NOVEMBER 2, 2004 FIELD RECONNAISSANCE OF THE NIIGATA-KEN CHUETSU EARTHQUAKE OF OCTOBER 23, 2004
Prepared by J. P. Bardet
On November 2, 2004, four members of the EERI-GEER reconnaissance team carried out a field reconnaissance of the October 23, 20004 Niigata-ken Chuetsu earthquake. The group was composed of J. P. Bardet, University of Southern California; Robert Kayen, US Geological Survey, Menlo Park; Scott Kieffer, Colorado School of Mines, Golden; and Hajime Tanaka, University of Tokyo, Japan. Figure 1 shows the complete GPS track log of the reconnaissance team, which starts at Sanjo to the North and extends 5 km to the East of Ojiya. Figure 2 shows a detailed GPS track 5 km to the East of Ojiya. The reconnaissance group investigated the southern part of the Yamakoshi area that was isolated from the rest of the world by landsliding along the Imuo Stream (a tributary of the Ueno River). Weeks before the earthquake, the Yamakoshi area received heavy rains and its steep terrains became susceptible to landsliding. The October 23, 2004 earthquake suddenly precipitated all incipient landslides at once, imposing a pervasive devastation to the communication, transportation and utilities networks. The Yamakoshi area became completely isolated after the earthquake (wireless phones were still not working on November 2). In response to the failure of communication, transportation, and utilities networks, the civilian authorities evacuated about 2000 villagers from the Yamakoshi area, mainly using helicopters. On November 2, the access roads to the Yamakoshi area were sealed off by police barrages. An access permit had to be obtained from the Mayor's office in the Nagaoka City Hall. We thank Yuki Yamakawa, Nagaoka University of Technology, Japan, for requesting and obtaining that permit. We also thank Hajime Tanaka, son of Yasuo Tanaka, Kobe University, for his assistance during our reconnaissance.
Figure 1. Complete GPS track log of the reconnaissance team on November 2, 2004.
Figure 2. Detailed GPS track log of the reconnaissance team on November 2, 2004. The GPS track log is interrupted as the investigator walked through a 400 m long tunnel .
Figure 3. Location of Figures 4 to 13.
Figure 4. A house damaged by failure of first floor after the earthquake (11/2/2004 11:39:44 AM, N37.29354 E138.85614).
Figure 5. Spalling of concrete in tunnel lining. This observation could not be investigated in further detail due to safety reasons (11/2/2004 11:45:08 AM, N37.30175 E138.85507).
Figure 6. Local failure of road due to small slope instability (11/2/2004 11:48:22 AM, N37.30390 E138.85580).
Figure 7. The slope failed close to these new houses and damaged only an unoccupied building (11/2/2004 11:50:54 AM, N37.30410 E138.85481).
Figure 8. A slope instability with two different failure surfaces (11/2/2004 11:55:32 AM, N37.30812 E138.85989).
Figure 9. Failure of the concrete lining of the bridge abutment, which poured down its fill material on the slope (11/2/2004 12:14:46 PM, N37.31815 E138.86430).
Figure 10. Denudation of steep slope next to a house. The mud line on the asphalt pavement indicates that the stream overflowed and almost flooded the house (11/2/2004 12:17:00 PM, N37.31798 E138.86426).
Figure 11. Temporary repairs to road damaged by the earthquake (11/2/2004 12:18:52 PM, N37.31803 E138.86385).
Figure 12. The bridge was apparently not damaged, in spite of its abutment damage (11/2/2004 12:26:36 PM, N37.31821 E138.86531).
Figure 13. Local failure of road (11/2/2004 12:27:00 PM, N37.31795 E138.86539).
Figure 14. Aerial photograph of the area to the East of the tunnel . The tunnel is located at the toe of the debris flow.
Figure 15. Location of Pictures 16 to 38 to the East of the tunnel.
Figure 16. As indicated by the mudline on the white and green house and the bent post, this area was flooded by the muddy stream after the earthquake (11/2/2004 12:35:42 PM, N37.31489 E138.86749).
Figure 17. This old traditional house was apparently undamaged by the earthquake and not flooded by the stream (11/2/2004 12:41:18 PM, N37.31401 E138.86760).
Figure 18. Mud and debris blocked the road. They clogged the culver beneath the road and contributed to flooding the area (11/2/2004 12:46:06 PM, N37.31319 E138.86850).
Figure 19. The mudline on the tree indicates the height of the muddy stream at this location. (11/2/2004 12:50:04 PM, N37.31343 E138.86890).
Figure 20. The area was flooded by water as shown by the mudline on the trees (11/2/2004 12:52:36 PM, N37.31361 E138.86922).
