Spatial pattern of landslides in Swiss Rhone Valley

The present study analyses the spatial pattern of quaternary gravitational slope deformations (GSD) and historical/present-day instabilities (HPI) inventoried in the Swiss Rhone Valley. The main objective is to test if these events are clustered (spatial attraction) or randomly distributed (spatial independency).Moreover, analogies with the cluster behaviour of earthquakes inventoried in the same area were examined. The Ripley's K-function was applied to measure and test for randomness. This indicator allows describing the spatial pattern of a point process at increasing distance values. To account for the non-constant intensity of the geological phenomena, a modification of the K-function for inhomogeneous point processes was adopted. The specific goal is to explore the spatial attraction (i.e. cluster behaviour) among landslide events and between gravitational slope deformations and earthquakes. To discover if the two classes of instabilities (GSD and HPI) are spatially independently distributed, the cross K-function was computed. The results show that all the geological events under study are spatially clustered at a well-defined distance range. GSD and HPI show a similar pattern distribution with clusters in the range 0.75-9 km. The cross K-function reveals an attraction between the two classes of instabilities in the range 0-4 km confirming thatHPI are more prone to occur within large-scale slope deformations. The K-function computed for GSD and earthquakes indicates that both present a cluster tendency in the range 0-10 km, suggesting that earthquakes could represent a potential predisposing factor which could influence the GSD distribution.Fil: Tonini, Marj. Universite de Lausanne; SuizaFil: Pedrazzini, Andrea. Universite de Lausanne; SuizaFil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos; Argentina. Universite de Lausanne; SuizaFil: Jaboyedoff, Michel. Universite de Lausanne; Suiz

Spatial pattern of landslides in Swiss Rhone Valley

The present study analyses the spatial pattern of quaternary gravitational slope deformations (GSD) and historical/present-day instabilities (HPI) inventoried in the Swiss Rhone Valley. The main objective is to test if these events are clustered (spatial attraction) or randomly distributed (spatial independency). Moreover, analogies with the cluster behaviour of earthquakes inventoried in the same area were examined. The Ripley's K-function was applied to measure and test for randomness. This indicator allows describing the spatial pattern of a point process at increasing distance values. To account for the non-constant intensity of the geological phenomena, a modification of the K-function for inhomogeneous point processes was adopted. The specific goal is to explore the spatial attraction (i.e. cluster behaviour) among landslide events and between gravitational slope deformations and earthquakes. To discover if the two classes of instabilities (GSD and HPI) are spatially independently distributed, the cross K-function was computed. The results show that all the geological events under study are spatially clustered at a well-defined distance range. GSD and HPI show a similar pattern distribution with clusters in the range 0.75-9km. The cross K-function reveals an attraction between the two classes of instabilities in the range 0-4km confirming that HPI are more prone to occur within large-scale slope deformations. The K-function computed for GSD and earthquakes indicates that both present a cluster tendency in the range 0-10km, suggesting that earthquakes could represent a potential predisposing factor which could influence the GSD distribution

Mass wasting and catastrophic collapse of natural dams in the Andean orogenic front (36º-38ºS): The Navarrete and Río Barrancas case studies

