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1.
Landslides triggered by the 1949 Khait earthquake, Tajikistan, and associated loss of life 总被引:3,自引:0,他引:3
Stephen G. Evans Nicholas J. Roberts Anatoli Ischuk Keith B. Delaney Galina S. Morozova Olga Tutubalina 《Engineering Geology》2009,109(3-4):195-212
Earthquake-triggered landslides are a major geological hazard in Central Asia. In July 1949, the M7.4 Khait earthquake triggered many hundreds of landslides in a mountainous region near the southern limit of the Tien Shan Mountains, central Tajikistan. These landslides involved widespread rock-slope failure as well as large numbers of flowslides in loess that mantles the steep slopes of the region. In the Yasman valley hundreds of loess landslides coalesced to form a massive loess flow (est. vol. 245 Mm3) that travelled up to 20 km on a slope of only 2°. In an adjacent valley, the Khait landslide involved transformation of an earthquake-triggered rockslide into a very rapid flow by the entrainment of saturated loess into its movement. It travelled 7.41 km over a vertical distance of 1421 m with an estimated average velocity of ~30 m/s. We estimate its volume as 75 Mm3, an order of magnitude less that previously published estimates. The Khait landslide was simulated using DAN. The number of casualties due to earthquake-triggered landslides in the epicentral region was considerable. Approximately 4000 people were killed in the Yasman valley loess flow as 20 villages (kishlaks) were overwhelmed. In the Khait landslide alone we estimate ca. 800 people lost their lives when the villages of Khait and Khisorak were overrun by rapidly moving debris. Our data indicates that a total of approximately 7200 people were killed by earthquake-triggered landslides in the epicentral region of the Khait earthquake and that, in terms of loss of life, the 1949 Yasman valley loess flow was one of the most destructive landslides in recent history. 相似文献
2.
History of landslide susceptibility and a chorology of landslide-prone areas in the Western Ghats of Kerala,India 总被引:3,自引:0,他引:3
Kerala is the third most densely populated state in India. It is a narrow strip of land, of which 47% is occupied by the most
prominent orographic feature of peninsular India, The Western Ghats mountain chain. The highlands of Kerala experience several
types of landslides, of which debris flows are the most common. They are called “Urul Pottal” in the local vernacular. The
west-facing Western Ghats scarps that runs the entire extent of the mountain system is the most prone physiographic unit for
landslides. The highlands of the region experience an annual average rainfall as high as 500 cm through the South-West, North-East
and Pre-Monsoon showers. A survey of ancient documents and early news papers indicates a reduced rate of slope instability
in the past. The processes leading to landslides were accelerated by anthropogenic disturbances such as deforestation since
the early 18th century, terracing and obstruction of ephemeral streams and cultivation of crops lacking capability to add
root cohesion in steep slopes. The events have become more destructive given the increasing vulnerability of population and
property. Majority of mass movements have occurred in hill slopes >20° along the Western Ghats scarps, the only exception
being the coastal cliffs. Studies conducted in the state indicates that prolonged and intense rainfall or more particularly
a combination of the two and the resultant pore pressure variations are the most important trigger of landslides. The initiation
zone of most of the landslides was typical hollows generally having degraded natural vegetation. A survey of post-landslide
investigation and news paper reports enabled the identification of 29 major landslide events in the state. All except one
of the 14 districts in the state are prone to landslides. Wayanad and Kozhikode districts are prone to deep seated landslides,
while Idukki and Kottayam are prone to shallow landslides. 相似文献
3.
Comparison between the two triggered landslides in Mid-Niigata, Japan by July 13 heavy rainfall and October 23 intensive earthquakes in 2004 总被引:3,自引:2,他引:3
On July 13, 2004, heavy rainfalls because of the intensive activities of the rain front occurred in the Mid-Niigata Region,
Japan. They were as much as 400 mm in 24 h, bringing about serious flooding by breaking the river banks. The heavy rainfalls
also triggered more than 3,500 landslides. Three months later, the southern region of Mid-Niigata was attacked by an earthquake
of magnitude 6.8 on the Richter scale on October 23, 2004. The main earthquakes were followed by intensive aftershocks, which
continued until December 2004. By these earthquakes, variable landslides of more than 4,400 also occurred in the hilly and
mountainous areas. Namely, different triggers brought about the variable landslides in the hilly mountains whose features
are very similar in geological and geomorphological points of view. Therefore, these two events are very useful for clearing
the difference in features of the landslides between the two. We have been researching on both landslides in the field just
after both occurred and later analyzing air photographs using the geographic information system (GIS). In this paper, we describe
the comparison in the distribution features using GIS analytical data between the heavy rainfall-induced and the intensive
earthquake-induced landslides. 相似文献