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Based on solid evidence, scientists attribute the global warming trend observed since the mid-twentieth century to the human expansion of the “greenhouse effect.” Extreme rainfall events have become more frequent worldwide, resulting in hydro-meteorological hazards creating more deaths and devastation. One of the most remarkable disasters of rain-induced rapid long-traveling landslides (RRLL) in Sri Lanka took place at Aranayake, 70 km east of Colombo, in 2016 (JICA Survey Team (2016), Survey results of Aranayake Disaster, JICA. URL: https://www.jica.go.jp/srilanka/english/office/topics/c8h0vm00006ufwhl-att/160720.pdf [Last accessed: April 14, 2020]). The fluidized landslide mass ran over an about 2 km distance claiming the lives of 125 people. This tragic event highlighted the importance of reliable early warning and disaster management mechanisms even more than ever because the presence of these hidden unstable soil masses, as well as their run-out distances, are hardly predicted. Once they start sliding, it is almost impossible to stop them. Since 2020 (after the preceding period of 2019), both the National Building Research Organization, Sri Lanka (NBRO) and the International Consortium on Landslides (ICL) have jointly started a new 5-year research project, “Development of early warning technology of Rain-induced Rapid and Long-travelling Landslides (Project RRLL),” within the framework of SATREPS. SATREPS, standing for “Science and Technology Research Partnership for Sustainable Development,” is a Japanese government program promoting international joint research. This article reports on the outline of the project, including its background, goals, plans of plots for developing critical technologies for the early warning system, etc.

In seismically active regions, loose saturated sandy soils are prone to liquefaction. A strong ground shake can create considerable excess pore water pressures in these soils and temporarily decreases the effective stress and shear strength, leading to strength loss, excessive ground settlements, and lateral spreading. Not to mention the immediate ground deformation, post-seismic settlement, and lateral ground spreading often build up slowly and steadily, causing problems for quick rehabilitations to lifeline facilities, etc. However, this long-lasting post-quake deformation buildup has caught less public attention, and quantitative pieces of evidence are less numerous than those about immediate impacts. This article reviews case histories, showing quantitatively that liquefied soils can remain soft for months.

The impact of a large inland earthquake is profound because of its intense shakes and the associated landslides and debris flows. The quake-induced landslides and debris flow are often the most devastating secondary effect of an earthquake in terms of all kinds of losses, causing long-lasting problems in post-quake rehabilitation activities. An earthquake-induced landslide is just one scene of ever-evolving mountain topography. Therefore, studying terrain dynamics is vital to comprehend the possibility of hazards and propose and apply rational rehabilitation tactics. Though serious, the damage caused by the Mid-Niigata Prefecture Earthquake of October 23, 2004, has given us a rare opportunity to study the landform changes caused by an earthquake that hit an active-folding mountainous terrain. To deal with rehabilitation problems in a scientific manner, a research program, “Earthquake damage in active-folding areas: the creation of a comprehensive data archive and suggestions for its application to remedial measures for civil-infrastructure systems,” was set up getting the Special Coordination Funds for Promoting Science and Technology, Ministry of Education, Culture, Sports, Science and Technology (MEXT). This article reviews some significant findings obtained through this project and even beyond it. The results show that essential aspects of quake-caused problems were linked to deep-seated tectonic displacements, namely the internal driving stress field associated with earthquakes to evolve the active-folding terrain.

The Kyoto Landslide Commitment 2020 (KLC 2020;Sassa [3]) has officially been launched since the online launching session of KLC 2020, 5 November 2020 in the midst of COVID19 pandemic (Sassa [4], [5]) In the field of capacity building, SE RIBC offers courses for postgraduate students in landslide mechanics, dynamics and stabilization, and landslide risk mitigation Since 2011, UB FMG has been a full member of the International Consortium on Landslides (ICL) and has gradually been intensifying its contributions to the ICL worldwide efforts for landslide risk reduction and international promotion of landslide research Since 2009, ITGIS has been a full member of the International Consortium on Landslides (ICL) and has been gradually intensifying its contributions to the ICL worldwide efforts for landslide risk reduction and international promotion of landslide research [Extracted from the article] Copyright of Landslides is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use This abstract may be abridged No warranty is given about the accuracy of the copy Users should refer to the original published version of the material for the full abstract (Copyright applies to all Abstracts )

