Landslides triggered by the September 4, 1984, Nagano-ken-Seibu earthquake in Japan

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6597189

Harp, E L; Keefer, D K

The September 14, 1984, Nagano-ken-Seibu earthquake (M 6.9) triggered several hundred landslides, including four particularly destructive slope failures-- three soil flows and one of the largest earthquake-generated rock avalanches in history. The rock avalanche originated on the flank of a historically active volcano. The initial basal sliding surface (whose slope was 25/sup 0/) was in weathered rhyolitic tuff. The soil flows had volumes as great as 5 x 10/sup 5/ m/sup 3/ and occurred in unconsolidated to weakly cemented colluvium and alluvium, weathered rhyolitic tuff, and ash. Liquefaction of saturated, unconsolidated ash deposits that are hydraulically confined by impermeable, weathered rhyolitic tuff may have triggered two of the soil flows. One of the flows was reported by an eyewitness to have attained speeds of 20 to 60 kph; another destroyed houses and killed 13 people. The extreme runnout distance of the rock avalanche and the fact that all of the deaths in the earthquake were from landslides point of the hazards posed by these types of destructive landslides. The presence of volcanic layers subparallel to surface slopes and interbedded with highly altered layers indicates that the geologic conditions under which the rock avalanche and soil flows occurred are similar to conditions which produced similar landslides in other historical earthquakes. The occurrence of these landslides emphasizes the fact that similar hazards may exist in volcanic and seismically active areas in the western US (such as the Cascade Range), even without the presence of active volcanism.

• Research Organization: Geological Survey, Menlo Park, CA (USA)
• OSTI ID: 6597189
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

29 ENERGY PLANNING, POLICY, AND ECONOMY
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58 GEOSCIENCES
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580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ASIA
DAMAGE
EARTHQUAKES
ENGINEERING
GROUND MOTION
HAZARDS
INJURIES
INSTITUTIONAL FACTORS
JAPAN
LANDSLIDES
MECHANICS
MOTION
RISK ASSESSMENT
ROCK MECHANICS
SAFETY
SEISMIC EVENTS
SLOPE STABILITY
SOCIO-ECONOMIC FACTORS
STABILITY
VELOCITY