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Abstract: External forces of marine weather, such as waves, currents and wind flows, affect the course and speed of a ship under way. As a result, marine accidents, such as collisions or grounding, may occur, particularly in inshore areas. On coasts where earthquakes and tsunamis occur frequently, such as the Japanese coast, a tsunami that advances into a bay from the open sea is influenced by the submarine topography. It grows into a huge wave that could cause tremendous damage to ships under way and at anchorage. A massive earthquake occurred in the Tohoku and Kanto regions of Japan on March 11, 2011. In response, a tsunami alert, a tsunami warning and an advisory were issued for the entire Pacific coast region. This research investigates the evacuation behaviour of ships by AIS (automatic identification system) data in Tokyo Bay after the tsunami warning was issued. The unusual behaviour observed was attributed to the emergency evacuation of ships.
Key words: Great east Japan earthquake, Tsunami, AIS, ship evacuation.
1. Introduction
The direction and velocity of ships at sea change depending on external forces including wind waves, surges, and tides. The pre-eminent effect of these forces can result in disasters such as shipwrecks and collisions at coastal areas, according to Japan Coast Guard [1]. In particular, the submarine topography of the coastal areas of Japan, where earthquakes and tsunamis frequently occur, transforms tsunamis entering the bay from the ocean into large waves. This results in environmental destruction and enormous damage of ships underway or at anchor. A gigantic earthquake occurred in the Tohoku and Kanto areas on March 11, 2011 and is considered an event that occurs once in 1,000 years. Subsequently, the major tsunami warning and tsunami warning or advisory were announced to all coastal areas along the Pacific Ocean. The author has done the investigation and research on a refuge situation of the vessel at the time of this Tsunami [2-4]. This study investigated the evacuation actions of the ships at the Tokyo Bay where tsunami warnings were announced. The result shows behaviors unique to emergency evacuation situations.
2. Status of Tsunami Caused by the Great East Japan Earthquake
The epicenter of the 9.0-magnitude earthquake on March 11, 2011 at 14:46 was off the Sanriku Coast. Accordingly, the coastal areas along the Pacific Ocean, especially the Hokkaido and Tohoku regions, experienced different sizes of tsunamis. At some locations, the tsunami reached a height of greater than 10 m as reported by Nagai [5]. The coastal regions along the Pacific Ocean in Iwate, Miyagi, and Fukushima Prefectures received the major tsunami warning at 14:49, 3 min after the earthquake. In addition, all coastal areas along the Pacific Ocean received the major tsunami warning followed by the tsunami warning or advisory, 44 min after the earthquake as reported by JMA (Japan Meteorological Agency) [6]. Fig. 1 shows a tsunami warning figure which JMA announced at 15:17, 15:32 and 16:13 on March 11, 2011. In Fig. 1, black lines indicate the major tsunami warning and broken lines indicate the tsunami warning and also white lines indicate the tsunami advisory. Fig. 2 shows Tokyo Bay of the ocean area for this research. The tsunami warning was issued in Tokyo Bay at 15:32 on March 11, 46 minutes after an earthquake occurrence. About the tsunami in Tokyo Bay, the first wave was observed at the Yokohama observatory at 16:09. The wave height at this time was +0.8m. Moreover, the maximum wave was observed at 17:37. The wave height at this time was +1.5 m by JMA.
3. Analysis of Ship Evacuation Using AIS Data
Ships are usually undocked and evacuated outside the port upon the arrival of tsunamis because anchoring inside the port is extremely dangerous. This study analyzes the movements of each ship in the Tokyo Bay, which received the major tsunami warning, by using the data obtained from the AIS(Automatic Identification System).
AIS is a type of automatic dependent surveillance-broadcast technology that provides useful information such as names of the ships and call signs for distinguishing ships as well as locations, velocity, and directions of the ships, as referred to at the literature of International Maritime Organization or others. The device automatically transmits information pertaining to destinations and loadings to the neighboring ships. IMO (International Maritime Organization) mandates sequential loadings for target ships (passenger ships and ships with a total of more than 300 tons for international voyages and ships with a total of more than 500 tons for non-international voyages). The data received by AIS is broadly classified into static data (such as names of the ships and the call signs), dynamic data (such as the current locations, navigation speed, and directions), and the voyage related data (such as the draft and destinations). Table 1 shows the data contents of AIS. On the basis of the data, the conditions with the frequent changes in the motion of the ships equipped with AIS were depicted. In addition, the ships that were evacuated because of the tsunami were selected and the distribution of the areas and the distance to which they evacuated were analyzed.
