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At least 451 records · Page 25Linked to original sources
USGS2009

Preliminary investigation of some large landslides triggered by the 2008 Wenchuan earthquake, Sichuan Province, China

The M s 8.0 Wenchuan earthquake or "Great Sichuan Earthquake" occurred at 14:28 p.m. local time on 12 May 2008 in Sichuan Province, China. Damage by earthquake-induced landslides was an important part of the total earthquake damage. This report presents preliminary observations on the Hongyan Resort slide located southwest of the main epicenter, shallow mountain surface failures in Xuankou village of Yingxiu Town, the Jiufengchun slide near Longmenshan Town, the Hongsong Hydro-power Station slide near Hongbai Town, the Xiaojiaqiao slide in Chaping Town, two landslides in Beichuan County-town which destroyed a large part of the town, and the Donghekou and Shibangou slides in Qingchuan County which formed the second biggest landslide lake formed in this earthquake. The influences of seismic, topographic, geologic, and hydro-geologic conditions are discussed. ?? 2009 Springer-Verlag.

Landslides↗
USGS2025

The influence of postfire root strength decay on shallow landslide susceptibility in western Oregon

Severe wildfires can increase the potential for postfire landslides, partly due to the loss of vegetation and root reinforcement. This study investigates the multi-year dynamics of root strength following wildfire in coniferous forests of western Oregon and evaluates implications for postfire slope stability. Root tensile strength was measured through laboratory testing of 969 roots collected from 26 test pits over four postfire timeframes: unburned conditions, 4–12 months postfire (Cedar Creek, 2022), 24–35 months postfire (Holiday Farm, 2020), and 59–67 months postfire (Eagle Creek, 2017). Variables analyzed include root diameter, tensile thread strength, stiffness, progressive tensile strength with displacement, time-dependent strength and ductility, root area ratio, and cohesion. Results indicate a 50% reduction in root strength after wildfire, with the lowest values occurring around 4 years postfire. Projections indicate it could take 10–22 years following fire for root strength to recover to 70% and 90% of the prefire original root strength, respectively. This timeline indicates a multi-year window of vulnerability for shallow landslides that reaches a maximum approximately 4 years following fire. Brittle failure behavior was observed in burned root systems compared to unburned root systems, signaling a more abrupt loss of strength at yield. Simple slope stability analyses show that reduced root strength can lead to instability on more gentle slopes and under less saturation in comparison to unburned conditions. These findings highlight the critical role of root reinforcement in postfire slope stability and the long-term implications of wildfire disturbance on landslide susceptibility.

Oregon↗
USGS1999

Slopewash, surface runoff and fine-litter transport in forest and landslide scars in humid-tropical steeplands, Luquillo Experimental Forest, Puerto Rico

Rainfall, slopewash (the erosion of soil particles), surface runoff and fine-litter transport at humid-tropical steepland sites in the Luquillo Experimental Forest, Puerto Rico (18??20' N, 65??45' W) were measured from 1991 to 1995. Hillslopes underlain by (1) Cretaceous tuffaceous sandstone and siltstone in subtropical rain (tabonuco) forest with vegetation recovering from Hurricane Hugo (1989), and (2) Tertiary quartz diorite in subtropical lower montane wet (colorado and dwarf) forest with undisturbed forest canopy were compared to recent landslide scars. Monthly surface runoff on these very steep hillslopes (24??to 43??) was only 0.2 to 0.5 per cent of monthly rainfall. Slopewash was higher in sandy loam soils whose parent material is quartz diorite (averaging 46 g m-2 a-1) than in silty clay loam soils derived from tuffaceous sandstone and siltstone where the average was 9 g m-2 a-1. Annual slopewash of 100 to 349 g m-2 on the surfaces of two recent, small landslide scars was measured initially but slopewash decreased to only 3 to 4 g m-2 a-1 by the end of the study. The mean annual mass of fine litter (mainly leaves and twigs) transported downslope at the forested sites ranged from 5 to 8 g m-2 and was lower at the tabonuco forest site, where post-Hurricane Hugo recovery is still in progress. Mean annual fine-litter transport was 2.5 g m-2 on the two landslide scars.

Earth Surface Processes and Landforms↗
USGS2016

Comment on “The reduction of friction in long-runout landslides as an emergent phenomenon” by Brandon C. Johnson et al.

