An Earthquake Early Warning System For Vulnerable Essential Facilities: The Example of A Potential Implementation for central Costa Rica from a large earthquake in the Nicoya, Seismic GapMarino Protti and Víctor González In developing countries, so many essential facilities are vulnerable to earthquakes that it is practically impossible to retrofit them all before the occurrence of another event. For this reason, a system that can warn the occupants of non-reinforced vulnerable structures a few seconds before the arrival of seismic waves could save many lives. A mature seismic gap exists under and off the Nicoya peninsula on the Pacific coast of northwestern Costa Rica. This gap, the Nicoya seismic gap, is a subduction segment of the Middle American Trench where the Cocos plate subducts under the Caribbean plate. Large earthquakes have occurred in this segment in 1853, 1900 and 1950. The distribution of aftershocks of large earthquakes in the segments adjacent to the gap, during the 1990s, has made it possible to map its geographic location and estimate its size. Without significant slip since 1950, a convergence rate of around 88 mm/yr, and an area ranging from 6,000 to 8,000 km2, the Nicoya gap has the potential to generate an earthquake with moment magnitude above 7.7. Costa Rica’s Central Valley, where the greatest concentration of population and infrastructure in the country is to be found, is located between 100 and 200 km from the potential rupture area of the Nicoya seismic gap. These distances are within the range of tested earthquake early-warning systems, making this region an excellent site for the operation of such a system. An early-warning system should not be seen as a substitute for a vulnerable structure reinforcement program; as a complement, however, it could prove invaluable. |
