Analysis of a spatial distribution of landslides triggered by the 2004 Chuetsu earthquakes of Niigata Prefecture, Japan

On October 23, 2004, a series of powerful earthquakes with a maximum Mw = 6.6 located near the western coast of northern Honshu struck parts of northern Japan, particularly Niigata Prefecture; these earthquakes were known as the Chuetsu event. Thousands of landslides, as a secondary geotechnical hazard associated with these earthquakes, were triggered over a broad area; these landslides were of almost all types. The purpose of this study was to detect correlations between landslide occurrence with geologic and geomorphologic conditions, slope geometry, and earthquake parameters using two indexes based on Geographic Information Systems (GIS). In the study area, the landslide–area ratio (LAR), which is defined as the percentage of the area affected by landslides, was 2.9%, and the landslide concentration (LC), the number of landslides per square kilometer, was 4.4 landslides/km2, which is much more than other reported cases of seismic activity with the same magnitude. This was possibly due to heavy rainfall just before the Chuetsu earthquakes. Statistical analyses show that LAR has a positive correlation with slope steepness and distance from the epicenter, while LC is inversely correlated with distance from the epicenter. The Wanazu Formation had the most concentrated landslide activity, followed by the Kawaguchi, Ushigakubi, Shiroiwa and Oyama Formations, although the Wanazu Formation occupied only 4.5% of the total area of geological units. With 8.2% of the area affected by seismic landslides, the Kawaguchi Formation had the highest LAR. It was followed by the Shiroiwa, Ushigakubi and Wanazu Formations with LAR ranging from 4.6% to 6.0%. For lots of geological subunits, landslides are more frequent in a range of slope angles between 15° and 40°. The susceptibility to landsliding of each geologic unit was thus evaluated to correlate with slope steepness. It was also noted that the effects of the earthquakes were made far worse by antecedent rainfall conditions induced by a␣typhoon, and further research emphasizing the role of antecedent rainfall was discussed.

[1]  D. Keefer.  Landslides caused by earthquakes , 1984 .

[2]  J. Bommer,et al.  Earthquake-induced landslides: 1980–1997 , 1999 .

[3]  D. Keefer.  Statistical analysis of an earthquake-induced landslide distribution — the 1989 Loma Prieta, California event , 2000 .

[4]  Characteristics of the Recent Landslides in the Mid Niigata Region - Comparison between the Landslides by the Heavy Rainfall on 13 July 2004, and by the Intensive Earthquakes on 23 October 2004 , 2005 .

[5]  Randall W. Jibson,et al.  Inventory of landslides triggered by the 1994 Northridge, California earthquake , 1995 .

[6]  D. Keefer,et al.  Investigating Landslides Caused by Earthquakes – A Historical Review , 2002 .

[7]  Ju-Jiang Hung,et al.  Chi-Chi Earthquake Induced Landslides in Taiwan , 2000 .

[8]  B. Khazai,et al.  Evaluation of factors controlling earthquake-induced landslides caused by Chi-Chi earthquake and comparison with the Northridge and Loma Prieta events , 2004 .

[9]  Edwin L. Harp,et al.  Shaking intensity thresholds for rock falls and slides: Evidence from 1987 Whittier Narrows and superstition hills earthquake strong-motion records , 1995 .

[10]  E. Mark Lee,et al.  Landslide Risk Assessment , 2023 .

[11]  E. Harp,et al.  Landslides triggered by the earthquake , 1990 .

[12]  Randall W. Jibson,et al.  Analysis of the seismic origin of landslides: Examples from the New Madrid seismic zone , 1993 .

[13]  N. Newmark.  Effects of Earthquakes on Dams and Embankments , 1965 .

[14]  Robert J. Hansen,et al.  Seismic design for nuclear power plants , 1970 .

[15]  David M. Cruden,et al.  LANDSLIDE TYPES AND PROCESSES , 1958 .

[16]  R. Jibson,et al.  A seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the 17 January, 1994 Northridge, California earthquake , 2000 .

[17]  G. Wieczorek,et al.  Map showing ground failures from the Greenville/Mount Diablo earthquake sequence of January 1980, Northern California , 1985 .

[18]  K. L. Lee,et al.  Research needs and priorities for geotechnical earthquake engineering applications , 1978 .

[19]  K. Sassa,et al.  The Hyogoken-Nanbu Earthquake and the Distribution of Triggered Landslides , 1995 .

[20]  A. Arias.  A measure of earthquake intensity , 1970 .