A magnitude 7.3 quake — 7.4 by some measurements — struck waters near Mexico and Guatemala, sending tremors across Central America, the Chosun Ilbo and Liberty Times reported. A tsunami watch was issued for the Pacific coast.

The Liberty Times reported that the quake was shallow and could generate a tsunami. Taiwan's Central Weather Administration said it was closely monitoring any tsunami effects.

Why here

The Pacific coast running from southern Mexico into Guatemala is a subduction zone where the Cocos Plate dives beneath the North American and Caribbean plates. It is among the most seismically active stretches on earth, and magnitude-7 events are not rare.

Focal depth is the key variable for damage. The shallower the quake, the stronger the surface shaking and the higher the chance the seafloor is displaced enough to raise a tsunami. With this one classed as shallow, agencies are checking wave-height readings first.

What a tsunami watch means

A tsunami watch does not mean waves have been observed; it signals that the conditions exist and people should leave the shore. The first wave is often not the largest, so the basic rule is not to return to the coast until the alert is lifted.

Central America and Mexico host Chinese communities with long histories. The Chinese commercial districts of Mexico City, Mexicali and Guatemala City sit mostly away from the epicenter, but for those trading in coastal cities, lifting the alert is the moment business resumes.

In early earthquake coverage Sinophone Bridge Times does not fix the scale of damage. First-day numbers almost always change. What is confirmed is that the ground shook and a watch was issued; the rest takes time to emerge.