Two consecutive tremors, felt in the towns of Solonópole and Jaguaribe—about 300 km away from Fortaleza, may have been caused by water infiltration from a weir in the region.
Francisco das Chagas Brandão Melo, head of the Civil Defense Seismology Center in Ceará, said that earthquakes like these are not uncommon in this area of Ceará backlands. Although there is no explanation for the tremors in Solonópole and Jaguaribe, some events may be explained by the so-called induced seismicity, considered human-caused earthquakes. One of them may be linked to Castanhão dam, built between 1995 and 2003 and considered the largest multi-purpose public dam in Brazil.
"Water from the dam infiltrated the land, passed through geological faults and acted as lubricant to the rocks. This ends up causing induced earthquakes." explained Brandão.
Castanhão dam's total capacity is 6.7 billion cubic meters.
Earthquakes happened Sunday afternoon (Mar. 6) and came as a shock to local residents. The first had magnitude of 3.1 on the Richter scale and the second of 3.4. The information is collected by the Seismological Laboratory of the Federal University of Rio Grande do Norte (LabSis / UFRN).
Translated by Amarílis Anchieta
Fonte: Agência Brasil.