En los Andes nor-neuquinos, existe una gran concentración de depósitos de avalanchas de roca que generan endicamientos naturales. El colapso temprano de estos diques generados por deslizamientos de ladera es el proceso evolutivo más probable. Paleocostas, profundas y agudas brechas de colapso, y depósitos de outburst flood permiten reconstruir las características de las lagunas asociadas a los respectivos diques. En esta región, el último evento glaciario ha creado pendientes abruptas y fracturación interna de los materiales, los que determinaron un aumento de la susceptibilidad al colapso de las pendientes por factores externos como sismicidad o precitaciones. La distribución de las avalanchas aparenta estar asociada a la intersección entre fallas con actividad cuaternaria y los valles glaciarios. Este trabajo mostrará actividad neotectónica en el valle del arroyo PichiNeuquén, donde se encuentra el retrocorrimiento Aguas Calientes, que presenta estratos de crecimiento cuaternarios en el labio colgante de la falla. Adicionalmente, se observan probables sismitas en la desembocadura del arroyo Colorado. Este trabajo tiene como objetivo comparar el origen, similitud de inductores (probable actividad sísmica) y ambiente geomorfológico de las avalanchas Río Barrancas y Navarrete, con énfasis en esta última. El primer dique natural mencionado ha colapsado catastróficamente (debido a un aumento del influjo de agua a la laguna) luego de 2,2 Ka de existencia. En el segundo caso, la edad del depósito de avalancha y sus causas de colapso son aún inciertas. La existencia de un flujo de detritos en la margen este de la laguna Navarrete y la similar cota entre la paleocosta y el tope del dique, permiten proponer distintas hipótesis acerca de las causas de colapso del dique.Mass wasting and catastrophic collapse of natural dams in the Andean orogenic front (36º-38ºS): The Navarrete and Río Barrancas case studies. A high concentration of rock avalanches, most of them resulting in natural dams, is possible to recognize in the Andes of the northern Neuquén. In landslide dams the most probable evolutionary process corresponds to their early collapses. Paleoshorelines, deep and narrow breaches, and outburst flood deposits permit to rebuild the characteristics of the related lakes. The last glaciation in this region, have created steep slopes and physical rock weathering. These facts determined an increase in the susceptibility to slope failure triggered by seismicity and precipitation. The distribution of rock avalanches seems to be related to the interaction between young deformation and the glacial valleys. The Aguas Calientes backthrust in the Pichi-Neuquén valley is associated with Pliocene to Quaternary growth-strata, and probable seismic triggered liquefaction of sediments in the Colorado creek, and has evidence of neotectonic activity in the entire study area. The aim of this work is to compare the Río Barrancas and Navarrete rock avalanches, with special emphasis in the last one, and establish similitude in their triggering factor (probable seismic activity) and geomorphic environment. The Río Barrancas dam has collapsed (due to an increase in the water influx into the lake) after 2,200 years of existence. For the Navarrete case, the age of slope failure and causes of the collapse of the natural dam are still unknown. The presence of a debris flow in the eastern margin of the lake, and the similar altitude between the paleoshoreline and the top of the dam, would permit to propose two different scenarios.Fil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Hermanns, Reginald L.. Canadian Geological Survey; CanadáFil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin

Landslides in the Andes and the need to communicate on an interandean level on landslide mapping and research

[EN] --- Landslides in the Andes are some of the highest natural threats to society with single events killing up to several thousand people. Landslide mapping and landslide research became a more widely spread discipline in geosciences in the Andean countries. However efforts today by far do not match the threat and both more investigations and more mapping activities are needed to support decision makers in land use planning. In this communication we discussed five key issues that we suggest to focus on in upcoming years: Impact of climatic change on landslides occurrence, landslides susceptibility and hazard maps, prediction of megalandslides, seismically triggered landslides, and temporal spatial distribution of mud and debris flows potential.[ES] --- Los deslizamientos en los Andes son unas de las mayores amenazas naturales a la sociedad, con eventos individuales que han causado la muerte de varios miles de personas. El mapeo e investigación de deslizamientos se convirtió en una disciplina ampliamente difundida en los países andinos. Sin embargo, los esfuerzos actuales no se corresponden aún con la amenaza, y más investigaciones y mapeo son necesarios para apoyar a los tomadores de decisiones en la planificación de usos del suelo. En esta comunicación se discuten cinco temas clave en los que se sugiere poner el foco en los próximos años: el impacto del cambio climático en la ocurrencia de deslizamientos, mapas de peligro y susceptibilidad a deslizamientos, predicción de megadeslizamientos, deslizamientos disparados sísmicamente, y la potencial distribución espacio-temporal de flujos de barro y detritos

Mass wasting processes in the retroarc of northern Neuquén (37°-38°s): conditioning factors and their implications on landscape modeling

