At 3:51 p.m. local time in Costa Rica, on August 24, 2020, the OVSICORI seismographic network located an earthquake of magnitude seismic moment MW 6.0, whose epicenter was located 12 km south of Jacó de Garabito.
This earthquake had a depth of 18 km, being located at the interface, where the Coco plate subducts below our country. Both the analysis of the seismic moment tensor and the polarity of the first arrivals of the P wave (see attached figure) confirm a rupture mechanism with inverse geometry, due to the system of compressive forces imposed by the subduction of the Coco plate below of the Caribbean plate.
Being 17:15 local time, the OVSICORI-UNA seismographic network has located a total of 10 aftershocks with a local magnitude (ML) no greater than 3.3.
An earthquake similar to the one that occurred today was generated on November 13, 2017, with a magnitude of MW 6.5 (3.16 times larger in amplitude) which released 5.62 times more energy than today’s earthquake. Due to the proximity between the rupture areas of both earthquakes, their waveforms have a very similar shape.
The figure below compares the seismic record of both earthquakes in the vertical component of the HDC3 seismic station, located on the Omar Dengo campus of the National University in Heredia. The seismogram in red (or light) represents the earthquake that occurred today, while the seismogram in black (or dark) corresponds to the earthquake that occurred in 2017. You can see the difference in amplitude between both earthquakes.