Surface water load and earthquake stress interactions near the Pirrís reservoir, Costa Rica

Abstract This study analyzes the relationships between stress changes produced by water load variations due to filling operations at Pirrís Reservoir, Costa Rica, and generated three relevant earthquakes after first impoundment. The differ in their magnitude, distance from reservoir depth. Two of them correspond a shallow crustal faulting, third earthquake corresponds subduction thrust-fault. began March 2011 daily time history levels was available until December 2017. seismicity has been recorded dense local network seismological stations operating since January 2008. Effects both types sources (water loads earthquakes) were combined obtain total Coulomb Failure Stress area, analyzing which dominant each case time. We then analyzed effects pore pressure diffusion on nearby including two studied earthquakes. Results lead different conclusions depending characteristics earthquake. An important result is observed occurrence earthquake, where coseismic become along entire eclipsing effect loading all depths. shows that regime stressed regional albeit its moderate distance, barely perceptible. In absence tectonic activity, however, impact notable.