Fig. 1 Tsunami warning announcement by Japan Meteorological Agency on March 11, 2011.
Fig. 2 Target area of this research.
Table 1 Contents of AIS data.
4. Analysis Results and Considerations
4.1 Analysis of Ship Evacuation Status during Tsunami
Fig. 3 and Fig. 4 show an example depicting the evacuation status of each ship during Tsunamis on the basis of AIS data obtained in Tokyo Bay. The black arrows indicate a moving ship, and the black triangles indicate an anchored ship. In addition, the broken lines show the paths of the ships during a 30-min period. Fig. 3a shows the usual ship situation of Tokyo bay at 14:30, before the earthquake. On the other hand, Fig. 3b shows the emergency ship situation of Tokyo Bay at 16:02, 30 min after the tsunami warning was issued. In particular, in the port of Chiba, many oil industrial complexes exist in the region shown by the ellipse; almost all of the tanker ships that could be confirmed from AIS data had started preparing for evacuation to outside each harbour. These ships moved to the closed-off section of Tokyo Bay, and completed evacuation.
Figs. 4a - 4c depict the status of ship evacuation and emergency ship anchoring at 1 h, 2 h and 3 h after the issuance of the tsunami warning. In the region shown by the ellipse, fluctuations in the anchorage status of each ship were observed. The large number of anchored ships shown by the black triangles in these figure is striking. In Tokyo Bay, almost all of the ships had been anchored by 21:00. Therefore, a state in which the flow of ship traffic inside the bay had almost stopped was observed. This state continued until March 13, at which time the tsunami warning was withdrawn. Such a state, which is unlikely under normal conditions, is considered a characteristic feature of evacuation activities by ships after issuance of the tsunami warning.
4.2 Comparison of Ship Flows in Usual and Emergency Situations
Fig. 5 shows the ship flows in usual and emergency situations (i.e. a week before the March 11 earthquake and a day after it, respectively) in Tokyo Bay. In each figure, the black dots indicate the one-day trajectory of a ship. Fig. 5b displays extremely few dashed lines that show ship movement immediately after the catastrophic disaster compared to Fig. 5a, which shows the ship movement one week earlier. In particular, a day after the earthquake, almost no ship entered the port or exited it to the harbors indicated by the ellipses.
Next, the number of ships that departed Tokyo Bay on both these days was determined using AIS data, by performing a statistical comparison of the passage of ships out of the Nakanose route, indicated by the region A in Fig. 5, between 0:00 and 23:59 on both days. Fig. 6 shows the results of comparison of the number of ships entering and departing Tokyo Bay on March 5 and March 12, 2011. As a result, it was confirmed that 136 and 102 ships entered Tokyo Bay on March 5 and March 12, respectively. Furthermore, it was confirmed that 179 ships departed the bay on March 5, but only 28 ships departed the bay on March 12. Further, about the difference of the number of ships of departing and entering Tokyo Bay, on March 5, the number of departing ships was 43 more than entering ships. In contrast, on March 12, the number of departing ships were 74 less than entering ships. That is, the inside of Tokyo Bay on March 12, 2011, during an emergency was overcrowded with ships. Fig. 7 shows this unusual overcrowded situations and usual situations of ships in Tokyo Bay. In each figure, the black arrows, triangles, and broken lines in the parts of this figure indicate moving ships, anchored ships, and the ship trajectories during a 30-min period, respectively. In Fig. 7b, extremely few black dashed lines which indicate the movement of a ship, and so many black triangles which indicate an anchored ship are seen as compared to those in Fig. 7a. This result suggests that ships that usually departed Tokyo Bay had stayed and taken evacuation inside the bay after the earthquake and Tsunamis.
Fig. 3 Status of emergency ship evacuation at Tokyo Bay.
Fig. 4 Status of ship evacuation and emergency ship anchoring at Tokyo Bay.
Fig. 5 Comparison of ship flows under usual and emergency situations at Tokyo Bay.
