Eastern Edge Research Articles

The magnetic field in the Flame nebula

Star formation drives the evolution of galaxies and the cycling of matter between different phases of the interstellar medium and stars. The support of interstellar clouds against gravitational collapse by magnetic fields has been proposed as a possible explanation for the low observed star formation efficiency in galaxies and the Milky Way. The Planck satellite provided the first all-sky map of the magnetic field geometry in the diffuse interstellar medium on angular scales of 5-15$'$. However, higher spatial resolution observations are required to understand the transition from diffuse, subcritical gas to dense, gravitationally unstable filaments. NGC 2024, also known as the Flame nebula, is located in the nearby Orion B molecular cloud. It contains a young, expanding region and a dense supercritical filament. This filament harbors embedded protostellar objects and is likely not supported by the magnetic field against gravitational collapse. Therefore, NGC 2024 provides an excellent opportunity to study the role of magnetic fields in the formation, evolution, and collapse of dense filaments, the dynamics of young regions, and the effects of mechanical and radiative feedback from massive stars on the surrounding molecular gas. We combined new 154 and 216 m dust polarization measurements carried out using the HAWC+ instrument aboard SOFIA with molecular line observations of and from the IRAM 30-meter telescope to determine the magnetic field geometry, and to estimate the plane of the sky magnetic field strength across the NGC 2024 region and the surrounding molecular cloud. The HAWC+ observations show an ordered magnetic field geometry in NGC 2024 that follows the morphology of the expanding region and the direction of the main dense filament. The derived plane of the sky magnetic field strength is moderate, ranging from 30 to 80 G. The strongest magnetic field is found at the eastern edge of the region, characterized by the highest gas densities and molecular line widths. In contrast, the weakest field is found toward the main, dense filament in NGC 2024. We find that the magnetic field has a non-negligible influence on the gas stability at the edges of the expanding shell (gas impacted by stellar feedback) and the filament (site of current star formation).

Characteristics and Trends of the Campbell Plateau Meander in the Southern Ocean: 1993–2020

AbstractMeanders are significant features of the Antarctic Circumpolar Current in the Southern Ocean and sites of enhanced upwelling, cross‐frontal tracer fluxes, and exchanges between the surface and deep ocean. They often overlap the locations of fronts and are linked to topographic features. While much is known about Southern Ocean fronts and how they are changing, the response of meanders to climate change is largely unexplored. In this study, we investigate the Campbell Plateau meander south of New Zealand. We apply a local gradient maxima method to satellite altimetry data to identify the position of the meander and estimate its width, geostrophic current speed, and associated trends from 1993 to 2020. We find that the position of the meander has been relatively fixed, except for a section downstream of the Plateau, which has shifted northward by about 0.4° latitude per decade. The meander has become flatter at the western edge of the Plateau, but steeper at the eastern edge of the Plateau. Overall, the meander has widened by 2 km per decade and accelerated by 0.01 m s−1 per decade, particularly downstream of the Plateau. These findings are consistent with other work on standing meanders in the Southern Ocean. Increases in eddy kinetic energy and of the South Pacific Gyre index support our hypotheses that changes in the downstream jet stability and the South Pacific Gyre contribute to these observed trends. The impacts of these trends on cross‐frontal transport remain to be evaluated.

Evolución de las cuencas Tumaco, Atrato y San Juan sobre una plataforma continua a lo largo del margen pacífico colombiano

Several authors have interpreted the Colombian Pacific margin as a succession of oceanic terrane accretions, with generation of forearc basins under a compressive-transpressive tectonic regime during the Late Cretaceous-Miocene. New data acquired in the last decade, consisting of reprocessed seismic lines, geological cross-sections, stratigraphic data from wells, and new stratigraphic columns, are analyzed in this study. We suggest that the proposed models of successive terrane accretions are not supported by the new data; rather, the onshore basins were likely controlled by a marine platform from the Late Cretaceous to the Middle-Late Eocene, with reef growth to the end of this period. In the Late Cretaceous, contemporary to the sedimentation stage, effusive magmatism, mainly basaltic, also occurred. Since Oligocene time, the basins were affected by three different tectonic processes. First, during the Oligocene-Early Miocene, an extensional-transtensional event occurred in the Tumaco Basin and San Juan Sub-basin, which produced horst and graben structures and domino faults, along with the emplacement of igneous bodies in the eastern flank of the basins. The Atrato Sub-basin was affected by local reverse faulting towards its eastern edge. Second, during the Mid-Late Miocene, the western side of the Tumaco Basin was uplifted, and transpressive deformation occurred in the San Juan Sub-basin as evidenced by the San Juan and Garrapatas fault systems. Finally, in the Atrato Sub-basin, a transpressional regime is evidenced by the Baudó anticline. Our results suggest there is no evidence of oceanic terrane accretions in the abovementioned basins during the Late Cretaceous-Middle Eocene. Furthermore, we do not see evidence of a subduction system during that period. We conclude that subduction in western Colombia could have begun during the Early Oligocene instead.

