Haiti: 14 August 2021, Earthquake 7.2 M, Depth 10km

Good afternoon,

Our thoughts are with Haiti.  Tragically, on 14 August 2021 at 8:29am (local time), a shallow (10km) earthquake of 7.2M occurred on the South West peninsula of Haiti 13 kilometres  southeast of Petit Troup de Nippes. The earthquake was felt across the region, including Haiti, Dominican Republic,  Jamaica, Cuba, and Puerto Rico.   Over one million people may have been exposed to very strong or severe shaking. 

A one-month state of emergency has been declared for Haiti.  As of 16 August 2021, 1,419 are believed to have lost their lives, more than 6,000 injured and many thousands displaced.  Tropical Depression Grace is likely to pass over the stricken area at the time of writing, bringing with it the risk of heavy rains, flooding, landslides and further loss of life. 

Aftershocks are occurring, and may do so for some time.  There is a small risk that this event is a foreshock to another event.

Fig 1: Location of the 14.08.2021 7.2M earthquake and aftershocks to 16.08.2021 plotted by the author. © Copyright remains with the author; all rights reserved, 2021.

Haiti Background

Haiti is located on the western side island of Hispaniola in the Greater Antilles Archipelago; the Dominican Republic occupies the eastern side of the island.  Two large fault zones cross the island: the Septentrional-Orient fault in the north and the Enriquillo-Plantain Garden Fault Zone in the south.

Fig 2:  Cropped image from one digitally altered by Mikenorton of the Gonâve Microplate (plate boundaries, main faults, islands and plates were added).  Source: Gonâve microplate

Hispaniola was formed from the collision of volcanic arcs with the North American Plate; the island is made up of 11 former island arcs.  Haiti has an estimated population of 11.4 million (2018).  The country is poor, politically unstable and yet to recover from the 2010 earthquake. 

While the island has a volcanic past, there has not been any reported volcanic activity in the Holocene.  There are two Pleistocene volcanoes in Haiti, the nepheline basalt scoria cones of Morne la Vigie, north of Port au Prince, and Thomazeau, east north east of Port-au-Prince, both of which were active around 1.5 million years ago; and, three in the Dominican Republic, the basaltic cinder cones of San Juan, trachyandesite lava domes and flows of the Dos Hermanos volcanic field and the rhyolitic to basalt Valle Nuevo volcanic field.  The presence of picrite in the Duarte Complex in central Hispaniola and enriched basalts in southern Haiti are thought to be indicative of earlier hotspot activity

Tektites have been found in the Beloc Formation, Haiti, which are thought to have originated from the asteroid impact in Yucatán Peninsula, Mexico, which caused the K-Pg mass extinction event 66 million years ago. 

2021 7.2 M Earthquake

The earthquake occurred in the Enriquillo-Plantain Garden Fault zone on the transform plate boundary between the Caribbean Plate and the North American Plate.  The faulting mechanism for this earthquake indicates oblique thrust faulting along the  fault zone.  This fault zone accommodates 7mm per year of the 20mm per year of the relative plate motion.  It is likely that this earthquake occurred in the same fault system as the devastating January 2010 7.0M earthquake which occurred near Port-au-Prince, the capital.

Fig 3: Moment tensor from USGS: M 7.2 – Nippes, Haiti (usgs.gov)

2010 7.0M Earthquake

According to the DEC, the January 2010 earthquake not only caused significant loss of life and damage but also severally impacted Haiti’s government and infrastructure: 25% civil servants died, 60% government buildings, 80% schools in Port-au-Prince and 60% schools in the South and West departments were destroyed. In all, over 220,000 were killed, more than 300,000 injured and around 300,000 homes damaged or destroyed. 

USGS note that four other large earthquakes are known to have occurred in the region: October 1751 in the Gulf of Azua at the eastern end of the Enriquillo-Plantain Garden fault zone; November 1751 at Plaine du Cul-de-Sac which destroyed Port-au-Prince; June 1770 which also destroyed Port-au-Prince; and, April 1860 which also caused a tsunami.

Recent Seismicity

We looked at the Caribbean Plate in February 2021 ( Mt. Pelée, La Soufrière St. Vincent And A Quick Tour Of The Plates Surrounding The Caribbean Plate). We have updated the plot to 16 August 2021 to show the location of the 2021 and 2010 earthquakes.

Fig 4:  Earthquakes and volcanoes surrounding the Caribbean Plate plotted by the author.  Green dots denote earthquakes, yellow circles those ≥6.0M and red stars those ≥7.0M. Earthquakes delineate plate boundaries. The location of the Haiti 2010 and 2020 earthquakes are also shown.  © Copyright remains with the author; all rights reserved, 2021.

Aid

It is expected that there will be a request for international aid. If you wish to help / donate to the aid effort, refer to your favourite international aid agency, in the first instance. 

The Armchair Volcanologist

© Copyright remains with the author; all rights reserved, 2021.

Sources and Further Reading

2021 earthquake information, USGS: M 7.2 – Nippes, Haiti (usgs.gov)

2010 earthquake information, DEC: Haiti Earthquake Facts and Figures | Disasters Emergency Committee (dec.org.uk)

Haiti: Haiti – Wikipedia

Raw earthquake data: USGS