Fig. 6 Comparison of number of ships entering and departing Tokyo Bay on March 5 and March 12, 2011.
Fig. 7 Comparison of ship status under usual and emergency situations at Tokyo Bay.
5. Conclusions
Using the data obtained from AIS, this study investigated the evacuation actions of the ships equipped with AIS in Tokyo Bay during the tsunami warning announcement. The result shows that most ships started evacuating approximately 30 min after the tsunami warning announcement and completed evacuation 120 min after the announcement. And, almost all ships were carrying out the anchoring after around 21:00. Therefore, the ship state where the flows of ship traffic inside the bay had almost stopped has been checked. This state continued during two days. This contributed in understanding the actual status of the ship evacuation. The results confirm that the tsunami not only caused direct damage but also adversely affected economic activity by stopping the physical distribution of goods.
Based on the results obtained in this study, the future study will be conducted further analysis for preparing a manual that provides appropriate evacuation instructions during a tsunami. The analysis will provide more comprehensive perspectives including evacuation behaviors of all ships.
References
[1] The Occurrence of Disasters and Accidents Causing Injury or Death at Sea and Rescue Status [Online], Jan. 27, 2012, http://www.kaiho.mlit.go.jp/05kanku/contents/ news/archives/cat10/cat13/2012/2012-01-27-1743-post-5 49.html (accessed Feb. 1, 2012).
[2] H. Makino, N. Wakabayashi, Y. Yano, S. Shiotani, Research on Trend of Ship Evacuation Behavior When Tsunami Warning, Japan Institute of Navigation, Vol. 125, 2011, pp. 191-197.
[3] S. Shiotani, H. Makino, D. Terada, Analysis of ship behavior in Tsunami using AIS data, in: Conference on Coastal Engineering, JSCE (Japan Society of Civil Engineering), Vol. 2, 2011, pp. 21-25.
[4] H. Makino, S. Kanfir, K. Hasegawa, Analysing subject ship behavior recorded by AIS to extract Tsunami effect―In case of the 2011 Tohoku earthquake and Tsunami, in: Proceedings of Spring Conference of JASNAOE 2012, Kobe, Japan, 2012.
[5] T. Nagai, The history and current status of tsunami observation by the nowphas and tsunami wave formation related to the great east Japan earthquake in 2011 captured by the NOWPHAS, in: Lecture Document Collection of Review Meeting on the Great East Japan Earthquake, Tokyo, Japan, 2011.
[6] Tsunami Information [Online], Mar. 11, 2011, http://www.jma.go.jp/jp/tsunami/ (accessed Mar. 13, 2011).
Key words: Great east Japan earthquake, Tsunami, AIS, ship evacuation.
1. Introduction
The direction and velocity of ships at sea change depending on external forces including wind waves, surges, and tides. The pre-eminent effect of these forces can result in disasters such as shipwrecks and collisions at coastal areas, according to Japan Coast Guard [1]. In particular, the submarine topography of the coastal areas of Japan, where earthquakes and tsunamis frequently occur, transforms tsunamis entering the bay from the ocean into large waves. This results in environmental destruction and enormous damage of ships underway or at anchor. A gigantic earthquake occurred in the Tohoku and Kanto areas on March 11, 2011 and is considered an event that occurs once in 1,000 years. Subsequently, the major tsunami warning and tsunami warning or advisory were announced to all coastal areas along the Pacific Ocean. The author has done the investigation and research on a refuge situation of the vessel at the time of this Tsunami [2-4]. This study investigated the evacuation actions of the ships at the Tokyo Bay where tsunami warnings were announced. The result shows behaviors unique to emergency evacuation situations.
