Preliminary simulation of the 2017 Mexico tsunami

Science Center Objects

Preliminary simulation of the tsunami from the September 8, 2017 M=8.1 intermediate-depth earthquake offshore of Chiapas, Mexico

A magnitude 8.1 earthquake struck offshore of the state of Chiapas, Mexico, at 4:49 a.m. UTC on September 8 (11:49 p.m. on September 7 local time). The largest earthquake ever recorded along Mexico’s southern coast, it caused extensive damage and dozens of deaths. It also triggered a tsunami in the Gulf of Tehuantepec, with maximum wave heights measuring 1.01 meter (3.3 feet) at Salina Cruz and 1.76 meters (5.8 feet) at Puerto Chiapas.

Why Wasn’t the Tsunami Bigger?

Most of the world’s tsunamis are generated by earthquakes on large faults, called “megathrusts,” along which an oceanic plate moves beneath a continental plate. Such a fault exists off southern Mexico, where the oceanic Cocos plate dives beneath the North American plate, but the break that produced the Chiapas earthquake actually happened below that megathrust, on a fault entirely within the diving Cocos plate. It occurred on a “normal” fault, along which one block of rock slid down and away from the other, at a depth of nearly 70 kilometers (more than 40 miles) below the Earth’s surface. That’s deeper than the quake that triggered the 2011 tsunami in Japan, which began with a break along the megathrust 29 kilometers (18 miles) below the surface. Because the Chiapas fault break was relatively deep, not much vertical movement was transferred up to the seafloor and from there to the overlying water. Hence the tsunami was mild—a lucky thing for coastal communities already coping with deadly shaking.

Read more detail about this event in the Sound Waves newsletter article, “A Tale of Two Tsunamis—Why Weren’t They Bigger? Mexico 2017 and Alaska 2018.”

Learn more about the influence of earthquake location on tsunamis in the USGS Sound Waves newsletter article, third figure.

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Map of oceans and continents with 3-D effect, with earthquake epicenter and cities and countries labeled.

Map shows location of earthquake epicenter (star). km, kilometers; mi, miles.

Map shows land and ocean with 3-D features of relief and depth and labeled locations such as cities and earthquake epicenter.

Map shows location of earthquake epicenter (star). km, kilometers; mi, miles.

Please note: The program used to create these simulations does not model nonlinear and breaking effects as waves travel into shallow water. Wave heights have been exaggerated to make details easier to see. 

3-D Animation shows the land in the distance with slow rippling waves that roll towards the land and then start sloshing.

Viewpoint looks to the northeast. The first 4 hours of propagation is shown. Look for the wave that reflects off the edge of the continental shelf and travels back toward shore.

3-D Animation shows the land in the distance with slow rippling waves that roll towards the land and then start sloshing.

Viewpoint looks to the southwest. The first 4 hours of propagation is shown.