Figure 21. Mud and debris came down from the hills above (11/2/2004 12:52:54 PM, N37.31361 E138.86925).
Figure 22. Debris and boulder were carried by gushing water (11/2/2004 12:54:40 PM, N37.31347 E138.86990).
Figure 23. The road disappeared at this location due to failure of its base (11/2/2004 1:01:14 PM, N37.31379 E138.87071).
Figure 24. Another section of the damaged road (11/2/2004 1:04:06 PM, N37.31371 E138.87061).
Figure 25. Part of the retaining wall failed and took with it the road above (11/2/2004 1:06:40 PM, N37.31407 E138.86995).
Figure 26. The road was destroyed by a landslide (11/2/2004 1:08:14 PM, N37.31413 E138.87036).
Figure 27. On its way to the tunnel, a car was left abandoned on the damaged road (11/2/2004 1:08:22 PM, N37.31413 E138.87038).
Figure 28. Another view of the abandoned car (11/2/2004 1:13:50 PM, N37.31424 E138.87115).
Figure 29. Two red cross volunteers patrolling the area on dirt bikes posed for a photograph with two members of our reconnaissance party (11/2/2004 1:17:30 PM, N37.31372 E138.87219).
Figure 30. A car blocked by a landslide was left abandoned with no damage at all (11/2/2004 1:24:24 PM, N37.31382 E138.87198).
Figure 31. A landslide fragmented the concrete lining of the slope and blocked the road (11/2/2004 1:31:24 PM, N37.31301 E138.87241).
Figure 32. The access road to the tunnel was damaged (11/2/2004 1:31:44 PM, N37.31307 E138.87247).
Figure 33. Debris and boulders covered the road just before the tunnel portal (11/2/2004 1:32:46 PM, N37.31289 E138.87283).
Figure 34. Boulders and dead trees littered the load at the tunnel entrance. They came down violently and bent two metal posts. The piece of asphalt pavement in the foreground must have be uplifted and transported by the gushing waters (11/2/2004 1:33:32 PM, N37.31269 E138.87256).
Figure 35. The hillside was washed out by a violent mudflow. As shown in the aerial photograph of Figure 14, the flow initiated from a higher terrace with water ponds (11/2/2004 1:38:44 PM, N37.31248 E138.87299).
Figure 36. The mud, debris and leaves hanging from the elevated transformer and the mudline at the entrance of the tunnel indicated the height and violence of the mudflow at this location (11/2/2004 1:38:54 PM, N37.31250 E138.87306).
Figure 37. Another view of the mudflow at the tunnel entrance (11/2/2004 1:39:36 PM, N37.31249 E138.87312).
Figure 38. The mud and debris entered the tunnel. During the winter, the village is usually sealed from the rest of the world as the roads are blocked with snow as thick as 5 m. Villagers use the tunnel to store their cars. After the earthquake, many cars were parked in the tunnel. None was damaged by the mud (11/2/2004 1:42:10 PM, N37.31223 E138.87347).
Figure 39. Location of Figures 40 to 79 the West of the tunnel.
Figure 40. A small truck fell down into a pond next to a fish hatchery (11/2/2004 1:55:44 PM, N37.30810 E138.88055).
Figure 41. The granite portal of a Shinto shrine collapsed among old trees. The tree ages imply that there were no landslide in this area for at least one hundred years (11/2/2004 2:01:10 PM, N37.30759 E138.88200).
Figure 42. The stone lions guarding the shrine entrance were tossed off from their pedestals by the earthquake acceleration (11/2/2004 2:02:54 PM, N37.30745 E138.88170).
Figure 43. The corner and edge stone of the monument fell down due to earthquake forces (11/2/2004 2:06:52 PM, N37.30758 E138.88188).
Figure 44. Half of the road slid down the slope and had been temporarily repaired with crushed gravel (11/2/2004 2:07:30 PM, N37.30767 E138.88211).
Figure 45. A small local road deformation (11/2/2004 2:08:59 PM, N37.30737 E138.88280).
Figure 46. Debris accumulated on top of an avalanche protection structure (11/2/2004 2:09:26 PM, N37.30735 E138.88280).
Figure 47. Collapse of the first floor of a traditional house (11/2/2004 2:13:04 PM, N37.30634 E138.88420).
Figure 48. The concrete walls of the fish pond were partially broken, but fish were alive. The fish raised in this area are sold all over Japan for aquarium and decorative ponds. The village was supposed to hold a fish contest on October 24, the day after the earthquake (11/2/2004 2:15:00 PM, N37.30655 E138.88429).
