A marine fault located between Mocha Island and the Tirúa area, south of the Bío Bío region, could have had an influence on the strong seismic movements that were felt during the night of last Saturday and early Sunday morning , where the most intense was 6.2 degrees, with its epicenter in the commune of Lebu. This was stated by the geologist and professor at the University of Concepción, Jorge Quezada, who published an investigation on the matter.
This weekend, several regions of the country felt a strong tremor with an epicenter in the commune of Lebu, in the Bío Bío, where the marine fault would have been involved, known as the Mocha Fracture Zone, which is located between the island of the same name and Tirúa.
Specifically, there were at least 8 earthquakes that occurred after 11 p.m. last Saturday. The largest magnitude was 6.2 degrees and generated a dozen aftershocks.
Mocha Fracture Zone
Shortly after 11 p.m., thousands of people were startled when the earth shook. began to move. It turns out that the tremor 6.2 , had a depth of 48 kilometers, which caused it to be felt in various regions of Chile.
However, what was said by the geologist and professor at the University of Concepción, Jorge Quezada, regarding to the telluric movement of Lebu.
The academic explained that the earthquake was caused by the subduction of the Nazca plate under the South American Plate, and indicated that there was a peculiarity probably related to the marine fault known as Mocha Fracture Zone.
This submarine opening is located between Tirúa (120 km from Lebu and 202 km from Concepción) and Isla Mocha (37, 7 km from Tirua).
The investigation that discovered the marine fault off Isla Mocha
The marine fault, or Mocha Fracture Zone – tirua, was discovered by Quezada along with other colleagues from the Penquista house of studies. His observations in this regard were published in the specialized magazine, Andean Geology, in 2020.
As explained by the academic, they first analyzed the area after the 8.8 earthquake in 2010. They repeated the same thing when there was another strong earthquake in 2011, the one that had an epicenter some 96 kilometers under the sea, from the coastal city of Temuco.
“We went back to the ground confirming a new uprising on Mocha Island and subsidence in Tirúa, indicating that the rupture occurred in the subduction plane,” the professional told the Ciencia en Chile site.
Thus, he explained that there is “a reverse crustal fault between Tirúa and Isla Mocha (Tirúa-Mocha Fault) whose activity began after the 1960″ earthquake. He added that the plates remained locked for almost 6 decades, including in 2010.
“The plates finally disengaged in that area during the 2011 earthquake. GPS geodetic evidence, seismicity analysis and physical-mathematical modeling also corroborated these facts”, he concluded.