Results from a highly idealized, 2-D computational model indicate that dynamic normal-stress rarefactions might cause friction reduction in long-runout landslides, but the physical relevance of the idealized dynamics has not been confirmed by experimental tests. More importantly, the model results provide no evidence that refutes alternative hypotheses about friction reduction mechanisms. One alternative hypothesis, which is strongly supported by field evidence, experimental data, and the predictions of a well-constrained computational model, involves development of high pore fluid pressures in deforming landslide material or overridden bed material. However, no scientific basis exists for concluding that a universal mechanism is responsible for friction reduction in all long-runout landslides.

Journal of Geophysical Research F: Earth Surface↗
USGS2005

Estimation of regional material yield from coastal landslides based on historical digital terrain modelling

High-resolution historical (1942) and recent (1994) digital terrain models were derived from aerial photographs along the Big Sur coastline in central California to measure the long-term volume of material that enters the nearshore environment. During the 52-year measurement time period, an average of 21 000 ?? 3100 m3 km-1 a-1 of material was eroded from nine study sections distributed along the coast, with a low yield of 1000 ?? 240 m3 km-1 a-1 and a high of 46 700 ?? 7300 m3 km-1 a-1. The results compare well with known volumes from several deep-seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature. In addition, a number of parameters are investigated to determine what influences the substantial variation in yield along the coast. It is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope-forming material. Coastal Highway 1 runs along the lower portion of the slope along this stretch of coastline, and winter storms frequently damage the highway. The California Department of Transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the Monterey Bay National Marine Sanctuary. This study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides, as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution. Published in 2005 by John Wiley & Sons, Ltd.

Earth Surface Processes and Landforms↗
USGS2013

New imaging of submarine landslides from the 1964 earthquake near Whittier, Alaska, and a comparison to failures in other Alaskan fjords

The 1964 Alaska M w 9.2 earthquake triggered numerous submarine slope failures in fjords of southern Alaska. These failures generated local tsunamis, such as at Whittier, where they inundated the town within 4 min of the beginning of shaking. Run-up was up to 32 m, with 13 casualties. We collected new multibeam bathymetry and high-resolution sparker seismic data in Passage Canal, and we examined bathymetry changes before and after the earthquake. The data reveal the debris flow deposit from the 1964 landslides, which covers the western 5 km of the fjord bottom. Individual blocks in the flow are up to 145-m wide and 25-m tall. Bathymetry changes show the mass transfer deposits originated from the fjord head and Whittier Creek deltas and had a volume of about 42 million m 3 . The 1964 deposit has an average thickness of ∼5.4 m. Beyond the debris flow, the failures likely deposited a ∼4.6-m thick megaturbidite in a distal basin. We have studied the 1964 submarine landslides in three fjords. All involved failure of the fjord-head delta. All failures eroded basin-floor sediments and incorporated them as they travelled. All the failures deposited blocks, but their size and travel distances varied greatly. We find a correlation between maximum block size and maximum tsunami run-up regardless of the volume of the slides. Lastly, the fjord’s margins were influenced by increased supply of glacial sediments during the little ice age, which along with a long interseismic interval (∼900 years) may have caused the 1964 earthquake to produce particularly numerous and large submarine landslides.

Alaska↗
USGS1981

Small landslide types and controls in glacial deposits: Lower Skagit river drainage, northern cascade range, Washington

Observations of 167 small, shallow landslides spanning a 22-year period on extensively logged slopes of Quaternary terraces in the lower Skagit and Baker Valleys, Washington, shows that there is a relationship between the common slope failures in this area and the slope angle, stratigraphy, and logging practices. Landslide frequency increases upvalley, as do mean annual precipitation and the frequency of perched water tables. Debris slides are most common, occur on steep slopes (>50%) composed of sand and gravel, and are most abundant in areas previously logged by the clear-cut method. Debris flows occur on shallower slopes (>30%) where the stratigraphy leads to perched water tables. Debris flows larger than 600 m2 in area appear to be unrelated to logging practices. Slump flows, described here for the first time, occur on similar slope angles and stratigraphic situations as debris flows. They differ mainly by the presence of semiconsolidated material, usually till, at the slide head. Where till is breached-commonly along road cuts-water infiltration is increased, saturating underlying fine-grained deposits, which then fail by debris flowage. Secondary slumping of till happens when the slope steepens during debris flow failure. Small landslides surrounding Lake Shannon may contribute up to 80% of the total particulate matter yield to the fluvial system at present, increasing lake sedimentation by a rate of 5 mm/yr. ?? 1981 Springer-Verlag New York Inc.

Environmental Geology↗
USGS1990

A suggested method for reporting a landslide

The Landslide Report is a Suggested Method developed by the International Geotechnical Societies' UNESCO Working Party on World Landslide Inventory for reporting the position, date, type, geometry, volume and damage of significant landslides.