2. Status of Tsunami Caused by the Great East Japan Earthquake
The epicenter of the 9.0-magnitude earthquake on March 11, 2011 at 14:46 was off the Sanriku Coast. Accordingly, the coastal areas along the Pacific Ocean, especially the Hokkaido and Tohoku regions, experienced different sizes of tsunamis. At some locations, the tsunami reached a height of greater than 10 m as reported by Nagai [5]. The coastal regions along the Pacific Ocean in Iwate, Miyagi, and Fukushima Prefectures received the major tsunami warning at 14:49, 3 min after the earthquake. In addition, all coastal areas along the Pacific Ocean received the major tsunami warning followed by the tsunami warning or advisory, 44 min after the earthquake as reported by JMA (Japan Meteorological Agency) [6]. Fig. 1 shows a tsunami warning figure which JMA announced at 15:17, 15:32 and 16:13 on March 11, 2011. In Fig. 1, black lines indicate the major tsunami warning and broken lines indicate the tsunami warning and also white lines indicate the tsunami advisory. Fig. 2 shows Tokyo Bay of the ocean area for this research. The tsunami warning was issued in Tokyo Bay at 15:32 on March 11, 46 minutes after an earthquake occurrence. About the tsunami in Tokyo Bay, the first wave was observed at the Yokohama observatory at 16:09. The wave height at this time was +0.8m. Moreover, the maximum wave was observed at 17:37. The wave height at this time was +1.5 m by JMA.
3. Analysis of Ship Evacuation Using AIS Data
Ships are usually undocked and evacuated outside the port upon the arrival of tsunamis because anchoring inside the port is extremely dangerous. This study analyzes the movements of each ship in the Tokyo Bay, which received the major tsunami warning, by using the data obtained from the AIS(Automatic Identification System).
AIS is a type of automatic dependent surveillance-broadcast technology that provides useful information such as names of the ships and call signs for distinguishing ships as well as locations, velocity, and directions of the ships, as referred to at the literature of International Maritime Organization or others. The device automatically transmits information pertaining to destinations and loadings to the neighboring ships. IMO (International Maritime Organization) mandates sequential loadings for target ships (passenger ships and ships with a total of more than 300 tons for international voyages and ships with a total of more than 500 tons for non-international voyages). The data received by AIS is broadly classified into static data (such as names of the ships and the call signs), dynamic data (such as the current locations, navigation speed, and directions), and the voyage related data (such as the draft and destinations). Table 1 shows the data contents of AIS. On the basis of the data, the conditions with the frequent changes in the motion of the ships equipped with AIS were depicted. In addition, the ships that were evacuated because of the tsunami were selected and the distribution of the areas and the distance to which they evacuated were analyzed.
Fig. 1 Tsunami warning announcement by Japan Meteorological Agency on March 11, 2011.
Fig. 2 Target area of this research.
Table 1 Contents of AIS data.
4. Analysis Results and Considerations
4.1 Analysis of Ship Evacuation Status during Tsunami
Fig. 3 and Fig. 4 show an example depicting the evacuation status of each ship during Tsunamis on the basis of AIS data obtained in Tokyo Bay. The black arrows indicate a moving ship, and the black triangles indicate an anchored ship. In addition, the broken lines show the paths of the ships during a 30-min period. Fig. 3a shows the usual ship situation of Tokyo bay at 14:30, before the earthquake. On the other hand, Fig. 3b shows the emergency ship situation of Tokyo Bay at 16:02, 30 min after the tsunami warning was issued. In particular, in the port of Chiba, many oil industrial complexes exist in the region shown by the ellipse; almost all of the tanker ships that could be confirmed from AIS data had started preparing for evacuation to outside each harbour. These ships moved to the closed-off section of Tokyo Bay, and completed evacuation.
Figs. 4a - 4c depict the status of ship evacuation and emergency ship anchoring at 1 h, 2 h and 3 h after the issuance of the tsunami warning. In the region shown by the ellipse, fluctuations in the anchorage status of each ship were observed. The large number of anchored ships shown by the black triangles in these figure is striking. In Tokyo Bay, almost all of the ships had been anchored by 21:00. Therefore, a state in which the flow of ship traffic inside the bay had almost stopped was observed. This state continued until March 13, at which time the tsunami warning was withdrawn. Such a state, which is unlikely under normal conditions, is considered a characteristic feature of evacuation activities by ships after issuance of the tsunami warning.
4.2 Comparison of Ship Flows in Usual and Emergency Situations
Fig. 5 shows the ship flows in usual and emergency situations (i.e. a week before the March 11 earthquake and a day after it, respectively) in Tokyo Bay. In each figure, the black dots indicate the one-day trajectory of a ship. Fig. 5b displays extremely few dashed lines that show ship movement immediately after the catastrophic disaster compared to Fig. 5a, which shows the ship movement one week earlier. In particular, a day after the earthquake, almost no ship entered the port or exited it to the harbors indicated by the ellipses.
