Research press release


Nature Geoscience

Apollo-era tectonic activity on the Moon



今回、Thomas Waltersたちの研究グループは、1969~1977年に4カ所のアポロ着陸地点(12、14、15、および16)の地震計で記録された28件の月震を調べた。まばらな地震観測網用のアルゴリズムを用いたことでこれらの月震の震源位置の推定が改善され、7件の浅い月震が、若い断層崖(月面が水平方向に収縮したことで生じた崖のような地形)から60キロメートル以内で起きていたこと、断層すべり事象が最も起きやすい潮汐応力が最大となる期間に起きていたことが明らかになった。Waltersたちは、断層崖近くでの月震は、巨岩の動きとレゴリス層(固体の岩石を覆う柔らかい堆積層)の擾乱と合わせて、月のテクトニック活動が現在活発であることを示唆していると結論付けている。

Some shallow moonquakes recorded during the Apollo programme were likely caused by tectonic activity, according to a paper published online this week in Nature Geoscience.

The discovery of young faults less than 50 million years old on the Moon by the Lunar Reconnaissance Orbiter Camera in 2010 has been interpreted as evidence of lunar tectonic activity. However, it is unclear how recent this activity is.

Thomas Watters and colleagues examined 28 moonquakes recorded by seismometers at four Apollo landing sites (12, 14, 15 and 16) from 1969 to 1977. Using an algorithm for sparse seismic networks, the authors were able to improve estimates of the epicentre locations of these moonquakes. They found that seven shallow moonquakes fell within 60 km (five of those within 30 km) of young fault scarps (cliff-like landform caused by horizontal contraction of the Moon’s surface), and occurred during peak tidal stress when a fault slip event was most likely. The authors conclude that the proximity of moonquakes to fault scarps, together with boulder movement and disturbance of the regolith (the upper layer of loose soil), suggest that the Moon is currently tectonically active.

doi: 10.1038/s41561-019-0362-2


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