The fact that these two were not viewed as different forces seemed to be the source of confusion. After joining the Earthquake Research Institute, Nakatani focused his research on the monitoring of the frictional strength of rocks. Frictional strength is determined by the area of two surfaces in contact. For metals, this contact area can be determined from the electrical resistance; however, electricity does not flow through rocks.
Instead, Nakatani successfully used ultrasonic waves to measure the frictional strength of rocks in a similar way to metals. Nakatani explains that when he was a child, he loved categorizing events from a statistical perspective and thinking about overall logical processes behind them. Through his studies he also discovered two things of great importance to him: taking an unbiased approach to data, and fully appreciating the obvious.
There might be something new to discover by thinking about why something happened or why the results were not as expected. Today Nakatani is focusing his efforts on trying to predict earthquakes.
The Challenge of Trying to Predict Earthquakes
All that is required now is an explanation of the mechanisms behind that process. This is an XY plotter that has been used for more than 30 years. The X axis represents the amount of motion and the Y axis the magnitude of force applied to the plane of movement. His presence resulted in our expanding the scope of experiments in the atmospheric pressure tension-torsion Instron machine, which is part of an NSF-funded Materials Research Lab at Brown University. This led to the findings of our Nature paper, namely that the friction got progressively lower as the slip speed increased.
This led to the discovery that the weakening is apparently due to the production of a lubricating layer of silica gel.
None of us would have done this without the contributions of the others. We all learned a lot from each other and had a great time doing it. Credit and Larger Version. Powdered rock from experiments as it sits in situ on top of rock samples after abrasion. Photo of the machine and sample assembly that the researchers used for their experiments. Terry Tullis of Brown University standing with the high-pressure abrasion apparatus. The salvaged horespower BMW motorcycle engine. Principal Investigators Terry E.
Co-Investigators David L. The National Science Foundation NSF is an independent federal agency that supports fundamental research and education across all fields of science and engineering. NSF funds reach all 50 states through grants to nearly 2, colleges, universities and other institutions.
Each year, NSF receives more than 50, competitive proposals for funding and makes about 12, new funding awards.
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During the passage of an earthquake rupture, that friction becomes dynamic as the two sides of the fault grind past one another. Dynamic friction evolves throughout an earthquake, affecting how much and how fast the ground will shake and thus, most importantly, the destructiveness of the earthquake.
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Yet the precise nature of dynamic friction remains one of the biggest unknowns in earthquake science. Previously, it commonly had been believed that the evolution of dynamic friction was mainly governed by how far the fault slipped at each point as a rupture went by—that is, by the relative distance one side of a fault slides past the other during dynamic sliding.
Analyzing earthquakes that were simulated in a lab, the team instead found that sliding history is important but the key long-term factor is actually the slip velocity—not just how far the fault slips, but how fast. Rubino is the lead author on a paper on the team's findings that was published in Nature Communications on June The team conducted the research at a Caltech facility, directed by Rosakis, that has been unofficially dubbed the "seismological wind tunnel. To simulate an earthquake in the lab, the researchers first cut in half a transparent block of a type of plastic known as homalite, which has similar mechanical properties to rock.
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