Evaluation of deep learning algorithms for national scale landslide susceptibility mapping of Iran

The identification of landslide-prone areas is an essential step in landslide hazard assessment and mitigation of landslide-related losses.In this study,we applied two novel deep learning algorithms,the recurrent neural network(RNN)and convolutional neural network(CNN),for national-scale landslide susceptibility mapping of Iran.We prepared a dataset comprising 4069 historical landslide locations and 11 conditioning factors(altitude,slope degree,profile curvature,distance to river,aspect,plan curvature,distance to road,distance to fault,rainfall,geology and land-sue)to construct a geospatial database and divided the data into the training and the testing dataset.We then developed RNN and CNN algorithms to generate landslide susceptibility maps of Iran using the training dataset.We calculated the receiver operating characteristic(ROC)curve and used the area under the curve(AUC)for the quantitative evaluation of the landslide susceptibility maps using the testing dataset.Better performance in both the training and testing phases was provided by the RNN algorithm(AUC=0.88)than by the CNN algorithm(AUC=0.85).Finally,we calculated areas of susceptibility for each province and found that 6%and 14%of the land area of Iran is very highly and highly susceptible to future landslide events,respectively,with the highest susceptibility in Chaharmahal and Bakhtiari Province(33.8%).About 31%of cities of Iran are located in areas with high and very high landslide susceptibility.The results of the present study will be useful for the development of landslide hazard mitigation strategies.     

Meiobenthos assemblages in the mekong estuarine system with special focus on free-living marine nematodes

Meiobenthos assemblages in eight estuaries of the Mekong river system were investigated in August 2008 (from the Cua Tieu estuary to the Tran De estuary). In each estuary, one sampling station was established for meiobenthos sampling. Twelve major taxa of meiobenthos were recorded in this estuarine system, including Nematoda, Copepoda, Turbellaria, Polychaeta, Oligochaeta, Tardigrada, Bivalvia, Ostracoda, Amphipoda, Cumacea, Gastrotricha, Gastropoda, and Crustacean Nauplii larvae. The densities of the meiobenthos range from 581 to 3168 inds/10 cm². Nematodes always occupy the highest numbers with a percentage ranging from 64–99%. There are 135 nematode genera recorded in this study with the following as dominant genera Desmodora, Leptolaimus, Halalaimus, Thalassomonhystera, Theristus, Daptonema, Rhynchonema, Parodontophora, and Oncholaimus. Although the biodiversity of the meiobenthos at higher taxa level is not high compared to other marine environments, the estimates of nematode biodiversity at the genus level indicates high values. The increase in number of genera with increasing sampling intensity illustrate that the diversity is underestimated and would have been higher if the authors had considered a larger number of individuals, more replicates per station, and more sampling stations.     

Nd and Sr isotopic compositions of tektite material from Barbados and their relationship to North American tektites

Isotopic analyses of Nd and Sr on individual microtektites and a bulk microtektite sample from Barbados show them to have a very well defined isotopic composition. These data plot on an ε_Srε_Nd diagram precisely within the narrow field determined by North American tektites (ε_Sr ≈ 111; ε_Nd ≈ ?6.2). They yield an Nd model age of 0.6 AE. These results show that the microtektites from the Oceanic beds of late Eocene age are derived from the same target as the North American tektites and should be associated with the same event. Samples of the deep sea sediments in which the Barbados microtektites occur are found to have isotopic signatures which appear to reflect ambient sea water and detrital sediments. They cannot be the source of Sr or Nd in the tektites. Following the arguments of Shaw and Wasserburg (1982) we conclude that the target area which produced the North American tektite field was composed of sediments (Eocambrian or younger) derived from very late Precambrian crust. Glass beads from Lake Wanapitei Crater are isotopically different from all other tektites (ε_Sr ≈ 960; ε_Nd ≈ ?31.4) and cannot be related to the North American tektites.     

Origin of the Permian-Triassic komatiites,northwestern Vietnam

Abstract Rare examples of Phanerozoic komatiites are found in the Song Da zone, NW Vietnam. These komatiites were erupted through continental crust and may belong to the SE extension of the Permo-Triassic Emeishan volcanic province located in SW China. They provide a good opportunity to study the source characteristics of starting plume magmas in a continental flood basalt province. Erupted on late-Permian carbonate rocks, the komatiitic rocks are interbedded with low-Ti olivine basalts. Basaltic komatiites display pyroxene spinifex textures, while more magnesian rocks (MgO up to 32 wt.%) are porphyritic, containing a single, cognate population of euhedral to elongated olivine phenocrysts with Fo up to 93.0%. This suggests a highly magnesian parental magma with 22–23 wt.% MgO. In terms of major and minor elements, the komatiites are similar to the ca. 89 Ma old Gorgona Island komatiites of Colombia. The Song Da komatiites are also strongly light-rare-earth-element- (LREE) depleted (Ce_N/Yb_N 0.30–0.62) and have unfractionated heavy rare earth element (HREE) patterns. The komatiites have high Os concentrations (up to 7.0 ppb), low but variable Re/Os ratios, and define an isochron with an age of 270±21 Ma, and an initial ¹⁸⁸Os/¹⁸⁷Os ratio of 0.12506± 0.00041 (_Os=+0.02±0.40). The Os isotopic systematics of the komatiites show no effects of crustal contamination. In contrast, their initial _Nd values range from +3 to +8, reflecting varying but generally small degrees of contamination with Proterozoic sialic basement material. Associated low-Ti basalts have low initial _Nd values (–0.8 to –7.5), high initial _Os values (15), flat or LREE-enriched REE patterns, and Nb-Ta depletion. These characteristics are also attributed to variable extents of crustal contamination.Editorial responsibility: T.L. Grove     