En la zona de transición entre los Andes Centrales y los Andes Patagónicos, se reconocen estructuras tectónicas que han deformado depósitos oligo-miocenos de la Fm. Cura Mallín y cuaternarios de la Fm. Cola de Zorro (5-1 Ma), constituyendo un frente montañoso de 400 metros. Esta actividad tectónica cuaternaria, ha dejado su impronta en la red de drenaje, que en algunos casos no ha logrado ajustarse al equilibrio perdido tras el desplazamiento de las estructuras. Sin embargo, uno de los principales indicadores de tectonismo activo son los movimientos en masa. En el área se identifican numerosos movimientos en masa, desprendidos principalmente de secuencias subhorizontales volcánicas, con volúmenes que alcanzan los 4 km3. Los movimientos en masa pueden ser divididos en dos grupos: 1) con zonas de arranque asociadas al trazo de estructuras tectónicas, y 2) con zonas de arranques ubicadas en áreas carentes de deformación. Los movimientos relacionados a estructuras presentan zonas de arranque con coronas que se extienden varios kilómetros aguas arriba desde el eje del valle, son generalmente los que involucran mayor volumen de roca, y en general son del tipo avalancha de rocas. Presentan alto grado de trituración de los materiales, pese a que en algunos casos se desarrollan en zonas con relieve local menor a 200 m. Los movimientos en masa con zonas de arranque ubicadas en secciones carentes de deformación, involucran volúmenes menores, alcanzando como máximo los 0,17 km3, y generalmente son deslizamientos rotacionales o volcamientos. Presentan bajo grado de trituración de los materiales, pese a que en ocasiones se dan en zonas con contraste de relieve de hasta 400 metros. Por lo tanto, el fracturamiento de los materiales en zonas de deformación tectónica es el principal control en las diferencias de ambos grupos. La datación de seis depósitos a partir del análisis de núcleos cosmogénicos (3He y 21Ne) y la asignación de edades relativas a partir de criterios estratigráficos y morfológicos, permite observar que los movimientos se distribuyen en un amplio rango temporal entre el holoceno y tiempos previos al Último Máximo Glacial. Tres movimientos presentan edades de alrededor de 6,6 Ka. Uno de ellos se sitúa sobre el trazo de la falla Chacayco y dos a 1 km de distancia de la misma. Esto podría sugerir que fueron disparados por un mismo evento sugiriendo que podrían haber sido disparados por un mismo evento sísmico relacionado con la falla mencionada. Por lo tanto la actividad tectónica sería detonante de los movimientos. Del contraste entre las tasas de incisión y las tasas de exhumación, se concluye que en el área de estudio el levantamiento orogénico desde el Plioceno superior, está siendo compensado por procesos erosivos. Los colapsos de ladera son importantes promotores de la degradación orogénica, y los glaciares y sus correspondientes corrientes glacifluviales son los principales agentes de transporte y exportadores de los materiales hacia el antepaís.Tectonic structures can be recognized in the transition zone between the Central and Patagonian Andes. This structures deformed Oligo-Miocene deposits from Fm. Cura Mallín and Quaternary deposits from Fm. Cola de Zorro (5-1 Ma), constituting a mountainous front 400 meters high. This Quaternary tectonic activity has left its imprint on the drainage network, which in some cases could not adjust to the equilibrium lost after the displacement of the structures. However, mass movements are one of the main indicators of active tectonism. Numerous mass movements can be identified in the area, detached mainly from subhorizontal volcanic sequences, with volumes up to 4 km3. Mass movements can be divides into two groups: 1) with headscarps associated to the path of tectonic structures, and 2) with headscarps located in areas without deformation. Movements related to structures have headscarps extending several kilometers upstream the valley axis. They usually involve the largest rock volumes, and are mostly of the rock avalanche type. They present a high degree of material crushing, despite that in some cases they develop in zones with local relief lower than 200 m. Mass movements with headscarps located in zones without deformation involve smaller volumes, reaching at most 0.17 km3, and are mostly rotational slides and topples. They present a low degree of material crushing, despite that on occasions they occurred in zones with local relief up to 400 m. Therefore, the material crushing in zones with tectonic deformation is the main control for the differences between both groups. Ages of six rockslides were determined by 3He and 21Ne surface exposure dating, and other deposits were assigned relative ages based on stratigraphic and morphologic criteria. The movements spanned a long temporal range between the Holocene and the Last Glacial Maximum. Three movements have ages around 6.6 ka. One of them is situated on the path of Chacayco fault, and the other two 1 km from the fault. This may suggest that they were triggered by a single seismic event related to the aforementioned fault. Therefore, tectonic activity would be the detonator of the movements. Based on the comparison between incision and exhumation rates, this study concludes that the orogenic uplift since the late Pliocene is being compensated by erosive processes in the study area. Slope collapses are important promoters of orogenic degradation, while glaciers and their related glaciofluvial currents, are the main agents of transport to the foreland.Fil:Penna, Ivanna Marina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Brackish-water desalination plant modulates ground deformation in the city of Cape Coral, Florida