Electrical Structure of Southwestern Longmenshan Fault Zone: Insights into Seismogenic Structure of 2013 and 2022 Lushan Earthquakes

On 1 June 2022, a magnitude 6.1 earthquake struck the southern segment of the Longmenshan fault zone on the eastern edge of the Tibetan Plateau, once again causing casualties and economic losses. Understanding the deep-seated dynamic mechanisms that lead to seismic events in the Lushan earthquake area and assessing the potential hazards in seismic gap areas are of significant importance. In this study, we utilized 118 magnetotelluric datasets collected from the Lushan earthquake area and employed three-dimensional electromagnetic inversion with topographic considerations to characterize the deep-seated three-dimensional resistivity structure of the Lushan earthquake area. The results reveal that the Shuangshi–Dachuan fault in the Lushan earthquake area can be divided into two relatively low-resistivity zones: a western zone dipping southeastward and an eastern zone with a steeper slightly northwestern dip. These two zones intersect at a depth of approximately 20 km, forming an extensional pattern resembling a “Y” shape. The epicenters of both the 2013 and 2022 Lushan earthquakes are primarily located in the upper constricted portion of the pocket-like low-resistivity body at depth. The distribution of seismic aftershocks is confined within the region enclosed by the high-resistivity body, following the pattern of the Y-shaped low-resistivity zone.

Expansion of winter ENSO‐associated rainfall affected area in Southeast Asia under warmer climate

AbstractThis paper examines the changes of El Niño–Southern Oscillation (ENSO) associated winter rainfall relationship in Southeast Asia (SEA) in the historical period (1981–2010) and future period (2071–2100) based on the Coupled Model Intercomparison Project Phase 6 (CMIP6) models simulations. Twenty general circulation models (GCMs) are chosen from the Scenario Model Intercomparison Project (ScenarioMIP) highest emission scenario—Shared Socioeconomic Pathway (SSP) 5‐8.5. This study focuses only on the GCMs that have been able to replicate the consistent associated patterns observed, referred to as “teleconnection‐consistent models” (TCMs). During historical period, ENSO has significant negative association with SEA winter rainfall, particularly over Indochina mainland, Maritime Continent (MC) and northern Borneo. The significant negative‐associated teleconnection affected area has increased under future climate, particularly over southern part of South China Sea (SCS). The weakening of south westerlies at Western North Pacific (WNP) centred near 20°N reduces the moisture transport from Indochina into south of China, increase the negative correlated affected area in the SEA regions above equator. The northeasterlies/easterlies that prevailed from the WNP anticyclone (AC) brings significant moisture flux into southern Borneo, causing increment of significant positive‐associated moisture flux convergence to that region. The weakening of upward motion in TCM results in less warm and moist air rising over SEA MC, reducing the rainfall availability. The 1° eastward expansion of WC downward branch eastern edge leads to suppression of convective activities, increasing the dry affected area. The results suggest that the ENSO has a larger influence on the negative‐associated SEA rainfall and atmospheric circulation in the December–January–February (DJF) late‐21st century when compared to the 1980–2010.

