Scientists have been studying the Sept. 5, 2012, Sámara earthquake and have concluded that there was a relationship between the event and a quake 450 kilometers to the northwest and nine days earlier.
That earlier quake was of 7.3 magnitude in El Salvador.
In addition, the heavily monitored Nicoya peninsula experienced a flurry of much smaller quakes about 35 minutes earlier.
These are the conclusions of a scientific paper in the prestigious Earth and Planetary Science Letters. Marino Protti of the Observatorio Vulcanológico y Sismológico de Costa Rica at Universidad Nacional was a coauthor.
The research is another effort by scientists to understand earthquakes and perhaps predict them.
The 8:42 a.m. Sámara quake was attributed to the subduction of the Cocos plate beneath the Caribbean. This is the usual cause of quakes in western Costa Rica. The depth was estimated at 40 kilometers, some 25 miles.
The magnitude was 7.6.
There were two deaths and a lot of damage, including in the community of Nicoya.
The quake was felt strongly in all of the country. Those in buildings in the Central Valley fled to the streets and parking lots. Some structures suffered superficial damage.
Protti and colleagues had long been warning of a major quake in the area.
The public quickly links distance quakes to nearer ones, but scientists are more cautious in concluding causation.
Still, the academic article’s abstract said “We observe a statistically significant increase in seismicity rate below the Nicoya Peninsula following the 27 August 2012 (MW 7.3) El Salvador earthquake . . . .”
The article also said that if earthquakes at such distances can induce significant increases in seismicity during the days before another larger event, this sequence strengthens the need for real-time seismicity monitoring for large earthquake forecasting.”
Other researchers on the project included Jacob Walter of the University of Texas at Austin and others from the Georgia Institute of Technology in Atlanta and the University of California.