s event happened in 1932 (M~6.8) and 1947 (M~6.8). Only a few years ago, in January 2020, a strike-slip rupture of the Oriente Fault Zone that originated about 200 km west of today’s earthquake caused a much large Mw7.7 earthquake. Although this earthquake was widely felt throughout the Caribbean, it caused little significant damage due to its location far offshore. However, it seems like it has been about 80 years since the last “big” earthquake struck close to land. Because this is still a relatively small event, it is a good wake-up call that a much larger (M7.5+) and more destructive earthquake could probably happen in this area.

Figure 8: Earthquakes recorded along the southern coast of Cuba. Events above M6.6 are labelled.

Where does the other ~1 cm/yr of plate motion between the Caribbean and North American Plates go? Well, geological history sometimes repeats itself.

The island Hispaniola is now bearing the brunt of the ongoing sideways collision with the farthest eastern edge of the Bahama Bank. Much like before, another strike-slip fault system has formed, which is once again trying to leave a sliver of crust behind so that the Caribbean Plate can continue eastward. That fault system, made up of the Walton Fault Zone and the Enriquillo-Plantain Garden Fault Zone, runs through southern Hispaniola and Jamaica before connecting up with the Cayman Trough. That fault system was responsible for the 2010 and 2021 Haiti earthquakes. The January 12, 2010 Haiti earthquake in particular stands out as by far the most destructive, despite its moderate magnitude of Mw7.0.

The main point of this tectonic tale that active faults of today are just the latest step in a plate tectonic dance that has played out over millions of years, and which is still being played out by Earth and unravelled by geologists. As always, we welcome corrections or clarifications about the geology of this complex region from our readers — please leave a comment!

References

Braszus, B., Goes, S., Allen, R. et al. Subduction history of the Caribbean from upper-mantle seismic imaging and plate reconstruction. Nat Commun 12, 4211 (2021). https://doi.org/10.1038/s41467-021-24413-0