On March 11, 2011, a large earthquake of Mw 9.0 shook north-eastern Japan and caused severe liquefaction-induced damage over a wide area of reclaimed lands along the coast of Tokyo Bay. Although regional mapping of the liquefaction hazard had been performed in many automounts bodies in Japan, it seems that the maps were not effectively used on all fronts of disaster-prevention management, because the maps only provide liquefaction susceptibilities and little quantitative information on how seriously the ground might deform in a scenario earthquake, which is absolutely necessary information for discussing what-if scenarios. Konagai et al. (2013) conducted air-borne LiDAR surveys to obtain liquefaction-induced ground deformations over the north-eastern stretch of the Tokyo Bay shore area, including Urayasu City, where approximately 85% of the city area was heavily liquefied. Meanwhile, the authors have developed a geotechnical database for liquefaction risk assessments, compiling all the available borehole logs and soil testing data provided by Urayasu City (2012). Given the potential risk of re-liquefaction in a future scenario earthquake, it is an overriding priority to develop a knowledge-sharing liquefaction hazard map reflecting precise records from the past, such as liquefaction-induced ground subsidence and liquefaction-related damage. This paper attempts to assess the liquefaction-induced damage risk on road network, examining the relationship between the liquefaction potential index and the actual ground subsidence. For this purpose, firstly, the spatial distribution of the liquefaction potential (PL) was estimated over Urayasu City based on the above-mentioned geotechnical database developed by the authors. Secondly, the spatial distribution of the PL values and the actual liquefaction-induced road subsidence confirmed through air-born LiDAR surveys were compared to develop an empirical rule for estimating the potential road subsidence in a scenario earthquake. This empirical rule was found to describe the actual damage to roads and manholes in a satisfactory manner. Therefore, it is expected that a risk map, developed on the basis of this empirical rule, will not only help to assess liquefaction-induced damage, but also to design countermeasures against the what-if scenarios of liquefaction.

A rapid and long-traveling landslide was triggered by a monsoon rainfall of a total of 446.5 mm for 3 days in the Aranayake area, Sri Lanka. The landslide destroyed 75 houses and killed 127 persons along the course of this landslide. The mechanism of this landslide was investigated by a joint team of the International Consortium on Landslides (ICL) and the National Building Research Organization (NBRO) of the Government of Sri Lanka in 2017 and 2018; the investigation was part of the WCoE and IPL projects. Physical properties of soil samples taken from the source area of the Aranayake landslide were examined through a series of undrained ring-shear tests, and the measured properties were used in a numerical method, LS-RAPID, to simulate initiations and motions of landslides in this area. The authors then tried to first reproduce a landslide, which was considered, from available pieces of evidence, to have most likely happened in the past, then, to assess the risk of a potential future landslide that is expected to occur close to the 2016 Aranayake landslide. Two possible sliding surfaces were assumed to develop through the soil mass, one along the boundary between the weathered surface soil and the jointed bedrock and another along a potential aquiclude inside the soil. This attempt to estimate movements of both past and future landslides based on the numerical reproduction of the 2016 Aranayake landslide hazard will help develop landslide hazard assessment technologies.

Kashmir earthquake of October 8, 2005, was the most devastating in the recent history of South Asia, causing more than 86,000 casualties, and was accompanied by numerous slope failures. Like many other earthquakes hitting the rugged mountainous terrains of developing countries, strong ground motion records of Kashmir earthquake were also deficient. In the absence of waveforms, source inversion analysis of the geodetic data is performed to reveal spatial distribution of slip on a 90 km × 30 km fault rupture plan with dip and strike angles of 29° and 320°, respectively. The largest asperity, having a maximum slip value of 7.5 m, has appeared at the same location where the large crustal deformation was detected. The slip distribution pattern near the ground surface is consistent with the crustal deformations. Also, seismic stresses are calculated for the epicentral areas for a stratified half-space through forward modeling. All the landslides triggered by Kashmir earthquake are spotted in the areas having high values of square root of the second principal invariant of deviatoric stress tensor ( $$\sqrt{{J}_{2}}$$ ), witnessing a relationship between co-seismic stresses and earthquake-induced landslides. This study will be helpful to rationally understand earthquake-induced damages, their scientific basis, and to establish a cause-and-effect relation between the seismic activity and damaged pattern which can be helpful for rehabilitation, disaster management, and preparedness for future seismic disasters.

