The goal of this article is to revise several aspects of the well-known classification of landslides, developed by Varnes (1978). The primary recommendation is to modify the definition of landslide-forming materials, to provide compatibility with accepted geotechnical and geological terminology of rocks and soils. Other, less important modifications of the classification system are suggested, resulting from recent developments of the landslide science. The modified Varnes classification of landslides has 32 landslide types, each of which is backed by a formal definition. The definitions should facilitate backward compatibility of the system as well as possible translation to other languages. Complex landslides are not included as a separate category type, but composite types can be constructed by the user of the classification by combining two or more type names, if advantageous.

The Varnes classification of landslide types, an update

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Landslide inventory maps: New tools for an old problem


 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

A review of statistically-based landslide susceptibility models

We review rainfall thresholds for the initiation of landslides world wide and propose new empirical rainfall thresholds for the Central European Adriatic Danubian South-Eastern Space (CADSES) area, located in central and southern Europe. One-hundred-twenty-four empirical thresholds linking measurements of the event and the antecedent rainfall conditions to the occurrence of landslides are considered. We then describe a database of 853 rainfall events that resulted or did not result in landslides in the CADSES area. Rainfall and landslide information in the database was obtained from the literature; climate information was obtained from the global climate dataset compiled by the Climate Research Unit of the East Anglia University. We plot the intensity-duration values in logarithmic coordinates, and we establish that with increased rainfall duration the minimum intensity likely to trigger slope failures decreases linearly, in the range of durations from 20 minutes to ∼12 days. Based on this observation, we determine minimum intensity-duration (ID) and normalized-ID thresholds for the initiation of landslides in the CADSES area. Normalization is performed using two climatic indexes, the mean annual precipitation (MAP) and the rainy-day-normal (RDN). Threshold curves are inferred from the available data using a Bayesian statistical technique. Analysing the obtained thresholds we establish that lower average rainfall intensity is required to initiate landslides in an area with a mountain climate, than in an area characterized by a Mediterranean climate. We further suggest that for rainfall periods exceeding ∼12 days landslides are triggered by factors not considered by the ID model. The obtained thresholds can be used in operation landslide warning systems, where more accurate local or regional thresholds are not available.

Rainfall thresholds for the initiation of landslides in central and southern Europe

http://meetingorganizer.copernicus.org/EGU2010/EGU2010-4437.pdf

Distribution pattern of earthquake-induced landslides triggered by the 12 May 2008 Wenchuan earthquake

Pore-pressure generation and movement of rainfall-induced landslides: effects of grain size and fine-particle content

Landslides induced by the 2008 Wenchuan earthquake, Sichuan, China

Landslides are gravitational mass movements of rock, debris or earth. Some move very slowly, thus conforming to the field of statics, but some move rapidly. Study of the initiation and motion of rapid landslides needs to develop “Landslide Dynamics” involving dynamic loading and dynamic generation/dissipation of excess pore-water pressure. New developments in science can be facilitated by new technological advances. This study aimed to develop a new apparatus that can geotechnically simulate the formation of the shear zone and the following long and rapid shear displacement that occurs in high-velocity landslides. Professor K. Sassa and his colleagues at DPRI (Disaster Prevention Research Institute), Kyoto University, have worked to develop an undrained dynamic-loading ring-shear apparatus for this purpose. A series of different types of apparatus (DPRI-3, 4, 5, 6, 7) have been developed from 1992 to the present. This paper describes the development of this apparatus and its application to the study of earthquake-induced landslides and the latest landslide-triggered debris flow in Japan. Also, tests of the latest version (DPRI-7) with a transparent shear box for direct observation of the shear zone during a rapid shearing are described.

Undrained dynamic-loading ring-shear apparatus and its application to landslide dynamics

Using a small flume, a series of tests has been conducted to cause rainfall-induced flowslides. Based on monitoring of sliding distance and pore pressures, the process of pore-pressure generation in relation to sliding distance is examined. A set of test results on the temporal and longitudinal variation of sliding velocity is presented. By changing the initial dry density and sample thickness in tests on a silica sand, the effects of these two factors on the pore pressure build-up after failure and flowslide motion have been analysed. The test results showed that there was an optimal density for pore pressure build-up, at which both the moving velocity and run-out distance were greatest, and this optimal density was dependent on sample thickness. Additionally, a series of tests on mixtures of silica sand with different loess contents has been carried out to investigate the effects of fine-particle content on the flowslide motion, in which different modes of flowslide motion were observed; these probably ...

Gonghui Wang

Papers

Distribution pattern of earthquake-induced landslides triggered by the 12 May 2008 Wenchuan earthquake

Pore-pressure generation and movement of rainfall-induced landslides: effects of grain size and fine-particle content

Landslides induced by the 2008 Wenchuan earthquake, Sichuan, China

Undrained dynamic-loading ring-shear apparatus and its application to landslide dynamics

Factors affecting rainfall-induced flowslides in laboratory flume tests