Seismic Microzonation Map of Chiang Mai Basin, Thailand

The seismic site effect which is controlled by local geological conditions is a key parameter of seismic hazards analysis. This paper presents an observational study of microtremor data to investigate the dynamic characteristics of soil in the Chiang Mai basin (Chiang Mai and Lumphun province), Northern Thailand. The Chiang Mai basin was formed on terrace sediments and alluvium sediments. The horizontal vertical spectral ratio (HVSR) analyses of ambient noise data at 101 sites in the basin were analyzed for an average smoothed HVSR curve to estimate the amplification factor and fundamental resonance frequency of each observation point. We also evaluated the shear wave velocity using the HVSR inversion technique based on the diffuse field assumption. Tests undertaken include a comparison of the HVSR of a significant earthquake that was detected at stations in the basin and a nearby bedrock site. The results indicate that the resonance frequency ranges between 0.15 - 0.4 Hz at sites having large thicknesses of soft sediments. The lowest resonance frequencies occur in the center of the basin, whereas higher resonance frequencies were observed in the areas of the shallowest bedrock in the west and east of the basin. It can be inferred that the western margin of the Chiang Mai basin is a steep slope, while the eastern margin of the basin is a low-angle west-dipping basement. The amplification factor ranges between 3 - 5 times, in the middle of the basin. Most of the Chiang Mai basin area is classified as site D soil (stiff soil) relative to alluvium sediments, and a region of class C soil (very dense soil) conforms to the terrace sediments located on the eastern edge of the basin. The soil classification is based on shear wave velocity (Vs30) determined by HVSR inversion. HIGHLIGHTS HVSR analysis and inversion of HVSR from 101 survey points in Chiang Mai basin The Chiang Mai basin area is at high risk from seismic amplification that amplifies a ground motion between 3 - 5 times in the middle of the basin at a dominant frequency range from 0.15 - 0.4 Hz The lowest Vs30 values location is in the middle of the basin classified as site class E (soft soil), while most of the basin area is classified as site D soil (stiff soil) corresponding to alluvium sediments. The class C soil (very dense soil) area conforms to the terrace sediments located on the eastern edge of the basin GRAPHICAL ABSTRACT

First record of Reticulinella? kaeveri in the Laffan and Ilam formations (Zagros fold and thrust belt, SW Iran): new constraints on the chronostratigraphic calibration of the Arabian Plate sequence stratigraphy

Over the past two decades, sequence stratigraphy has proven to be a valuable tool in addressing challenges arising from the inconsistent application of lithostratigraphic nomenclature across diverse geological provinces. It has been particularly successful in achieving regional correlations within the Cretaceous deposits of the Arabian Plate. The key sequence stratigraphic surface in the currently adopted standard sequence stratigraphic scheme is the K150 SB, marking the transition from a passive to an active margin along the eastern edge of the Arabian plate. Despite its importance, the chronostratigraphic age of this surface is poorly constrained. In the Zagros FTB, the uppermost part of the Sarvak Formation, just below the K150 SB, was recently assigned to the upper part of middle Turonian to upper Turonian, based on the presence of Reticulinella? kaeveri. Our research reveals that the range of R.? kaeveri extends above the K150 SB as this species is also present in the Laffan and base of Ilam formations. The Last Occurrence of this taxon provides a new chronostratigraphic marker of the upper Turonian within the Ilam Formation. This finding proves that more Turonian deposit are present in the study area than was previously recognized. We have studied the deposits enclosing the K150 SB in outcrop sections and wells along a transect from basin to platform margin to inner platform setting. Based on planktonic foraminifera and calcareous nannofossils biostratigraphy of basinal sections and sequence stratigraphic correlation to carbonate platform sections, the age of the uppermost part of the Sarvak Formation, immediately below the K150 SB, is firmly constrained within the interval lower Turonian–lower part of middle Turonian. Sequence stratigraphic correlation from basin to platform interior reveals also that the oldest deposits above the K150 SB are not younger than late Turonian. Our new data represents a significant improvement in the chronostratigraphic calibration of sequence stratigraphy in the Cretaceous of the Zagros fold-and-thrust belt.

Exoscopy of Detrital Zircons from Niamey Neoproterozoic Sandstones (Eastern Edge of the West African Craton, Southwestern Niger): Interpretation of Detrital Sediments Provenance

Exoscopy of Detrital Zircons from Niamey Neoproterozoic Sandstones (Eastern Edge of the West African Craton, Southwestern Niger): Interpretation of Detrital Sediments Provenance

Petrographic and Petrophysical Characterization of Sandstones from Rio Bonito Formation, Paraná Basin (Southern Brazil).

