Automating global landslide detection with heterogeneous ensemble deep-learning classification

With changing climatic conditions, we are already seeing an increase in extreme weather events and their secondary consequences, including landslides. Landslides threaten infrastructure, including roads, railways, buildings, and human life. Hazard-based spatial planning and early warning systems are cost-effective strategies to reduce the risk to society from landslides. However, these both rely on data from previous landslide events, which is often scarce. Many deep learning (DL) models have recently been applied for landside mapping using medium- to high-resolution satellite images as input. However, they often suffer from sensitivity problems, overfitting, and low mapping accuracy. This study addresses some of these limitations by using a diverse global landslide dataset, using different segmentation models, such as Unet, Linknet, PSP-Net, PAN, and DeepLab and based on their performances, building an ensemble model. The ensemble model achieved the highest F1-score (0.69) when combining both Sentinel-1 and Sentinel-2 bands, with the highest average improvement of 6.87 % when the ensemble size was 20. On the other hand, Sentinel-2 bands only performed very well, with an F1 score of 0.61 when the ensemble size is 20 with an improvement of 14.59 % when the ensemble size is 20. This result shows considerable potential in building a robust and reliable monitoring system based on changes in vegetation index dNDVI only.Comment: Author 1 and Author 2 contributed equally to this wor

Combined three-dimensional electric and seismic tomography study on the Aknes rockslide in western Norway

We present a combined 3-D geoelectric and seismic tomography study conducted on the large Aknes rockslide in western Norway. Movements on the slope are strongly influenced by water infiltration, such that the hydrogeological regime is considered as a critical factor affecting the slope stability. The aim of our combined geophysical study was to identify and visualize the main shallow tension fractures and to determine their effect on hydraulic processes by comparing the geophysical results with information from borehole logging and tracer tests. To resolve the complex subsurface conditions of the highly fractured rock mass, a three-dimensional set-up was chosen for our seismic survey. To map the water distribution within the rock mass, a pattern of nine intersecting 2-D geoelectric profiles covered the complete unstable slope. Six of them that crossed the seismic survey area were considered as a single data set in a 3-D inversion. For both methods, smoothing-constraint inversion algorithms were used, and the forward calculations and parameterizations were based on unstructured triangular meshes. A pair of parallel shallow low-velocity anomalies (<1400 m/s) observed in the final seismic tomogram was immediately underlain by two anomalies with resistivities <13 k Omega m in the resistivity tomogram. In combination with borehole logging results, the low-velocity and resistivity anomalies could be associated with the drained and water-filled part of the tension fractures, respectively. There were indications from impeller flowmeter measurements and tracer tests that such tension fractures intersected several other water-filled fractures and were responsible for distinct changes of the main groundwater flow paths. (C) 2009 Elsevier B.V. All rights reserved

Using geographic information systems for radon exposure assessment in dwellings in the Oslo region, Norway

Radon exposures were assigned to each residential address in the Oslo region using a geographic information system (GIS) that included indoor radon measurements. The results will be used in an epidemiologic study regarding leukemia and brain cancer. The model is based on 6% of measured residential buildings. High density of indoor radon measurements allowed us to develop a buffer model where indoor radon measurements found around each dwelling were used to assign a radon value for homes lacking radon measurement. <br><br> Intraclass correlation coefficients (ICCs) were used to study the agreement between radon values from the buffer method, from indoor radon values of measured houses, and from a regression model constructed with radiometric data (<i>e</i>_Th, <i>e</i>_U) and bedrock geology. We obtained good agreement for both comparisons with ICC values between 0.54 and 0.68. <br><br> GIS offers a useful variety of tools to study the indoor-radon exposure assessment. By using the buffer method it is more likely that geological conditions are similar within the buffer and this may take more into account the variation of radon over short distances. It is also probable that short-distance-scale correlation patterns express similarities in building styles and living habits. Although the method has certain limitations, we regard it as acceptable for use in epidemiological studies

Breaking the Grenville–Sveconorwegian link in Rodinia reconstructions

The Grenville, Sveconorwegian, and Sunsas orogens are typically inferred to reflect collision between Laurentia, Baltica, and Amazonia at ca. 1.0 Ga, forming a central portion of the Rodinia supercontinent. This triple‐junction configuration is often nearly identical in otherwise diverse Rodinia reconstructions. However, available geological data suggest that although the Grenville and Sveconorwegian provinces shared a similar tectonic evolution from pre‐1.8 to ca. 1.5 Ga, they record distinctly different tectonic histories leading up to, during, and possibly following Grenville–Sveconorwegian orogenesis. Moreover, palaeomagnetic data suggest the two continents were separated at peak orogenesis, further invalidating any direct correlation. A number of possible interpretations are permissible with available geological and palaeomagnetic data, of which a “classic” triple‐junction configuration appears least likely. In contrast to the commonly inferred intertwined Proterozoic evolution of Baltica and Laurentia, the possibility remains that they were unrelated for a billion years between 1.5 and 0.45 Ga

The vesicular Sainte-Sophie dykes: a chemically distinct, near-surface facies of the Grenville Dyke Swarm?

