科学美国人:Radar Scans Detail North Korean Nukes

60秒科学节目(SSS)是科学美国人网站的一套广播栏目,英文名称:Scientific American - 60 Second Science,节目内容以科学报道为主,节目仅一分钟的时间,主要对当今的科学技术新发展作以简明、通俗的介绍,对于科学的发展如何影响人们的生活环境、健康状况及科学技术,提供了大量简明易懂的阐释。

North Korea has promised to close its underground nuclear test site at Mount Mantap later this month. Shortly thereafter, President Trump is set to meet North Korea's leader Kim Jong-un in Singapore. 

Regardless of how that goes, there’s a now an additional tool to investigate covert subterranean tests: radar. Specifically, a type called synthetic aperture radar, which works day and night, and through clouds. 

Scientists already use seismic data in their nuclear detective work. "We use the kind of techniques that earthquake seismologists use to figure some aspect of what that explosion did." Roland Bürgmann, a geophysicist at University of California, Berkeley. He says they can also measure isotopes in the air, as well as optical images pre- and post-explosion.

Now Bürgmann and his team have used synthetic aperture radar data from German and Japanese satellites to gather more clues about North Korea's biggest blast, in September 2017. Comparing before and after scans of the test site, their analysis found that the mountain bulged a dozen feet in one direction, and sunk a foot and a half. 

Using computational modeling, they then simulated what sort of blasts could have produced those movements. Their estimate: the blast was at least six times as strong as the bomb the U.S. dropped on Nagasaki in World War II. The details are in the journal Science. [Teng Wang et al, The rise, collapse, and compaction of Mt. Mantap from the 3 September 2017 North Korean nuclear test]

"I think our study shows this is an especially valuable observation that can be thrown into the mix." When the US and India launch their synthetic aperture radar satellite, called NIDAR, in 2020, we'll have even more of this new kind of data. The hope is that no unauthorized nuclear tests will take place to be discovered.

—Christopher Intagliata

[The above text is a transcript of this podcast.]

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