The groundwater abstraction and injection cycle in coastal aquifer systems can locally change the piezometric head in aquifer system, leading to differential settlement on the ground that may compromise infrastructure safety. Furthermore, long-term, extensive groundwater extraction may cause significant damage to water resources. Ironically, Florida, a state known for its abundant water resources, has been experiencing major water supply issues in some areas that began to intensify with rapid population growth over the last five decades. As the demand for drinking water in Florida continues to rise, local authorities have turned to using brackish and saline water sources. As of 2022, more than 80% of the desalination plants in the United States are concentrated in the coastal areas of central and south Florida. Using satellite radar interferometry, we have investigated the spatiotemporal evolution of surface subsidence driven by groundwater pumping for brackish-water reverse osmosis (BWRO) desalination facilities in the City of Cape Coral, Florida. We employed Persistent Scatterer Interferometry (PSI) to process all available Sentinel 1A and 1B scenes over the region along two ascending orbits. The deformation time-series obtained from independent SAR data sets are compared spatiotemporally with the groundwater level that provides feed water to the BWRO facilities. The deformation pattern shows one main lobe of subsidence with rates of up to 25 mm/year centred around the operating wells in the north BWRO wellfield that we interpret as human-induced compaction. The spatial correlation between the subsiding area and the active production wells argues in favour of surface deformation induced by the BWRO operations. Based on the InSAR-derived displacement field and well data, we propose a model to explain the spatial heterogeneity of the subsidence process. The ground deformation is reproduced by an elastic model mimicking the reservoir compaction using planar negative closing dislocations. Modelling of the subsidence shows ∼ 0.67 Mm3 yr−1 vol loss due to compaction of the aquifer. The subsidence deformation was also used to compute the cumulative drainage area of the producing wells

Spatial pattern of landslides in Swiss Rhone Valley

The present study analyses the spatial pattern of quaternary gravitational slope deformations (GSD) and historical/present-day instabilities (HPI) inventoried in the Swiss Rhone Valley. The main objective is to test if these events are clustered (spatial attraction) or randomly distributed (spatial independency).Moreover, analogies with the cluster behaviour of earthquakes inventoried in the same area were examined. The Ripley's K-function was applied to measure and test for randomness. This indicator allows describing the spatial pattern of a point process at increasing distance values. To account for the non-constant intensity of the geological phenomena, a modification of the K-function for inhomogeneous point processes was adopted. The specific goal is to explore the spatial attraction (i.e. cluster behaviour) among landslide events and between gravitational slope deformations and earthquakes. To discover if the two classes of instabilities (GSD and HPI) are spatially independently distributed, the cross K-function was computed. The results show that all the geological events under study are spatially clustered at a well-defined distance range. GSD and HPI show a similar pattern distribution with clusters in the range 0.75-9 km. The cross K-function reveals an attraction between the two classes of instabilities in the range 0-4 km confirming thatHPI are more prone to occur within large-scale slope deformations. The K-function computed for GSD and earthquakes indicates that both present a cluster tendency in the range 0-10 km, suggesting that earthquakes could represent a potential predisposing factor which could influence the GSD distribution.Fil: Tonini, Marj. Universite de Lausanne; SuizaFil: Pedrazzini, Andrea. Universite de Lausanne; SuizaFil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos; Argentina. Universite de Lausanne; SuizaFil: Jaboyedoff, Michel. Universite de Lausanne; Suiz

Natural dams in the headwater of the Lileo valley (Neuquén province, Argentina)

