SOILS AND FOUNDATIONS Vol. 47, No. 6, 1075–1087, Dec. 2007 Japanese Geotechnical Society

CAUSES OF SHOWA BRIDGE COLLAPSE IN THE 1964 BASED ON EYEWITNESS TESTIMONY

NOZOMU YOSHIDAi),TAKASHI TAZOHii),KAZUE WAKAMATSUiii),SUSUMU YASUDAiv), IKUO TOWHATAv),HIROSHI NAKAZAWAvi) and HIROYOSHI KIKUvii)

ABSTRACT Testimony from eyewitnesses of the Showa Bridge collapse was collected with the objective of pinning down the cause of the collapse. On the basis of this testimony, a chronology of events was established. The bridge collapsed about 70 seconds from the beginning of the earthquake, i.e., long after the strong shock. The liquefaction-induced ‰ow occurred after the collapse of the bridge. By studying these times of occurrence, as well as observed earthquake records, the cause of the Showa Bridge collapse was deduced. The possibility of inertia force in the superstructure and liquefaction-induced ‰ow is low as the main cause of the collapse of the Showa Bridge. There is a high possibility that it was due to increased displacement of the ground in circumstances where pile deformation occurred more easily due to liquefaction.

Key words: bridge, earthquake, foundation, liquefaction, (liquefaction-induced ‰ow) (IGC:E8)

Showa Bridge was designed based on the most advanced INTRODUCTION earthquake-resistant engineering at that time and was The 16 June 1964 Niigata earthquake is well known as completed just before the earthquake. A brief review of the earthquake during which liquefaction caused serious past researches is as follows: damage to structures and is thus important in geotechni- The Society of Civil Engineers (JSCE) study cal engineering. The collapse of the Showa Bridge was showed the following as possible causes of the bridge col- one of the damages caused by the earthquake that attract- lapse, from the damage observed to the superstructure ed considerable attention (Fig. 1, Photo 1), but even and foundation structure of the bridge and to the ground now, more than 40 years later, no common under- (JSCE, 1966): 1) Horizontal movement of the left bank standing has been obtained in identifying the cause of the side ground of about 3 m towards the center of the river, collapse. 2) liquefaction of the ground, 3) horizontal external force Many studies took place immediately after the earth- worked on the bridge girder resulting from horizontal quake to investigate the cause of collapse, because the movement of the abutment on left bank side, 4) large

Fig. 1. Elevation view of the collapsed Showa Bridge (modiˆed from JSCE, 1966) (unit: m) (M: moveable bearing, F: ˆxed bearing, numbers at the bottom of the ˆgure represent horizontal displacement of the ground at each pier)

i) Tohoku Gakuin University, Japan (yoshidan＠tjcc.tohoku-gakuin.ac.jp). ii) Shimizu Corporation, Japan. iii) National Research Institute for Earth Science and Disaster Prevention, Japan. iv) Tokyo Denki University, Japan. v) The University of Tokyo, Japan. vi) Port and Airport Research Institute, Japan. vii) Kanto Gakuin University, Japan. The manuscript for this paper was received for review on August 24, 2006; approved on July 18, 2007. Written discussions on this paper should be submitted before July 1, 2008 to the Japanese Geotechnical Society, 4-38-2, Sengoku, Bunkyo-ku, Tokyo 112-0011, Japan. Upon request the closing date may be extended one month.

1075 1076 YOSHIDA ET AL.