Undeformed and unmetamorphosed diabase dykes up to 5 m wide occur in an area of 100 km2 about 50 km northwest of Montreal near the village of Sainte-Sophie. The dykes are subvertical and oriented east–west. The most common phenocryst phase is plagioclase (1–2 mm, exceptionally 10 mm), followed by olivine, and in one dyke, pyroxene. Most dykes have vesicles 0.1–10 mm in diameter and fine-grained margins. Alteration is extensive: plagioclase is partly sericitized, olivine is serpentinized, and zeolites and carbonate are developed in the vesicles and matrix. Ar–Ar dating was challenging, but the weighted mean of two plateau ages indicates intrusion and cooling at 591.6 ± 2.5 Ma. The overall characteristics of these dykes suggest that they may be a facies of the much larger Grenville dyke swarm to the west. However, there are distinct chemical differences that suggest they were fed from a different, generally more enriched mantle source. This zone may be related to the one that produced the alkaline Monteregian intrusions some 470 million years later in the same region. If the Sainte-Sophie dykes are part of the Grenville dyke event, then the use of chemical fingerprints to identify components of this swarm must be used with caution. Another difference between the SainteSophie and main Grenville dykes is the presence of vesicles and zeolites in the former, which suggests the dykes were emplaced close to the surface; hence, this crustal block has seen little erosion during the last 600 million years. Des dykes de diabase non déformés et non métamorphisés atteignant jusqu’a` 5 m de largeur sont présents dans une région de quelque 100 km2 située a` environ 50 km au nord-ouest de Montréal, près du village de Sainte-Sophie. Ces dykes sont subverticaux et d’orientation est–ouest. La phase phénocristique la plus abondante est le plagioclase (1–2 mm, exceptionnellement 10 mm), suivi de l’olivine et, dans un dyke, du pyroxène. La plupart des dykes présentent des vésicules de 0,1–10 mm de diamètre et des bordures a` grains fins. Ils présentent en outre une altération intense, le plagioclase étant partiellement séricitisé, l’olivine, serpentinisée, et des zéolites et des carbonates étant présents dans les vésicules et la matrice. La datation Ar–Ar s’est avérée difficile, mais la moyenne pondérée de deux âges plateau indiquent une intrusion et un refroidissement a` 591,6 ± 2,5 Ma. Les caractéristiques générales de ces dykes portent a` croire qu’ils pourraient constituer un faciès du beaucoup plus grand essaim de dykes de Grenville plus a` l’ouest. Des différences claires sur le plan chimique indiqueraient toutefois qu’ils proviennent d’une source mantellique distincte généralement plus enrichie, qui pourrait être reliée a` la zone qui a produit les intrusions alcalines montérégiennes, il y a quelque 470 millions d’années dans la même région. Si les dykes de Sainte-Sophie découlent effectivement du même épisode que les dykes de Grenville, l’utilisation de signatures chimiques pour identifier des éléments de cet essaim nécessiterait donc une certaine prudence. Une autre différence entre les dykes de Sainte-Sophie et les dykes de l’essaim de Grenville est la présence de vésicules et de zéolites dans les premiers, qui donne a` penser que ces dykes se sont mis en place près de la surface et, donc, que ce bloc crustal a subi peu d’érosion au cours des dernières 600 millions d’années

The Sveconorwegian orogeny: reamalgamation of the fragmented southwestern margin of Fennoscandia

The Sveconorwegian orogeny encompasses magmatic, metamorphic and deformational events between ca. 1140 and 920 Ma at the southwestern margin of Fennoscandia. In recent years, the tectonic setting of this nearly 200 Myr-long evolution has been debated, with some workers arguing for collision with an unknown continent off the present-day southwest coast of Norway, and others advocating accretionary processes inboard of an active margin. Recently, it has been suggested that orogeny may have been gravity-driven by delamination and foundering of heavy subcontinental lithospheric mantle in an intraplate setting, in some ways similar to proposed sagduction processes in the Archaean. Resolving the tectonic setting of the Sveconorwegian orogen has implications for correlation with other orogens and Rodinia supercontinent reconstructions and for assessments of the evolution of plate tectonics on Earth, from the Archaean to the present. Here, we present new mapping and geochronological data from the Bamble and Telemark lithotectonic units in the central and western Sveconorwegian orogen – the former representing a critical region separating western parts of the orogen that underwent long-lived high- to ultrahigh-temperature metamorphism and magmatism from parts closer to the orogenic foreland that underwent episodic high-pressure events. The data show that the units constituting the Sveconorwegian orogen most likely formed at the southwestern margin of Fennoscandia between ca. 1800 and 1480 Ma, followed by fragmentation during widespread extension between ca. 1340 and 1100 Ma marked by bimodal magmatism and sedimentation. A summary of Sveconorwegian magmatic, metamorphic and depositional events in the different units shows disparate histories prior to their assembly with adjacent units. The most likely interpretation of this record seems to be that episodic, Sveconorwegian metamorphic and deformational events in the central and eastern parts of the orogen represent accretion and assembly of these units. This process most likely took place behind an active margin to the southwest that sustained mafic underplating in the proximal back-arc, resulting in high- to ultrahigh-temperature metamorphism in the western parts. In this interpretation, all features of the Sveconorwegian orogen are readily explained by modern-style plate tectonic processes and hypotheses involving some form of vertical, intraplate tectonics are not supported

