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The IAEG Commission on Landslides and other Mass Movements on Slopes has proposed English and French names for 19 identifiable features of slope movements and for 7 dimensions of those features. The Commission intends to publish this list in other languages and to supplement and revise it from time to time.
Newmark's sliding-block model is widely used to estimate coseismic slope performance. Early efforts to develop simple regression models to estimate Newmark displacement were based on analysis of the small number of strong-motion records then available. The current availability of a much larger set of strong-motion records dictates that these regression equations be updated. Regression equations were generated using data derived from a collection of 2270 strong-motion records from 30 worldwide earthquakes. The regression equations predict Newmark displacement in terms of (1) critical acceleration ratio, (2) critical acceleration ratio and earthquake magnitude, (3) Arias intensity and critical acceleration, and (4) Arias intensity and critical acceleration ratio. These equations are well constrained and fit the data well (71% < R2 < 88%), but they have standard deviations of about 0.5 log units, such that the range defined by the mean ?? one standard deviation spans about an order of magnitude. These regression models, therefore, are not recommended for use in site-specific design, but rather for regional-scale seismic landslide hazard mapping or for rapid preliminary screening of sites. ?? 2007 Elsevier B.V. All rights reserved.
Landslides are ubiquitous along the Oregon coast. Many are large, deep slides in sedimentary rock and are dormant or active only during the rainy season. Morphology, observed movement rates, and total movement suggest that many are at least several hundreds of years old. The offshore Cascadia subduction zone produces great earthquakes every 300–500 years that generate tsunami that inundate the coast within minutes. Many slides and slide-prone areas underlie tsunami evacuation and emergency response routes. We evaluated the likelihood of existing and future large rockslides being triggered by pore-water pressure increase or earthquake-induced ground motion using field observations and modeling of three typical slides. Monitoring for 2–9 years indicated that the rockslides reactivate when pore pressures exceed readily identifiable levels. Measurements of total movement and observed movement rates suggest that two of the rockslides are 296–336 years old (the third could not be dated). The most recent great Cascadia earthquake was M 9.0 and occurred during January 1700, while regional climatological conditions have been stable for at least the past 600 years. Hence, the estimated ages of the slides support earthquake ground motion as their triggering mechanism. Limit-equilibrium slope-stability modeling suggests that increased pore-water pressures could not trigger formation of the observed slides, even when accompanied by progressive strength loss. Modeling suggests that ground accelerations comparable to those recorded at geologically similar sites during the M 9.0, 11 March 2011 Japan Trench subduction-zone earthquake would trigger formation of the rockslides. Displacement modeling following the Newmark approach suggests that the rockslides would move only centimeters upon coseismic formation; however, coseismic reactivation of existing rockslides would involve meters of displacement. Our findings provide better understanding of the dynamic coastal bluff environment and hazards from future subduction-zone earthquakes.
Piezometric responses to rainfall on hillslopes commonly dictate the timing of landsliding. Insight to this phenomenon can be gained by evaluating the timescales for pore pressure perturbations to propagate normal and parallel to the ground surface, and these timescales can be estimated using characteristic values of hydraulic diffusivity [ Iverson , 2000 ]. However, Montgomery et al. [2002] employed an erroneous definition of hydraulic diffusivity, leading to flawed assessment of the piezometric response timescales identified by Iverson [2000] . This comment aims to rectify the errors of Montgomery et al. [2002] and clarify the methods used by Iverson [2000] to estimate piezometric response timescales at the CB1 field site studied by Montgomery et al.
We have established for the first time a size frequency distribution for carbonate submarine slope failures. Using detailed bathymetry along the northern edge of the carbonate platform north of Puerto Rico, we show that the cumulative distribution of slope failure volumes follows a power-law distribution. The power-law exponent of this distribution is similar to those for rock falls on land, commensurate with their interpreted failure mode. The carbonate volume distribution and its associated volume-area relationship are significantly different from those for clay-rich debris lobes in the Storegga slide, Norway. Coupling this relationship with tsunami simulations allows an estimate of the maximum tsunami runup and the maximum number of potentially damaging tsunamis from landslides to the north shore of Puerto Rico. Copyright 2006 by the American Geophysical Union.
