Dynamic Triggering of Earthquakes in Costa Rica

Abstract We document, for the first time, the dynamic triggering of earthquakes in Costa Rica due to the wavefield from teleseismic events. Dynamically triggered failure is typically observed in volcanic or geothermal settings, characterized by the presence of high pore pressures weakening fault settings by reducing the normal effective stress, and is less common in continental or local faults. Using the local network in Costa Rica, we analyzed the seismic records from 25 teleseismic events from 2010 until February 2023. From these, two events were identified as prime examples of triggering during the surface-wave passage: the 2018 Mw 7.5 North of Honduras earthquake and the 2023 Mw 7.8 Türkiye earthquake. Both earthquakes share similarities as they have a distinctive strike-slip focal mechanism and are supershear events. Our results reveal that the triggered seismicity primarily happened in the northern volcanic areas of Costa Rica. However, we also observed triggering along the subduction zone in the southern Pacific coast and in crustal shallow faults in central Costa Rica, a shear zone with a high population density. Indicating that dynamically triggered earthquakes highlight the presence of weakened faults in Costa Rica.