The April 25, 2015 Gorkha earthquake jolted the central region of Nepal causing extensive damage to buildings and earthen structures in both mountainous and urban areas of Nepal. Kathmandu-Bhaktapur road, one section of the Araniko Highway, crosses a small valley in the center of the Kathmandu Basin with an embankment. This embankment and adjacent area were deformed in the earthquake. To examine the cause of this ground deformation, several in-situ tests such as micro-tremor measurements, standard penetration tests (SPT), multi-channel analyses of surface waves (MASW), and C 14 dating were conducted. These tests show that a silty sand layer with low plasticity has most likely been liquefied 5 to 8 meters underground. It is also shown that groundwater lowering using existing wells can decrease the liquefaction-prone area by 81%.

Landslides 18(1). https://doi.org/10.1007/s10346-020-01588-z 2 Konagai K (2021b) More than just technology for landslide disaster mitigation - signatories to the Kyoto Landslide Commitment 2020 - no. 2, Kyoto Landslide Commitment 2020. Landslides 18(2). https://doi.org/10.1007/s10346-021-01620-w 3 Konagai K (2021c) More than just technology for landslide disaster mitigation - signatories to the Kyoto Landslide Commitment 2020 - no. 3, Kyoto Landslide Commitment 2020. The Kyoto Landslide Commitment 2020 (KLC 2020, Sassa [4]) has officially been launched since the online launching session of KLC 2020, 5 November 2020, in the midst of COVID19 pandemic (Sassa [5], [6]). As an associate member of the International Consortium on Landslides (ICL) since 2018, NDSU has been contributing to the ICL efforts on landslide risk reduction and the international promotion of landslide research. [Extracted from the article] Copyright of Landslides is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Influenced by the recent global climate change, extreme rainfall events have become more frequent worldwide and resultant hydro-meteorological hazards are creating more deaths and devastations. One of the most remarkable disasters of rain-induced rapid long-travelling landslides (RRLL) in Sri Lanka took place at Aranayake, 70 km east of Colombo in 2016 (JICA Survey Team 2016) (JICA Survey Team in Survey results of Aranayake Disaster, 2016). The fluidized landslide mass ran over an about 2 km distance claiming the lives of 125 people. This tragic event has thus highlighted the importance of sophisticated early warning and disaster management mechanism even more than ever, because the presence of these hidden unstable soil masses as well as their run-out distances are very difficult to predict, and once they start sliding, it is almost impossible to stop them. Both the National Building Research Organisation, Sri Lanka (NBRO) and the International Consortium on Landslides (ICL) have jointly compiled a research proposal within the framework of SATREPS, standing for “Science and Technology Research Partnership for Sustainable Development,” a Japanese government program that promotes international joint researches, and it passed the final round of selection on May 16, 2019. Thus, the new 5-years SATREPS project for Sri Lanka with regard to “Development of early warning technology of Rain-induced Rapid and Long-travelling Landslides (Project RRLL)”, starts in 2020. This article reports on the outline of the project including its goals, plans of plots for developing individual technologies for the early warning system, etc.

This review article summarizes some important findings in recent past earthquakes. One of these findings is that multiple landslides in the epicentral area of the 2004 Chuetsu Earthquake were found along stripes of large co-seismic stress changes, which appeared far away from a surface seismic fault trace. A similar pattern of stress changes may have occurred over and over in the same epicentral area, thus suggesting that we will perhaps be able to be prepared for the next knowing these patterns. Also, it is shown herein that a multiple linear regression analysis for the geometric parameters of many landslides in the epicentral area of the 2018 Hokkaido earthquake can give us the average values of frictional coefficients on both hill slopes and flat depositional areas. These values can help estimate possible runout distances in this area. The observed geometric features of these landslide masses have a striking resemblance to those in the other earthquake-hit area draped with volcanic products, in terms of not only their appearances but also their runout distances.