Bulletin of the International Association of Engin↗
USGS2010

Landslide-dammed lake at Tangjiashan, Sichuan province, China (triggered by the Wenchuan Earthquake, May 12, 2008): Risk assessment, mitigation strategy, and lessons learned

Landslides and rock avalanches triggered by the 2008 Wenchuan Earthquake produced 257 landslide dams, mainly situated along the eastern boundary of the Qinghai-Tibet Plateau where rivers descend approximately 3,000 m into the Sichuan Basin. The largest of these dams blocked the Tongkou River (a tributary of the Fujiang River) at Tangjiashan. The blockage, consisting of 2.04 × 10 7 m 3 of landslide debris, impounded a lake with a projected maximum volume of 3.15 × 10 8 m 3 , potentially inundating 8.92 km 2 of terrain. Its creation during the rainy season and the possibility of an uncontrolled release posed a serious, impending threat to at least 1.3 million people downstream that could add substantially to the total of 69,200 individuals directly killed by the earthquake. Risk assessment of the blockage indicated that it was unlikely to collapse suddenly, and that eventual overtopping could be mitigated by notching the structure in order to create an engineered breach and achieve safe drainage of the lake. In addition to the installation of monitoring and warning instrumentation, for emergency planning we estimated several outburst scenarios equivalent to 20, 25, 33, and 50% of the dam failing suddenly, creating, respectively, 3.35, 3.84, 4.22, and 4.65 km 2 of flooded area, and overbank water depths of 4.6, 5.1, 5.7, and 6.2 m, respectively, in Mianyang, the second largest city in Sichuan Province, 48 km downstream from the blockage. Based on these scenarios, recommendations and plans for excavating a sluiceway, draining the lake, and downstream evacuation were proposed and later were implemented successfully, with the blockage breached by overtopping on June 10, less than a month after dam emplacement. The peak discharge of the release only slightly exceeded the flood of record at Mianyang City. No lives were lost, and significant property damage was avoided. Post-breaching evaluation reveals how future similar mitigation can be improved. Although initial breach erosion was slow, later erosion was judged uncontrollably rapid; increased slope of the engineered channel and adoption of a compound, trapezoid–triangular cross-section can be considered, as can other measures to control the rate of breach incision. Evacuees from Mianyang City spent an unnecessarily long time (12 days) in temporary settlements; more precise risk management planning can reduce this time in the future.

Sichuan Province↗
USGS2001

Tectonic controls on large landslide complex: Williams Fork Mountains near Dillon, Colorado

An extensive (~ 25 km2) landslide complex covers a large area on the west side of the Williams Fork Mountains in central Colorado. The complex is deeply weathered and incised, and in most places geomorphic evidence of sliding (breakaways, hummocky topography, transverse ridges, and lobate distal zones) are no longer visible, indicating that the main mass of the slide has long been inactive. However, localized Holocene reactivation of the landslide deposits is common above the timberline (at about 3300 m) and locally at lower elevations. Clasts within the complex, as long as several tens of meters, are entirely of crystalline basement (Proterozoic gneiss and granitic rocks) from the hanging wall of the Laramide (Late Cretaceous to Early Tertiary), west-directed Williams Range thrust, which forms the western structural boundary of the Colorado Front Range. Late Cretaceous shale and sandstone compose most footwall rocks. The crystalline hanging-wall rocks are pervasively fractured or shattered, and alteration to clay minerals is locally well developed. Sackung structures (trenches or small-scale grabens and upslope-facing scarps) are common near the rounded crest of the range, suggesting gravitational spreading of the fractured rocks and oversteepening of the mountain flanks. Late Tertiary and Quaternary incision of the Blue River Valley, just west of the Williams Fork Mountains, contributed to the oversteepening. Major landslide movement is suspected during periods of deglaciation when abundant meltwater increased pore-water pressure in bedrock fractures. A fault-flexure model for the development of the widespread fracturing and weakening of the Proterozoic basement proposes that the surface of the Williams Range thrust contains a concave-downward flexure, the axis of which coincides approximately with the contact in the footwall between Proterozoic basement and mostly Cretaceous rocks. Movement of brittle, hanging-wall rocks through the flexure during Laramide deformation pervasively fractured the hanging-wall rocks. ?? 2001 Elsevier Science B.V. All rights reserved.