Figure 49. The pond cracked and the water drained, killing all fish (11/2/2004 2:24:28 PM, N37.30738 E138.88754).
Figure 50. The head scarp of the largest landslide in the Yamakoshi area. The landslide was deeply seated, and extended over 1 km in length. The inclined trees are located on the block that rotated (11/2/2004 2:27:00 PM, N37.30764 E138.88780).
Figure 51. The mid part of the landslide displayed many ground cracking due to extension (11/2/2004 2:27:44 PM, N37.30772 E138.88788).
Figure 52. Another view of the mid part of the landslide (11/2/2004 2:27:52 PM, N37.30773 E138.88789).
Figure 53. The head scarp of the largest landslide in the Yamakoshi area displayed a circular failure surface (11/2/2004 2:28:42 PM, N37.30775 E138.88789).
Figure 54. Another view of the mid part of the landslide (11/2/2004 2:31:30 PM, N37.30771 E138.88770).
Figure 55. The hill to the South of the landslide underwent only shallow landslides and denudation of vegetation cover (11/2/2004 2:31:56 PM, N37.30770 E138.88770).
Figure 56. On the mid part of the landslide, terraces and fish ponds were barely recognizable (11/2/2004 2:32:44 PM, N37.30767 E138.88770).
Figure 57. Another view of the hill to the South of the landslide (11/2/2004 2:34:00 PM, N37.30772 E138.88780).
Figure 58. The mid section of the landslide viewed from another location (11/2/2004 2:44:32 PM, N37.30570 E138.88867).
Figure 59. The toe of the landslide extended far and was difficult of access (11/2/2004 2:44:46 PM, N37.30567 E138.88870).
Figure 60. The mid section of the landslide viewed from another location (11/2/2004 2:45:22 PM, N37.30553 E138.88881).
Figure 61. The dirt road on the hill to the South of the large landslide were blocked by many small landslides (11/2/2004 2:51:06 PM, N37.30524 E138.88922).
Figure 62. The toe of the landslide viewed from another location (11/2/2004 2:54:44 PM, N37.30513 E138.88969).
Figure 63. The head scarp of the large landslide viewed from another location (11/2/2004 2:54:52 PM, N37.30513 E138.88969).
Figure 64. Another view of the head scarp of the landslide (11/2/2004 2:55:18 PM, N37.30511 E138.88969).
Figure 65. The golden fish raised in the village have a distinctive red and white color with black spots. The largest fish can retail as much as 1 million yen, about $10,000 (11/2/2004 3:12:10 PM, N37.30641 E138.88429).
Figure 66. Another view of the old traditional house that collapsed during the earthquake (11/2/2004 3:13:56 PM, N37.30609 E138.88425).
Figure 67. No apparent damage to modern houses. They were however abandoned as all the inhabitants of the village had to be evacuated (11/2/2004 3:15:20 PM, N37.30576 E138.88472).
Figure 68. Many fish died after the earthquake, as they were left unattended by the villagers who were evacuated (11/2/2004 3:16:17 PM, N37.30547 E138.88501).
Figure 69. Damaged house displaying large shear deformation at the first floor (11/2/2004 3:16:54 PM, N37.30537 E138.88513).
Figure 70. The house collapsed while its roof was being repaired (11/2/2004 3:17:26 PM, N37.30525 E138.88519).
Figure 71. The fire truck of the village (11/2/2004 3:22:50 PM, N37.30486 E138.88480).
Figure 72. Shear deformation of the first floor of this old house (11/2/2004 3:28:16 PM, N37.30428 E138.88470).
Figure 73. No damage to these modern houses with a reinforced concrete basement (11/2/2004 3:31:02 PM, N37.30364 E138.88481).
Figure 74. A small landslide at the top of the ridge (11/2/2004 3:31:46 PM, N37.30344 E138.88504).
Figure 75. A damaged shack (11/2/2004 3:32:08 PM, N37.30342 E138.88510).
Figure 76. The recently built bridge and abutment showed no sign of damage; the road settled in front it (11/2/2004 3:39:30 PM, N37.30582 E138.88391).
Figure 77. A traditional home left abandoned but apparently undamaged by the earthquake (11/2/2004 3:41:08 PM, N37.30671 E138.88371).
Figure 78. Landslide above the tunnel portal without damage to the tunnel. The light posts were undamaged, in contrast to those on the other tunnel entrance which were completed destroyed by the debris flow (11/2/2004 3:48:13 PM, N37.30896 E138.87854).
Figure 79. Aerial photograph of the area to the West of the tunnel (Courtesy of Hasshu).