The deep submarine eastern flanks of Mauna Kea, Kohala, and Haleakala volcanoes were mapped for the first time with a multibeam bathymetric and sidescan sonar system during joint Japan-US cruises aboard the JAMSTEC vessel R/V Yokosuka in 1999. The Pololu slump off northeast Kohala is overlain by a carbonate platform in the shallow region and the deeper areas are incised by downslope oriented channels. It is cut by several faults and slump scars and appears to override an older slide located farther east, here named the Laupahoehoe slump. The structures characteristic of the Laupahoehoe slump are NW-SE oriented scarp-and-bench topographic features analogous to the Hilina slump on the mobile SE flank of Kilauea. Enclosed basins lie at 3000-5000 m, fronted by ridges on their seaward sides. The basins may result from local rotational slumps or from uplift above discontinuous thrust faults. The Laupahoehoe slump appears to be overlapped by shield margins of both Kohala and Mauna Kea and thus may have been derived from an elongate Kohala edifice. A large debris apron continues from the base of the two-slide complex, abutting the distal Hana Ridge (Haleakala east rift zone). The tip of the Hana Ridge displays a curious steepsided arcuate rift tip that resembles the classic amphitheater scarp of a landslide. Numerous flat-topped volcanic domes are distributed along the broad crest of the lower rift zone. Similar cones, though fewer in number, are also present on the Hilo Ridge, which may be the continuation of a Kohala rift zone.
This chapter contains sections titled: introduction seafloor surveys of the nuuanu and wailau landslides discussion
Earthquakes on strike-slip faults can produce devastating natural hazards. However, because they consist predominantly of lateral motion, these faults are rarely associated with significant uplift or tsunami generation. And although submarine slides can generate tsunami, only a few per cent of all tsunami are believed to be triggered in this way. The 12 January Mw 7.0 Haiti earthquake exhibited primarily strike-slip motion but nevertheless generated a tsunami. Here we present data from a comprehensive field survey that covered the onshore and offshore area around the epicentre to document that modest uplift together with slope failure caused tsunamigenesis. Submarine landslides caused the most severe tsunami locally. Our analysis suggests that slide-generated tsunami occur an order-of-magnitude more frequently along the Gonave microplate than global estimates predict. Uplift was generated because of the earthquake?s location, where the Caribbean and Gonave microplates collide obliquely. The earthquake also caused liquefaction at several river deltas that prograde rapidly and are prone to failure. We conclude that coastal strike-slip fault systems such as the Enriquillog-Plantain Garden fault produce relief conducive to rapid sedimentation, erosion and slope failure, so that even modest predominantly strike-slip earthquakes can cause potentially catastrophic slide-generated tsunamig-a risk that is underestimated at present. ?? 2010 Macmillan Publishers Limited. All rights reserved.
Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever documented worldwide. Precursory deformation began decades before failure, and the event left a distinct sedimentary record, showing that geologic evidence can help understand past occurrences of similar events, and might provide forewarning. The event was detected within hours through automated seismological techniques, which also estimated the mass and direction of the slide - all of which were later confirmed by remote sensing. Our field observations provide a benchmark for modeling landslide and tsunami hazards. Inverse and forward modeling can provide the framework of a detailed understanding of the geologic and hazards implications of similar events. Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains.
In the last 7 years, spaceborne synthetic aperture radar (SAR) data with resolution of better than a meter acquired by satellites in spotlight mode offered an unprecedented improvement in SAR interferometry (InSAR). Most attention has been focused on monitoring urban areas and man-made infrastructure exploiting geometric accuracy, stability, and phase fidelity of the spotlight mode. In this paper, we explore the potential application of the COSMO-SkyMed® Spotlight mode to rural areas where decorrelation is substantial and rapidly increases with time. We focus on the rapid repeat times of as short as one day possible with the COSMO-SkyMed® constellation. We further present a qualitative analysis of spotlight interferometry over the Slumgullion landslide in southwest Colorado, which moves at rates of more than 1 cm/day.
A small landslide block left a trail about 81 meters long on an 11½-degree slope in the Tuxer Voralpen, Austria. The movement is explained in terms of fluid pressure mechanics; hypothetically, the requisite pore pressure was caused by the loading of contiguous saturated segments of the slide path during rapid sliding.
In August 2004, a National Forest fire crew extinguished a 1.2 ha fire in a wilderness area ~40 km northeast of Santa Barbara, California. Examination revealed that the fire originated on a landslide dotted with superheated fumaroles. A 4 m borehole punched near the hottest (262 °C) fumarole had a maximum temperature of 307 °C. Temperatures in this borehole have been decreasing by ~0.1 °C/d, although the cooling rate is higher when the slide is dry. Gas from the fumaroles and boreholes is mostly air with 3–8 vol% carbon dioxide and trace amounts of carbon monoxide, methane, ethane, and propane. The carbon dioxide is 14 C-dead. The ratios of methane to ethane plus propane [C 1 /(C 2 + C 3 )] range from 3.6 to 14. Carbon isotope values for the CO 2 range from −14‰ to −23‰ δ 13 C. 3 He/ 4 He values range from 0.96 to 0.97 times that of air. The anomalous heat is interpreted to be due to rapid oxidation of iron sulfide augmented by combustion of carbonaceous matter within the formation.
