We often think of earthquakes as sudden, violent events that shake the ground beneath our feet. However, there is a hidden type of seismic activity called slow earthquakes that can have subtle yet significant effects on the Earth's crust. Recently, a group of seismologists from the Institute of Geophysics (IGEF) at the National Autonomous University of Mexico (UNAM) achieved a groundbreaking milestone by measuring the rotation of the ocean floor during a slow earthquake. This scientific feat not only provides frontier data for understanding the origins of tsunamis but also represents a significant step forward in the future prediction of earthquakes.
The ambitious project, running from 2016 to 2022, was a collaborative effort between the IGEF and the University of Kyoto in Japan. With funding of 6.5 million dollars, primarily provided by Japan and supplemented by Mexico through organizations like CONACYT (now CONAHCYT) and UNAM, the project aimed to explore the rotation of the ocean floor caused by slow earthquakes in Mexico's coastal areas.
Director of IGEF, José Luis Macías Vázquez, explained, "This result was made possible through a UNAM project that spanned from 2016 to 2022 and was an international collaboration between the Institute of Geophysics at UNAM and the University of Kyoto, Japan. The project received a funding of 6.5 million dollars, with two-thirds provided by Japan and one-third by Mexico, through institutions such as CONACYT and UNAM."
Through the installation of an amphibious network consisting of instruments both on land and at sea, the researchers were able to study the slow earthquakes occurring in Mexico's coastal regions. This network, deployed on the seabed off the Mexican coasts, included cutting-edge geodetic stations and inclinometers that measured the movement of the ocean floor following slow earthquakes.
Over the course of seven oceanographic campaigns conducted aboard the UNAM ship El Puma, 85 researchers contributed to the project, resulting in 24 international scientific publications and culminating in this groundbreaking discovery.
The study focused on the Guerrero Seismic Gap, an area prone to slow earthquakes. Geodetic stations were strategically placed on the seabed, and the collected data from the inclinometers provided valuable insights into the rotation of the ocean floor. These slow earthquakes, which occur between the Cocos and North American tectonic plates, go unnoticed by human beings due to their low intensity and extended duration. In Mexico, they have a periodicity of approximately 3.5 years in Guerrero and 1.5 years in Oaxaca, primarily in the southern regions of the country.
Victor Manuel Cruz Atienza, the project leader, and researcher at IGEF, explained, "Slow earthquakes appear to be a necessary condition, but not sufficient, for the occurrence of a major earthquake. Since their discovery in 1997, slow earthquakes have preceded some earthquakes. However, not all slow earthquakes have resulted in devastating seismic events. Hence, monitoring these phenomena with advanced networks, such as the one developed in this project, is crucial to identifying indicators that may signal the possibility of an earthquake."
By analyzing the data collected from the inclinometers during various oceanographic campaigns, the scientists were able to determine the extent of rotation in the seabed caused by two slow earthquakes. The first slow earthquake occurred between July and September 2021, while the second took place from January to April 2022. The researchers employed a proprietary mathematical and computational method called ELADIN (Elastostatic Adjoint Inversion) to analyze the data and calculate the rotational movement.
"We developed ELADIN, led by Josué Tago Pacheco, a geomodeler and professor at the Faculty of Engineering. It is a robust and powerful tool with unique qualities tailored to answer our research questions," Cruz Atienza explained.
Using ELADIN, the researchers concluded that the first slow earthquake most likely triggered the magnitude 7 Acapulco earthquake on September 8, 2021. The proximity of the slow earthquake's hypocenter to the subsequent significant seismic event provided valuable evidence of the connection between slow earthquakes and major earthquakes.
Vladimir Kostoglodov, the head of the IGEF Seismology Department, emphasized the importance of understanding these processes, stating, "Prevention is our way of combating nature. However, our ability to understand these processes heavily depends on the data we have access to. In marine geodesy, real-time information is crucial, and the data we currently possess is only updated annually."
With the collaboration between UNAM and the University of Kyoto concluding last year, the IGEF scientists are now seeking new sources of funding for their pioneering research. Acquiring and installing measurement equipment both at sea and on land is essential for enhancing their research capabilities. In light of this, the researchers have issued a call to investors interested in supporting this scientific field, which promises to advance our knowledge of earthquakes and better prepare us for the frequent seismic events that occur in Mexico.
Mexico's achievement in measuring the rotation of the ocean floor during slow earthquakes marks a significant milestone in earthquake research. It not only deepens our understanding of these complex phenomena but also provides valuable insights for predicting and mitigating the risks associated with earthquakes. With continued investment and research, we can hope for further breakthroughs that will ultimately make our world a safer place.