Thermal metamorphism of primitive meteorites—X. Additional trace elements in Allende (C3V) heated to 1400° C

We report data for Ag, As, Cd, Cs, Co, Cu, Rb, Sb, Te, Tl and Zn in Allende samples subjected to week-long heating at 400–1400°C in a low-pressure H₂ environment. Temperatures of incipient release for these 11 and 5 additional elements tend to be ordered in a manner similar to postulated condensation sequences during cooling of nebular material but there are differences. Losses progress with temperature but neither the extent of loss nor apparent activation energies for mobilization would have been predictable to even a zeroth order approximation. Elemental retentivity trends and interelement correlation patterns for Allende (C3V) and Murchison (C2) differ markedly indicating a substantially different trace element siting, hence loss trends for these two chondrites.     

Beatrice Ketchemen-Tandia’s contributions to isotope hydrology in sub-Saharan Africa

Hydrogeology Journal -     

The Interactive Effects of Natural Factor and Pollution Source on Surface Water Quality in the Lower Mekong River Basin,Southwestern Vietnam

Water Resources - Surface water quality could be interactively affected by the natural factor (seasonal variation) and human pollution source (industrial, agricultural, and residential sources)....     

Bioaccumulation of Heavy Metals in Soft Tissues of Bivalve Mollusks from Natural Lakes in Eastern Sikhote Alin (Russia) and the Mekong Delta (Vietnam)

Doklady Earth Sciences - The concentrations of seven heavy metals (HMs) in tissues of bivalve mollusks of the families Unionidae (genera Ensidens, Scabies, Kunashiria) and Cyrenidae (genus...     

Structural controls on the occurrence and morphology of karstified assemblages in northeastern Vietnam: a regional perspective

Karstified assemblages occur widely in, and distinctively shape, the geological landscape of the northeastern part of Vietnam. These carbonate rocks were deposited during three major periods of basinal evolution including: (1) Late Cambrian, (2) Early Devonian to Early Carboniferous, and (3) Carboniferous to Earliest Triassic. These sedimentary units contain primary sedimentary structures and have undergone numerous post-depositional geological processes including multiple deformational events, which can be regionally correlated. Several thrusting events and associated folding have led to significant thickening of the carbonate units. The subsequent post-thrusting cross-folding events, followed by several phases of brittle faulting and fracturing further modified the spatial geometry and outcrop of these rocks. The combination and interaction of the primary structures with those formed during the long-lived and complicated deformational history is an important controlling factor in local and regional hydrogeological systems in the region. The geological structures now recorded in the carbonate units ultimately govern the formation of the unique modern surface and sub-surface geomorphology of the karstic terrains in northeastern Vietnam. These structures should be further investigated in the context of water resource assessment and natural hazard prediction and mitigation.     

The Khao Que-Tam Tao gabbro-granite massif, Northern Vietnam: A petrological indicator of the Emeishan plume

New data obtained on the Khao Que-Tam Tao gabbro-granite pluton (Northern Vietnam) are discussed. It was established that this pluton was formed at the Permian-Triassic boundary (250.5 ± 3.2 Ma, ⁴⁰Ar/³⁹Ar isotopic age). Morphologically, it represents a hypabyssal fracture intrusion. The first stage was marked by the intrusion of the picrobasaltic melt, the differentiation of which resulted in the formation of the layered peridotite-gabbro series and the quartz-bearing monzodiorites and granophyres in its endocontact at the final stage. At the second stage, the Khao Que peridotite-gabbro massif was broken in its central part by a fault, along which the Tam Tao granodiorite-granite massif was localized. Numerical simulation using the COMAGMAT program for the basic system and geochemical estimates for the granite system allow the statement that the mafic and granitic melts evolved independently, and their final products were quartz-bearing monzodiorite and granophyre, on the one hand, and aplites and pegmatites, on the other hand. The compositional correlation of the Permian-Triassic magmatic associations in Northern Vietnam (the Nui Chua gabbro pluton and the Khao Que-Tam Tao gabbro-granite and Pia Bioc granite plutons) and in Southeast China (flood basalts) allows these complexes to be regarded as a part of a single large igneous province produced by the Emeishan plume activity.