This study focuses on the laboratory-scale petrophysical characterization of sandstones from the Rio Bonito Formation (Lower Permian), Paraná Basin, carried out from drill core samples from well PN-14-SC.02 obtained by CPRM-Brazilian Geological Service in the 1980s on the eastern edge of the Basin. This study includes integrating experimental data from routine petrophysics, sedimentary petrography, and nuclear magnetic resonance (NMR) obtained from 6 samples arranged in the normal direction of the stratification, present between 40 and 200 m deep. It was possible to conclude that the values of the permeability and porosity properties obtained from the NMR technique correlated in a very satisfactory way, with correlation coefficient R2 = 0.957 and Root Mean Squared Error (RMSE) = 0.208 about the porosity reference results offered by routine petrophysics, with lower values being less than a porosity unit (+/- 1 p.u.), in the range between 8 and 14%. The same was observed for the estimated permeability, R2 = 0.885 and RMSE = 0.152, by the Timur Coates method, with values in the range between 0.096 and 2.42 mD, which were well supported by the spectra information, as well as by petrographic analyses.

Indonesian Tungsten Mineralogy and Processing Concept

Tungsten minerals which are major as Wolframite and Scheelite mineral are by-product minerals of Tin mineral known as Cassiterite. Tin minerals are mostly found in Bangka Island which is one of the islands in the Southeast Asian tin belt that makes Indonesia the largest Tin (Sn) producer in the world. This research aims to characterize the mineralogy of Tungsten and associated minerals for potential mineral processing to gain the Tungsten concentrates. The Tungsten minerals were collected from the eastern edge of Klabat Granite in Toboali District, South Bangka. The Tungsten minerals were magnetically separated up to 14000 Gauss. The magnetic and non-magnetic fractions were identified to analyze the associated mineral of Tungsten with SEM analysis. The associated minerals in the Tungsten mineralization system in Toboali were found along with Silicates, Oxides, Sulphides, and Carbonates where Silicates dominated up to 91.8% of the non-magnetic minerals while Wolframite presence up to 0.9% in the non-magnetic fraction. At magnetic fraction found that Silicates dominates also up to 84.6% while Wolframite existed at 1.1%. The results of element deportment in the non-magnetic fraction show that Tungsten is associated with iron minerals and also in liberated form. The potential Tungsten mineral is Wolframite (Fe,Mn) WO4 in the magnetic and non-magnetic fraction. Mineral locking at P100 size 18.8 μ. shows that 84.4% Wolframite was locking with 3 (three) other minerals, 10.4% locking with 2 (two) other minerals, and only 4.8% Wolframite was 100% free in the magnetic fraction while in non-magnetic fraction P100 size 31.5 μ 77.5% Wolframite was locking with 3 (three) other minerals 18.3% locking with 2 (two) other minerals and only 4.2% Wolframite was 100% free. The processing concept is to liberate Tungsten from the associated minerals either with comminution or a combination of roasting alkali and leaching process and concentrate it up to marketable Tungsten concentrates.

Preliminary discussion on pyrrhotite, gold killer in Wells-Barkerville, British Columbia, Canada

The Wells-Barkerville area of the Cariboo gold mining district is situated within the Quesnel Highlands on the eastern edge of the Interior Plateau in central British Columbia, Canada of the eastern Circum-Pacific volcanicmetallogenic belt. Recorded gold production from the area totals more than 4.0 million ounces, including an estimated 2.7 million ounces from placer mining from 101 creeks and 1.3 million ounces from lode mining. There are five principal types of lode gold deposits in the district; namely, auriferous pyrite replacement, including replacement in limestone and that in calcareous clastic rock; pyrite-quartz vein/veinlet lode gold, including strike vein, diagonal vein, orthogonal vein, and quartz veinlets; basalt-hosted auriferous pyrrhotite-pyrite lode gold; and associated gold in porphyry copper styles. This area is historically a famous gold production area in western Canada, including the initial alluvial gold and later and current lode gold. This original short article uses drilling results to illustrate that pyrrhotite in this area is the killer of gold. Wherever there is pyrrhotite, the gold grade is very poor or even contains no gold. In other words, gold grade is inversely related to pyrrhotite content. Then, the spatial distribution characteristics of the pyrrhotite anomaly zone(s) existing in this area were summarized, including the approximate thickness of zone(s). On this basis, several deep drill holes are recommended to verify whether there is considerable gold mineralization beneath the pyrrhotite anomaly zone(s).

