A magnitude 7.3 earthquake struck off the Pacific coast of southern Mexico this morning, setting off a tsunami alert for parts of Mexico and Guatemala. If you are on or headed to Costa Rica’s Pacific coast, the short version is that forecasters do not expect meaningful wave activity here. The Pacific Tsunami Warning Center placed Costa Rica in its lowest forecast tier, with any sea-level change expected to stay under 0.3 meters (about one foot), small enough that most people at the beach would not notice it.
The quake hit at 8:48 a.m. local Mexico time, roughly 48 kilometers (30 miles) southwest of Aquiles Serdán, a coastal town in Chiapas state near the Guatemala border, according to the United States Geological Survey. Mexico’s Servicio Sismológico Nacional put the magnitude slightly higher at 7.4 after initially reporting 6.8. Both agencies placed it at a shallow depth of roughly 10 to 15 kilometers (6 to 9 miles), which is part of why the shaking was felt so widely, reaching Oaxaca, Mexico City, Guatemala and El Salvador.
Why Costa Rica sits in the clear comes down to distance and direction. The epicenter is more than a thousand kilometers up the coast, and the energy that drives a tsunami toward any given shoreline falls off sharply over that kind of separation. The waves that matter are aimed at the coastline closest to the rupture, in this case the Chiapas and Guatemala shoreline, where authorities warned of stronger currents and rising water. Mexico’s navy tsunami center said parts of the Chiapas and Oaxaca coast could see the sea rise by up to 105 centimeters (about 3.4 feet) and urged people there to stay off the beaches until the alert lifted.
For anyone in Costa Rica right now, the forecast points to little or no change along Costa Rica’s Pacific beaches, so a normal beach day is not affected by this quake. The standing advice still holds any time you are near the water and feel strong or prolonged shaking: move to higher ground and wait for an official all-clear rather than going down to watch the sea. Friday’s earthquake, though, does not call for that response on this side of the region.
As of this afternoon, authorities in Mexico had not reported any deaths or serious damage, and assessment teams were still checking for effects near the epicenter. Mexico’s navy secretary, speaking at the president’s daily briefing, described the event as causing no serious harm. Figures on magnitude and any damage remain preliminary and may be revised as agencies complete their reviews.