sliding of the left bank into the river, which caused large deformation of the P6 pier resulting in the G6 girder col- lapse. Kubo (1981) has pointed out several competing factors: 1) a reduction in bearing capacity of sand layer due to liquefaction, 2) insu‹cient width to carry the gird- er at the top of the piers, 3) roller support of G6 and G7 girders on P6 pier. Several researches put the cause down to liquefaction- induced ‰ow. Hamada et al. (1986) showed that the earthquake caused considerable horizontal ‰ow displace- ment of the revetments along the from measurements using aerial photographs taken before and after the earthquake, the horizontal displacement of the revetments in the vicinity of the Showa Bridge towards the center of the river was 8 m, which is extremely large. Hamada (1992) focused on the fact that, from the tes- timony of witnesses, the Showa Bridge collapsed not at the time of the main shock but after the main shock, which makes it easier to explain the damage as occurring due to liquefaction-induced ‰ow. But he does not men- tion exactly how liquefaction-induced ‰ow in‰uenced the collapse of the bridge. Sento et al. (2001) have suggested that liquefaction-induced ‰ow occurred because of the failure at the top of the liqueˆed layer by the ‰ow of ex- Photo 1. Collapsed Showa Bridge (Modiˆed from National Informa- cess pore water pressure from downward in the process of tion Service for ) excess porewater pressure dissipation, and that this mechanism also caused the collapse of the Showa Bridge. But their research assumes a gradient in the liqueˆed layer horizontal displacement of the foundation resulting from in the direction perpendicular to ‰ow, while ignoring the ground displacement, 5) reduction in lateral ground gradient in the direction of ‰ow. resistance due to liquefaction, and 6) loss of bearing The causes set out above for the earthquake damage to capacity due to poorly welded pile joints. the Showa Bridge can be classiˆed as follows from the Several possibilities have been proposed that inertia point of view of external load: force played an important role. One of them is that piles 1) Inertia force: signiˆcant inertia force worked at yielded at the river bed position (Kuribayashi, 1987). the time of the earthquake. Another cause is that, because the predominant period of 2) Liquefaction: liquefaction reduced lateral sub- the P6 pier, by which girders are roller supported, was grade reaction, or pile displacement increased diŠerent from the other piers such as P5 and P7, by which when ground displacement occurred as apparent one girder is roller supported and the other simply sup- length above the ground surface became large. ported; phase diŠerence was generated in the piers, and 3) Liquefaction-induced ‰ow: liquefaction-induced this caused the collapse at the roller supported G6 and G7 ‰ow aŠected the pile foundations causing con- girders loaded on the P6 pier (Public Works Research In- siderable deformation to the piles, or the horizon- stitute, 1965; Arakawa et al., 1982). Tazoh et al. (1985) tal movement of the left bank pushed bridge gird- have pointed out the possibility that the damage resulted ers towards the center of the river. from ground deformation, i.e., kinematic interaction, Considering the relation between these causes and the because the location of residual bending deformation on time of the bridge collapse, it can be predicted that if iner- the P4 pier piles, matches the boundary between the soft tia force had caused the collapse, the collapse would have and stiŠer soil layers. started from the time of largest acceleration; if liquefac- As researches attributing the cause to liquefaction, tion were the cause, the collapse would have started from Okubo et al. (1966) suggested from seismic response anal- the time ground displacement increased, and if ysis, as a possible cause of the collapse, the increase in liquefaction-induced ‰ow were the cause it would have displacement due to decrease of soil rigidity through li- started after ‰ow had occurred. However, it is unclear at quefaction as well as increase of the predominant period what time the bridge collapsed and liquefaction-induced of the pier and piles structural system, combined with the ‰ow occurred. horizontal displacement of the bridge abutment. Okamo- The existing research mentioned above only suggests to (1971) has argued that liquefaction occurred in the possible causes of the damage without substantiation. coarse sand with 10 meters thickness in the river, reducing Furthermore, where analytical studies have been under- the length of the embedded section of the piers, and mak- taken, they state only how the collapse might be ex- ing the pier supports easier to bend. Added to this was the plained through hypothetical mechanisms, and have not CAUSES OF BRIDGE COLLAPSE IN NIIGATA EARTHQUAKE 1077 considered how this relates to the actual time of the col- identiˆed from G6 to the ˆnal girder on the left bank side. lapse. Thus, although a number of causes have been But the girders on the right bank side suŠered no major oŠered on the collapse of the Showa Bridge, none has damage except deformation of handrail above pier P9 reached the stage of gaining universal acceptance. (JSCE, 1966). The three phenomena that have so far been suggested The damaged P4 pier was pulled out for examination; as causes: the inertia force, liquefaction, and liquefac- there was no residual deformation in the pile for about 4 tion-induced ‰ow, are important factors for earthquake- m up from the tips, that local buckling occurred about 4 resistant design of foundations. If they are all taken into m from the pile head. The pile deformation suggested account together, the result may be over-design, but if that horizontal displacement of about 1 m in the direction they are taken into account individually the design may of the right bank (center of river) occurred around the risk danger. In order to utilize the Showa Bridge collapse pile heads (JSCE, 1966). as a lesson for future earthquake-resistant design, it is vital to clarify whether the cause was a single factor or the combination of a number of factors. However, more EYEWITNESS TESTIMONY than 40 years have passed since the Niigata Earthquake Eyewitnesses and it is now impossible to obtain any physical evidence For this study, 27 people who witnessed the collapse of relating to the cause of the bridge collapse. the bridge and the ground deformation in the vicinity of For this study, therefore, we collected testimony from the bridge provided testimony about the earthquake. eyewitnesses of the Showa Bridge collapse with the objec- Table 1 shows the location of the main eyewitnesses at tive of pinning down the cause of the collapse. On the ba- the time of the earthquake and what they were doing, and sis of this testimony we established a chronology of their major experiences after the earthquake. The dis- events, including the timing of the strong shocks of the tance from each of these witnesses to the Showa Bridge earthquake, the bridge collapse and the occurrence of was less than 200 m, with the exception of one at Niigata liquefaction-induced ‰ow. By studying these times, as Meikun High School (850 m). well as information on the earthquake motion and the The testimony of the main eyewitnesses listed in Table response found in earthquake records, we have deduced 1 is broadly classiˆed according to their location as fol- the cause of the Showa Bridge collapse. lows:1)onorbelowtheShowaBridge,2)atorinthevi- cinity of Hakusan High School, 3) in Niigata University o‹cial residence, and 4) at Niigata Meikun High School. OUTLINE OF DAMAGE TO SHOWA BRIDGE All the testimony given below, with the exception of that The Showa Bridge was a ˆrst-class bridge crossing the of Mr. Yoshida, was heard by the authors directly from Shinano River, 303.9 m in length and 24.0 m in width, the eyewitnesses, however some parts overlap with the with 12 spans. It was a simple steel girder bridge, and the content of JSCE (1966) and Horii and Miyahara (1966). spans were 27.64 m, with 13.75 m spans G1 and G12 at the ends of the bridge (JSCE, 1966). The bridge piers and abutments were of multiple column structure, with one row of 9 steel columns of 609 mm outer diameter. Table 1. Location of main eyewitnesses at the time of the earthquake The bridge was hit by the earthquake just 15 days after Location of Circumstances at No. Eyewitnesses completion, and 5 of the 12 spans fell down (G3¿G7) as eyewitnesses time of earthquake shown in Fig. 1 and Photo 1. Eyewitness testimonies of a Fukuda Corpora- the collapse were recorded in several reports including the 1 On the Showa Bridge tion employee and a Traveling in vehicles JSCE earthquake damage survey report (JSCE, 1966; Fuji taxi driver Horii and Miyahara, 1966; Miyamura, 1964). According Under the Showa 5peopleemployedAbout to restart water to the majority of eyewitnesses ˆrst the G6 girder fell 2 Bridge near left bank by or associated with pipe installation work down taking down pier P6, and caused great splashing. abutment Fukuda Corporation after lunch break Next the G5 and G7 girders fell down in tandem, fol- Hakusan High School 6 teachers of Niigata On lunch break in lowed by G4 and G3. A survey of the raised girders con- 3 concrete building (left City Hakusan High staŠ room ˆrmed that G7 had fallen on top of G6, backing up the bank) School validity of the eyewitness reports (JSCE, 1966). G6 and Hakusan High School 2 pupils of Niigata On lunch break in G7 were supported by P6 pier, and clearly the fact that 4 wooden building (left City Hakusan High classroom both girders were roller supported contributed to the col- bank) School lapse of G6 (Kubo, 1981). River bank in front 7 pupils of Hakusan The embankment of the approach road on the left 5 of Hakusan High Relaxing with friends High School bank side suŠered subsidence, many ˆssures appeared on School (left bank) the road surface, and the left bank abutment slid and tilt- Niigata University alecturerofNiigataPreparing lecture in 6 ed. Hardly any damage was caused to the abutment and residence (right bank) University study road on the right bank side; compared with the right Meikun High School 1 pupil of Niigata Relaxing on 4th ‰oor 7 bank, the left bank side suŠered much greater damage. (left bank) Meikun High School veranda Damage indicating the pounding between girders was 1078 YOSHIDA ET AL.

