TALLINN - According to the Estonian Safety Investigation Bureau, the first two days of the preliminary investigation of the wreck of the MS Estonia passenger ferry were fruitful -- surveys of the shipwreck and the surrounding seabed were carried out with a multibeam sonar, as a result of which the researchers received an initial overview of the ship's condition.
"On Friday, July 9, at 3 p.m., we started surveying the shipwreck with a multibeam sonar as planned to map the position of the ship and the condition of the surrounding seabed," Rene Arikas, head of the Safety Investigation Bureau, said. "The survey of the first day took a long time, and we did not finish the work until late in the evening, when it started getting dark outside and the work was interrupted by the increasing wind and waves, which hindered the activities of the Swedish research vessel Electra af Asko. Despite the waves, the data and image quality achieved with the multibeam sonar is surprisingly good. For the night, the research mother ship EVA-316 sailed to Lehtma and Electra af Asko to the Finnish port of Hanko. At night, the data of the multibeam sonar survey were processed, and in the morning we were able to return to the site of the MS Estonia accident."
According to Arikas, the bow, keel and stern of the MS Estonia wreck are clearly distinguishable in the image created by the multibeam sonar. One can see the bridge, the deck structure, the rows of windows on the upper decks and the anchor, propeller and other details. Deformations in the middle of the hull are also visible.
"In the area around the wreck to the north of the ship, the image shows a ridge that is thought to have formed as a result of the ship's sinking," Arikas said. "There is a 5-7, at some point 10 meter wide channel between the ridge and the hull. A channel has also formed in the stern of the ship. The reason for the formation of the channels is probably that the ship has collapsed downwards from its original position towards the south and east, as it lies on a ridge made of an unstable layer of clay. A total of four smaller and larger collapses can be seen, the last of which occurred during the covering of the wreck in 1995-1996, when the entire bow and stern as well as the southern part were covered with geotextile, it was anchored with warps, covered with gravel, and nearly 300,000 cubic meters of sand was dumped on top of that. Apparently the dumping did not succeed and as a result there were collapses, which we can see today with the sonar surveys."
On Saturday, surveys of the entire area were conducted with a sub-bottom profiler. According to Arikas, the image shows a cross-section of the central part of the Estonian wreck. "From this, it can be estimated that the central part of the ship rests on a harder moraine on which the ship has stopped, and the bow and stern part on softer clay. We saw from the surveys that the middle part of the ship is rather higher and hogging has occurred. As a result, these are very likely to be deformations, which we plan to detect in more detail in the next few days."
On Sunday, Brian Abbott, a Mesotech 3D scanning expert from the United States, joined the team. The equipment was tested and the exact coordinates were prepared for the use of the Mesotech sonar. A 3D scanner on a tripod is planned to be placed in 20-25 different locations around the wreck to obtain very accurate survey data on both the hull damage and the seabed immediately surrounding the ship.
"After the 3D scanner survey, we will quickly carry out the initial data processing, and based on that, we will make decisions about the future course of the investigation. If the transparency of the water allows, we plan to call in an underwater robot in the coming days to study the already known deformations in the hull -- stern, middle and starboard -- in more detail and measure their exact location," Arikas said.
The transparency of seawater around the wreck is checked regularly.