Hasil untuk "Geology"

C. Barton, M. Zoback, D. Moos

R. Borcherdt

F. Hrouda

Baohang Wang, Guangrong Li, Chaoying Zhao et al.

Potential tropospheric noise is a critical factor that undermines the effectiveness of deformation monitoring in Synthetic Aperture Radar Interferometry (InSAR) technologies. In most scenarios, many point targets within the InSAR deformation monitoring area either do not undergo deformation or exhibit only minimal deformation trends. The phases of densely distributed stable points can effectively respond to spatial tropospheric delays, particularly turbulent atmospheric phases. This study proposes a data-driven InSAR atmospheric correction method by exploring how to use these densely stable InSAR time series to model atmospheric phase delays. Our focus is on selecting stable InSAR time series point targets and evaluating the impact of different densities of stable points on atmospheric correction performance. Analysis of 645 interferograms derived from 217 Sentinel-1A SAR images, spanning from 13 June 2017 to 15 November 2024, demonstrates that the proposed method reduces the Root Mean Square Error (RMSE) by 70%, 59%, and 69% compared to the terrain-related linear approach, the General Atmospheric Correction Online Service, and common scene stacking methods, respectively. In addition, simulation data and leveling data were used to validate the proposed method. This article does not develop an independent InSAR atmospheric correction method. Instead, the proposed approach starts with the InSAR deformation time series, allowing for easy integration into existing InSAR workflows and widely used atmospheric correction strategies. It can serve as a post-processing tool to improve InSAR time series analysis.

Rui MIAO, Zenghao ZHAO, Zeyuan CAI et al.

Glycerol dialkyl glycerol tetraethers (GDGTs) derived from microorganisms are important tools for the study of paleoclimate changes. Incubation experiments are helpful to clarify the mechanisms for the responses of GDGTs to environmental parameters, and to test the reliability of related climatic proxies. However, previous GDGT incubation experiments were mainly conducted on a single strain or suffered from the influence of a background signal, hampering systematically understanding the precise response of this biomarker to environmental factors in a soil environment. In this paper, artificial soils without GDGTs were incubated under the same temperature but different soil water content (SWC) conditions. The results showed that: (1) The abundances of GDGTs were positively correlated with SWC, but phosphate buffer could inhibit the production of GDGTs; (2) The branched and isoprenoid tetraether index (BIT), a soil moisture proxy developed in natural soils, was not significantly correlated with SWC; (3) 6-methyl brGDGTs were more abundant than 5-methyl brGDGTs, resulting in extremely high values of MBT'5ME and low MBT'. The results suggest that the BIT soil moisture proxy may indirectly (rather than directly) respond to SWC changes and confirm that high relative abundance of 6-methyl brGDGTs can affect the applicability of the MBT'5ME paleothermometer in soils. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202405240120.

W. Bang, J. T. Carlin, K. Kim et al.

<p>Winter precipitation types (WPTs) are controlled by many factors, including thermodynamic and microphysical processes. Therefore, realistically simulating interactions between precipitation particles and the atmosphere is important when diagnosing the WPT. In the present study, we analyze the performance of a modified version of the one-dimensional spectral bin model (SBM; version 1DSBM-19M) of Carlin and Ryzhkov (2019), which simulates the change in the physical characteristics of precipitation particles of various sizes as they fall from the cloud top to the ground and diagnoses surface WPTs. We compare the performance of the SBM and four other diagnostic methods that use the following variables: (1) atmospheric thickness, (2) wet-bulb temperature, (3) temperature and relative humidity, and (4) wet-bulb temperature and low-level lapse rate. Three reference WPTs (snow (SN), rain (RA), and RASN) are obtained from particle size velocity (PARSIVEL) disdrometer data using a newly proposed decision tree algorithm. The results show that the SBM has the highest overall hit rate for all cases among five diagnostic methods. In contrast, the hit rate of the SBM for each WPT shows lower performance for RA than for the other methods. These results indicate that the SBM simulations tend to underestimate melting compared to observations. We thus explore the effects of the SBM's microphysics scheme on the extent of melting in cases of misdiagnosed RA. An optimized SBM that uses the climatological snow density–diameter relationship for the Pyeongchang region produces an increased amount of melting and achieves improved skill scores compared to the current SBM, which uses a snow density–diameter relationship for the Colorado region.</p>

NIU Zihao 1, 2, ZHU Zhende 3, QUE Xiangcheng 3, XIE Xinghua 4, JIN Kai 1, 2

With the construction and commissioning of major hydropower projects represented by Baihetan of Jinsha River, it is of great significance to clarify the mechanical and seepage characteristics of engineering rock mass under complex stress environment with high confining pressure and high water pressure. Based on the field survey data and the structural characteristics of the columnar jointed basalt of dam foundation, two kinds of columnar joint similar material model samples with different dip angles β, quadrangular prisms and hexagonal prisms, are prepared, and the true triaxial stress-seepage coupling tests are carried out. The test results show that the columnar jointed rock mass with different cross-section characteristics has strong permeability anisotropy, and the permeability coefficient k is positively correlated with β at different loading stages. During the true triaxial loading process, the volume strain εV of the sample can be used as an effective characterization parameter of k. At the volume compression stage, k shows a low level, and at the volume expansion stage k shows a rapid growth trend. The final failure mode of the samples exhibits three typical forms, and the most dangerous failure mode is the structural failure dominated by the shear slip failure of the joint surface, which mainly occurs in the samples with β=45°, 60°. Correspondingly, the lateral support of this kind of rock mass should be strengthened in the construction design of surrounding rock of tunnels and rock mass of dam foundation.

