A shallow and fully locked portion of Colombia’s Caribbean subduction zone has been identified using data from a GPS network, raising the possibility of a big earthquake and tsunami risk for the northwest of the country.
According to Sindy Lizarazo of Nagoya University in Japan, who presented the work at the Seismological Society of America (SSA2021 )’s Annual Meeting, the locked patch south of Cartagena city can produce an earthquake of magnitude 8.0 once every 600 years.
Colombia is located in a complicated tectonic zone where the South American, Caribbean, and Nazca plates, as well as other smaller tectonic blocks, collide.
The sluggish convergence of the Caribbean plate, which is causing the northern section of Colombia to move at a rate of 7 millimeters per year, may in part account for the absence of frequent big earthquakes in northwest Colombia.
“The only recent historical record of a disastrous (magnitude 6.4) earthquake in the Colombian Caribbean region was on May 22, 1834 close to Santa Marta,” said Lizarazo. “However, there is no seismic event that meets the magnitude estimated by our study, nor tsunamis in the historical record on the northern part of Colombia.”
Lizarazo and associates examined data from the statewide GPS network known as GeoRED (GEOdesia: Red de Estudios de Deformación in Spanish) to better comprehend the intricate movements and crustal deformation occurring in the area.
The only recent historical record of a disastrous (magnitude 6.4) earthquake in the Colombian Caribbean region was on May 22, 1834 close to Santa Marta. However, there is no seismic event that meets the magnitude estimated by our study, nor tsunamis in the historical record on the northern part of Colombia.
Sindy Lizarazo
The Geological Survey of Colombia has been running the network since 2007, and there are 150 permanent stations that are always operational. The motions and crustal deformation of the tectonic plates interacting can be estimated using GPS data.
Lizarazo and colleagues’ analysis of the data indicated motion of the northern portion of the North Andean Block, a “microplate” wedged between the Nazca and South American plates that interacts with the Caribbean plate that is subducting.
The researchers calculated the amount and degree of interplate locking at this boundary, where stresses may develop without being released in an earthquake, using these data coupled with a realistic slab shape.
The study “provides the first evidence of a shallow locked region south of Cartagena,” Lizarazo said. “This indicates that this segment of the Caribbean-South America plate boundary in northwestern Colombia can be the locus of significant earthquake and tsunami hazard.”
Major-scale geological mapping, as well as other investigations looking for tsunami and large earthquake evidence, are necessary for researchers to completely assess this hazard potential.
“It is also necessary to continue with the densification of the GPS network in the country, increasing its coverage and operation in real time,” Lizarazo said.