Two major earthquakes highlighted in this review article are the 2016 Kumamoto Earthquakes and the 2018 Hokkaido Eastern-Iburi Earthquake. These two events that hit the southern and northern Japanese islands known as Kyushu and Hokkaido, respectively, have one thing in common from geological and geotechnical viewpoint; the quake-hit areas are covered and/or underlain by volcanic matters. These volcanic matters such as pumice and volcanic ash have crushable nature that can cause large ground deformations, thus resulting in significant service interruption of lifelines and hindering quick recovery of the quake-hit areas. The phenomena to be discussed in this article include a never-seen-before ground subsidence that occurred on a flood plain west of Mt. Aso in Kyushu, and multiple landslides in Hokkaido with the total area of the exposed bare earth reaching 13.4 km2; the largest area that we’ve ever recorded since the Meiji era. The observed geometric features of the multiple landslide masses have a striking resemblance to those in a past event; the fact thus inspires a feeling of hope that this resemblance will allow for quick estimation of runout distances of these landslide masses with a simple empirical equation.

The distance to the surface rupture zone has been commonly regarded as an important influencing factor in the evaluation of earthquake-triggered landslides susceptibility. However, the obvious surface rupture zones usually do not occur in some buried-fault earthquakes cases, which mean lacking of the information about the distance to the surface rupture. In this study, a new influencing factor named coseismic ground deformation was added to remedy this shortcoming. The Mid-Niigata prefecture earthquake was regareded as the study case. In order to select a more suitable model for generating the landslides susceptibility map, three commonly used models named Logistic Regression (LR), Artificial Neural Networks (ANN) and Support Vector Machines (SVM) were also conducted to assess the landslides susceptibility. The performances of these three models were evaluated with the receiver operating characteristic (ROC) curve. The calculated results showed the ANN model has the highest AUC (area under the curve) value of 0.82. As the earthquake triggered more landslides in the epicenter area, which makes it more prone to landslides in further earthquakes, the landslides susceptibility in the epicenter area was also further evaluated.

A rapid and long-traveling landslide was triggered at Aranayaka, Kegalle district, Sri Lanka on 17 May 2016 by exceptionally heavy rainfall associated with a slow-moving tropical cyclone. The precipitation that accumulated within the last 3 days from May 14 to 17 reached 446.5 mm. The landslide mass traveled over an approximately 2-km distance killing 127 people and destroying 75 houses. To deduce the failure mechanism of the Aranayaka landslide, shear behavior of two samples taken from the initial landslide area were examined through ring-shear tests. The first sample (S1) was taken from the weathered soil layer on the left scarp of the landslide. The second sample (S2) was taken from the weathered granitic gneiss at the bottom of the depression in the middle part of the landslide area. The layer was affected by intense tectonic crushing and subsequent deep weathering. A high value of shear resistance at steady state was measured on the sample S1 while the sample S2 obtained a much smaller steady state shear resistance. This indicated that the sliding surface of the landslide was located in the weathered granitic gneiss associated with the sample S2. A series of computer simulations of this landslide was then carried out given the soil parameters from the ring-shear tests and pore-water pressure ratio estimated from the rainfall records using the “SLIDE” model. In the simulation, the landslide initiated from the middle part of the source area, close to the location from where sample S2 was taken. Moreover, the time of occurrence from the simulation was similar to that observed in the real event. This is a very important information to assess further rapid landslides in areas with similar conditions. This study also indicates the importance of selecting soil samples and suggests that the ring-shear apparatus and computer simulations are effective tools to reproduce the process of landslides.

Rational estimation of debris flow velocity is one of the key issues in debris hazard mitigation. Among the various procedures, back-calculation of debris flow velocity is one of the most frequently used approaches. Back-calculation includes determination of super-elevations and channel properties, and velocities are calculated using the forced vortex equation. Super-elevation and bend radius are biasing parameters in the back-calculation scheme. Therefore, an iterative approach based on simplified assumptions is developed to avoid the direct and subjective determination of bend radius. Besides, as only the highest mud prints are visible after the disaster, this misreads the actual super-elevation. To seek better ways to fix this anomaly, a series of three-dimensional numerical curved flume tests using smoothed particle hydrodynamics are carried out. Estimated velocities from highest flow marks underestimate the actual velocities near the source, while they converge on the actual velocities as the distance to source increases. A best-fit line is then proposed to adjust the mud-marks-derived velocities to the real velocities. The assumption taken during development of the iterative approach for determining bend radii is also justified from the numerical simulations. The law of similarity allows application of these findings to real debris flow disasters. Thus, two real debris flow disasters in Japan are examined for validation of the developed procedure and adjusted velocities are proven to be consistent with verbal evidences and previous analyses.