ДЕНДРОКЛИМАТИЧЕСКИЙ АНАЛИЗ РАДИАЛЬНОГО ПРИРОСТА СОСНЫ ОБЫКНОВЕННОЙ В ЮЖНОЙ ТАЙГЕ НА ВОСТОЧНОЙ ОКРАИНЕ РУССКОЙ РАВНИНЫ

Regional dendroclimatological studies demonstrate the most accurate results when climatic responses of woody plantsto changes in climatic factors are identified in one particular region. Coniferous trees are the most frequent object of observation in suchstudies as they are more longevous and sensitive to changes in external factors. The paper presents the results of dendroclimatic investigation of growth variability of Scotch pine (Pinus sylvestris) growing in the southern taiga on the eastern edge of the Russian Plain. Chronology construction and data analysis were performed using CooRecorder, CDendro, COFECHA, ARSTAN and R programs. The obtainedtree-ring chronology of Scotch pine covers the time interval from 1822 to 2022, with a series duration of 201 years. The maximum growthwas observed in 1950 (1.21 mm), 1984 (1.25 mm), 2010 (1.37 mm). The minimum increment was in 1914 (0.75 mm), 1942 (0.77 mm),1977 (0.78 mm), and from 2015 to 2017. The analysis of correlation dependence of Scotch pine growth and climatic conditions showedthat the growth and development of the studied trees have been most influenced by changes in air temperature in June of the of the previousyear and current years, the correlation coefficient (R) is 0.068 and 0.156, respectively, as well as in October of the previous and currentyears - 0.352 and 0.221, respectively. The amount of precipitation has a smaller impact on growth. Thus, the factor of growth and development of Scotch pine on the eastern edge of the Russian Plain in the southern taiga subzone is mainly the air temperature in the fall monthsof the previous year and current year as well as the June temperature of the current year.

Geophysical exploration methods on bauxite reservoirs in L gasfield, Ordos Basin

Introduction: The L gasfield on the eastern edge of the Ordos Basin mainly focuses on the exploration and development of coalbed methane and tight sandstone gas. As the overlying strata of Majiagou Formation of Lower Ordovician in Lower Paleozoic, bauxite has always been considered a regional cap rock and has not been widely followed with interest. The drilled wells has revealed that bauxite can be used as a unconventional reservoir with good reservoir properties. In the future, it will become a new natural gas exploration target in the L region. This article is dedicated to the comprehensive study of geophysical methods for the bauxite exploration in the L region.Methods: Firstly, we use seismic data to restore paleo-geomorphology of the Lower Paleozoic. Secondly, we analyze the well log data of different paleo-geomorphic unit. Then, we establish a mineral model based on the logging data to calculate the lithological composition and porosity, and use imaging logging to evaluate the pore structure and fluid type.Result and Discussion: Finally, we obtained favorable reservoir development zones for bauxite, guiding exploration and evaluation of bauxite.

Alaska’s climate sensitive Yukon–Kuskokwim Delta supports seven million Arctic-breeding shorebirds, including the majority of six North American populations

Abstract Baseline information about declining North American shorebird populations is essential to determine the effects of global warming at low-lying coastal areas of the Arctic and subarctic, where numerous taxa breed, and to assess population recovery throughout their range. We estimated population sizes on the Yukon–Kuskokwim Delta (YKD) in western Alaska on the eastern edge of the Bering Sea. We conducted ground-based surveys during 2015 and 2016 at 589 randomly selected plots from an area of 35,769 km2. We used stratified random sampling in 8 physiographic strata and corrected population estimates using detection ratios derived from double sampling on a subset of plots. We detected 11,110 breeding individuals of 21 taxa. Western Sandpiper (Calidris mauri), Red-necked Phalarope (Phalaropus lobatus), Dunlin (subspecies C. alpina pacifica), and Wilson’s Snipe (Gallinago delicata) were the most abundant taxa. We estimated that ~7 million individual shorebirds were breeding on the entire YKD in 2015 and 2016. Our surveys of this region provided robust population estimates (coefficient of variations ≤ 0.35) for 14 species. Our results indicate that the YKD supports a large proportion of North America’s breeding populations of the Pacific Golden-Plover (Pluvialis fulva), the western population of a Whimbrel subspecies (Numenius phaeopus hudsonicus), a Bar-tailed Godwit subspecies (Limosa lapponica baueri), Black Turnstone (Arenaria melanocephala), a Dunlin subspecies (C. alpina pacifica), and Western Sandpiper. Our study highlights the importance of breeding shorebirds of this relatively pristine but climatically sensitive deltaic system. Estuaries and deltaic systems worldwide are rapidly being degraded by anthropogenic activities. Our population estimates can be used to refine prior North American population estimates, determine the effects of global warming, and evaluate conservation success by measuring population change over time.

