It is an often repeated falsehood that Brazil is unaffected by natural disasters. The floods that cause destruction in cities and villages around the country’s Southeast on an annual basis are an easy way to debunk this claim — while aggravated by nonsensical urban planning and lack of investment in damage limitation measures, these heavy rains are undoubtedly natural phenomena.
However, the sentiment behind the statement that “Brazil doesn’t have natural disasters” is really referring to earthquakes, hurricanes, tsunamis, and volcanic eruptions. In this respect, yes, Brazil is almost completely untouched by these potentially deadly events. But, according to a new study by researchers from the University of Campinas and the University of Córdoba in Argentina, this may be about to change — and human interference is to blame.[restricted]
Disturbing the peace
The study in question focuses on the city of Manaus, which sits upon a vast shale gas basin that the Mines and Energy Ministry has coveted for potential fracking projects. The practice, which involves injecting high-pressure fluids into fractured bedrock to extract shale gas, has a risk of disrupting and increasing stress on local underlying tectonic plates — the result of which may be increased seismic activity, which could cause catastrophe in a city such as Manaus.
The lack of earthquakes in Brazil can be explained by the fact that the entire country sits on the massive South American tectonic plate, which also spans far over the Atlantic Ocean toward Africa. On the west side of the continent, however, the South American Plate meets the Nazca Plate in the Pacific Ocean, which created the Andes mountain range and causes a number of earthquakes from Ecuador down to Chile.
While the practice of fracking does not directly disturb local tectonics and lead to earthquakes, byproducts from the process have been proven to affect seismic activity. After the hydraulic fracturing is carried out, the water injected to extract the gas has to be disposed of. Typically, it is stored in huge wells for long periods of time, thus penetrating into tectonic faults and causing a higher risk of earthquakes.
The study points to other examples in the literature that show increased seismic activity caused by hydraulic fracturing in the U.S., Canada, and China.
Fracking: the risk for Manaus
A large part of the 1.8 million population of Manaus live in precarious housing. There are some 653,000 dwellings in the city proper and, according to data from the Brazilian Institute of Geography and Statistics (IBGE), over half are of a poor standard, be they in slums, unlicensed settlements, or in makeshift homes built on stilts at the banks of the Negro River. Basic sanitation infrastructure and necessary services are already lacking in these areas, and they would be extremely vulnerable in the case of increased seismic activity in the Manaus metropolitan region.
Considering the probabilities of induced tremors and earthquakes, the researchers estimated that the city would incur average yearly losses of USD 189 million in building damages were fracking activities to be set up close to its metropolitan boundaries.
Furthermore, the characteristics of the precarious housing in Manaus means that even relatively mild seismic events could result in significant destruction. The study calculated high values of loss even when earthquakes of a maximum magnitude of 5.0 were expected.
According to Luiz Vieira, one of the study’s researchers, the extent of the potential damage lies in the fact that Brazil has never had to contest with earthquakes before, and as such, its building codes do not take these risks into account — a problem exacerbated in a city such as Manaus, with so many homes build irregularly.
“Brazilian construction rules are not prepared to design buildings that are protected from seismic shocks, as it’s not something that happens a lot in the country. This study intends to show what could happen, and how we can prevent it,” he explained.[/restricted]