Testimony of Eyewitnesses at the Showa Bridge taking a passenger to the golf course on the left bank side. At the time of the earthquake water pipes were being On the G7 girder he felt a big jolt as though all four tires installed under the Showa Bridge. For this purpose had punctured and he stopped the vehicle. The vehicle scaŠolding had been set up under the bridge, and pipes 5 was stopped directly over an expansion joint. He got out m long and 300 mm in diameter had been placed on top and peered under the vehicle to examine his tires. He saw of the scaŠolding. On the day of the earthquake, these that the expansion joint was on the point of separating, were being welded together, the procedure being that at realized the danger and quickly jumped back in the vehi- each welding location materials were lowered from a cle. But the vehicle was shaking violently and he could small truck on the top of the bridge. Mr. Teiji Shuto was not proceed. At that moment the light truck of Fukuda driving the truck at low speed from left to right bank Corporation went past. He drove in low gear over the towards the welding location, and Mr. Shigeru Yoshida groaning bridge towards the right bank. In low gear his was waiting on the bridge at the welding location. speed was likely to have been about 10 km/h. Driving As Mr. Shuto drove across the G3 girder closer to the was very di‹cult because the bridge was moving violently left bank he felt the truck tilt and heard a loud noise be- from side to side and up and down, but he managed to hind him. He got out and checked the back of the truck reach the bank. After crossing the bridge he looked in his but could not identify the cause of the noise. He then saw rear view mirror and the bridge had already fallen down. up and down motion at the expansion joint and realized After that he heard the Showa oil storage tank explosion there was an earthquake. He drove the truck at a speed of and saw a column of thick smoke. 20¿30 km/h and when he reached the G7 girder he saw Mr. Shuzo Hidano (supervisor), Mr. Mito Yokoyama, the stationary Fuji taxi and he too stopped. But he felt Mr. Masaru Abe, Mr. Koji Wada, Mr. Seisaku Kita and another powerful shake and so drove oŠ in panic for the several women employees of Fukuda Corporation were right bank. When he reached the approach road on the directly under the Showa Bridge in the vicinity of the P1 rightbankhestoppedthetruck,andbythetimehehad pier (Fig. 2, point F), involved in the pipe laying work. walked back to the approach road of the bridge, the With the resumption of work at 1 pm several of them bridge had already fallen down. were about to enter the scaŠolding area under the bridge. Mr. Yoshida, who was waiting on the bridge in the vi- A road runs under the G1 girder, as shown in Photo 2, cinity of the P5 pier for the truck to arrive, describes his and from P1 pier under the bridge towards P2 pier there experience in reference Horii and Miyahara (1966) as fol- was scaŠolding for this work. lows. ``After the noon recess of that day, when I was From the abutment side of the river revetment Mr. going to start my welding work of water pipes, I felt a Hidano was watching Mr. Wada climb a ladder set up by considerable shock normal to the bridge. Some boat con- P1 pier. Mr. Yokoyama, nearby, was also watching. As veying gravel might collide against a pier, I thought. But, Mr. Wada climbed and reached out to the scaŠolding he next moment, the bridge started to rotate and vibrate up thought someone was shaking the ladder for fun and and down. When I was near pier P5, and looking towards shouted, `Don't shake the ladder!' But no-one was near the prefectural government o‹ce, the expansion joints it, and Mr. Yokoyama answered, `There's no-one there!' were moving up and down, so I thought, the bridge might At that moment one of the women yelled, `It's an earth- fall at that rate. Then, I ran away to the direction of the quake!' Mr. Kita, who was following Mr. Wada up the Niigata station, but on seeing that E (G6) girder had ladder, told exactly the same story. fallen to the water, I made up my mind to walk slowly, Mr. Wada heard the bridge abutment groaning so he for the girder to which I ran might happen to fall. The jumped down from the ladder and moved out from under bridge was vibrating as before at that time. After coming the bridge. At that moment there was a loud noise and he near the pier P11, I ran away from the bridge at my best. witnessed the bridge collapse, one section falling after A taxi (of the Fuji taxi Co., Ltd.) and a midget truck (of another starting from around the center and sending up a the Fukuda Corporation1) running on the bridge, made lot of spray. When Mr. Wada jumped down from the their good escape from the bridge. There were few men ladder, Mr. Yokoyama witnessed concrete of the left on the bridge, and an auto bike was running from the bank abutment of the Showa Bridge breaking and falling right shore side to the left. There might have been seven oŠ. Afterwards, ˆssures opened up in the road and water or eight men working under the bridge, I thought. During came spouting up. At that point Mr. Wada took shelter the earthquake, I could not hear any sound of girders due on the bank at the side of Hakusan Elementary School by to their collision, but could notice suddenly both the ˆre a pile of lumber for making rafts (Fig. 2, point G). As from the Syowa Oil Co.1, Ltd. and a black column of Mr. Wada moved away from the bridge on the down- water arising from the Sinano River1. I remember its posi- stream (Hakusan Elementary School) side, the revetment tion was at about 10 m distance from the shore of Haku- collapsed towards the river quickly. san High School. (Sic)'' Mr. Kita jumped down from the ladder and moved Fuji taxi driver Mr. Saburo Yamada experienced the away towards a mound of gravel (Fig. 2, point H) on the earthquake on the Showa Bridge, on his return trip after revetment in front of Hakusan Elementary School. But before he reached it he heard a great roar. When he 1 Fukuda Gumi Co., Ltd, Syowa and Sinano are used as Fukuda Cor- looked towards the bridge just afterwards, the girders poration, Showa, and Shinano, respectively, in the original paper. had fallen down. At almost exactly the same time as the CAUSES OF BRIDGE COLLAPSE IN NIIGATA EARTHQUAKE 1079

Fig. 2. Location of eyewitnesses and facilities at the time of the earthquake (modiˆed from Niigata Univ. and Fukada Geological Institute, 1964)

