Giant Landslides Triggered by the 1718 Tongwei Earthquake in Pan'an, Gansu Province, China

Great earthquakes in mountain areas always trigger severe geologic hazards such as landslides, debris flows and rock falls, thereby causing tremendous property damage and casualties. On 19th June, 1781, a Ms 7.5 earthquake occurred in Tongwei of Pan＇an, Gansu Province, west China,

The Identification of Large-Giant Bedrock Landslides Triggered by Earthquake in the Longmenshan Tectonic Belt

The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mechanism of seismic landslides （Bijan Khazai et al., 2003; Chong Xu et al., 2013; Lewis a. Owen et al., 2008; Randall W. Jibson et al., 2006）. However, few researches have focused on the early identification indicators of large-giant bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.

Landslides and Slope Fissures Triggered by the April 14,2010 Yushu Earthquake, China

On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036 landslides were determined from visual interpretation of aerial photographs and high resolution remote sensing images, and verified by selected field investigations. These landslides covered a total area of about 1. 194km~. Characteristics and failure mechanisms of these landslides are listed in this paper, including the fact that the spatial distribution of these landslides is controlled by co- seismic main surface fault ruptures. Most of the landslides were small scale, causing rather less hazards, and often occurring close to each other. The landslides were of various types, including mainly disrupted landslides and rock falls in shallows and also deep-seated landslides, liquefaction induced landslides, and compound landslides. In addition to strong ground shaking, which is the direct landslide triggering factor, geological, topographical, and human activity also have impact on the occurrence of earthquake triggered landslides. In this paper, five types of failure mechanisms related to the landslides are presented, namely, the excavated toes of slopes accompanied by strong ground shaking; surface water infiltration accompanied by strong ground shaking; co- seismic fault slipping accompanied by strong ground shaking; only strong ground shaking; and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by co-seismic ground shaking. Besides the main co-seismic surface ruptures, slope fissures were also delineated from visual interpretation of aerial photographs in high resolution. A total of 4814 slope fissures, with a total length up to 77. lkm, were finally mapped. These slope fissures are mainly distributed on the slopes located at the southeastern end of the main co-seismic surface rupture zone, an area subject to strong compression during the earthquake.

Insights into some large-scale landslides in southeastern margin of Qinghai-Tibet Plateau

The southeastern margin of Qinghai-Tibet Plateau(SMQTP)is of a typical large landslide-prone area due to intense tectonic activity,deeply incised valleys,high geostress and frequent earthquakes.To gain insights into large landslides in southeastern margin of Qinghai-Tibet Plateau,an area covering 3.34×105 km2 that extends 80e150 km on both sides of the Sichuan-Tibet traffic corridors(G318)was used to examine the spatial distribution and corresponding characteristics of landslides.The results showed that the study area contains at least 629 large landslides that are mainly concentrated on 7 zones(zones IeVII).Zones IeVII are in the southern section of the Longmenshan fault zone(with no large river)and sections with Dadu River,Jinsha River,Lancang River,Nujiang River and Yarlung Zangbo River.There are more landslides in the Jinsha River section(totaling 186 landslides)than the other sections.According to the updated Varnes classification,408 large landslides(64.9%)were recognized and divided into 4 major types,i.e.flows(275 cases),slides(58 cases),topples(44 cases)and slope deformations(31 cases).Flows,which consist of rock avalanches and iceerock avalanches,are the most common landslide type.Large landslide triggers(178 events,28.3%)are also recognized,and earthquakes may be the most common trigger.Due to the limited data,these landslide type classifications and landslide triggers are perhaps immature,and further systematic analysis is needed.

A Major Landslide Involving an Inverted Paleochannel in Sierra County, New Mexico

A landslide that probably dates to the end of the Pleistocene has been found in Sierra County. The feature consists of three sub-parallel segments, covering an area about 8 km wide and 10 km long. The head of the slide deposits consists of a northeast-trending paleochannel forming an inverted topography. The paleochannel deposits contain many boulders with sizes up to 1.5 meter diameter, indicating flow rate as high as 100 m3/s. The paleochannel ridge is mostly underlain by the hidden lateral contact of the Cretaceous Crevasse Canyon Formation and by the Tertiary Love Ranch and is sharply defined by Yoast Draw valley that cuts a water gap through the 25 m high inverted ridge. The landslide body consists of Love Ranch Formation overlain by a substantial cover of Quaternary fanglomerate. A series of northwest-trending faults have influenced the landslide. The broad western upslope segment of the slide has been washed away, leaving only trace evidence of a landslide. A low slide plane angle of less than 1% slope suggests a seismic trigger.

Geoinformation techniques in natural hazard modeling:Preface

There are number of geoinformation approaches and modeling tools to the numerical measurement of natural hazards,including direct and indirect heuristic approaches,and deterministic,probabilistic,statistical and data mining approaches（Pradhan and Buchroithner,2012;Pradhan et al.,2012,2014;Pradhan,2013）.In this thematic section of Geoscience Frontiers,a set of six contributions are assembled that provide a window on various parameters,