Digital Geological Map of the Upper Laja River Basin, Guanajuato, Mexico

A new geological map of the Upper Laja River Basin at 1:200,000 scale is presented, covering an area of ∼11,600 km2 in the northern part of Guanajuato. This map was edited based on local and regional geological studies available in the literature, photo interpretations, field verification of contacts and faults and structural data acquisition. The main objective of this map is to provide a regional geological framework for future local geological and hydrological studies in the region. It displays the geology of the basin, divided into seven chronostratigraphic groups, as well as the main faults that shape the basin. In contribution to the geological knowledge of the area, five new U-Pb ages are presented, obtained from samples collected at the eastern and western edges of the basin.

Exploring the Moho beneath the Northern Canadian Cordillera, with seismically constrained gravity inversion

The geometry and depth of the Moho beneath the Northern Canadian Cordillera and adjacent North American craton are modeled through the application of both cokriging and 3-D inversion of gravity data, integrated with sparse seismic depth estimates. Models require a regional density correction, with lower densities beneath the Cordillera than the craton. The lower densities are primarily attributed to a reduction in upper mantle density, ascribed to thermal expansion under regionally higher temperatures. The eastern margin of this low-density zone is broadly aligned with the rapid westward shallowing of the lithospheric–asthenospheric boundary. From the Cordillera to the North American craton, the Moho is broadly flat at a depth of ∼32 km. A zone of deeper Moho (up to ∼38 km) beneath the Mistry Creek embayment has a modeled mantle density that is of a colder cratonic signature, akin to the Mackenzie craton, and is interpreted to represent the preserved remnants of an old rift basin that is a local focus of the diffuse seismicity. Southeast of the Fort Norman structure, seismicity is broadly focused along the eastern edge of the low-density zone. Major structures such as the Denali and Tintina faults, with 100’s km of right-lateral displacement, separate zones of higher and lower upper mantle density, supporting the interpretation of their continuation into the upper mantle. Within the North American craton, upper mantle density steadily increases toward the Great Bear magmatic zone but increases more rapidly beneath the Slave craton in tangent with a deepening of the Moho.

The geodynamic origin of Los Humeros volcanic field in Mexico: insights from numerical simulations

Compared to normal arc-related volcanic eruptions, the formation of a volcanic caldera is a relatively atypical event. During caldera formation a series of large volumes of magma are erupted, reducing the structural support for the rock above the magma chamber and creating a large depression at the surface called caldera. Los Humeros volcanic field (LHVF) represents one of the largest volcanic calderas in Mexico. It is located some 400 km from the trench at the eastern edge of the Trans Mexican Volcanic Belt where the depth to the Cocos slab is more than 300 km. In this study we employ high-resolution two-dimensional thermomechanical numerical simulations of magma intrusions and a horizontal tectonic strain rate to better understand the influence of crustal deformation for the formation of Los Humeros caldera. A minimum number of three thermal anomaly pulses of hydrated mantle material (with diameter of 15 km or more) and a regional strain rate of 7.927 × 10–16 s−1 are required for magma to reach the surface. Modeling results show that regional extension coupled with deep thermal anomalies (with a temperature excess of ΔT ≥ 100 °C) that come in a specific chain-type sequence produce surface deformation patterns similar to LHVF. We propose an asthenospheric sub-slab deep source (> 300 km depth) for the thermal anomalies where previous studies showed the existence of a gap or tear in the Cocos slab.

Reduced contribution of microbial necromass carbon to soil organic carbon following tunnel construction in the eastern Qinghai-Tibet Plateau

