www.weather.gov webpage. GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. Geostationary describes an orbit in which a satellite is always in the same position with respect to the rotating Earth. This allows GOES to hover continuously over one position on Earth's surface, appearing stationary. As a result, GOES provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms and hurricanes.For updated information about the storm system, visit NOAA's WPC website: www.hpc.ncep.noaa.gov/For more information about GOES satellites, visit: www.goes.noaa.gov/ or goes.gsfc.nasa.gov/Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy.NASA Goddard Space Flight Center enables NASAâs mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASAâs accomplishments by contributing compelling scientific knowledge to advance the Agencyâs mission.Follow us on TwitterLike us on FacebookFind us on Instagram" data-caption="The monster winter storm that brought icing to the U.S. southeast moved northward along the Eastern Seaboard and brought snow, sleet and rain from the Mid-Atlantic to New England on February 13. A new image from NOAA's GOES satellite showed clouds associated with the massive winter storm stretch from the U.S. southeast to the northeast.Data from NOAA's GOES-East satellite taken on Feb. 13 at 1455 UTC/9:45 a.m. EST were made into an image by NASA/NOAA's GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Md. The clouds and fallen snow data from NOAA's GOES-East satellite were overlaid on a true-color image of land and ocean created by data from the Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Aqua and Terra satellites.The image showed that the clouds associated with the storm were blanketing much of the U.S. East Coast.At 3:11 a.m. EST, a surface map issued by the National Weather Service or NWS showed the storm's low pressure area was centered over eastern North Carolina. Since then, the low has continued to track north along the eastern seaboard. By 11 a.m. EST, precipitation from the storm was falling from South Carolina to Maine, according to National Weather Service radar. By 11 a.m. EST, the Washington, D.C. region snow and sleet totals ranged from 3" in far eastern Maryland to over 18" in the northern and western suburbs in Maryland and Virginia. NWS reported that snow, sleet and rain were still falling and more snow is expected as the back side of the low moves into the region.The New York City region remained under an NWS Winter Storm Warning until 6 a.m. on Friday, February 14 and the National Weather Service expects minor coastal impacts Thursday into Friday afternoon.New England was also being battered by the storm. At 10:56 a.m. EST, Barnstable, Mass. on Cape Cod was experiencing rain and winds gusting to 28 mph. An NWS wind advisory is in effect for Cape Cod until 7 p.m. EST. Further north, Portland, Maine was experiencing heavy snow with winds from the northeast at 6 mph. The National Weather Service in Gray, Maine noted "Significant snowfall is likely for much of western Maine and New Hampshire as this storm passes by. There will be a mix or changeover to sleet and freezing rain over southern and coastal sections tonight...before all areas end as a period of snow Friday (Feb. 14) morning." On February 13 at 10 a.m. EST, NOAA's National Weather Service noted "An abundance of Atlantic moisture getting wrapped into the storm will continue to fuel widespread precipitation...which should lift through the Mid-Atlantic States and Northeast Thursday into Friday. A wide swath of heavy snow accumulations are expected with this storm...but air [moving] off the warmer ocean water should change snow over to rain along the coastal areas. Also...a narrow axis of sleet and freezing rain will be possible within the transition zone...which is expected to set up near the I-95 corridor." For updates on local forecasts, watches and warnings, visit NOAA's www.weather.gov webpage. GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. Geostationary describes an orbit in which a satellite is always in the same position with respect to the rotating Earth. This allows GOES to hover continuously over one position on Earth's surface, appearing stationary. As a result, GOES provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms and hurricanes.For updated information about the storm system, visit NOAA's WPC website: www.hpc.ncep.noaa.gov/For more information about GOES satellites, visit: www.goes.noaa.gov/ or goes.gsfc.nasa.gov/Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy.NASA Goddard Space Flight Center enables NASAâs mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASAâs accomplishments by contributing compelling scientific knowledge to advance the Agencyâs mission.Follow us on TwitterLike us on FacebookFind us on Instagram" data-credit="NASA Goddard Photo and Video/Flickr">
科学の世界では、ずっと以前から地球が奇妙な低周波のハムノイズ（ブーンという雑音）を立てており、人間には聞こえないものの地震観測装置では検出できることを知っていた。しかし、この「微小地震」活動の原因については、科学者は確信が持てなかった。
これまでは、だ。
新しい研究が2015年2月10日に学会誌「ジオフィジカル・リサーチ・レターズ」オンライン版で発表され、次のような結果が発表された。このハムノイズは主に海洋波によるもので、私たちの惑星をかすかに震わせている。研究グループの表現で言えば「共鳴」しているのだ。
「この現象の解明に向けて大きな進歩がありました」とファビリース・アードアン博士は書面でハフポストUS版の取材に答えた。博士は、フランスのブレストにある国立科学研究センター（海洋科学）の上級科学研究員だ。「現段階で、この共鳴の由来が判明しました。次の段階は、それにどう対応するかです」
問題の原因を探ってみる。科学情報サイト「ライブ・サイエンス」によると、海洋、風、海底のコンピュータモデルに助けられ、研究グループは、ハムノイズを引き起こす海洋波の正確な種類と方法を明示することができたという。
研究グループは、海洋波間の衝突が一部の地震活動を生じることを発見した。大部分が巨大で動きの遅い海洋波の運動と圧力で、海底までずっと広がって地球にハムノイズを出させていた。
左の図は、海底に到達する巨大な波の計算高度を示している。右の写真は嵐の最中の波の種類で、フランスのボルドー南部の海岸で見られたもの。このような長い海洋波が海底に及ぼす圧力は地震波を生じて地球を振動させると、研究グループは述べている。
ハムノイズが役に立つことがある。巨大な海洋波によって引き起こされた微震活動は、地球のマントルの奥深くまで入り込む。地核まで達するという可能性もある。科学者グループによると、それを記録することにより、研究グループは私たちの惑星の内部のより詳細な実態を把握できるという。
高周波の場合、つまり人間の可聴域にあったら、その雑音はどのようなものだろうか？
「ハムノイズの1万倍の速度になれば、古いテレビがチャンネルの間で出すような『ホワイトノイズ』を聞くことができるでしょう」とアードアン博士は、ハフポストUS版の取材に答えた。
うーむ。そんな音は聞こえなくてもいいかもしれない。
この記事はハフポストUS版に掲載されたものを翻訳しました。
【関連記事】
ハフィントンポスト日本版はFacebook ページでも情報発信しています。
ハフィントンポスト日本版はTwitterでも情報発信しています。@HuffPostJapan をフォロー