Researchers don’t always understand why certain tsunamis are so devastating: take, for instance, the 2018 tsunami that struck Sulawesi in Indonesia, killing more than 4,300 people – and triggered by a (not particularly severe) magnitude 7.5 earthquake. “It looked like a bulldozer had come in and leveled the town,” Costas Synolakis, a professor of civil engineering at the University of Southern California, in an interview with the University of Illinois. “This is why it is so important that we try to understand what really happened.” Recently, professors from the University of Illinois Urbana-Champaign and the California Institute of Technology worked with researchers (including Synolakis) to leverage supercomputing to better understand these events.
The focus of the research was “strike-slip faults,” where the two sides of a fault slide horizontally against each other. Strike-slip faults are found in many key at-risk areas, such as the San Francisco Bay Area. “Whenever we saw large tsunamis triggered by earthquakes along strike-slip faults, people assumed that perhaps the earthquake had caused an undersea landslide, displacing water that way,” said Ares Rosakis, a professor at the California Institute of Technology and co-lead of the study.
The researchers modeled tsunamis stemming from earthquakes on these strike-slip faults using the Blue Waters supercomputer at the National Center for Supercomputing Applications (NCSA).
There have been studies of these sorts of earthquakes before, but, the authors said, most of them had been location-specific to a fault. “What is unique about our study is that instead of considering a location-specific event, we focused on the fundamentals of a strike-slip fault system interacting within the boundaries of a narrow bay,” said Ahmed Elbanna, co-lead of the study and a professor at the University of Illinois Urbana-Champaign. “Having this simplified baseline model allows us to generalize to any place on the planet that may be at risk.”
The researchers found that intersonic earthquakes – which are so fast that their movement outpaces the waves generated by that movement – along strike-slip faults have a few phases that can trigger tsunamis, including shaking of the coastal land, water displacement and gravity-driven movement of the wave.
The study also helped identify regions at risk from these sorts of earthquakes and tsunamis, including areas in northern California, Egypt and Turkey. “The physics-based model used in this study provides critical insight about the hazard associated with strike-slip faulting, particularly, the need to account for such risk to mitigate future damage to other bays traversed by strike-slip faults,” said Illinois graduate student Mohamed Abdelmeguid, who helped run the simulations.
To learn more, read the coverage from Lois Yoksoulian here.