The temporal coincidence between rapid late Pleistocene sea-level rise and large-scale slope failures is widely documented. Nevertheless, the physical mechanisms that link these phenomena are poorly understood, particularly along nonglaciated margins. Here we investigate the causal relationships between rapid sea-level rise, flexural stress loading, and increased seismicity rates along passive margins. We find that Coulomb failure stress across fault systems of passive continental margins may have increased more than 1 MPa during rapid late Pleistocene–early Holocene sea-level rise, an amount sufficient to trigger fault reactivation and rupture. These results suggest that sea-level–modulated seismicity may have contributed to a number of poorly understood but widely observed phenomena, including (1) increased frequency of large-scale submarine landslides during rapid, late Pleistocene sea-level rise; (2) emplacement of coarse-grained mass transport deposits on deep-sea fans during the early stages of marine transgression; and (3) the unroofing and release of methane gas sequestered in continental slope sediments.
This paper studies a parsimonious model of landslide motion, which consists of the one-dimensional diffusion equation (for pore pressure) coupled through a boundary condition to a first-order ODE (Newton's second law). Velocity weakening of sliding friction gives rise to nonlinearity in the model. Analysis shows that solutions of the model equations exhibit a subcritical Hopf bifurcation in which stable, steady sliding can transition to cyclical, stick-slip motion. Numerical computations confirm the analytical predictions of the parameter values at which bifurcation occurs. The existence of stick-slip behavior in part of the parameter space is particularly noteworthy because, unlike stick-slip behavior in classical models , here it arises in the absence of a reversible (elastic) driving force. Instead, the driving force is static (gravitational), mediated by the effects of pore-pressure diffusion on frictional resistance.
A paper recently published in this journal (Pirulli & Pastor, 2012) uses numerical modelling to study the important problem of entrainment of bed material by landslides. Unfortunately, some of the basic equations employed in the study are flawed, because they violate the principle of linear momentum conservation. Similar errors exist in some other studies of entrainment, and the errors appear to stem from confusion about the role of bed-sediment inertia in differing frames of reference.
Many techniques are available for reducing landslide hazards; 27 are described in this paper. Prerequisites for the successful use of these techniques are hazard information understandable to nongeologists and adequate communication of this information to those who will, or are required to, use it. It is concluded that certain factors needed to ensure the lasting effectiveness of these techniques are usually beyond the control of the public planner, engineer, and decisionmaker.
Numerical simulations of hazard cascades downstream from moraine-dammed lakes commonly must specify linkages between models of discrete processes such as wave overtopping, dam breaching, erosion, and downstream floods or debris flows. Such linkages can be rather arbitrary and can detract from the ability to accurately conserve mass and momentum during complex sequences of events. Here we describe an alternative methodology in which we use high-resolution lidar topography and 2-D, two-phase conservation laws to seamlessly simulate all stages of a hazard-cascade that culminates in a debris flow. Our simulations employ our depth-integrated numerical model D-Claw to evaluate hazards from prospective breaching of a moraine dam that impounds Carver Lake on the eastern flank of South Sister volcano in central Oregon, USA. We simulate a “worst-case scenario” sequence of events that begins with a hypothetical 1.6 million m3 landslide that originates near the summit of South Sister and enters Carver Lake. Wave generation and displacement of lake water then leads to dam overtopping, breach erosion, and a downstream debris flow that funnels into Whychus Creek and eventually reaches the community of Sisters, Oregon, about 20 km away. Notably, our simulations predict that much of the debris is directed away from Sisters as a result of natural avulsion and flow diversion that occurs near the head of a low-gradient alluvial fan upstream from Sisters. Consequently, predicted hazards to downtown Sisters are less severe than those predicted by 1-D shallow-water simulations of a Carver Lake dam breach that were performed in the 1980s.
Man should proceed with caution if modifications such as loading, excavation, or changes of the water regime are contemplated for slopes in Allegheny County, especially those slopes described on the map as highly sensitive to disturbance by man. Features indicative of unstable slope conditions include: cracks in buildings, yard walls, and pools; doors and windows that jam; fences and other linear features bowed out of line; tilted trees and utility poles; cracks and steplike ground features; hummocky ground; and water seeps. Geologic factors related to the landsliding process include rock types, layering, fracturing, and attitude; nature of soil cover; permeability of rocks and soils; and steepness of slope.