En este trabajo analizamos tres endicamientos naturales por depositación de movimientos en masa que tuvieron lugar en las nacientes del arroyo Lileo (Cordillera de los Andes, norte neuquino), dos de ellos ocurrieron en los últimos 50 años. El primero ocurrió en el Holoceno, por desprendimiento de 0,14 km3 de volcanitas en la ladera oeste del valle, cerca de las nacientes del arroyo La Tregua. Este bloqueo originó una laguna permanente de 0,44 km2. En los años '60, la depositación de una avalancha de detritos originada en la ladera opuesta del valle, frente a la escarpa de la avalancha de rocas, ocluyó la brecha labrada por erosión fluvial en el depósito de avalancha de rocas, generando un segundo cuerpo lacustre de tipo efímero. El último endicamiento, que tuvo lugar entre >1962-1962- < 1985, was caused by a sudden progradation of a conoid developed in the mouth of La Tregua creek, due to an important contribution of material by a debris flow originated in the same zone of detachment as the aforementioned case. The continuous deposition of material in the conoid zone has buried the poles of the Loma de la Lata - Talcahuano gas pipeline, built in 1998. As the zone of detachment of the eastern side of La Tregua valley shows signs of instability, we consider it is possible that a new mass movement may cause another dam.Fil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Hermanns, Reginald L.. Geological Survey; NoruegaFil: González, María Paz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentin

Multiple slope failures associated with neotectonic activity in the Southern Central Andes (37° -37°30's), Patagonia, Argentina

Quaternary tectonic activity in the transition area between the Central and Patagonian Andes is closely associated with an anomalous cluster of rockslides: 19 rockslides with volumes up to 4 × 109 m3 developed in plateau basalts. We divided them into two groups: (A) rockslides related to neotectonic activity and (B) rockslides not related to neotectonic activity. Thirteen rockslides, with a total volume of ~10 km3, which lie on either folds or faults, have been displaced parallel to the structures and perpendicular to the valleyaxis, and they exhibit headscarps several kilometersaway from the valley axis. Most of them are larger than 109 m3, and are generally of rock avalanche type with a high degree of crushing of rocks, although local relief in some cases does not exceed 200 m. Nine rockslides with a total volume of 8.9 km3 are related to folds, while four with a total volume of 1.3 km3 are related to faults. The six rockslides not related to neotectonic activity have a totalvolume of 0.25 km3 (of which the largest one accounts for 0.17 km3), and are rotational slides and block topples with a low degree of rock fragmentation, although local relief is up to 400 m. The 3He and 21Ne surface exposure ages for six of these slides, as well as relative age assessment based on stratigraphic relation with glacial deposits and the drainage development on the rockslide deposit, suggest that the rockslide ages spread rather randomly betweenpre-glacial and mid Holocene, discarding climatic conditions as a common triggering factor. The absence of structures that can represent ideal sliding planes shows that rock fracturing due to neotectonic activity is a major conditioning factor for failures and that the magnitude of landslides is strongly controlled by the type of deformation.Fil: Penna, Ivanna Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Laboratorio de Tectónica Andina; ArgentinaFil: Hermanns, Reginald L.. Geological Survey of Norway; NoruegaFil: Niedermann, Samuel. Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum; AlemaniaFil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Laboratorio de Tectónica Andina; Argentin

Semi-empirical prediction of dam height and stability of dams formed by rock slope failures in Norway

Based on an inventory of 69 dams formed by rock slope failures in southwestern Norway and published inventories from other parts of the world, we developed semi-empirical relationships linking the maximum dam height (HD.max in metres) to dam volume (VD in 106 m3) and other relevant parameters such as valley width (WV in metres) or dam area (AD in square kilometres). Power laws are obtained for HD.max=f(VD) and HD.max=f(VD, WV), while a linear relationship links HD.max to the ratio VD∕AD. For dams in southwestern Norway, the linear relationship HD.max=1.75×VD/AD has the least uncertainties and provides the best results when comparing predicted dam heights with a validation dataset composed of existing dams in northern Norway and numerically modelled dams for possible rock slope failures. To assess the stability of future dams, we use the predicted dam heights in the dimensionless blockage index (DBI) and relating this index to the probability of dam failure derived from our dataset and other published databases on landslide dams. This study underlines the potential of semi-empirical relationships for assessing dam height and stability that needs to be included in preliminary hazard and risk assessment for unstable rock slopes, because damming of a river is an important secondary effect of landslides due to upstream flooding and possible outburst floods in the case of dam failure