The Gorkha earthquake of April 25, 2015 has caused many landslides along the Trishuli River in the Rasuwa District. A numerical approach has been taken to assess the remaining risk of landslides. The debris mass movements are described in simulations with only three parameters, namely, the critical angle if, Gauckler–Manning roughness coefficient n, and angle of repose id. The optimum set of these three parameters, obtained through a batch of numerical simulations to minimize the prediction error, was then used to identify locations of unstable colluvium deposits remaining along gullies on steep valley walls of the Trishuli River.

Recent near-field earthquakes accompanied by large soil deformations have been clouding the notion that mountain tunnels would be safe places during earthquakes. One of the recent eye-openers was the damage to railway tunnels in the 2004 Mid-Niigata Prefecture earthquake. Changes in stresses in the interior of a half-space of stratified sedimentary rocks, as a representative of the earthquake-hit region, are obtained using the authors’ previous works on co-seismic deformations of this region to study the damage mechanism of deeply embedded railway tunnels. The values of square root of the second invariant of the stress deviator tensor, [Formula: see text], and the first invariant of Cauchy stress tensor, [Formula: see text], are compared with the reported damages along the entire stretch of selected tunnels and a very good correlation is observed between the peak values of [Formula: see text] and the damaged sections of the tunnels. A yield surface is defined as the boundary between clusters of points for damaged and undamaged tunnel sections in the scatter diagram of [Formula: see text] and [Formula: see text]. This yield surface and rock–soil deformability can be used to examine the margin of safety of both existing and new tunnels as well as for hazard zonation in a given scenario earthquake.

Debris flows, i.e., combined flows of watery mud, chunks of boulders, trees, etc., can be extremely destructive to life and property and can exhibit complicated mechanical features. These complicated features of heterogeneous debris-flow surges can be rationally modeled by considering the rheological behaviors of solid, liquid, and interaction-force phases. Herein, we present the simulation results obtained using a numerical method for a runout process of debris flows based on the depth-averaged equation of motion implemented with the material point method. This method enabled us to describe the debris-flow behaviors in a more adequate manner than previous methods, by simulating debris flows using a depth-averaged model. The simulation results were verified by comparing them with the results of flume tests on dry and wet sand flows. The test results were calibrated to identify the key parameters for simulating the runout process of soil flows. In addition, a real debris-flow event was simulated, and important features of the simulated debris flow, i.e., the geographical dimensions of the depositional zones, conformed well to the observed dimensions of the real debris flow.

The use of super-elevations that a forced vortex flow leaves on the valley walls of a curved flume is a plausible approach toward estimating debris flow velocities in earthquake-induced geo-hazard studies. The centrifugal force of a speeding flow is responsible for a higher flow depth on the outer bend. However, in reality, a flow is not steady, and only the highest flow-marks are left at the outer and inner bends of the flow, which can lead to an inaccurate estimation of the actual velocity. Seeing the real scenario of the field, a series of numerical flume tests using smoothed particle hydrodynamics (SPH) is conducted to validate the estimation of debris flow velocities from flow-marks. Velocities estimated from flow-marks are lower than real velocities near the source region, but they converge to real velocities as the distance to the source increases. Based on several simulations, a best-fit line is proposed for adjusting debris flow velocity from mud-marks, and it is used to estimate flow velocities of the well-documented debris event called “Shiraito river debris flow,” which happened near the rim of the Hakone Crater, Kanagawa Prefecture, Japan, ensuing from the 1923 Great Kanto earthquake.