Next, the number of ships that departed Tokyo Bay on both these days was determined using AIS data, by performing a statistical comparison of the passage of ships out of the Nakanose route, indicated by the region A in Fig. 5, between 0:00 and 23:59 on both days. Fig. 6 shows the results of comparison of the number of ships entering and departing Tokyo Bay on March 5 and March 12, 2011. As a result, it was confirmed that 136 and 102 ships entered Tokyo Bay on March 5 and March 12, respectively. Furthermore, it was confirmed that 179 ships departed the bay on March 5, but only 28 ships departed the bay on March 12. Further, about the difference of the number of ships of departing and entering Tokyo Bay, on March 5, the number of departing ships was 43 more than entering ships. In contrast, on March 12, the number of departing ships were 74 less than entering ships. That is, the inside of Tokyo Bay on March 12, 2011, during an emergency was overcrowded with ships. Fig. 7 shows this unusual overcrowded situations and usual situations of ships in Tokyo Bay. In each figure, the black arrows, triangles, and broken lines in the parts of this figure indicate moving ships, anchored ships, and the ship trajectories during a 30-min period, respectively. In Fig. 7b, extremely few black dashed lines which indicate the movement of a ship, and so many black triangles which indicate an anchored ship are seen as compared to those in Fig. 7a. This result suggests that ships that usually departed Tokyo Bay had stayed and taken evacuation inside the bay after the earthquake and Tsunamis.
Fig. 3 Status of emergency ship evacuation at Tokyo Bay.
Fig. 4 Status of ship evacuation and emergency ship anchoring at Tokyo Bay.
Fig. 5 Comparison of ship flows under usual and emergency situations at Tokyo Bay.
Fig. 6 Comparison of number of ships entering and departing Tokyo Bay on March 5 and March 12, 2011.
Fig. 7 Comparison of ship status under usual and emergency situations at Tokyo Bay.
5. Conclusions
Using the data obtained from AIS, this study investigated the evacuation actions of the ships equipped with AIS in Tokyo Bay during the tsunami warning announcement. The result shows that most ships started evacuating approximately 30 min after the tsunami warning announcement and completed evacuation 120 min after the announcement. And, almost all ships were carrying out the anchoring after around 21:00. Therefore, the ship state where the flows of ship traffic inside the bay had almost stopped has been checked. This state continued during two days. This contributed in understanding the actual status of the ship evacuation. The results confirm that the tsunami not only caused direct damage but also adversely affected economic activity by stopping the physical distribution of goods.
Based on the results obtained in this study, the future study will be conducted further analysis for preparing a manual that provides appropriate evacuation instructions during a tsunami. The analysis will provide more comprehensive perspectives including evacuation behaviors of all ships.
References
[1] The Occurrence of Disasters and Accidents Causing Injury or Death at Sea and Rescue Status [Online], Jan. 27, 2012, http://www.kaiho.mlit.go.jp/05kanku/contents/ news/archives/cat10/cat13/2012/2012-01-27-1743-post-5 49.html (accessed Feb. 1, 2012).
[2] H. Makino, N. Wakabayashi, Y. Yano, S. Shiotani, Research on Trend of Ship Evacuation Behavior When Tsunami Warning, Japan Institute of Navigation, Vol. 125, 2011, pp. 191-197.
[3] S. Shiotani, H. Makino, D. Terada, Analysis of ship behavior in Tsunami using AIS data, in: Conference on Coastal Engineering, JSCE (Japan Society of Civil Engineering), Vol. 2, 2011, pp. 21-25.
[4] H. Makino, S. Kanfir, K. Hasegawa, Analysing subject ship behavior recorded by AIS to extract Tsunami effect―In case of the 2011 Tohoku earthquake and Tsunami, in: Proceedings of Spring Conference of JASNAOE 2012, Kobe, Japan, 2012.
[5] T. Nagai, The history and current status of tsunami observation by the nowphas and tsunami wave formation related to the great east Japan earthquake in 2011 captured by the NOWPHAS, in: Lecture Document Collection of Review Meeting on the Great East Japan Earthquake, Tokyo, Japan, 2011.
[6] Tsunami Information [Online], Mar. 11, 2011, http://www.jma.go.jp/jp/tsunami/ (accessed Mar. 13, 2011).