Breakthrough in Seismology: UNAM Scientists in Mexico Track Undersea Earthquake Rotations

A pioneering discovery has been made by researchers from the National Autonomous University of Mexico (UNAM), who have been able to measure the rotation caused by a slow earthquake in the underwater earth’s crust for the first time ever. This development is crucial for understanding the genesis of major tsunamis and marks a significant step forward in the pursuit to forecast destructive earthquakes.

Dr. Víctor Manuel Cruz Atienza, the head scientist of the research team, spoke about the unexpected nature of this discovery and the development of the formulas that can interpret the earth’s crust rotation triggered by earthquakes. The method, called ELADIN (Elastostatic Adjoint Inversion), is a new approach to this type of research.

The six-year-long study was conducted in the Guerrero Gap, off Mexico’s west coast, in collaboration with the University of Kyoto in Japan. The research involved installing deep-sea stations equipped with integrated inclinometers for monitoring the condition of the unit.

Analyzing data from these inclinometers, the team discovered they could gauge the extent to which the ocean floor had shifted due to two slow earthquakes that took place under the sea between July and September 2021 and January and April 2022. These findings were made possible by combining various device records.

The ELADIN method indicated that the first of these slow seismic events likely triggered the magnitude 7 Acapulco earthquake on September 8, 2021, given its proximity to the earthquake’s hypocenter in the two months preceding the substantial seismic event.

Cruz Atienza explained that the real breakthrough is not merely the observation of these slow undersea earthquakes, which have been noted recently in New Zealand and Japan. Rather, the true achievement is the novel data and innovative methodologies that facilitated the detection and analysis of these events.

The Guerrero Gap, which produces the world’s most powerful slow earthquakes, may be the optimal testing ground for understanding these seismic phenomena, Cruz Atienza suggests.

Slow earthquakes, a mystery to seismologists discovered merely two decades ago, typically precede devastating earthquakes. The initial results of this research were shared at an international conference on slow earthquakes in Nara, Japan, in September 2022, and later at the American Geophysical Union’s Annual Congress in Chicago, USA, in December.

Previously, underwater rotation had only been detected in Nankai, Japan, by researchers from the Japan Agency for Marine-Earth Science and Technology, just a few months before the Mexican team’s observations in Guerrero. Cruz Atienza noted that signs of rotation in the Guerrero Gap were observed even earlier, though their implications were not yet understood.

This discovery is critical because the subduction zones at the sea’s floor, where tectonic plates meet, are the birthplaces of major earthquakes and tsunamis. In Mexico, most destructive earthquakes originate beneath the coastline, which puts nearby populations, such as Acapulco, at significant risk for tsunamis.

Cruz Atienza stresses the importance of this finding for Mexico and the urgent need for more resources to protect lives from earthquakes and tsunamis. He and his team are actively seeking funding to establish a comprehensive seismic monitoring network both offshore and on land.

Existing instruments with integrated inclinometers in Alaska, Chile, New Zealand, and Japan can now benefit from this discovery by UNAM. These instruments can now continuously provide geodetic data on the submarine rotation of the crust.

Cruz Atienza views this discovery as a way to challenge the “scientific colonialism” of wealthy nations exploiting the human and technical resources of developing regions. He believes that the data obtained should not be monopolized by the investing countries’ universities and institutions.