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Haiti - Environment : The earth shook 1,647 times in Haiti in 2021
The Bureau of Mines and Energy (BME) in its Annual Bulletin 2021, reveals that between January and December 2021, 1,647 earthquakes of magnitudes between 1.0 (very minor) and 7.2 (major) on the Richter scale, were recorded throughout the national territory.
Compared to the year 2020 (499 earthquakes between 1.0 and 4.9) the year 2021 recorded an increase of 1.148 earthquakes, an increase of 230%.
Earthquake of August 14, 2021:
This increase is due to the major earthquake of magnitude 7.2 on the Richter scale that occurred on Saturday August 14, 2021 in the department of Nippes at 8h29'07'' (local time) https://www.haitilibre.com/en/news-34479-haiti-flash-magnitude-72-earthquake-in-the-nippes-updated-10am.html According to the first calculations, the epicenter of this event was located on the Enriquillo Plantain Garden fault system at 18.49 degrees North latitude and -73.59 degrees West longitude, at a depth of 10 km. This earthquake occurred more precisely in the commune of Baradères, 12 km from Saint-Louis du Sud, 6 km from L’Asile and 10 km from Petit Trou de Nippes.
According to the preliminary results, the earthquake occurred in two stages : a first segment broke between the municipalities of L'Asile and Baradères, releasing most of the energy, 40% (greater than 'in 2010) ; the rupture then propagated westward in the Pic Macaya-Maniche-Camp-Perrin area, becoming more superficial. The earthquake ruptured a fault segment of about 50 km in length (from L'Asile in the east to Pic Macaya in the west). The average slip on the fault is about 2 meters (Calais et al.)
Seismic periods, consequences of the August 14 earthquake :
The recording of earthquakes during the year 2021 shows two periods. The first extends from January 1 to August 13, during which 280 earthquakes (17%) were recorded and the second goes from August 14 to December 31 which experienced 1,367 earthquakes (83%).
If we consider the earthquakes recorded by geographical department, we see that during the first period, from January 1 to August 13, 2021, the departments most affected do not differ too much from those observed in 2020. Indeed, the North-West, the South-East and West have always retained their high seismic activity in the territory, while Grand'Anse, North-East and Center still showed less activity.
During the second period from August 14 to December 31, 2021, the situation has changed drastically since the August 14 earthquake in the Nippes. Indeed, the three departments most affected by this earthquake, namely, Nippes, Grand'Anse and the South occupied the top of the ranking during the last five months of the year 2021. This situation is very understandable for the Nippes where the epicenter of the magnitude 7.2 earthquake was located and around which aftershocks were expected. In addition, a few hours after the shock, ground motion calculations showed that the earthquake was violent in a region extending from the commune of Les Cayes to that of L'Asile and over the entire width of the Southern Peninsula. More than 900 aftershocks were subsequently recorded, including 400 of magnitude greater than 3 likely to cause damage to buildings and cause landslides. The mountainous parts of the municipalities including Corail, Pestel, Camp-Perrin, Maniche, Torbeck, Asile, Arnaud, were the most affected. After the shock, the aftershocks extended over 80 km in length in the East-West direction in the Southern Peninsula and seem to correspond to the two rupture planes mentioned.
The earthquake of August 14 seems to have led to a seismic crisis in Grand'Anse which recorded 396 tremors from August 14 to December 31 and whose certain epicentres are located at sea around the North-Grand'Anse-Nippes fault highlighted in 2017 by the "Grand'Anse multi-risk mapping project". This 220 km long fault has a seismic potential of 7.2 according to the studies of the United Nations Development Program (UNDP) it is distant about fifteen km north of the town of Jérémie, it was perhaps activated by the earthquake of August 14 and we continue to record tremors in Grand'Anse at the beginning of 2022, which raises fears of a major earthquake on this fault followed by a tsunami which would be harmful for the north coast of the southern peninsula.
In conclusion, in an interval of 11 years (2010-2021), Haiti was hit twice by major earthquakes of magnitude 7 (January 12, 2010) and 7.2 (August 14, 2021). In both cases, there were enormous damages. considerable loss of human and economic lives (earthquake of August 14 https://www.haitilibre.com/en/news-34681-haiti-earthquake-latest-assessment-of-civil-protection.html ).
Faced with these recurring disasters, the BME emphasizes "[...] it is high time to have a seismic risk reduction plan in Haiti at the national level, because the hazard is national, and to practice continuously prevention, the only means of reducing the population's vulnerability to the effects of unpredictable seismic hazards.
Also, we launch an appeal to our dear compatriots to ask them to become more aware of this natural phenomenon, to work tirelessly to safeguard the environment of their country and to always strive to place it on the path of seismic safety by thinking of better constructions and by applying the instructions of the Civil Protection."
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