from the school buildings or nearby (Miyamura, 1964; JSCE, 1966; Horii and Miyahara, 1966). The authors ob- tained testimony from a total of 15 eyewitnesses, as shown in Table 1. The main points from that testimony are as follows: Four teachers, Mr. Hitoshi Kobayashi, Ms. Masako Otsuka, Mr. Masao Aida, and Mr. Kimiro Sano, were in a second-‰oor staŠ room in the central section of Haku- san High School's RC building (Fig. 2, point A). At the time of the earthquake, Mr. Kobayashi was standing in front of a bookcase about 2 m tall positioned in the cen- ter of the room. The three others were sitting at their desks. They all described the onset of the earthquake in the same way, as everything lurching, and Mr. Kobayashi Photo 2. Ground failure of left bank immediately upper portion of and Mr. Aida remembered that the bookcase looked as the Showa Bridge (modiˆed from photo taken by investigative team though it would fall over. of Civil Engineering Dept. of the University of Tokyo) Ms. Otsuka was eating lunch at her desk some distance from the windows on the river side of the building. The building suddenly shook strongly two or three times. She bridge collapse the revetment subsided. After that he rushed to the window and saw 15 or 20 pupils on the river moved for safety to the top of the gravel mound, but bank who seemed to be jumping up and down on the cracks opened up in it and the gravel began to shift as if revetment. The pupils, screaming, ran back towards the being drawn into the cracks, so he moved away to the school building, but cracks were opening up in the road at Hakusan Elementary School side. their feet. At that time there were choppy waves on the Mr. Abe ran with Mr. Yokoyama along the road at the surface of the river, as if someone were shaking a basin. back of the revetment where ˆssures had opened up, but She looked up when she heard someone shout, `The he thought the whole road was going to be drawn into the bridge has collapsed!' and she saw the spray of water river and he felt the ground sliding at his feet. thrown up by the collapse. It seemed as if `there was shaking, shaking and more shaking, and an aftershock Testimony of Eyewitnesses in the Vicinity of Hakusan brought the bridge down'. One of the pupils referred to High School on the Left Bank of the Shinano River above who was on the dike2 at the time of the earthquake Hakusan High School was at a distance of only about stated, `For a moment I thought my friends had pushed 30 m from the Showa Bridge on the left bank of the Shinano River. On the day the earthquake struck, many 2 The revetment is a sheet pile quay wall, and teachers and pupils called pupils and teachers witnessed the collapse of the bridge a cap of the sheet pile as dike 1080 YOSHIDA ET AL. me from behind. We got to safety by jumping across the doesn't recall which girder fell ˆrst, but the G6 and G7 top of the revetment, careful not to fall in the river. Af- girders by P6 pier fell into a V shape. After that G5, G4 terwards I realized it had been caused by an earthquake.' and G3 girders collapsed one after another. The bridge Mr. Aida felt a shake, then the bookcase in the middle began to collapse after the violent shaking had stopped. of the staŠ room began to rock and he realized it was an He remembers a car on the bridge driving towards the left earthquake. He looked towards the staircase on the north bank, and the girders it drove over collapsed immediately side of the staŠ room, and saw pupils from higher ‰oors afterwards in succession. It reached the approach road on running down like ‰eeing rabbits. Then he went down to the left bank side and managed not to fall into the cracks the ground ‰oor and ran towards the wooden school that had opened up in the surface. The river bed about 5 building (Fig. 2, point B). By the entrance to that build- m from the bank rose up in a volcanic shape about 15 m ing he witnessed the collapse of the Showa Bridge. in diameter. Then the revetment close to the bridge col- Mr. Hideji Nakagawa, a teacher at Hakusan High lapsed into the river and the school building tilted School, was watching pupils practicing cheer-leading rou- towards the bridge. tines on the sports ground to the west (upstream side) of Ms. Sumiko Watanabe, a ˆrst year pupil at Hakusan the concrete school building from a window projecting High School, was on a gravel barge moored in front of out on the north side of the building's second ‰oor. Then the school, talking with her friends. The barge began to he saw the pupils start to run towards the river dike, and rock and she thought someone was doing it deliberately wondered what was going on. Just then muddy water as a prank. The rocking grew stronger and stronger and started spurting up from the base of the prefectural gym- the barge moved about 1 m away from the bank. When nasium building (Fig. 2, point D), ˆssures began to open the barge moved back to the bank she quickly jumped up with a splitting noise, running towards the building he onto the bank. Immediately afterwards the Showa Bridge was in, and the spurting mud came closer. Wondering collapsed with a crashing noise. She stood watching the what it could be, he ran across the corridor to the staŠ bridge collapse to the end, staring in shock, and then room on the building's south (river) side, and there he felt quickly ran back towards the school building. Earth ˆs- a jolt and realized it was an earthquake. At that time the sures about 20 cm wide were opening up at her feet and bookcase in the center of the staŠ room looked as if it she was afraid she might fall into one as she ran. She did would fall over. After that he witnessed the collapse of not notice at what point the revetment collapsed, but she the Showa Bridge from the staŠ room window. The gird- believes it was after she turned her back to the river and ers collapsed in turn from the center of the bridge at 3 to 5 started to run to safety. second intervals, making loud crashes. Ms. Misako Wakui, a ˆrst year pupil at Hakusan High Mr. Shigetaka Nagumo, a ˆrst year student at Haku- School, was sitting on the revetment near the Showa san High School, was in a classroom in the school's woo- Bridge talking to her friends (see Fig. 2 for location). The den building (Fig. 2, point B). Realizing it was an earth- revetment started shaking and she thought some boys quake everyone started to panic, so he rushed out to the were doing it deliberately. The shaking grew gradually corridor to leave the building. But the ‰oorboards of the stronger and when she felt herself jolted by it, she realized corridor were being ripped up and he couldn't walk it was an earthquake. The surface of the river had started across them. Because of this he went back to the class- getting choppy, and the Showa Bridge was swaying con- room and escaped through the window towards the river. siderably to left and right. She saw a car driving across Outside he saw telegraph poles lurching violently, with the bridge, and after it had crossed, the girders from tilting or uprooting and recovering repetition. He started around the center began to collapse one after another. walking towards the Showa Bridge but ˆssures were She set oŠ at a run towards the passage that crossed be- opening up in front of him and moving in the direction of tween the concrete and wooden buildings of the school. the bridge. At this point no water or mud was spurting up At her feet the revetment subsided, falling towards the through the ˆssures. When he reached the end of the river, and she was afraid that the river water would come wooden school building (Fig. 2, point E), the Showa surging up. When she started to run the passage seemed Bridge collapsed with a great crashing noise. Immediately to undulate, and the passage and wooden building tilted afterwards someone shouted, `The dike's collapsing. It's over and sank. So she escaped towards the tennis courts, dangerous!' so he escaped towards the city baseball stadi- past the front of the concrete building, but on the way the um. After some time the ground in the center of the stadi- road was so severely cracked she could not get through. um began to rise and water came spurting out with a gur- In front of the school entrance (Fig. 2, point C) a deep gling sound. Alarmed, he moved away with others ˆssure had opened up and she escaped to the stands of the towards the stands. baseball stadium through swirling groundwater. She re- Mr. Kazuei Satomura, a third year pupil of Hakusan called that after the restoration work of the revetments High School, was close to the river revetment with three was ˆnished, there was a sandbar in the river in front of of his friends (see Fig. 2 for location). The ground began the school building that had not been there before the to shake and from the downstream direction there was a earthquake. loud noise like a train passing through a tunnel. The noise Ms. Emiko Narita, a ˆrst year pupil at Hakusan High then changed to something like oil drums rolling along, School, was sitting on the revetment in front of the woo- and after that the Showa Bridge began to fall down. He den school building relaxing with her classmates Ms. CAUSES OF BRIDGE COLLAPSE IN NIIGATA EARTHQUAKE 1081

