Sun, May 19, 2019 - Page 9 News List

Quakes show moon, gradually shrinking, is tectonically active
「月震」頻繁發生 證實月球逐漸縮小中

The image released by NASA on Monday shows new surface features (outlined in blue) of the Moon, discovered in a region called Mare Frigoris.

Photo: AFP

The moon may be dynamic and tectonically active like Earth — not the inert world some scientists had believed it to be — based on a new analysis disclosed on Monday of quakes measured by seismometers in operation on the moon from 1969 and 1977.

Researchers examining the seismic data gathered during NASA’s Apollo missions traced the location of some of the quakes to step-shaped cliffs called scarps on the lunar surface that formed relatively recently, in geological terms, due to the ongoing subtle shrinking of the moon as its hot interior cools. “It means that the moon has somehow managed to remain tectonically active after 4.5 billion years,” said Smithsonian Institution planetary scientist Thomas Watters, who led the research published in the journal Nature Geoscience.

Earth’s tectonic activity is driven by its hot interior. The moon, which orbits our planet at a distance of about 385,000km, has a diameter of about 3,475km, a bit more than a quarter of Earth’s diameter. Images from NASA’s Lunar Reconnaissance Orbiter showed that the moon has delicately shriveled as its interior has cooled over the eons, akin to a plump grape transforming into a smaller raisin. As a result, it has acquired thousands of small surface wrinkles in the form of surface features called thrust fault scarps.

These faults push one part of the lunar crust up and over the adjoining part, said University of Maryland geologist and study co-author Nicholas Schmerr. They can reach up to about 100m tall and extend for many kilometers. “This is exciting as it wasn’t clear if the moon had already gone through this period billions of years ago and was tectonically dead, or if it was still active in the present,” Schmerr said.


1. tectonic adj.

地殼的 (di4 ke2 de5)

2. seismometer n.

地震儀 (di4 zhen4 yi2)

3. seismic adj.

地震的 (di4 zhen4 de5)

4. scarp n.

陡坡 (dou3 po1)

5. shrivel v.

萎縮 (wei1 suo1)

6. thrust fault phr.

逆斷層 (ni4 duan4 ceng2)

US astronauts placed seismometers on the lunar surface during the Apollo 11, 12, 14, 15 and 16 missions, recording 28 shallow quakes up to almost 5 magnitude, which is moderate strength. Eight quakes occurred close to faults. Other events such as meteorite impacts can produce quakes, but those would produce different seismic signatures. Boulder movements and disturbed soil near the scarps also indicated tectonic activity. Watters said experts must be mindful that quakes may strike near these scarps when planning sites for future lunar exploration and a long-term human presence on the moon.








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