The quake was reported 63 kilometers south of Coalcomán de Vázquez Pallares, off the coast of Michoacán state, according to Mexico's National Seismological Service.
Government officials have indicated that at least one death in the port of Manzanillo was caused by the earthquake when a department store roof collapsed.
According to the US Geological Survey (USGS), "very strong" to "severe" shaking was reported in Calimo, a city about 185 kilometers north of the epicenter. Video footage purported to show a collapsed part of the Punto Bahia Mall in Manzanillo, Colima state.
Violent shaking was also seen across Michoacán state, that closest to the epicenter.
The quake was felt 465 kilometers away in the capital of Mexico City, where it reportedly caused buildings to "sway a bit." However, in Puerto Vallarta, almost as far away but laying along the same fault line, significantly more shaking was reported.
The unmistakable eerie ring of the warning sirens can be heard echoing through Mexico City streets in videos posted on social media, although it only seemed to cause some tree branches and traffic lights to swing. People could be seen gathering in the streets.
The quake has struck on the anniversary of two other devastating earthquakes: one in 1985 that killed 10,000 people, and another in 2017 that killed 360. Incidentally, many areas of the city reportedly held earthquake response drills earlier in the day. The 1985 quake, a mega-powerful 8.1, occurred in the Michoacán seismic gap, just like Monday's quake. It was the most intense earthquake ever recorded in Mexico, being regarded as having a maximal Mercalli intensity of IX (Violent).
Tsunami Evacuations Begun
The US Geological Survey (USGS) said Monday's earthquake was a thrust quake, in which rapid vertical displacement occurs, and happened at a shallow depth of just 15 kilometers. Thrust quakes are more likely to produce tsunamis than lateral strike-slip quakes, the other major kind of earthquake.
About an hour after the quake, the water level reportedly peaked in Puerto Vallarta about 40 centimeters above normal. All along the region's coast, tsunami evacuation orders have been given.
About 90 minutes after the quake, another, smaller one was reported in the same area, with a magnitude of 5.1, according to the National Seismological Service.