Nagai and Ms. Wakui (see Fig. 2 for location). A small boat was tied up at the river bank in front of her. She felt herself being shaken but because she was watching the boat rocking, she thought her eyes were playing tricks. But then the roof of the wooden school building started a rolling movement and she realized it was not a hallucina- tion but an earthquake. She noticed a small truck driving on the Showa Bridge from right to left bank. She thinks it was immediately afterwards that the girder at the center started to collapse. She thinks the girder to the left of cen- ter collapsed ˆrst and then the girder to the right, and she saw 5 girders fell in total. She could not be sure how much time had passed to that point but it felt like a minute. After that she started running along the road on the river bank towards the sports ground. As she ran cracks opened up in the road, grew wider and she thought she might injure her feet. Groundwater was spurting up Fig. 3. Floor plan of the Mr. Yamagishi's house (see Fig. 2 for loca- through the cracks with a bubbling sound. She thinks the tion) ground ˆssures started to appear after the Showa Bridge had collapsed. She ran to the sports ground where pupils had been practicing cheerleading routines, but the groun- shifttowardstheriver.Heheardtheexplosionsofthe dwater was spurting up even more strongly than at the Showa oil tanks after he got away to the prefectural river bank, so she escaped towards the baseball stadium athletics ˆeld. and tennis courts. As she did not see the revetment col- lapse, it must have happened after she ran oŠ. Testimony of Eyewitness in Niigata University Residence Ms. Eiko Nagai, a ˆrst year pupil at Hakusan High on the Right Bank of the Shinano River School, was relaxing with her friends on the river bank in At the time of the earthquake Mr. Hiromasa front of the wooden school building (see Fig. 2 for loca- Yamagishi, a lecturer of Niigata University, was at his tion). Someone said, `The boys are shaking the dike university residence, a wooden, single-story house behind again'. After that she happened to look towards the Sho- the revetment on the right bank of the river (see Fig. 2 for wa Bridge and saw a vehicle like a light van cross from location). It was about 170 m away from the Showa right to left bank. Immediately after, the girder started to Bridge. He was sitting at his desk in his study at the back fall down from the center, making a crashing noise. Until of his house (see Fig. 3 for location) preparing a lecture. the bridge collapsed she did not realize it was an earth- He felt a sudden strong shock, an up-down shake, as if quake. Wanting to run to safety she looked towards the struck from below. He realized the earthquake's epicen- school building but it was sinking. Realizing it was dan- ter must be close and thought it dangerous to stay inside, gerous she ran in a daze towards the baseball stadium so he headed for the front door. But the key was the old- with earth ˆssures opening up all around her. She does fashioned screw-in type, and in his panic he could not get not recall seeing the revetment slip. the door unlocked. He gave up going out that way and as Mr. Hiroshi Nunokawa, a ˆrst year pupil at Hakusan he returned to his study the plaster was falling from the High School, was with two friends at the time of the walls. He thought he would escape through the study earthquake about 50 m upstream of the Showa Bridge on window and climbed onto the window frame. To get out- the revetment looking out across the river (see Fig. 2 for side he had to get over the window frame, which was location). Suddenly he felt a shake in the transverse direc- about waist-high, and outside, broken glass had fallen to tion to the river and heard a crashing noise. At ˆrst he did the ground, so he hesitated momentarily to get out that not realize it was an earthquake. But someone said it was way. As a result it took a little time to get outside. an earthquake and he happened to look towards the He went as far as the bank of the river, but the ground bridge. Then the central girder of the bridge collapsed, was shaking violently and cracks were visible in the followed by the girders on either side. ground so he thought it dangerous to be on the river bank He felt it was like a movie set falling apart. The bridge and moved back to a hedge growing in front of the house began to collapse about 30 seconds after he felt the ˆrst (Fig. 3). Grasping hold of the hedge he looked towards shake of the earthquake. The water spray from the col- the river and saw cracks open in the revetments and lapse reached the road. He thinks the order in which the Hakusan High School and the river surface shaking vio- girders fell was G6, G5, G7, G4, and G3. G6 fell ‰at to lently. Towards the estuary he saw black smoke rising. the water surface. Calling `Let's get away!' he started He had not heard any explosions so he did not think this running. At that time the ground was still shaking and he was the result of an explosion and ˆre. At this point the saw earth ˆssures running along the ground. Water came Showa Bridge had not collapsed. It was as the shaking spurting out of the cracks and the revetment seemed to died down and he began to feel reassured that he heard a 1082 YOSHIDA ET AL. great crashing noise. Wondering what it was, he went towards the river bank and looked in the direction of the ESTIMATION OF THE TIMINGS OF THE SHOWA bridge. The bridge began to collapse really slowly, as BRIDGE COLLAPSE AND THE OCCURRENCE OF though he was watching a ˆlm in slow motion. The sec- LIQUEFACTION-INDUCED FLOW tions shook as they fell, like falling leaves. He thought it Estimation of the Timing of the Showa Bridge Collapse took several seconds to the end. Estimation Based on Mr. Shuto's Testimony The authors visited with Mr. Yamagishi to the loca- Mr. Shuto's major movement at the time of the earth- tion, now an empty lot, and got him to re-enact his move- quake is summarized. as follows. The time it took for ments twice. This was recorded on video, and the amount him to get out, inspect the vehicle and get in again was es- of time that each action took was measured. The ˆrst timated through a reconstruction the authors undertook time Mr. Yamagishi oŠered some explanations, so he to be 15 to 20 seconds. The speed of the vehicle according pointed out that the second re-enactment was likely to be toMr.Shutohadbeenanaverage20to30km/h(5.6to more accurate and those time measurements were used. 8.3 m/s). We can deduce that the time for Mr. Shuto to According to those measurements, the Showa Bridge be- ˆnish crossing the Showa Bridge from the moment he gan to collapse about 69 seconds after the ˆrst jolt of the started the vehicle on the G3 girder was 31 to 49 seconds earthquake, and ˆnished collapsing about 91 seconds af- (The distance from the P2 pier side of the G3 girder to the ter the ˆrst jolt. Mr. Yamagishi's testimony is recorded in right bank abutment was about 257 m). Here, Dt1 the JSCE (1966) and Horii and Miyahara (1966) reports, represents the time required to slow down and stop the but he was not aware of this until the present authors in- vehicle on the G7 girder. Also, hypothesizing that a little formed him. His testimony and the re-enactment of his time was needed from the time he ˆnished crossing the behavior were made more than 40 years after the earth- bridge until it collapsed, this time is represented as Dt2. quake, but they are precisely consistent with the tes- Thus the time from the ˆrst major shake of the earth- timony he made immediately after the earthquake that quake until the bridge collapsed can be shown as: was recorded in reports at the time. (15¿20) secs＋(31¿49) secs＋Dt1 secs＋Dt2 secs ＝ (46¿69)＋(Dt ＋Dt ) secs Photographs Taken from Niigata Meikun High School 1 2 Mr. Yutaka Takeuchi, a third year student at Niigata Estimation Based on Mr. Yamada's Testimony Meikun High School, was in the corridor of his 4th ‰oor Mr. Yamada drove the distance all in low gear and his classroom (Fig. 2, building M) when the earthquake struck. He had brought his camera to school that day and when the shaking seemed to be subsiding he went back in the classroom to get his camera and took a series of shots of muddy water spurting up in the school yard from the 4th ‰oor corridor. Then he moved to the school building L and went on taking photos of earthquake damage. Mr. Takeuchi did not witness the Showa Bridge collapse, but he took a series of photos including some parts of the col- lapsed bridge and of the school building that had shifted due to liquefaction-induced ‰ow. Some were included in the JSSMFE report (1966) and all the photographs have recently been made public (JGS, 2004). The authors felt sure that establishing the times that Mr. Takeuchi's photos were taken would oŠer important clues for determining the times when sand boiling, liquefaction-induced ‰ow, etc., occurred. Mr. Takeuchi twice re-enacted his behaviour at Meikun High School at that time and we established the times when all the photo- graphs were taken (Wakamatsu et al., 2004). According to the time measurement, the ground water started spurt- ing up from the schoolyard after 3 minutes and 15 sec- onds from the time he felt the shaking. The depth of the water in the yard reached approximately 50 cm after 5 minutes and 40 seconds. After 5 minutes and 49 seconds, the buildings L and M in Fig. 2 had separated 2 meters, which were connected before the earthquake. After ap- proximately 10 minutes when he went the roof of the Photo 3. Collapse of the revetment of the Shinano River in front of school building, he came to recognize the Showa Bridge Hakusan High School and locations of the witnesses. The photo had collapsed. was taken from the Showa Bridge toward upper stream, (modiˆed from Nakagawa et al., 1965) CAUSES OF BRIDGE COLLAPSE IN NIIGATA EARTHQUAKE 1083 speed is estimated at about 10 km/h (2.27 m/s) maxi- mum. The distance from the joint between the G6 and G7 girders to the right bank abutment is 152 m, so the time needed to ˆnish crossing the bridge can be estimated as 152 m/(2.27 m/s), or 67 seconds. The girders that collapsed were from G3 to G7, so it is possible that the G7 girder collapsed after he had passed it but before he reached the right bank abutment. If the G7 girder collapsed immediately after he crossed over it, thetimethathadelapsedwouldbe27.64m/(2.27m/s)or 12 seconds. Therefore the time elapsed from the moment Mr. Yamada started the taxi until the bridge collapsed must be between 12 and 67 seconds. Mr. Yamada started the taxi after Mr. Shuto's vehicle had passed him, but the exact time is unclear.