Microbial necromass carbon (MNC) is one of the primary sources of stable soil organic carbon (SOC), playing a crucial role in global carbon cycling. Despite its significance, the impact of tunnel construction, a commonly adopted human activity in railway development, on MNC and its underlying mechanisms remains underexplored. To address this gap, a field survey was conducted in shrubland ecosystems on the eastern edge of the Qinghai-Tibet Plateau. Our study aimed to investigate the influence of tunnel construction on MNC and its contribution to SOC along an altitudinal gradient (3240 m, 3420 m, and 3600 m) and at two soil depths (0–10 cm and 10–30 cm). Results indicated that tunnel construction did not exert a significant impact on SOC and MNC. However, it led to a substantial decrease in the contribution of MNC to SOC (15.6%–19.9% in tunnel-affected areas) compared to the control areas (19.04%–30.97%). This outcome was likely attributed to the decreased bacterial necromass carbon (BNC) and the increased input of underground plant-derived carbon. MNC at 10–30 cm was significantly lower than that at 0–10 cm, and it exhibited a notable decrease at 3420 m compared to both 3240 m and 3600 m. These observations were closely related to reduced carbon input and microbial necromass stability. Principal component structural equation modeling revealed that soil microbial activities were the most important for MNC and SOC accumulation. Consequently, tunnel construction influenced SOC formation by altering the relative contributions from plant and microbial sources. This study provides valuable evidence for assessing the impacts of engineering construction on SOC and its sources in the context of climate change. Moreover, it offers scientific support for ecosystem conservation and sustainable development in the Qinghai-Tibet Plateau region during engineering construction.

A DEEP LEARNING APPROACH USING VERY-HIGH SPATIAL RESOLUTION GAOFEN-2 IMAGES TO SUPPORT THE UNITED NATIONS SUSTAINABLE DEVELOPMENT GOAL INDICATOR 11.7.1 ASSESSMENT

Abstract. Since the proposal of the "2030 Agenda", the United Nations Sustainable Development Goal indicator 11.7.1 aims to calculate the accessibility and quality of urban open spaces(UOS). An accurate and rapid assessment framework of UOS is of great significance for urban sustainable development. Previous research on UOS has mainly focused on the evolution patterns of UOS, with little research on assessments of their accessibility for different population structures (i.e., men vs. women, young vs. older). In this study, a U-Net deep learning network was used for training from 3072 annotated samples of urban green spaces(UGS) which was created based on Gaofen-2 remote sensing images. The trained model was used to identify UGS within five districts of Beijing at sub-meter level, incorporated with Open Street Map and area of interest data. A spatial analysis was conducted for accessibility of UOS, finding that most of the UOS in the central urban area of Beijing can be reached within 10 minutes, but access to the eastern and western edges is poorer (more than 30 minutes). Finally, using Worldpop data, the accessibility of UOS was statistically analyzed for different ages and genders. The results show that UOS accessibility rate for the elderly and children reaches over 90% (10 minutes accessibility).

Insights on the 2023 Kahramanmaraş Earthquake, Turkey, from InSAR: fault locations, rupture styles and induced deformation

SUMMARY We successfully detected widely distributed ground displacements for the 2023 Kahramanmaraş, Turkey, earthquakes by conducting interferometric synthetic aperture radar (InSAR) analyses using a ScanSAR observation mode. Major deformation extended approximately 350 and 150 km along the southern and northern strands bifurcating in the west of the East Anatolian Fault, produced by the main shock and the largest aftershock. The deformation map reveals that the ruptures propagated on the Erkenek, Pazarcık and Amanos segments on the southern strand and the Çardak segment on the northern strand. The fault plane of the northern strand bends approximately 45° at both edges with Z-shaped crank geometry. The bending fault at the western edge runs just along the Çardak segment but does not reach the Savrun segment, while at the eastern edge it deviates from known active faults such as Sürgü, Malatya faults and Doğansehır fault zone. A 3-D displacement map demonstrates that almost pure left-lateral fault motions were distributed along the two strands, with little vertical deformation. The moment magnitudes estimated from the slip distribution model were 7.82 and 7.66 for the southern and northern strands, respectively, with the Erkenek and Çardak segments having the largest released seismic moments on each strand, corresponding to approximately 31 and 57 per cent of the total, respectively. The Coulomb Failure Function change values indicate that the main shock can promote the largest aftershock with a standard value of the effective friction coefficient. Additionally, the unclamping effect controlled by the frictional property of the rock was a key factor in pulling the trigger of the seismic event on the northern strand. The historically accumulated and released seismic energies were imbalanced for the Pazarcık and Erkenek segments, suggesting that the 2023 event does not support a simple characteristic earthquake model; rather, it may be consistent with a supercycle model, in which the slip remnants from the characteristic earthquakes have been historically accumulated as coupling on a fault and released as huge earthquakes at longer intervals.