謎の津波の原因は、鳥島付近の海底火山噴火かもしれません。
２０２３年１０月９日に太平洋側の広い範囲で津波が観測されました。ただ、津波は観測されたものの、その原因となる海底地震などが観測されず、「謎の津波」と報じられていました。「謎の津波」は、東京都の八丈島八重根で60センチ、高知県土佐清水市で40センチ、千葉県館山市布良・鹿児島県南大隅町で30センチなど、本州や九州、四国を含む広い範囲で観測されました。
「謎の津波」は小さな津波が重なってできた物でした。
１０月２７日、東京大学地震研究所がこの「謎の津波」について、研究発表を行いました。研究発表によると、この「謎の津波」は短時間に津波が連続して発生し、重なり合って約2倍の高さに増幅されていました。具体的には、9日の午前5時ごろから午前6時半ごろの間に、津波が13回観測されました。この津波の発生間隔は徐々に短くなっており、後半に起きた6回は、前の津波の周期と次の津波の周期が重なり合って約2倍の高さに増幅された、とのことでした。
「謎の津波」は海底火山の活動が原因かもしれません。
１１月２９日、海洋研究開発機構の発表によると、「謎の津波」の発生海域で、火山活動によるカルデラが見つかりました。カルデラとは、火山活動によりできた大きな凹地のことです。実際、１０月２０日には、鳥島から西に約50キロの海域で南北約80キロにわたって軽石とみられる浮遊物が見つかっており、海底火山の噴火によって津波が起きたとの見方もありました。カルデラは鳥島から南に80 kmほど離れた海底にあり、直径6 kmほどの大きさです。１０月に津波を発生させた現象は特定されていませんが、付近を研究船で緊急調査した海洋研究開発機構によりますと当時、「T波」という地震波がこのカルデラ周辺から出ていて、火山活動が地震や津波の原因であった可能性があるということです。このエリアを監視できる観測網はほとんどなく、今回、海底に6つの地震計が設置されました。12月に回収し、カルデラ周辺の火山や地震の状況について分析が進められるそうです。
海は広くて大きいため、分からない所も多いです。
海は非常に広大です。また、海底は海上からは分かりにくいため、海底の地形を把握するは音波探査（ソナー）を利用するしかありません。ソナーで探索できる範囲は狭いため、海底地形を把握できる面積は、広大な海の中では非常に小さい領域に限られます。そのため、今回のように全く観測機器が無い海域も多々あります。現在、南海トラフ沖地震が危惧されているので、地震計などは南海トラフ付近に多く設置されています。今回のように、観測機器が無い海域で新規海底火山などが出来ているかもしれません。
海底は海上からは分かりにくいので、実際に見てみると様々な発見があります。海洋研究開発機構ほど本格的では無くても、水中ドローンで観察した海底は十分に興味深い発見があります。是非、一度身近な海や湖の海底・湖底を観察してみませんか？当社では水中ドローンを格安でレンタルしております。
#津波 #鳥島 #水中ドローン
The cause of the mysterious tsunami may be an undersea volcanic eruption near Torishima.
On October 9, 2023, a tsunami was observed over a wide area on the Pacific side. However, although a tsunami was observed, no submarine earthquake was observed, leading to the report calling it a "mysterious tsunami." The "mysterious tsunami" was 60 cm in Yaene, Hachijojima, Tokyo, 40 cm in Tosashimizu City, Kochi Prefecture, and 30 cm in Fura, Tateyama City, Chiba Prefecture, and Minamiosumi Town, Kagoshima Prefecture, over a wide area including Honshu, Kyushu, and Shikoku. It was observed in
The "mysterious tsunami" was created by small tsunamis overlapping each other.
On October 27th, the Earthquake Research Institute of the University of Tokyo made a research presentation regarding this "mysterious tsunami." According to a research report, this "mysterious tsunami" was a series of tsunamis that occurred in a short period of time, and when they overlapped, they were amplified to about twice the height. Specifically, tsunamis were observed 13 times between around 5 a.m. and around 6:30 a.m. on the 9th. The interval between these tsunamis has gradually become shorter, and the six waves that occurred in the latter half were amplified to about twice the height as the cycle of the previous tsunami overlapped with the cycle of the next tsunami. did.
The "mysterious tsunami" may be caused by submarine volcanic activity.
On November 29, the Japan Agency for Marine-Earth Science and Technology announced that a caldera caused by volcanic activity was discovered in the area where the "mysterious tsunami" occurred. A caldera is a large depression created by volcanic activity. In fact, on October 20, floating objects that appeared to be pumice were found in a sea area about 50 kilometers west of Torishima, stretching about 80 kilometers north to south, leading some to believe that the tsunami was caused by the eruption of an undersea volcano. The caldera is located on the ocean floor about 80 km south of Torishima and has a diameter of about 6 km. The phenomenon that caused the tsunami in October has not been identified, but according to the Japan Agency for Marine-Earth Science and Technology, which conducted an emergency survey of the area using a research vessel, seismic waves called "T waves" were being emitted from around the caldera at the time, indicating volcanic activity. This means that it may have been the cause of the earthquake and tsunami. There are few observation networks that can monitor this area, and this time, six seismometers were installed on the ocean floor. It is said that it will be recovered in December and that an analysis of the volcanic and earthquake conditions around the caldera will be carried out.
The ocean is vast and large, so there are many places we don't understand.
The ocean is very vast. Additionally, since the ocean floor is difficult to see from the sea, the only way to understand the topography of the ocean floor is to use sonar. Because the area that can be searched using sonar is narrow, the area in which the ocean floor topography can be determined is limited to a very small area within the vast ocean. As a result, there are many areas in the ocean where there is no observation equipment at all, like this time. Currently, there are concerns about an earthquake off the coast of the Nankai Trough, so many seismometers and other equipment are being installed near the Nankai Trough. As in this case, new submarine volcanoes may be forming in areas where observation equipment is not available.
The ocean floor is difficult to see from the sea, so there are many discoveries to be made when you actually look at it. Even if it is not as serious as the Japan Agency for Marine-Earth Science and Technology, there are plenty of interesting discoveries to be made on the ocean floor observed using underwater drones. Why not take a look at the ocean and lake bottoms of your local oceans and lakes? We rent underwater drones at low prices.
#Tsunami #Torishima #UnderwaterDrone