Geomorphology↗
USGS2002

Influence of the Portuguese Bend landslide on the character of the effluent-affected sediment deposit, Palos Verdes margin, southern California

Historic accretion of sediment on the Palos Verdes margin off Los Angeles County, CA, is dominated by two sources, effluent from Whites Point outfall and sediment eroded from the toe of Portuguese Bend landslide. In this paper, we document the recent history of sedimentation from these non-marine sources from 1937 until the late 1990s, and attempt to estimate the amount of material preserved on the shelf. Toward that end, we characterized offshore sediment by physical and geotechnical testing, using non-destructive gamma-ray whole-core logging techniques and conventional geotechnical strength tests, and X-ray diffraction. Results are reported within a geographic information system framework that allows for: (1) the evaluation of the spatial variability of the measured properties, and (2) assessment of the influence of these properties on processes affecting the effluent-affected Sediment layer. In the inner shelf, material eroded by wave action from the toe of the Portuguese Bend landslide since 1956 has contributed 5.7-9.4 million metric tons (Mmt) of sediment, from a total eroded mass of 12.1 Mmt. A lesser fraction (???2.7Mmt) of sediment is incorporated into the mid- and outer-shelf effluent-affected sediment layer. Evidence from X-ray diffractograms clearly indicates that landslide material has mixed with the mid- and outer-shelf effluent. From 1937-1987, it is estimated that 3.8 Mmt of solid anthropogenic effluent was discharged into the water column and onto the Palos Verdes Shelf.

Continental Shelf Research↗
USGS2020

Twelve-year dynamics and rainfall thresholds for alternating creep and rapid movement of the Hooskanaden landslide from integrating InSAR, pixel offset tracking, and borehole and hydrological measurements

The Hooskanaden landslide is a large (~600 m wide × 1,300 m long), deep (~30 – 45 m) slide located in southwestern Oregon. Since 1958, it has had five moderate/major movements that catastrophically damaged the intersecting U.S. Highway 101, along with persistent slow wet‐season movements and a long‐term accelerating trend due to coastal erosion. Multiple remote sensing approaches, borehole measurements, and hydrological observations have been integrated to interpret the motion behaviors of the slide. Pixel offset tracking of both Sentinel‐1 and Sentinel‐2 images was carried out to reconstruct the 3‐D displacement field of the 2019 major event, and the results agree well with field measurements. A 12‐year displacement history of the landslide from 2007 to 2019 has been retrieved by incorporating offsets from Light Detection and Ranging (LiDAR) digital elevation model (DEM) gradients and Interferometric Synthetic Aperture Radar (InSAR) processing of ALOS and Sentinel‐1 images. Comparisons with daily/hourly ground precipitation reveal that the motion dynamics are predominantly controlled by intensity and temporal pattern of rainfall. A new empirical threefold rainfall threshold was therefore proposed to forecast the dates for the moderate/major movements. This threshold relies upon antecedent water‐year and previous 3‐day and daily precipitation and was able to represent observed movement periods well. Adaptation of our threshold methodology could prove useful for other large, deep landslides for which temporal forecasting has long been generally intractable. The averaged characteristic hydraulic conductivity and diffusivity were estimated as 6.6 × 10 −6 m/s and 6.6 × 10 −4 m 2 /s, respectively, based on the time lags between rainfall pulses and slide accelerations. Hydrologic modeling using these parameters helps to explain the ability of the new rainfall threshold.

Oregon↗
USGS2025

Detection of landslide-generated tsunami by shipborne GNSS precise point positioning

Precise point positioning (PPP) of ships using Global Navigation Satellite System (GNSS) data reveals the precise movements of marine vessels. This method may quantify anomalies in sea surface height with implications for oceanographic monitoring, exploration, and tsunami warning. The GNSS PPP data from the R/V Sikuliaq , a research ship of the University of Alaska Fairbanks, were processed to detect a small local tsunami generated by the Lowell Point landslide, which occurred near Seward, Alaska, on 8 May 2022 (UTC). The GNSS receiver aboard the R/V Sikuliaq recorded the waves generated by the landslide, with a maximum wave amplitude of 6 cm and wave periods between 40 and 50 s. These results are consistent with simulations of the landslide event.

