A moderate magnitude 5.0 earthquake struck off the Pacific coast of southern Mexico on Friday, 64 km south-southwest of Puerto Madero, at a crustal depth of 36.8 km. USGS telemetry, as relayed by the Earthquake Today monitoring service, put the event at 5:23 PM UTC and sized the energy release at roughly 477 tons of TNT equivalent.
Figures show a moderate class event: strong enough to lightly or moderately damage flimsy construction, and noticeable across communities for dozens of kilometers around. The estimated shaking radius runs about 100 to 250 km, with a potential damage zone of 30 to 50 km.
Where It Was Felt
Instrumental shaking models put Puerto Madero itself, 64 km from the epicenter, at MMI IV — light shaking felt by many indoors, with dishes and windows rattling and walls creaking. Guatemala City, 244.4 km east, lands at MMI III, weak: felt indoors, hanging objects swinging slightly, a vibration like a passing light truck. San Salvador, 384.2 km east, registers MMI II, very weak, felt only by a few people at rest, especially on upper floors. No felt reports had been logged for the event at the time of the initial telemetry posting.
Why It Happened
The rupture sits on one of the world’s most active subduction margins. Southern and central Mexico sits over the Middle America Trench, a boundary where oceanic plates — Cocos and Rivera — subduct under the North American Plate — a boundary that produces frequent intermediate and megathrust earthquakes. At 36.8 km, this event broke inside the brittle upper crust, and shallow ruptures produce the sharpest surface shaking and the greatest peak ground acceleration.
no tsunami warning, watch or advisory went out: the Pacific Tsunami Warning Center and USGS judged the depth and magnitude insufficient to generate hazardous vertical seafloor displacement. Aftershocks should follow across days and weeks; per Omori’s Law and Bath’s Law, secondary tremors decline in frequency over time, with the biggest historically about 1.0 to 1.2 magnitude units weaker than the mainshock.
Scale Check
For context, magnitude scales are logarithmic: each whole step multiplies ground motion amplitude tenfold and radiated kinetic energy by roughly 31.6 times. A 5.0 event sits at the bottom of the moderate band — rattling and minor structural damage at worst — while events from 6.0 upward bring destructive shaking within 160 km, and 8.0-plus quakes cause catastrophic destruction across large zones. Residents near the epicenter were advised to stay alert for aftershocks, particularly around older structures and unreinforced masonry.
