A powerful earthquake followed by five significant aftershocks rattled southern Mexico on Friday morning, prompting emergency evacuations in major cities and the activation of state and federal security and verification protocols. A total of 17 earthquakes have struck the coastal waters, triggering tsunami bulletins to be issued for Mexico, the U.S. and Canadian West Coast, and Hawaii. As of now, there have been no tsunamis or active tsunami threats to the U.S. including Hawaii and Alaska nor Canada. The tremor was felt across large portions of southern Mexico, Guatemala, and El Salvador.
The National Weather Service’s Pacific Tsunami Warning Center in Honolulu, Hawaii has been issuing advisories since the initial 7.3 magnitude earthquake struck near the coast of Chiapas, Mexico this morning at 9:48 am. This afternoon, they issued a final bulletin that read, “Based on all available data, the tsunami threat from this earthquake has now passed.” They also added minor tsunami was observed along the Mexico Coast, with 1.1 feet tsunami measured at both Chiapas and Puerto Madero, Mexico.
Today’s magnitude 7.3 earthquake struck the Middle America Trench off the southern Pacific coast of Mexico, right along the border with Guatemala. According to the USGS, its epicenter was located about 30 miles southwest of Aquiles Serdán in the state of Chiapas. This region is a highly active subduction zone where the Cocos Plate is sliding beneath the North American Plate, which causes frequent tectonic fault line activity along the coast. The Cocos plate subducts northeastward beneath Mexico and Central America at the Middle America Trench. Based on the focal mechanism, this event occurred as a result of reverse thrust faulting, on or near the subduction zone plate interface. At the location of this event, the Cocos plate converges with North America at a rate of approximately 76 mm/yr, in a northeast direction.
While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Reverse faulting events of the size of the July 17, 2026, earthquake are typically about 60 km x 30 km in size (length x width).
Two small foreshocks preceded the July 17 earthquake, including a magnitude 4.1 on July 14 and a magnitude 4.7 88 minutes prior to the mainshock. USGS says there is a well-documented history of moderate to large earthquakes along this plate boundary. Since 1950, 50 previous earthquakes of magnitude 7 or larger have occurred in Central America on or near the active plate boundary interface. Seven earthquakes of magnitude 7 or larger have occurred within 155 miles of today’s earthquake since 1950. This earthquake is located in a similar rupture region to earthquakes of magnitude 7.3 in 1970 and magnitude 7.2 in 1993, and it is located at the southern extent of an magnitude 8.2 earthquake that occurred in 2017. The 2017 earthquake resulted in around 20 fatalities and generated a destructive regional tsunami. Shaking in the 1993 magnitude 7.2 earthquake caused one fatality and considerable damage in Guatemala. Magnitude 7 and larger earthquakes in Mexico and Guatemala have led to varying societal impacts, with the impacts largely dependent on the proximity of these earthquakes to major population centers.
USGS says  that significant damage is likely from today’s earthquake and that some fatalities are possible. Approximately six million people experienced moderate to strong shaking.
There have been 17 earthquakes/aftershocks in the area today and USGS says more are likely. Intensity has ranged from 4.3 to 7.3 with the strongest after the 7.3 being a 6.0, 5.3, 5.2, and many 5.1 magnitude events.
Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel towards land, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.
A tsunami is a series of waves not simply a single event. The time between wave crests can vary from 5 minutes to an hour. The hazard may persist for many hours or longer after the initial wave. Impacts can vary significantly from one section of coast to the next due to local bathymetry and the shape and elevation of the shoreline. Impacts can also vary depending upon the state of the tide at the time of the maximum tsunami waves.
