Scientists are now able to decode the causes of the devastating magnitude-7.2 earthquake in Haiti's southwest. This community-science initiative was launched in response to Haiti's 2010 magnitude-7 earthquake that left more than 100,000 dead. It has helped reveal details about Haiti's seismic activity.
The community-seismology program provides vital data in a country where official seismic-monitoring stations can sometimes go down due to limited resources. The network is currently detecting aftershocks, which continue to shake the region. The network's seismometers transmit data to a system that displays real-time information on the location and magnitude of Haitian earthquakes via a web portal.
It is not professional equipment and it has many limitations, according to Dominique Boisson, a geologist from the State University of Haiti in Port-au-Prince, who manages the network. Some results are quite nice.
Difficult work
This network shows how far Haitian seismology has come over the past 11 years. Boisson says that Haiti had only one seismic-monitoring station and no seismologists when the 2010 earthquake hit near Port-au-Prince. There are now several professional seismologists in Haiti, along with 7 stations in the national network that is managed by Haitis Bureau of Mines and Energy and 15 in the community science network.
Teams of scientists and technicians drove towards the epicenter of the earthquake on August 14, carrying seismometers, and other instruments, within days. Researchers can monitor the Earth immediately following a earthquake with scientific instruments to help them understand the causes and potential consequences. Foreign researchers had to wait weeks for instruments to be deployed in Haiti after the 2010 earthquake.
Many of these foreign teams cannot travel to Haiti this year due to COVID-19 restrictions, political instability, and the assassination of Jovenel Moe, Haiti's president. Instead, Haitian seismologists are leading the work, including Steeve Symithe at the State University. He was streaming Facebook Live presentations on the science behind the earthquake to the Haitian public before he entered the field.
The EnriquilloPlantain Gardens fault zone was the location of both the 2010 and 2021 earthquakes. It is a complex network of fractures in Earth's crust that allows the North American and Caribbean plates to slide past each other. It runs west to south along Haiti's southern peninsula. It was on an previously undiscovered fault in this zone that the 2010 earthquake occurred. The province of Nippes is 100 km to the west of the epicentre of the 2021 earthquake.
The 14 August earthquake claimed the lives of at least 2,100 people, but the final count is still unknown. According to the US Geological Survey, there may have been more than 10,000 people killed. Many of the survivors were forced to seek shelter outdoors after being battered by heavy rain and wind from a tropical storm. Boisson tells Nature that scientists on their way to the area spent the night in cars, as the rain fell, softening ground and creating landslides aftershocks shake the ground. He says it was quite difficult.
DIY seismology
In 2019, the community-seismology program was born out of the challenges of fieldwork in Haiti. Eric Calais, a Parisian seismologist who had been studying Haiti's earthquakes for many years, came across a company selling seismic stations to hobbyists. He used the money he had saved from a grant to purchase some stations. They are called Raspberry Shakes and contain tiny accelerometers which detect ground shaking and transmit that information to other stations.
These US$500 stations may not be as advanced as Haiti's official monitoring stations, which cost $50,000. Calais says that they are very good at locating earthquakes, determining magnitude and basic seismology. Because they are located in people's homes or workplaces, they have access to reliable Internet access and power. Calais and Symithe were part of the team that recruited volunteers to host the stations. Boisson kept one in his garden up until last week when he took it down to move it closer the the epicenter of the 14 August earthquake. Calais says that the host of the Raspberry Shake was upset that his station was offline due to the earthquake. He immediately went out and filled up his Internet plan and the station soon resumed normal operations.
Calais and his team have maintained the network of 15 stations for two years thanks to international donors. They plan to increase their number to 50 stations in the near future. Calais says that while other community-seismology networks exist, the Haiti network is unique because it provides data in an area that has very few seismic data.
The Haitian community-seismology data are fed into an experimental system called Ayiti -Sismes. It is hosted on a website managed by the Cte dAzur University, Nice, France. Ayiti-Sismes pulls data from both Haitian official seismic stations and those in neighboring countries like the Dominican Republic or Cuba. This creates a map showing the aftershocks that have been affecting southwestern Haiti in orange and red shades. Susan Hough, a seismologist from the US Geological Survey Pasadena in California who has been working in Haiti for many decades, even after the 2010 earthquake, said that the network is still alive and well.
Future risk
Calais says that the quakes epicentre lies close to magnitude 6 and 5 quakes which occurred in 1952, 1953. The EnriquilloPlantain Garden fault could still produce another major earthquake in the future. Boisson says that it is not over in this region. Many speculate that the 2010 earthquake contributed to the current one by shifting stress towards the region that just burst. The seismic risk in Port-au-Prince, as well as much of the EnriquilloPlantain Gardens fault zone, remains high.
Boisson points out that scientists are concerned about another major geological area in Haiti's north. This is the Septentrional fault Zone. It unleashed a major earthquake in 1842. He says that we assumed it would be this fault which would cause future earthquakes after 2010. It was then in the south.
Calais says that 600 aftershocks were detected so far from the 14 August earthquake, compared to 10 during the same period following the 2010 quake. However, there are undoubtedly many more that weren't detected. He says that we now have excellent information on not only the location of the [14 August] earthquake, but also the extent of the rupture and the direction in which the fault was dipping. This information is crucial to understand the cause of the earthquake and what we can expect for the future.
This article was published with permission on August 20, 2021.
