12 May 2025—In Guilherme de Melo’s small hometown in northeastern Brazil, he remembers constant droughts that plagued the town’s twin livelihoods of agriculture and livestock and led to shortages of potable water. To remedy this, a large dam was built in the early 2000s on the river that flows through the town. Just a few years later, the news carried reports of earthquakes in the area after unusual floods raised the reservoir level behind the dam.
“This unexpected phenomenon piqued my curiosity, as I had learned in geography classes that earthquakes only occurred at tectonic plate boundaries,” said de Melo, a Ph.D. student at GEOMAR Helmholtz Centre for Ocean Research Kiel. “This personal experience when I was young, between my middle to high school level, sparked my curiosity about seismology, leading me to want to understand earthquakes better, as well as the exact cause of those events at the dam near my hometown.”
de Melo started his studies with a seismology course located about 700 kilometers away from his small town at the nearest university, the Federal University of Rio Grande do Norte (UFRN),which had been monitoring the dam’s seismicity. But there were few opportunities to study induced seismicity at the university when he started the undergraduate degree, so de Melo’s research turned toward the sea. His first major project analyzed seismic data from a single broadband station installed at the Saint Peter and Saint Paul Archipelago islets, located in the equatorial Atlantic Ocean above one of the largest transform fault systems in the sea.
His research today focuses on these faults, a special kind of slip-strike fault that occurs between ocean tectonic plates. His Ph.D. work asks an interesting but relatively under-investigated question: does rupture length and magnitude scale the same way in oceanic and continental earthquakes?
Digging into the literature, de Melo found studies from the 1990s and 2000s on the relationship of rupture length and moment magnitude for continental and continental margin earthquakes, but none on oceanic lithosphere.
However, there were some studies that investigated rupture length of the 2004 M 9.0 Sumatra earthquake, using hydroacoustic signals or T-waves. “If we have T-waves, and the method has already been used in subduction zones, we could use the same to investigate ruptures in transform faults,” says de Melo. “That’s when I started developing my method to measure ruptures and compare them with previous continental results.”
Most recently, de Melo published a paper with his advisor Ingo Grevemeyer and others that concludes earthquakes along ocean transform faults have longer rupture lengths than comparable continental earthquakes, likely because the hydrated ocean lithosphere is less rigid.
de Melo’s passion for oceanic seismology grew steadily throughout his career, with a master’s degree at UFRN, internships and visiting research positions at Institut Universitaire Européen de la Mer, Lamont-Doherty Earth Observatory and Scripps Institution of Oceanography, where he later finished a second master’s degree.
Much of his research throughout his career has used hydrophone arrays, acoustic sensors moored within the water column. “Hydrophone instruments are rich scientific tools as they can record not only acoustic waves generated by seafloor earthquakes—P and T waves—but also several other acoustic wave sources like seafloor landslides, seafloor volcanic activity, ice breaking, or animal communications like those from whales,” he explains.
Asked about his life after the Ph.D., de Melo says he plans to work in a few postdoctoral positions with the hope of pursuing an academic career as a professor. “I also plan to volunteer as a teacher for children in poor African communities for some months after my Ph.D.,” he said.
“My region of Brazil is one of the driest in the country. Despite this, our government has always sought ways to keep us with clean water in the city, such as the dam built in 2000. However, I know that the situation is even worse in many communities in Africa,” de Melo noted.
He admires efforts to educate these children in the face of this challenge. “At the same time, many communities are located near volcanoes. It surprises me to imagine that they still must survive with volcanic activity in addition to the lack of water and food, adding to the misery caused by wars and a dire economy,” he added. “I feel the desire to help with volunteer activities, teach, make donations, and learn more about their culture through the activities.”
His dream project within seismology remains firmly fixed on the ocean floor. “I would deploy ocean bottom instruments with seismometer/hydrophone sensors and seafloor geodesy instruments in some oceanic transform faults with uncommon features,” de Melo says, “to investigate both the local seismicity behavior over time and the link between the seafloor morphology and the underlying mantle using different imaging techniques.”
SSA At Work is a monthly column that follows the careers of SSA members. For the full list of issues, head to our At Work page.