Costa Rica Faults Display Response to Distant Earthquakes through Dynamic Triggering
Costa Rica, nestled amidst two oceans and multiple tectonic plates, is renowned for its stunning natural landscapes and diverse wildlife. However, it also grapples with a hazardous geological setting marked by active volcanoes and frequent seismic activity, including occasional powerful earthquakes.
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Costa Rica
New research reveals that Costa Rica’s intricate network of seismic faults harbors weak and potentially unstable zones that can respond to distant major earthquakes’ shaking. This phenomenon, known as dynamic triggering, is commonly observed in geothermal and volcanic sites but less frequently along continental faults. Over the past decade, seismologists reported two significant earthquakes unsettling faults in Costa Rica due to dynamic triggering, as presented at AGU’s Annual Meeting 2023 in San Francisco.
Costa Rica experiences seismic activity approximately every decade, with events exceeding magnitude 7 causing intense shaking and substantial damage. Notably, in 2012, the second-largest earthquake in the country’s recorded history, a magnitude 7.6 quake off the Nicoya Peninsula, resulted in $45 million in damages. Seismologists have debated whether seismic waves from major global earthquakes can trigger distant faults where stress has been accumulating, a phenomenon observed in Southern California but not previously detected in Costa Rica.
Seismologist Esteban Chaves and undergraduate student Sonia Hajaji conducted a thorough analysis, examining data from a seismic station network across Costa Rica, recording seismic activity before, during, and after the 25 most significant earthquakes in the Americas since 2010. They specifically focused on the magnitude 7.8 earthquake on the Türkiye-Syria border on February 6, 2023, as it was the most recent major event at the time.
The researchers sought evidence of increased seismic activity following distant large earthquakes, analyzing high-frequency local seismic activity shortly after the arrival of low-frequency waves from those events. They identified such upticks after a magnitude 7.6 earthquake in 2018 in the Caribbean Sea off Honduras and the Türkiye-Syria magnitude 7.8 earthquake.
The study’s novel approach to dissecting local seismic data to reveal high-frequency waves drew praise from seismologist Joan Gomberg of the U.S. Geological Survey. Gomberg suggested that dynamic triggering might be more common than previously thought, offering insights into areas potentially ripe for earthquakes if faults are exceptionally sensitive shortly before an event.
