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Supercomputer simulation details Kaikoura earthquake's unusual features

Scientists now have a better understanding of how complex successions of fault ruptures play out.

By
Brooks Hays
The 2016 Kaikoura earthquake featured an unusually complex pattern of fault ruptures. Photo by Ulrich/Gabriel/LMU
The 2016 Kaikoura earthquake featured an unusually complex pattern of fault ruptures. Photo by Ulrich/Gabriel/LMU

March 20 (UPI) -- Thanks to a high-resolution simulation run by a supercomputer in Germany, scientists are learning new details about New Zealand's 2016 Kaikoura earthquake and its underlying geophysical processes.

The Kaikoura earthquake was one of the best documented earthquakes in history, but it was also one of the most unusual. To better understand the causes of the multi-segment earthquake, scientists in New Zealand, Germany and Hong Kong simulated the earthquake with unprecedented precision.

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Researchers described their high-resolution earthquake simulation in the journal Nature Communications.

The perplexing complexity of the Kaikoura earthquake was product of its fragmented nature. Kaikoura featured ruptures of 20 segments of a fault network.

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"Looking at the pattern of surface faults affected by the quake, one finds large gaps of more than 15 kilometers in between them," Alice-Agnes Gabriel, a geophysicist at the Ludwig Maximilian University of Munich, said in a news release. "Up to now, analyses of seismic hazard have been based on the assumption that faults that are more than five kilometers apart will not be broken in a single event."

Kaikoura's complex patterns weren't relegated to dry land. Though the earthquake originated on land, the ruptures triggered the largest tsunami in the region in several decades, suggesting the ruptures spread to ocean faults, displacing portions of the seafloor.

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As a result of the research, scientists now have a better understanding of how complex successions of fault ruptures play out.

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"This was made possible by the realistic nature of our model, which incorporates the essential geophysical characteristics of fault failure, and realistically reproduces how subsurface rocks fracture and generate seismic waves," said Gabriel.

The new models showed that Kaikoura's series of ruptures spread in a zig-zag fashion. While the speeds of individual ruptures were relatively quick, the succession of slips proceeded slowly across the fault network.

Prior to Kaikoura, scientists assumed only a large initial force could trigger such a complex and far-reaching succession of ruptures, but the latest research confirmed that Kaikoura's triggering force was relatively weak.

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"The rupture of such a weakly loaded fault was boosted by very gradual slippage or creep below the faults, where the crust is more ductile and low levels of frictional resistance, promoted by the presence of fluids," Gabriel said. "In addition, high rupture velocities generally result in the rapid dissipation of frictional resistance."

Researchers hope their model will help scientists simulate the similar fault networks elsewhere. More accurate models of local fault networks can help scientists better predict the risk of future earthquakes.

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