It's been described as the strongest earthquake to hit Mexico since 1932.
Here's what we know so far.
- The quake is Mexico's strongest since 1932
- Waves rose as high as 0.7 metres, but a tsunami threat has passed
- Authorities say there have been dozens of aftershocks and more are likely
How big was it?
The magnitude-8.1 quake struck off Mexico's southern coast on Thursday night (local time).
The US Geological Survey (USGS) said its epicentre was in the Pacific Ocean, 87 kilometres southwest of the town of Pijijiapan and at a depth of 69 kilometres.
At least 58 people have died.
Which city was hit hardest?
The southern town of Juchitan in Oaxaca state, which is near the epicentre, was hit very hard.
Some sections of the town hall and other buildings have been reduced to rubble.
Juchitan mayor Gloria Sanchez described the situation as "critical".
There have been 45 confirmed deaths in the state of Oaxaca, 10 in Chiapas and three in Tabasco.
Is this the strongest one they've had?
Well, the last time the country faced a magnitude-8.1quake was in 1932.
That hit Jalisco, a state in the country's west on June 3.
It's said to have lasted just 95 seconds, but killed at least 400 people in both Mexico and Guatemala.
Thousands of homes were also lost.
It was then followed by two magnitude-7 quakes some weeks later, resulting in more deaths and injuries.
How does it rate against the quake that hit in 1985?
This event was stronger than that one, but far less damaging.
That quake, which struck on September 19, 1985, hit Mexico City, killing more than 5,000 people and left thousands homeless.
The difference between the two was the 1985 event hit just 322 kilometres from Mexico City.
This quake was 756 kilometres from the city.
Is there still a tsunami warning in place?
No, the threat has passed according to authorities.
The Pacific Tsunami Warning Centre said waves rose as high as 0.7 metres in the immediate aftermath of the quake.
What happens now?
Emergency services are assisting with the rescues of people in collapsed buildings.
President Pena Nieto has advised people to check their homes and office buildings for damage and gas leaks.
Authorities have said there have been dozens of aftershocks already.
And there's a chance there will be even more.