Here's How Earthquakes Can Bring On Tsunamis

by Priscilla Totiyapungprasert
AFP/AFP/Getty Images

A massive earthquake struck off the southwest coast of Mexico late Thursday, resulting in at least five deaths. Residents of the nearby Chiapas state fled swaying buildings and exploding electrical transformers as homes, schools, and hospitals suffered power outages. To make matters worse, the National Tsunami Warning Center has now reported a tsunami threat to the coast of Mexico, a direct impact from the earthquake. Initial waves reached 1 meter, and the warning center forecasts hazardous tsunami waves could reach more than 3 meters above the tide along the Pacific Coast of Mexico.

It's not uncommon for earthquakes to generate tsunamis. More than 80 percent of the world's tsunamis occur in the Pacific along the Ring of Fire. This horseshoe-shaped area covers the entire west coast of the Americas and curves along the Aleutian Islands between Alaska and Russia before covering Japan, the Philippines, Indonesia, and New Zealand. The collision of tectonic plates suddenly moving past each other on the ocean floor can cause large earthquakes to rupture, and the area where collision occurs is called the epicenter. The epicenter for Thursday's earthquake occurred about 60 miles off the coast of Chiapas, near the border of Guatemala.

Earthquakes can displace large areas of the ocean floor, which displaces water, disturbs the ocean surface, and then generates long and high waves — the tsunami. The time between waves can vary from minutes to hours, and a tsunami can travel far from the earthquake source, which is why weather officials had to determine if the Mexican coast earthquake would pose a tsunami threat to Hawaii (the state received an "all clear" early Friday morning). People as far as Mexico City, 600 miles away from the epicenter, said they felt tremors.

Not all earthquakes produce tsunamis. According to the International Tsunami Information Center, it usually takes an earthquake with a Richter magnitude exceeding 7.5 to generate a destructive tsunami. The Mexican Seismological Institute said the earthquake on Thursday measured 8.4 in magnitude. It's the most powerful earthquake to hit Mexico since 1985 when an 8.0 magnitude earthquake shook Mexico City and killed at least 5,000 people.

As emergency workers aid people on the streets and check rubble, the Civil Defense in Chiapas has warned residents to prepare for aftershocks. Meanwhile, the Pacific Tsunami Warning Center reports that waves as high as 1 meter, or 3.3 feet, have already been spotted off the coast of Mexico. Warnings for further waves have been issued for Mexico and Central America, but no warnings have been issued for California, Washington, or Oregon. Residents in threatened areas should stay on alert for any updates.