Was Baltica part of Rodinia?

Late Ediacaran opening of the Iapetus Ocean is typically considered to reflect separation of Baltica and Laurentia during final breakup of the Rodinia supercontinent, with subsequent closure during the Caledonian Orogeny. However, evidence of the pre-opening juxtaposition of Baltica and Laurentia is limited to purportedly similar apparent polar wander paths and correlation of Rodinia-forming orogenic events. We show that a range of existing data do not unequivocally support correlation of these orogens, and that geologic and palaeomagnetic data instead favour separation of Baltica and Laurentia as early as 1.1–1.2 Ga. Furthermore, new detrital zircon U–Pb age and Ar–Ar thermochronological data from Norway point towards an active western Baltican margin throughout most of the Neoproterozoic and early Palaeozoic. These findings are inconsistent with the majority of palaeogeographic reconstructions that place Baltica near the core of the Rodinia supercontinent

Early Cenozoic denudation of central west Britain in response to transient and permanent uplift above a mantle plume

Upwelling mantle plumes beneath continental crust are predicted to produce difficult to quantify, modest uplift and denudation. The contribution of permanent and transient components to the uplift is also difficult to distinguish. A pulse of denudation in Britain in the Early Paleogene has been linked, although with some controversy, with the arrival of the proto-Iceland mantle plume. In this contribution we show that combining apatite and zircon (U-Th-Sm)/He and apatite fission track analyses from central west Britain with numerical modeling clearly identifies a pulse of early Cenozoic denudation. The data indicate that rock uplift and denudation were centered on the northern East Irish Sea Basin and 1.0–2.4 km of rocks were removed during the latest Cretaceous-early Paleogene. Uplift and erosion appears to have started a few million years before the earliest magmatism in the region. The regional denudation pattern mirrors the distribution of low-density magmatic rocks that has been imaged in the deep crust. However, the injection of the underplating melt is not enough to account for the total denudation. An additional regional uplift of at least 300 m is required, which is consistent with a transient thermal effect from the hot mantle plume. The rapid exhumation event ceased by ~40 Ma and the data do not require significant Neogene exhumation

Tectonic evolution and paleogeography of the Kırşehir Block and the Central Anatolian Ophiolites, Turkey

In Central and Western Anatolia two continent-derived massifs simultaneously underthrusted an oceanic lithosphere in the Cretaceous and ended up with very contrasting metamorphic grades: high pressure, low temperature in the Tavsanli zone and the low pressure, high temperature in the Kirsehir Block. To assess why, we reconstruct the Cretaceous paleogeography and plate configuration of Central Anatolia using structural, metamorphic, and geochronological constraints and Africa-Europe plate reconstructions. We review and provide new Ar-40/Ar-39 and U/Pb ages from Central Anatolian metamorphic and magmatic rocks and ophiolites and show new paleomagnetic data on the paleo-ridge orientation in a Central Anatolian Ophiolite. Intraoceanic subduction that formed within the Neotethys around 100-90 Ma along connected N-S and E-W striking segments was followed by overriding oceanic plate extension. Already during suprasubduction zone ocean spreading, continental subduction started. We show that the complex geology of central and southern Turkey can at first order be explained by a foreland-propagating thrusting of upper crustal nappes derived from a downgoing, dominantly continental lithosphere: the Kirsehir Block and Tavsanli zone accreted around 85 Ma, the Afyon zone around 65 Ma, and Taurides accretion continued until after the middle Eocene. We find no argument for Late Cretaceous subduction initiation within a conceptual "Inner Tauride Ocean" between the Kirsehir Block and the Afyon zone as widely inferred. We propose that the major contrast in metamorphic grade between the Kirsehir Block and the Tavsanli zone primarily results from a major contrast in subduction obliquity and the associated burial rates, higher temperature being reached upon higher subduction obliquity.European Research Council ; Netherlands Organization for Scientific Research (NWO