다른지구·미래/다른에너지

Atmosphere Above Japan Heated Rapidly Before M9 Earthquake

영원오늘 2011. 5. 20. 13:57


나사, 지진 예보 돌파구 찾았다

 기사입력 2008-06-06 12:39
지구 상공 100∼600㎞ 상공의 전리층에서 전자를 비롯한 이온화 입자의 밀도에변화가 일어나는 전기 장애 현상은 위성을 통해 매우 여러 차례 포착됐으며 대만 학자들은 지하 35㎞ 이내에서 발생하는 거의 모든 지진에 앞서 전리층에서 뚜렷한 전기장애가 일어나는 것을 발견했다.

이들은 지진의 원인인 지각 판의 이동으로 거대한 압력을 받은 바위가 마치 배터리처럼 전류를 방출하며 이 전류는 폴(phole)이라고 불리는 특수한 형태의 전자로 이루어져 있어 실험실에서 먼 거리를 이동한다고 설명했다.

이런 전류가 지구 표면에 도달하면 표면은 양전자를 띠게 되며 그 전기량은 전리층에 장애를 일으킬 정도로 강력하다. 이런 폴들이 지구 표면에서 다시 합쳐지면 흥분상태로 들어가며 마침내 흥분이 가라앉으면서 중파장 적외선 입자, 즉 광자를방출해 위성으로 관측할 수 있었다는 것이다.

NASA 연구진은 쓰촨성에서 일어난 규모 7.8의 대지진 이전에도 전리층에서 ‘거대한’ 신호가 나타나는 것을 관측했다고 밝혔다.

일부 과학자들은 대기권의 전기 신호와 다가오는 지진을 결부시키는데 매우 회의적이지만 NASA 연구진은 “특정 지진과 지진 전의 특정 신호 사이에 명백한 상관관계가 있음을 입증할 수 있을 것”이라면서 이를 입증하기 위한 일련의 실험을 준비중이라고 말했다.

지진을 예측하려는 과학자들의 오랜 노력에도 불구하고 아직까지 믿을만한 지진예보 시스템은 개발되지 않은 상태이지만 많은 학자들은 어떤 형태로든 조기 경보시스템이 개발돼 수많은 인명을 구할 수 있을 것으로 보고 있다.

/economist@fnnews.com이재원기자

Atmosphere Above Japan Heated Rapidly Before M9 Earthquake

Infrared emissions above the epicenter increased dramatically in the days before the devastating earthquake in Japan, say scientists.

KFC 05/18/2011

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Geologists have long puzzled over anecdotal reports of strange atmospheric phenomena in the days before big earthquakes. But good data to back up these stories has been hard to come by.

In recent years, however, various teams have set up atmospheric monitoring stations in earthquake zones and a number of satellites are capable of sending back data about the state of the upper atmosphere and the ionosphere during an earthquake.

Last year, we looked at some fascinating data from the DEMETER spacecraft showing a significant increase in ultra-low frequency radio signals before the magnitude 7 Haiti earthquake in January 2010

Today, Dimitar Ouzounov at the NASA Goddard Space Flight Centre in Maryland and a few buddies present the data from the Great Tohoku earthquake which devastated Japan on 11 March. Their results, although preliminary, are eye-opening.

They say that before the M9 earthquake, the total electron content of the ionosphere increased dramatically over the epicentre, reaching a maximum three days before the quake struck.

At the same time, satellite observations showed a big increase in infrared emissions from above the epicentre, which peaked in the hours before the quake. In other words, the atmosphere was heating up.

These kinds of observations are consistent with an idea called the Lithosphere-Atmosphere-Ionosphere Coupling mechanism. The thinking is that in the days before an earthquake, the great stresses in a fault as it is about to give cause the releases large amounts of radon.

The radioactivity from this gas ionises the air on a large scale and this has a number of knock on effects. Since water molecules are attracted to ions in the air, ionisation triggers the large scale condensation of water.

But the process of condensation also releases heat and it is this that causes infrared emissions. "Our first results show that on March 8th a rapid increase of emitted infrared radiation was observed from the satellite data," say Ouzounov and co.

These emissions go on to effect the ionosphere and its total electron content.

It certainly makes sense that the lithosphere, atmosphere and ionosphere are coupled in a way that can be measured when one of them is perturbed. The question is to what extent the new evidence backs up this idea.

The Japan earthquake is the largest to have struck the island in modern times and will certainly turn out to be among the best studied. If good evidence of this relationship doesn't emerge from this data, other opportunities will be few and far between.

Ref: arxiv.org/abs/1105.2841: Atmosphere-Ionosphere Response to the M9 Tohoku Earthquake Revealed by Joined Satellite and Ground Observations. Preliminary Results.