Estimation Based on Mr. Yamagishi's Testimony According to the time measurement of Mr. Photo 4. Aerial photograph of the area around Meikun High School taken on 19th June, three days after the earthquake (modiˆed from Yamagishi's major actions, it took 69 seconds from the photo taken by Kokusai Kogyo Co. Ltd.) ˆrst shake of the earthquake until the bridge began to collapse and 91 seconds until it ˆnished collapsing.

Estimation of the Timing of the Occurrence of Liquefaction-induced Flow Estimation Based on Photographs Taken by Mr. Takeuchi Photos taken by Mr. Takeuchi of Niigata Meikun High School capture the damage to the ground and buildings after the earthquake. Four of these photos were used in an attempt to determine the time that liquefaction-in- duced ‰ow occurred. Photo 4 is an aerial photograph of the area around Meikun High School taken on 19th June, three days after the earthquake. It shows the buildings after they had shifted horizontally towards the river due to liquefaction- induced ‰ow. Looking at buildings J and K, a line linking the corners of these buildings intersects a line c-c? along the top of the parapet on the roof of building L in the ratio 0.62: 0.38. Photo 5 is a photo taken by Mr. Takeuchi at about 1.08 pm on the day of the earthquake. The buildings L and M in this photo are the same as in Photo 5. Photo taken by Mr. Takeuchi at about 1.08 pm on the day of the earthquake Photo 4. The space that can be seen between buildings L and M in Photo 5 did not exist before the earthquake and occurred as a result of liquefaction-induced ‰ow. This means that 6 minutes after the earthquake struck liquefaction-induced ‰ow had already occurred in the school grounds. Of the photos Mr. Takeuchi took before Photo 5, Photo 6 (taken at about 1.05 pm) shows buildings J and K, seen in Photo 4. A line drawn through the corners of buildings J and K, as in Photo 4, intersects the line c-c? in the ratio 0.19: 0.81. If building L did not move, and only building K moved towards the river, the c? side value should be relatively higher, and at the time Photo 6 was photographed we can infer that either building L had not shifted towards the river due to liquefaction-induced ‰ow, or that the degree of shift was still small. Thus it can be deduced that at the time Photo 6 was taken (about 1.05 Photo 6. Photo taken by Mr. Takeuchi at about 1.05 pm on the day pm), which was about 3 minutes after the earthquake oc- of the earthquake 1084 YOSHIDA ET AL.

Mr. Wada to run from the bridge to the lumber dump, a distance of about 50 m. Estimating his speed at 3 m/s, the time can be assumed to be 50 m/(3 m/s), or around 17 seconds. According to Mr. Yamagishi's testimony, as sown in Fig. 3, the bridge collapsed around 69 seconds after the ˆrst shock of the earthquake, which makes the timing of the occurrence of liquefaction-induced ‰ow at left bank near the bridge abutment 69 sec (bridge col- lapse)＋17 sec＝86 seconds after the ˆrst shock.

Relation between the Time of Showa Bridge Collapse and Time That Liquefaction-induced Flow Occurred In the estimations of timing based on testimony, the Photo 7. Photo of wave front on the Shinano River taken by Mr Takeuchi immediately before Photo 6, at about 1.05 pm (contrast time the eyewitnesses felt the earthquake is the baseline. enhancement) However, feeling an earthquake depends on circum- stances. For example, according to the Japan Meteoro- logical Agency (JMA)'s seismic intensity scale (JMA, curred, no liquefaction-induced ‰ow that had a sig- 1949; 1978), at an intensity of 2 `most people indoors feel niˆcant eŠect on the structures had yet occurred. the shake'; this would apply to Mr. Yamagishi. At an in- The argument above assumes either that buildings J tensity of 4, people walking felt the shake. Some people and K did not move due to liquefaction-induced ‰ow, or driving might also have noticed it', and so this would that they shifted horizontally without any relative dis- apply to the pupils of Hakusan High School. It can be as- placement between them. As a result the above conclu- sumed that Mr. Shuto also noticed the earthquake at this sion is not watertight. But considering that the ratio stage. According to the JMA an intensity of 2 is equiva- changed signiˆcantly between Photos 4 and 6, we can lent to an acceleration of 2.5¿8cm/s2 and an intensity 4 conclude that after Photo 6 was taken at about 1.05 pm to 25¿80 cm/s2. Figure 4 shows the acceleration and dis- some considerable liquefaction-induced ‰ow took place placement records obtained at the Kawagishicho prefec- that had a major eŠect on the structures. We cannot, tural government apartment located 1.3 km west of the however, deduce when the liquefaction-induced ‰ow be- Showa Bridge. Referring to this, we can assume that Mr. gan from these photos. Yamagishi felt the earthquake immediately after it began, Photo 7 was photographed immediately before Photo while the pupils of Hakusan High School and the Fukuda 6, at about 1.05 pm. It shows the wave front on the Corporation workers felt it as the shaking grew stronger 5 Shinano River to be parallel to the revetment (evaluation seconds or so later. of wave front by Japanese Identiˆcation Center of Foren- In order to conˆrm people's awareness of seismic mo- sic Science Co., Ltd.). This type of wave front parallel to tion, a 3-dimensional shaking table test was undertaken. ‰ow is not normally seen. Thus, assuming that this wave The seismic records observed at the Kawagishicho prefec- front resulted from the movement of the revetment due tural government apartments (Kudo et al., 2000) were in- to liquefaction-induced ‰ow, it means that liquefaction- put without warning and 9 people (6 in 20 s, 1 in 30 s, 1 in induced ‰ow had occurred within 3 minutes after the 40s,and1in50s)wereaskedtoraisetheirhandswhen earthquake. This wave formation occurred in an area they felt the earthquake ˆrst time and when they felt about 50 m out from the revetment, and the time taken strong shakes. They were positioned so that they could for the wave front due to the revetment shift to arrive at a not see each other and 6 tests were undertaken with them distance 50 m from the revetment can be calculated as standing and sitting. In all cases they felt the earthquake follows: ˆrst time immediately after the acceleration began, and According to shallow water theory, ‰ow speed is ex- the strong shakes 3.5¿7.7 secs (averaging 6.1 secs) later. pressed as the square root of the product of depth and From this we can assume that most people felt the earth- gravitational acceleration. Taking the water depth as 3 m, quake around 6 secs after it started, and we hypothesize the speed of transmission of the wave movement is thus below that the people on the bridge felt the shakes 6 5.4 m/s. It would therefore take about 10 seconds to seconds after the earthquake started. move about 50 m out from the revetment, and so we may Mr. Shuto's and Mr. Yamada's movements are shown assume that this wave movement was generated about 10 in diagrammatic form in Fig. 4. The horizontal axis seconds before the time the photo was taken (which was shows position on the bridge and the vertical axis the time about 3 minutes after the earthquake). elapsed after the earthquake struck. For better compre- hension the bridge structure and the NS component ac- Estimation Based on Testimony of Workers Under the celeration and displacement records at the Kawagishi-cho Showa Bridge on the Left Bank apartment are also shown. Here, the time lost when Mr.

