Two professors at the University of Rhode Island have used computer modeling to examine the deadly Anak Krakatau volcano collapse and resulting tsunami that occurred in December 2018.
Steven Carey, a professor emeritus of oceanography, and Stephan Grilli, department chair and professor of ocean engineering, have used available data to simulate the collapse. The collapse of the volcano led to a large amount of material falling into the ocean, which created a deadly tsunami.
Grilli said in five to 10 seconds after the volcanic collapse, approximately one-fourth to one-third of a cubic kilometer of material fell into the ocean.
“We can visually and physically, with the models, solve the equations that describe the behavior of the materials that slid into the water and the behavior of the water, and then the interaction of that water with the topography,” Grill said.
Carey and Grilli said the data that is currently available resembles the model simulations of the event. Current data points come from satellite imagery, Google Earth imagery, tidal gauges and preliminary field reports from other scientists who have already been on the site.
“This is kind of a validator that the source we managed to create is reasonable,” Grilli said.
The two professors, among others on their team, originally received a grant from the National Science Foundation (NSF) to travel to Indonesia and study the site of the 1883 Krakatau volcanic explosion. It is likely that some members of the team will still travel to Indonesia in the summer and examine both the 1883 explosion as well as the new collapse.
“Since we’ll be on site, rather than just looking at the old deposits of 1883, we can also take a look at the newer ones,” Grilli said.
Grilli said that testing the model outputs versus actual data collected around the site of the December collapse and tsunami will allow them to fine tune the model. This increases the likelihood that model simulations of the 1883 explosion will be more accurate.
Although preliminary data has confirmed the model simulations, Grilli said piecing together exactly what happened will take time.
“It is going to be a gradual [process of] rebuilding the understanding of what happened,” Grilli said.
Carey said there will be several important studies to conduct in Indonesia over the summer. He said a study of the wave level on the coast will be done, which can help the team determine how tall the tsunami wave was.
Drone footage that was already recorded depicts loss of vegetation and erosion of land sediment. This helps show how high water levels reached from the tsunami.
Additionally, the team will examine how much of the volcano collapsed underwater verus how much of the collapse occurred above water.
“One of the things that is the highest priority is to do a survey basically of the submarine slope of the volcano,” Carey said. “A critical input of [the] models is how much material slid into the sea. We know the part that is above land is pretty well constrained but we don’t know how much underwater failed as well.”
The team has also used the computer models to examine potential risks facing the United States. Grilli is working with the University of Delaware to map hazards all along the East Coast that could occur from a volcanic collapse and tsunami.
He said they have assembled high resolution maps for approximately one-third of the East Coast regarding such hazards.
“Just like a storm inundation map, you have an inundation map,” Grilli said. “You’re either in or out [of the inundation zone].”
However, Grilli said they will eventually have more advanced information regarding the hazards the East Coast faces from volcanic collapses and tsunamis. They hope to provide guidance for new constructions that takes into account potential flooding hazards.
Additionally, they hope to provide guidance for how far offshore boats should go in order to avoid a tsunami. Tsunami waves are smaller further away from the coast, according to Grilli.
“All these things are very important,” he said. “They are
Grilli said there has only been one recorded tsunami on the East Coast. It occurred in 1929 following a landslide. The tsunami produced damage along the coast, especially north of Maine in Newfoundland.
Due to the low frequency of such events, Grilli said it is hard to convince people to prepare for them.
“It is the same thing for volcanic eruptions,” Carey said. “It is difficult to convince people to start thinking about it when you have repose periods of tens to hundreds of years.”
However, Grilli said that as new critical facilities are built, it is essential that risks associated with volcanoes and tsunamis are used to prepare facilities.
Carey and Grilli said their work is part of a larger collaborative project. Other team members include another URI professor and several researchers in the United Kingdom. The project is in its first year, and will be funded for three total years by the NSF and it’s European equivalent.