Metal 3D printed model offers insight into seismic waves from earthquakes –


It seems like no matter where you live, there’s some sort of extreme weather situation to deal with; I’m in Ohio, so we have tornadoes all spring. In more tropical climates, such as Australia, India, and the Gulf Coast of North America, hurricanes occur, and blizzards are fairly common in the upper Midwest and Great Plains, although they can also hit high altitude peaks in the tropics.

In the west, and in places like Nepal and Haiti, there are earthquakes, which have always seemed really scary to me; more than 9,000 people were killed in a massive earthquake in Mexico City in 1985, even though its epicenter was more than 200 miles away. But researchers from University of Chicago are using 3D printing to learn more about how the ground shakes after an earthquake and how layers underground can increase or decrease damage.

University of Chicago geoscientist Sunyoung Park shows simulations of seismic waves from a new technique that uses metal 3D printers to better understand earthquake shaking.

Different layers, accumulated over billions of years, make up the soil, and they are all different – some can be brittle, others soft. During an earthquake, these layers all react differently and seismic waves can ricochet depending on the intensity and depth of the earthquake, in addition to nearby geography. It is therefore very difficult to predict the damage that an earthquake could cause. For example, Mexico City is built on an ancient basin surrounded by mountains, and researchers believe that the region’s soft foundations made the shaking stronger, resulting in terrible damage. Computer models help a little, but they are not completely accurate.

“Simulating all of this is really hard to do, not only because it’s computationally intensive, but we don’t know enough about the physics on a small scale, that is, up to a mile in diameter or less. For example, if there are water-filled aquifers or magma chambers, how does this affect the waves? We don’t know for sure,” said Sunyoung Park, a geophysicist at the University of Chicago.

Physical models of the ground have also been tried, but they take a long time to make, and range and range are limited at best. But 3D printing might be a better approach to modeling an earthquake. Park and the other researchers published a paper about their work, describing how they used a Concept Laser M2 Cusing metal 3D printer and its direct metal laser melting (DMLM) technology to better understand how seismic waves travel through the ground. The printer’s laser heats the stainless steel powder to form multiple layers on top of each other, and by changing the speed and intensity of the laser, it can actually simulate different types of rocks by making the layers denser or porous.

“We know you would feel the same earthquake differently if you were in a basin or on a mountain, but predicting or simulating that is really difficult, partly because it’s hard to get the level of detail you have. need. With these 3D models, you can get a level of granularity that really helps you see patterns you wouldn’t otherwise see. It’s a really cool technique,” ​​explained Park, who was the study’s lead author.

Park, center, works with his group members Sifang Chen, left, and Jiong Wang, right.

The team wanted to study how seismic waves of different frequencies propagate through the ground, and focused specifically on high-frequency waves, as they are thought to be responsible for more damage to buildings and infrastructure. Using the printer, they 3D-printed an 8-inch-long, 250,000-to-1 scale replica of the rock beneath Los Angeles, which is no different from the rock beneath Mexico City. Using lasers and other equipment, the researchers simulated an earthquake and monitored the 3D printed model to see how the waves moved through the layers.

According to Park, the results were very similar to data recorded during actual earthquakes, but they were surprised by some findings, such as that “high-frequency waves are more diminished” in the basin, “which is almost exactly the opposite”. what we thought before. Because other scientists observed that low frequency waves were amplified in a pond environment, they thought the same would be true for high frequency waves. But using the 3D-printed metal model, the UChicago team discovered that the high-frequency waves seemed to reflect off the edge of the pool.

Park explained: “This seems to imply that what we have understood for low frequency waves does not hold for high frequency waves, and that we might need a different framework to understand these jerks.”

Setup for seismic experiments on the 3D printed model. The thin arrows indicate the locations of the laser source (red) and receiver (blue). A thick red arrow indicates the direction in which the laser is scanned along the top side of the model.

Besides the fact that it only takes a few hours to print one of these models, they can also be reused; Park said the team had used their Los Angeles replica in more than 2,000 experiments. Plus, she thinks these models could also be used for similar types of research.

“We could even do other planets; for example, we know from seismic sensors on the moon and Mars that they experience earthquakes and moonquakes, but their records are quite different from those of earthquakes. One could imagine creating scale models of the Moon or Mars to try to understand,” she concluded.

Park is holding a prototype model, which is made out of a translucent material to show off the layers. The metal block on the left is a completed model representing the ground beneath Los Angeles.

(Source: University of Chicago / Photos by Jason Smith)


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