Mr. Wada's movement after he realized the earthquake Shuto stopped the truck by Mr. Yamada's taxi, Dt1 ,is was summarized as follows. The time between the bridge shown as 10 seconds, and the time that elapsed after Mr. collapse and the revetment collapse was the time it took Shuto reached the right bank until he saw the bridge col- CAUSES OF BRIDGE COLLAPSE IN NIIGATA EARTHQUAKE 1085

Fig. 4. Time of the Showa Bridge collapse and occurrence of liquefaction-induced ‰ow estimated from eyewitness testimony. (Seismic acceleration and displacement waves recorded at the Kawagishi-cho apartment are after Kudo et al. (2000))

lapse, Dt2, is shown as 30 seconds. nessed or experienced the bridge collapse have been coor- The earliest estimate of the time Showa Bridge col- dinated in one diagram. lapsed is the time Mr. Yamada ˆnished crossing the G7 Next, we examined the time that liquefaction-induced girder. Assuming that to be the time he started the taxi ‰ow occurred. According to Mr. Wada's testimony it oc- immediately after Mr. Shuto had passed him, and taking curred 17 seconds after the bridge collapse, as discussed the time as the mid point of Mr. Shuto's lengthier move- above. If we assume the time that Mr. Yamagishi wit- ments (40 seconds), the time he ˆnished crossing the G7 nessed the start of the bridge collapse and the time Mr. girder was 53 seconds. This is shown on Fig. 4 as the Wada witnessed the bridge collapse to be the same, we earliest time for the bridge collapse. The latest estimate is can conclude that liquefaction-induced ‰ow commenced the time Mr. Shuto witnessed the bridge collapse after he 86 seconds after the earthquake occurred, and this is the had reached the right bank (112 seconds) and this is earliest time estimate. From an analysis of Mr. shown in Fig. 4 as the latest time for the bridge collapse. Takeuchi's photograph in Photo 7, liquefaction-induced In other words, from the movements of the two people on ‰ow in the vicinity of the revetment had occurred within 3 the bridge we can infer that the Showa Bridge had not minutes of the onset of the earthquake. The locations of collapsed before 53 seconds had passed after the onset of the Showa Bridge and Niigata Meikun High School are the earthquake, and that it had completely collapsed by diŠerent, but it can be assumed that liquefaction-induced 112 seconds after the onset. ‰ow occurred between the time (86 seconds) shown for On the left side of Fig. 4, timings related to people Mr. Wada in Fig. 4 and the time (about 3 minutes) shown other than those on the bridge is shown enclosed in a dot- for Meikun High School. The fact that liquefaction-in- ted line. The time during which Mr. Yamagishi witnessed duced ‰ow occurred after the Showa Bridge collapsed thebridgecollapse(69¿91 seconds) and Hakusan High cannot be shown in terms of timings, but is corroborated School pupil Ms. Narita's testimony (6＋60＝66 seconds) by the testimony of the Hakusan High School pupils. are included. The testimonies of those who directly wit- 1086 YOSHIDA ET AL.

Deduction of the Causes of the Showa Bridge Collapse duced ‰ow as the main cause of the collapse of the As mentioned in the Introduction, the causes of Showa Bridge is relatively low. There is a high pos- damage according to past studies can be summarized as sibility that it was due to increased displacement of the following three types: the ground in circumstances where pile deformation 1) Signiˆcant inertia force at the time of the earthquake occurred more easily due to liquefaction. 2) Lateral subgrade reaction of the ground was reduced due to liquefaction, and considerable ground dis- placement occurred where the apparent length above ACKNOWLEDGEMENTS the ground surface became large. This study was conducted as a part of activities of the 3) Piles suŠered considerable deformation due to Subcommittee for Utilization of Earthquake Disaster liquefaction-induced ‰ow, or the horizontal move- Record (Chairperson: Kazue Wakamatsu) of Japanese ment of the left bank associated with the liquefac- Geotechnical Society. The authors gained kind coopera- tion-induced ‰ow pushed bridge girders towards the tion of many people in carrying out this study. First, we centeroftheriver. gratefully acknowledge the following people who accept- If we assume that the bridge started to collapse about ed a number of our interviews concerning their personal 70 seconds after the onset of the earthquake, the main experiences during the 1964 Niigata earthquake; Mr. Yu- shocks were all but over, as shown in Fig. 4, and so the taka Takeuchi, Mr. Hiromasa Yamagishi, Mr. Shuzo possibility of a collapse due to inertia force (1) is obvious- Hidano, Mr. Teiji Shuto, Mr. Mitoo Yokoyama, Mr. ly low. From eyewitness testimony we can assume that Koji Wada, Mr. Seisaku Kita, Mr. Masaru Abe, Mr. liquefaction-induced ‰ow at the revetment occurred after Saburo Yamada, Ms. Masako Otsuka. Mr. Katsuyoushi the bridge had collapsed, and therefore the possibility Kobayashi, Mr. Hideji Nakagawa, Mr. Masao Aida, Mr. that liquefaction-induced ‰ow caused the collapse (3) is Kimiro Sano, Mr. Hitoshi Kobayashi, Mr. Syuji Ikariya, also relatively low. Thus, of the three possible causes, it is Mr. Kazuei, Satomura, Mr. Shigetaka Nagumo, Ms. most likely that (2) ground deformation occurring when Sumiko Watanabe, Ms. Misako Wakui, Ms. Emiko Nari- the pile heads were easily displaced as a result of liquefac- ta, Ms. Eiko Nagai, Mr. Hiroshi Nunokawa, Mr. Hiroshi tion caused the collapse. Nogawa, Mr. Kouichi Wakabayashi, Mr. Tetsuyoshi Displacement time history shown in Fig. 4 indicates Yokogi, Mr. Takeji Kobayashi, and Mr. Yasuo Naito. displacement is greatest at around 70 seconds, estimated Especially, they wish to thank Mr. Takeuchi who pro- time when the Showa Bridge collapsed. Kudo et al. (2000) vided valuable photographs taken immediately after the indicates that as the long period motion around 7 seconds earthquake and a useful suggestion on the estimation of was S-wave arrival, the essential nature of the long period the timing of the occurrence of ground ‰ow. motion is attributed to the earthquake source. Yoshida They also express their sincere gratitude to the follow- and Kudo (2000) conˆrmed this idea by showing that li- ing people; Mr. Takeaki Ishii of Niigata City Board of quefaction occurred around 12 seconds. This indicates Education and Mr. Yutaka Yagawa of Fukuda Corpora- that incident wave at recorded site and the Showa Bridge tion who helped us to ˆnd eyewitnesses, Mr. Hisao Hon- is similar. In addition, liquefaction occurred in both site. ma of Shimizu Corporation who provided us useful Therefore, pattern of vibration is considered to be simi- materials and information concerning the collapse of the lar. Then, this large displacement can be the likely cause Showa Bridge, Mr. Takao Suzuki of Japanese Identiˆca- of the bridge collapse. tion Center of Forensic Science Co., Ltd. who conducted scientiˆc identiˆcation of wave front on the Shinano River in the photograph, and students of Kanto-Gakuin CONCLUSIONS University who undertook experimental subject of shak- Based on a study of eyewitnesses' testimonies, estima- ingtabletestsforawarenessofseismicmovement. tions have been made of the times that the Showa Bridge collapsed and liquefaction-induced ‰ow occurred. As a result the following conclusions have been reached: REFERENCES 1) The time of the onset of the collapse of the Showa 1) Arakawa, N., Kimata, T., Kondo, M., Tokida, K. and Takamatsu, Bridge can be estimated as about 70 seconds after the S. (1982): Earthquake response analysis of the Showa Bridge con- ˆrst shock of the earthquake. sidering , Proc. 17th Japan National Conference on Soil Mechanics and Foundation Engineering, 1941–1944 (in 2) Signiˆcant liquefaction-induced ‰ow toward the Japanese). river center occurred after the Showa Bridge col- 2) Bhattacharya, S. (2003): Pile Instability during Earthquake Li- lapsed, and its timing is estimated to be at least 86 quefaction, A dissertation submitted for the degree of Doctor of seconds after the ˆrst shock of the earthquake in the Philosophy at the University of Cambridge, U.K., 3.3–3.9. left bank of the Showa Bridge. At Niigata Meikun 3) Hamada, M., Yasuda, S., Isoyama, R. and Emoto, K. (1986): Observation of permanent ground displacement induced by soil li- High School (about 850 m upstream of the Showa quefaction, Journal of Japan Society of Civil Engineers, (376, Bridge) it is estimated to have occurred within 3 III–6), 211–220, 1986 (in Japanese with English Abstract). minutes. 4) Hamada, M. (1992): Large ground deformations and their eŠects 3) Considering these two points, the possibility of iner- on lifelines: 1964 Niigata Earthquake, Case Studies of Liquefaction tia force in the superstructure or liquefaction-in- and Lifeline Performance during Past , Japanese Case CAUSES OF BRIDGE COLLAPSE IN NIIGATA EARTHQUAKE 1087

