Field Reconnaissance: 17 November 2004

Landslides east of Yamakoshi Village

Ellen Rathje, Randy Jibson, Keith Kelson, James Bay, and Robert Pack

GEER Beyond Reconnaissance Team

 

The largest density of landslides occurred to the east and south of the town of Yamakoshi.  On 17 November, the reconnaissance team investigated the landslides located east of Yamakoshi.  The team drove to the center of Yamakoshi and parked at the Yamakoshi Village Office.  The team hiked from the village office to points east (Figure 1) along Roads 23 and 24.  Team members Jim Bay and Bob Pack investigated the large landslide at the west portal of the tunnel on Road 24, while team members Ellen Rathje, Randy Jibson, and Keith Kelson traveled to the landslides east of the tunnel (Figure 1).  Team members were accompanied by Prof. I. Towhata of the University of Tokyo, Profs. Y. Yamakawa, N. Inukai, and H. Toyota of Nagaoka University, and several students from the University of Tokyo and Tokyo Denki University.  

 

 

 

Fig. 1.  Satellite image of reconnaissance route and locations of Figures 2 through 28 (satellite image courtesy of DigitalGlobe, imagery acquired 24 October 2004).

 

 

 

 

Fig. 2.  Landslide at west portal of tunnel on Road 24 (37.3291N, 138.895E).

Road had been covered by landslide debris and was being cleared at this time.

 

 

 

 

Fig. 3.  View upslope of landslide at west portal of tunnel (37.3291N, 138.895E)

 

 

 

 

Fig. 3b. Side scarp of landslide above west portal of tunnel (37.3291N, 138.895E)

 

 

 

 

Fig. 3c.  Ridge-top cracking along ridge-top road close to top of landslide. Note the damage starts where the road enters ridge from a flat.

 

 

 

 

Fig. 3d.  Close-up of severe damage to a concrete road at the crest of the ridge.

 

 

 

 

Fig. 3e.  Landslide debris buried several automobiles. (37.3291N, 138.895E)

 

 

 

 

Fig. 4.  Landslide debris also blocked west portal of tunnel (37.3291N, 138.895E)

 

 

 

 

Fig. 5.  Landslide-blocked west portal of tunnel (37.329N, 138.895E)

 

 

 

 

Fig. 6.  Damage to east portal of tunnel (37.329N, 138.903E).  Within the tunnel, the base near the east portal experienced significant heave.

 

 

 

 

Fig 7.  Failure of road fill spanning swale immediately east of tunnel (37.329N, 138.903E)

 

 

 

 

Fig. 8.  Failure of steep slopes (37.329N, 138.912E)

 

 

 

 

Fig. 9.  Lateral spread deformation in terraced rice patty (37.329N, 138.909E)

 

 

 

 

Fig. 10.  Deep seated landslide failure (37.3267N, 138.913E)

 

 

 

 

 

Fig. 11.  Failure of hillside road way fill (37.3267N, 138.910E)

 

 

 

 

Fig. 12.  Close-up of failure of hillside roadway fill.  The presence of sandbags, most likely placed before the earthquake, indicates some movement of the fill prior to the earthquake. 

(37.3267N, 138.910E)

 

 

 

 

Fig. 13.  Failure of slope at edge of flat playing field.  This area may have been constructed by flattening the top surface and end dumping fill around the edge.

(37.3267N, 138.910E)

 

 

 

 

Fig. 14.  Large landslide at dairy farm (looking south).  Soil consists of weakly cemented sandstone and pre-earthquake slope angle approximately 45 degrees.

(37.3216N, 138.910E)

 

 

 

 

Fig. 15.  QuickBird satellite image (acquired 2004 October 24) of landslide at dairy farm.  Note that at this time the failure only extends to the midpoint of structures.  Previous figure shows that landslide expanded to the southern edge of structures sometime after the earthquake.

 

 

 

 

Fig. 16.  Northern edge of landslide at Dairy Farm (37.3216N, 138.910E)

 

 

 

 

Fig. 17.  Central section of landslide at Dairy Farm (37.3216N, 138.910E)

 

 

 

 

Fig. 18.  Southern edge of landslide at Dairy Farm on November 17, 2004

(37.3216N, 138.910E)

 

 

 

 

Fig. 19.  Ground deformation behind head scarp of landslide at Dairy Farm

(37.3216N, 138.910E)

 

 

 

 

Fig. 20.  Dairy cows placed in pen to be airlifted out by helicopter (37.3216N, 138.910E)

 

 

 

 

Fig. 21.  Landslide debris and impounded reservoir downslope from Dairy Farm

(37.3216N, 138.910E)

 

 

 

 

Fig. 22.  Reservoir impounded by landslide debris from Dairy Farm (37.3216N, 138.910E)

 

 

 

 

Fig. 23.  Reservoir inundating homes upstream from landslide debris (37.3216N, 138.910E)

 

 

 

 

Fig. 24.  Large landslide that took out a large section of road (37.3345N, 138.9125E)

 

 

 

 

Fig. 25.  Landslide movement translated and uplifted pavement (37.3345N, 138.9125E)

 

 

 

 

Fig. 26.  Failed pavement at same landslide (37.3345N, 138.9125E)

 

 

 

 

Fig.27.  Looking upslope at failed landslide area (37.3345N, 138.9125E)

 

 

 

 

Fig. 28.  Another large landslide that took out road and forced reconnaissance team to turn back (37.3336N, 138.9153E)