Angkatan laut Inggris merilis beberapa gambar hasil survey dasar laut dari kapal The Royal Navy's HMS Scott.
Ada dua hipotesa mekanisme tsunami yg terjadi di Aceh kemaren. Yang satu akibat pengangkatan dasar laut yg kedua akibat longsoran bawah laut, atau kombinasi keduanya bersama/berurutan. Hasil survey angkatan laut Inggris ini memberikan pandangan baru tentang tsunami, serta gempa sebagai pemicu. Kalau benar bahwa longsoran dapat menyebabkan tsunami besar, maka pemetaan dasar samodra menjadi sangat penting utk dilakukan. Disamping identifikasi titik2 kritis gempa seperti yg dilakukan Danny dkk, maka identifikasi lokasi2 lereng2 kritis menjadi titik rawan dimana kemungkinan tsunami terjadi juga sangat penting untuk memperkirakan potensi tsunami. Seperti yg disinggung kemaren soal tsunami Selat Makassar, dimana tsunami disana lebih banyak disebabkan oleh longsoran bawah laut yg terpicu oleh gempa. Maka potensi tsunami bisa saja tidak hanya menyangkut gempa saja namun juga termasuk pemetaan lereng kritis. Nah sekali lagi kolaborasi ilmu2 yg berkaitan sangat diperlukan, antara ahli longsor permukaan dan longsor bawah permukaan dapat berkolaborasi melihat gejala-gejala ini. ah banyak yg mesti dilakukan ... RDP =================================== Tsunami 'landslide' revealed >From correspondents in London February 10, 2005 From: Agence France-Presse Tsunami / MOD Epicentre ... this image shows a rift in the earth's crust deeper than the Grand Canyon in the US. Pic: UK Ministry of Defence. THE British Navy has released the first images of the seabed at the epicentre of last year's killer earthquake and tsunami that reveal the massive canyons and ridges left by the collision of two of the earth's plates. The Royal Navy's HMS Scott has been taking underwater sonar readings off the Indonesian island of Sumatra to try to find out how the earthquake unfolded and then produced the giant waves that have killed nearly 300,000 people in 11 countries. The ship's officers presented the readings in the form of coloured digital mapping at the United Kingdom Hydrographic Office in Somerset, England, indicating a large landslide some 100m high by 2km in length. HMS Scott's Commanding Officer Steve Malcolm said initial assessments by scientists indicate two of the earth's tectonic plates clashed together, causing a ridge on the seabed which forced sea water to travel upwards to form the devastating tsunami on December 26. It must have occurred "like the rumpling up of a carpet," he said. He said he hoped the survey would give a warning as to when this could happen again "with the aim of removing the likelihood of such a terrible loss of life". The survey will provide the "base map" for future extensive research into the process of how earthquakes work and how they produce tsunamis. Data will help produce charts to build a picture of what happened on December 26 and what might happen next. The commander said it was hoped the Indonesian government would permit the release of as much information as possible to the wider local community "to give warning to prevent such a tragedy happening again". He said the survey and its images, though unable to give exact predictions of when earthquakes will occur, could indicate a level of risk. The depth of the water in the area of the epicenter varies between 200m and 5000m metres, all of which is within the HMS Scott's capability, scientists say. The epicenter of the quake, which measured a massive 9.0 on the Richter scale, lies within the Indonesian Exclusive Economic Zone. The survey will fall under the definition of Marine Scientific Research under the UN Convention on Law of the Sea. HMS Scott sailed from Plymouth's Devonport Naval Base in November last year to undertake a program of military-based data gathering in the North Atlantic, Arabian Sea and Indian Ocean. Scientists from Southampton Oceanography Centre and the British Geological Survey have been working with the crew on the Scott since January 26. The images show bands of colour representing different seabed depths due to ridges and canyons in the seabed structure. Those in blue are some 4300m deep (canyons) while those in red are shallower at around 1000m deep (ridges). The naval staff said they believed that after the collision of the plates, high ridges in the structure of the seabed crumbled to form a "canyon". The images show the "canyon" created from the landslide movement in blue. Commander Malcolm described this movement as like "scree sliding down the side of a quarry". Royal Navy Captain Ian Turner told the conference: "I believe from a scientific perspective the images from the seabed of Sumatra are no less exciting or significant than the images we saw recently beamed back from space from the surface of the planet Triton." The earthquake's epicentre is shown on the images with a small yellow dot and the centre of movement of the plates is shown with a red dot. -- my blog : http://putrohari.tripod.com/Putrohari/ --------------------------------------------------------------------- To unsubscribe, send email to: [EMAIL PROTECTED] To subscribe, send email to: [EMAIL PROTECTED] Visit IAGI Website: http://iagi.or.id IAGI-net Archive 1: http://www.mail-archive.com/iagi-net%40iagi.or.id/ IAGI-net Archive 2: http://groups.yahoo.com/group/iagi Komisi Sedimentologi (FOSI) : Deddy Sebayang([EMAIL PROTECTED])-http://fosi.iagi.or.id Komisi SDM/Pendidikan : Edy Sunardi([EMAIL PROTECTED]) Komisi Karst : Hanang Samodra([EMAIL PROTECTED]) Komisi Sertifikasi : M. Suryowibowo([EMAIL PROTECTED]) Komisi OTODA : Ridwan Djamaluddin([EMAIL PROTECTED] atau [EMAIL PROTECTED]), Arif Zardi Dahlius([EMAIL PROTECTED]) Komisi Database Geologi : Aria A. 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