Earthquake-triggered landslides are some of the most destructive natural disasters. Although remote detection of landslides is economic and efficient, it may miss the more subtle signs of hidden landslides. The Kizawa Tunnel and facilities in its vicinity were severely damaged in the 2004 mid-Niigata Prefecture earthquake. After investigation of the most prominent cracks, the damage was attributed to the slip along a hidden weakness plane. Evidence supporting this argument is summarized in this paper. However, the extent of the shear plane is not limited to the interior of the northern part of the tunnel. The dislocation observed in the two wells to the south of the Kizawa Tunnel together with other findings from previous studies indicates that Kizawa hamlet lies on the southern extension of the same shear plane. Taking account of the presence of flat sedimentary structures, the shear plane may extend in all directions. The authors also surveyed other signs of damage along the perimeter where the shear plane intersects the ground surface. The geological and geomorphological features of the hidden landslide are discussed. Reactivation of interlayer sliding is a threat to the local residents, and thus more attention should be paid to monitoring the movement of the slope to avoid devastating damages.

Simulation of the in situ behavior of pile foundation is necessary in the seismic design and assessment of piles for target structural integrity and performance during earthquakes. Having the mere presence of the soil and the pile in this foundation system, the complex behavior of piles is generally captured by the soil-pile interaction. In this research, a simple parameter called the active pile length, L a, which is reflective of the deformation of pile relative to the stiffness of the soil, is explored to describe the ultimate lateral resistance of the soil. The idea is based upon the deformation of flexible piles commonly used in engineering practice. When piles are induced by a lateral load, the pile deforms significantly in the region near the ground surface and decreases with increasing depth. This region of significant deformation down to the negligible point along the pile depth is defined as the active pile length, L a. During the event of nonlinear excitation, a soil wedge is formed in the passive region along this active pile length. This soil wedge is indicative of the ultimate side soil resistance, and thus can be inferred to be described by L a. To simply investigate, a simple plane strain condition using 2-D finite element method in nonlinear analysis is done to obtain the behavior response of a single pile embedded in a homogeneous soft soil. The elasto-plastic behavior of the soil is modeled using the subloading t ij model and the pile is modeled as a 2-D continuum based beam element. Deformation of the pile and corresponding surrounding lateral soil deformation are analyzed. The potential of this simple concept of active pile length to describe the nonlinear response of piles embedded on soft soils is presented for more practical approach in the seismic design and assessment of piles.

東北地方太平洋沖地震によって埋立地の大部分が液状化した千葉県浦安市において，著者らは地震発生直後から航空レーザ測量，粒度分析，SWS試験などを行い，液状化による地盤の変動を継続的にかつ定量的に把握してきた。これらの調査より，(1) 浦安市の埋立地では地盤沈下が広範囲に生じており，その沈下量の分布は家屋・ライフラインの被害と対応している。(2) 同時期の埋立地（未改良地区）で，被害程度が大きく異なる場所がある。(3) 広範囲に採取した噴砂の粒度およびSPT試料の粒度は，大量の噴砂と再液状化が確認されているニュージーランド・クライストチャーチのケースと非常に似通っている。(4) 液状化により地盤の貫入抵抗は大きく低下し，その後2ヶ月程度で強度は回復・安定するが依然として低い値を示している。本稿では以上の知見より，同地区の再液状化の可能性についても検討する。

On February 9 2010, the landslide dam formed in the Kashmir earthquake that occurred on Oct 8 2005 at Hattian Bala in Pakistan was breached after incessant rains. The authors had been involved in a research project to monitor the long-lasting change of the landslide mass at regular 6 monthly intervals since June 2008, and they noticed that air-exposed pieces of sandstones and mudstones of the landslide mass had disintegrated and crumbled due to slaking that dated back to the breach. The change in the landslide mass shape observed between June 2008 and November 2009, did not seem so significant except for a 300 m-long gulley that appeared all of a sudden at the toe of the mass during winter time from 2008 to 2009. Displacements from GPS-measurements conducted in June and November 2009 showed that the crest part subsided by about 10 cm while the toe part heaved slightly up where the overflowed water fell into the eroded gully. A field survey was conducted over the breached landslide dam in April 2010, two months after the breaching event. A severely eroded breach channel was observed along the spillway, which was excavated immediately after the formation of the dam. Given the chronological change in precipitation of the catchment area of Hattian Bala obtained from the TRMM (Tropical Rainfall Measuring Mission) satellite data, the dam is considered to have been breached due to the overtopping of water over the landslide mass of slakable nature. The slakable nature of the material is discussed through both standard slaking tests and advanced unconventional direct shear tests on prepared specimens. Significant creep deformation and a reduction in their peak strength were observed as the slaking developed in the specimens, suggesting that the slakable nature of the mudstones might have been responsible for the breach of the landslide dam.