Alaska↗
USGS2025

Anomalous shear stress variation in wet granular medium: Implications for landslide lateral faults

Landslide assessments typically focus on the mechanical properties of the basal shear zone, but lateral faults are frequently overlooked, possibly due to their lower normal stresses and variably saturated conditions. Using double-cylinder shear experiments on wet granular systems as analogs for landslide lateral faults, we observe anomalous shear stress variations with fluid volume fractions, defying an expected unimodal relationship associated with capillary cohesion. At low fluid volume fractions, shear strength weakens as the wet grain assembly experiences reduced lateral pressure and increased boundary slip. This boundary slip subsequently vanishes, with an abrupt strengthening due to the dilation of the grain assembly against fluid surface tension as saturation approaches. Strike-slip motion and confinement in this system explain the strength anomaly, highlighting a critical role of lateral faults in landslide stability, particularly in cases where dynamics cannot be adequately explained by monitored pore-water pressure or basal friction.

Geophysical Research Letters↗
USGS2026

Widespread landslide activity in an extreme wet season and implications for regional sediment management, eastern San Francisco Bay area, California

Watershed sediment production is expected to increase in a warmer future with more extreme rain, with cascading effects throughout drainage and sediment-transport networks. This study investigated landscape-scale sediment movement in the eastern San Francisco Bay area, California, USA, during the extreme 2016–2017 wet season that brought major rainfall, landslides, and flooding. Mapping 8,928 landslides across a 1,050-km 2 study area revealed new sediment yield of 510–956 t/km 2 , equivalent to denudation of 193–361 mm/ky. These results correspond closely to long-term denudation rates in the northern and central California Coast Ranges, indicating that mass wasting in very wet years dominates long-term sediment mobilization. However, due to long residence times in drainage networks, the 2017 landslides contributed at most ∼1%–2% of the estimated locally derived fluvial sediment transport to San Francisco Bay. Although the amount of sediment mobilized did not threaten municipal water supplies, small rangeland impoundments in this mixed-use landscape lost storage capacity to new sedimentation. Considering regional sediment supply and demand, even the exceptionally large sediment delivery in an extreme wet year cannot meet the need for sediment to accrete tidal wetlands in the bay. To keep pace with rising sea levels, this abnormally high terrestrial sediment input would need to occur in 50 of the next 75 years, an unlikely occurrence due to the prevalence of recent drought years. Shoreline protection and restoration in the bay would need additional sources of sediment, such as through management of dredged sediment through beneficial-reuse programs.

California↗
USGS2000

Radar structure of earthquake-induced, coastal landslides in Anchorage, Alaska

Ground-penetrating radar (GPR) was used to investigate the internal structure of two large landslides in Anchorage, Alaska that resulted from the great 1964 earthquake. The Government Hill and Turnagain Heights landslides occurred in similar stratigraphic and geographic settings, yet the style of ground deformation is different at each site. GPR data are compared with previous investigations and are shown, under certain conditions, to have utility in the identification of ancient landslides. Reflection surveys accurately reproduced the subsurface geometry of horst and graben structures and imaged finer scale features such as ground cracks and fissures. Where more complete disintegration of the bluff occurred, GPR reflections from within the slide mass are generally chaotic and include no recognizable evidence of the original stratigraphy. Common midpoint surveys estimated GPR velocity in the sediment and allowed the conversion of travel times to depths.

Alaska↗
USGS1995

Giant blocks in the South Kona landslide, Hawaii

A large field of blocky sea-floor hills, up to 10 km long and 500 m high, are gigantic slide blocks derived from the west flank of Mauna Loa volcano on the island of Hawaii. These megablocks are embedded in the toe of the South Kona landslide, which extends ∼80 km seaward from the present coastline to depths of nearly 5 km. A 10–15-km-wide belt of numerous, smaller, 1–3-km-long slide blocks separates the area of giant blocks from two submarine benches at depths of 2600 and 3700 m depth that terminate seaward 20 to 30 km from the shoreline. Similar giant blocks are found on several other major submarine Hawaiian landslides, including those north of Oahu and Molokai, but the South Kona blocks are the first to be examined in detail using high-resolution bathymetry, dredging, and submersible diving. Dredging of two of the giant blocks brought up pillowed tholeiitic lava. Observations from the U.S. Navy submersible Sea Cliff on the asymmetrically steep eastern flank of one block 10 km long and 300 m high revealed a succession of fractured massive basalt, laminar lava flows, hyaloclastite, and pillow lavas. Chemical analyses of dredged lava identified 19 units that overlap compositionally with lavas from the south rift-zone ridge of Mauna Loa. Sulfur content indicates that most of the lavas were erupted in subaerial and shallow submarine (<200 m depth) sites, but some were erupted in deeper submarine sites. These results indicate that the megablocks were carried by a late Pleistocene giant landslide 40–80 km west from the ancestral shoreline of Mauna Loa volcano before growth of the midslope benches by later slump movement.

Hawaii↗