Studies (ed. by Hamada, M. and O'Rourke, T. D.), February 17, 1, http://nisee.berkeley.edu:8080/images/servlet/ 3–28. EqiisBrowse?group＝Niigata1964–01. 5) Horii, K. and Miyahara, H (1966): Bridges spanning over the lower 16) Niigata University and Fukada Geological Institute (1964): Maps course of the river Shinano, Bulletin of Science and Engineering Showing Ground Failures Caused by the Niigata Earthquake (in Laboratory, Waseda University, (34), Special Issue on Niigata Japanese). Earthquake, Science and Engineering Laboratory, Waseda Univer- 17) Okamoto, S. (1971): Seismic Engineering, Tokyo, Ohmsha, 272– sity, 151–170. 273. 6) Japan Meteorological Agency (1949, 1978): Seismic Intensity Scale. 18) Okubo, T., Kuribayashi, E. and Iwasaki, T. (1966): On the damage 7) Japan Society of Civil Engineers (JSCE) Investigation Committee and response analysis of the Showa-Ohashi Bridge, Report of the for Niigata Earthquake, (1966): Report of the Damage Investiga- National Research Institute for Earth Science and Disaster Preven- tion of the 1964 Niigata Earthquake, 376–395 (in Japanese). tion, (12), 11–20 (in Japanese). 8) Japanese Geotechnical Society (2004): Photographs and Motion 19) The Public Works Research Institute, Ministry of Construction Picture of the Niigata City Immediately After the Earthquake in (1965): Report on Niigata Earthquake, Report of The Public 1964, Maruzen Publishing Division, Tokyo. Works Research Institute, Ministry of Construction, (125), 226–239 9) Japanese Society of Soil Mechanics and Foundations Engineering (in Japanese). (1966): Brief explanation on pictures taken at the moment of Niiga- 20) Sento, N., Kazama, M., Akahori, K. and Ohmura, H. (2001): ta earthquake, Soil and Foundation, 6(1), i–vi. Mechanism, and prediction of ‰ow deformation due to seepage af- 10) Kubo, K. (1981): Earthquakes and Civil Engineering Structures, ter earthquake, Proc. 15th ICSMGE, Lessons Learned from Recent Kajima Publishing Co., Tokyo, 66–67. Strong Earthquakes, Earthquake Geotechnical Engineering Satel- 11) Kudo, K., Uetake, T. and Kanno T. (2000): Re-evaluation of Non- lite Conference, Istanbul, Turkey, 369–374. linear Site Response during the 1964 Niigata Earthquake using the 21)Tazoh,T.,Nakahi,S.,Shimizu,K.,Kimata,H.andKogawa,T. Strong Motion Records at Kawagishi-cho, Niigata City, Proc. (1985): Considerations on seismic damage to foundation piles, 12WCEE, Auckland, New Zealand, Paper No. 0969. Proc. 20th Japan National Conference Soil Mechanics and Founda- 12) Kuribayashi, E. (1987): Lessons learned from 1964 Niigata earth- tion Engineering, 773–776 (in Japanese). quake (bridge)–disaster of Showa Bridge–, Kisoko, 15(5), 24–30 (in 22) Wakamatsu, K., Tazoh, T., Yasuda, S., Towhata, I., Yoshida N., Japanese). Kanatani, M., Kiku, H. and Nakazawa, H. (2004): Special Session 13) Miyamura, K. (1964): Experience Notes of the Niigata Earthquake, for the 40th Anniversary of the 1964 Niigata Earthquake, Witnesses Niigata Hakusan High School (in Japanese). of the Soil Liquefaction, Tsuchi-to-Kiso, 52(12), 15–20 (in 14) Nakagawa, Y., Tanaka, S. and Ishikawa, Y. (1965): Investigation Japanese). Report on Damage to Water Utilities Caused by the Niigata Earth- 23) Yoshida, N. and Kudo, K. (2000): Geotechnical re-evaluation of li- quake, Survey Report of Waterworks Bureau of Tokyo Metropoli- quefaction at Kawagishi-cho site during 1964 Niigata earthquake, tan Government, (17) (in Japanese). Summaries of the Technical Papers of Annual Meeting of AIJ, 15) National Information Service for Earthquake Engineering: EQIIS Tohoku, Structure II, 293–294 (in Japanese). Image Database Niigata, Japan 1964,