Landslides triggered by earthquakes are one of the most damaging natural disasters. Recently, cutting-edge technologies such as Light Detection and Ranging (LiDAR), Interferometric Synthetic Aperture Radar (InSAR) method have allowed us to combine a spatial data set of landslides with topographical information etc. However, remote detection of landslides may cause missing slightest signs of hidden landslides. Damages to Kizawa Tunnel and other facilities in its vicinity in the 2004 Niigata-ken Chuetsu Earthquakee are firstly introduced. Moreover, two wells at #1 and #2 respectively to the south of Kizawa tunnel were found dislocated in further survey. Dislocated wells together with other previous findings indicate that Kizawa helmet are all lying on about the same plane suggesting the presence of large shear plane and therefore the importance of thorough investigations.

The 8th October 2005 Kashmir Earthquake of magnitude 7.6 triggered a huge landslide 3.5 km upstream of Hattian Bala town in the state of Azad Jammu Kashmir of Pakistan. The debris mass blocked two tributaries of the Karli branch of the Jhelum River and was breached on 9th February 2010. This debris dam provided us with a rare opportunity to keep careful and continuous eyes on its post-earthquake behavior especially as it was a serious threat to people living along the lower reaches of both the Karli and Jhelum Rivers. This paper describes post-formation behaviors of the debris mass, breaching-inflicted changes of not only the debris mass but also both upstream and downstream reaches based upon laser-scanned images of landforms and Differential Global Positioning System survey results.

The Hattian landslide, which was triggered by the 2005 Kashmir earthquake, formed one of largest landslide dams in the world and it has posed a serious threat of flooding to people living in the lower reach of the Jhelum River. In order to understand deformation occurring in the body of the dam, physical measurements using a Differential Global Positioning System (DGPS) were conducted. Gradual deformation and slowly developing backward erosion initially were observed, leading eventually to a sudden creation of a deep hollow on the downstream slope of the landslide dam. The dimensions of this eroded gully were determined by laser scanning, and the results showed a significant loss of soil volume and a large change in the body of the dam. A breach formation model was used to predict the outflow hydrograph generated by constant downcutting of dam during a breaching event. A run-off analysis of the outflow hydrograph was conducted to evaluate inundation levels of flood waves in case the dam is breached. Hazardous downstream locations were identified near the junction of the Karli and Jhelum Rivers, suggesting a need for early warning system in order to avoid loss of lives.

This is a reconnaissance report on the damage to buildings, bridges, and other structures caused by the 2009 L'Aquila, Italy earthquake. The authors conducted site investigation during the period of April 18–21, 2009. A detailed discussion on the damage of buildings, bridges, and other facilities, as well as possible damage mechanisms, is presented. Geotechnical damage and ground motions are also presented.

本研究は，常時微動を用いた簡易な地盤調査と，それとの精度のバランスを考えた地盤モデル化手法を組み合わせる新しい方法を提案するものである．線状地下構造物の耐震解析では，2地点間の軸方向ひずみの評価が重要で，広域にわたって地盤の地震応答を評価する必要がある．ここでは，地表の単点で実施する常時微動測定によって，実際の多層地盤を卓越振動数の等しい基盤上の一様表層地盤に置き換える．この簡易な地盤モデルは，特に低い周波数帯で多層地盤の応答を良く表現し，一方，高次モードの近似は良くない．そこで，地盤深さ方向に1次の振動モードを仮定し，さらなる簡便化を図る．例として不整形な多層地盤の固有振動問題を考え，詳細な地盤物性を与えた3次元有限要素解析と本地盤モデルによる解析とを比較したところ，ほぼ同様な結果が得られた．