Yingying Xu, Qiying Yu, Chengshuai Liu et al.

Study region: Typical basin in humid areas in the Huaihe River Study focus: Accurate flood forecasting is essential for making timely decisions regarding flood control and disaster reduction. The theory of watershed runoff generation and convergence serves as a crucial foundation for flood forecasting, while the calculation of runoff is necessary to simulate flood discharge. Identifying watershed runoff generation mechanisms has been a challenging task, particularly under complex underlying surface conditions. To improve the accuracy of flood simulation, this study examines the underlying surface information in the watershed, such as particle composition and content, soil bulk density, geological slope, land use, and other spatial attributes, aiming to analyze the mechanisms of runoff generation. In the study of sub-watersheds, various combinations of runoff generation mechanisms are identified to determine the patterns of runoff. Subsequently, a semi-distributed hydrological model is developed, which incorporates both saturation-excess and infiltration-excess runoff, utilizing the information obtained from the underlying surface. The model is validated using rainfall-runoff data from 14 events at the Xiagushan watershed. New hydrological insights for the region: The analysis of the fundamental physical conditions of the underlying surface of the watershed revealed that 69.70% of the area is prone to saturation-excess runoff, with an additional 30.30% of the area being susceptible to infiltration-excess runoff. The model considers the spatial distribution of runoff patterns by incorporating complex underlying surface information and demonstrates high accuracy in simulating flood events (NSE= 0.87, Epeak = 12.08%, Wpeak = 13.16%, Tpeak = 0.14 h, R2 = 0.90). The model is straightforward, practical, and exhibits promising potential in terms of timeliness and applicability, thus lending itself well to further application in other watersheds, contributing to the scientific foundation of flood warning and forecasting efforts.

Sattik Ghosh, Stephanie Pulford, Arnold J. Bloom

Students who completed the online version of an introductory course on climate change performed 2% worse than those who completed the in-person version, according to a study of 1790 undergraduate students in California, USA.

C. Zou, Guosheng Zhang, Zhi Yang et al.

Abstract Petroleum geology is evolving into two branches, conventional petroleum geology and unconventional petroleum geology, with the latter becoming a new theoretical frontier in the petroleum industry. The core of conventional hydrocarbon geological study is based on identifying the match between source rock, reservoir, caprock, migration, trap, preservation and timing; the core of unconventional hydrocarbon geological study evaluates if the oil and gas is part of a continuous accumulation, where stress is placed on the evaluation of “lithology, physical properties, brittleness, oiliness, source rock features, stress anisotropy” and their configuration. The oil and gas accumulation mode and theoretical formula at various low limits of pore throat diameter have been established, as well as the “L” type production curve. Theoretical production prediction models for unconventional oil and gas, and formation mechanism and development patterns for unconventional oil and gas are being revealed. The connotation, characteristics, potential and technology for unconventional oil and gas have been observed, and two key marks to identify unconventional hydrocarbon have been put forward: (1) continuous distribution of hydrocarbon-bearing reservoirs over a large area, with no obvious trap boundary; and (2) no natural stable industrial production, and no obvious Darcy flow. Systematic research shows that the proportion of global unconventional to conventional hydrocarbon resources is 8:2, in which the unconventional oil is almost equal to conventional oil, and the unconventional gas is about 8 times that of conventional gas. In China, unconventional oil resources are about 240×108 t and unconventional gas resources are about 100×1012 m3. In recent years the development of tight gas and tight oil should be strengthened to realize industrial reserves and increase production. Construction of shale gas pilot plants and shale oil research should be strengthened. Unconventional oil and gas industrial systems and research should be set up, including unconventional hydrocarbon geology, fine particle sedimentology, unconventional reservoir geology, seismic reservoir prediction, massive fracturing of horizontal wells, “factory-like” operation, low cost management and subsidy policy and personnel training.

O. Selinus

W. H. Lipscomb, G. R. Leguy, N. C. Jourdain et al.

<p>The future retreat rate for marine-based regions of the Antarctic Ice Sheet is one of the largest uncertainties in sea-level projections. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) aims to improve projections and quantify uncertainties by running an ensemble of ice sheet models with atmosphere and ocean forcing derived from global climate models. Here, the Community Ice Sheet Model (CISM) is used to run ISMIP6-based projections of ocean-forced Antarctic Ice Sheet evolution. Using multiple combinations of sub-ice-shelf melt parameterizations and calibrations, CISM is spun up to steady state over many millennia. During the spin-up, basal friction parameters and basin-scale thermal forcing corrections are adjusted to optimize agreement with the observed ice thickness. The model is then run forward for 550 years, from 1950–2500, applying ocean thermal forcing anomalies from six climate models. In all simulations, the ocean forcing triggers long-term retreat of the West Antarctic Ice Sheet, especially in the Filchner–Ronne and Ross sectors. Mass loss accelerates late in the 21st century and then rises steadily for several centuries without leveling off. The resulting ocean-forced sea-level rise at year 2500 varies from about 150 to 1300 mm, depending on the melt scheme and ocean forcing. Further experiments show relatively high sensitivity to the basal friction law, moderate sensitivity to grid resolution and the prescribed collapse of small ice shelves, and low sensitivity to the stress-balance approximation. The Amundsen sector exhibits threshold behavior, with modest retreat under many parameter settings but complete collapse under some combinations of low basal friction and high thermal forcing anomalies. Large uncertainties remain, as a result of parameterized sub-shelf melt rates, simplified treatments of calving and basal friction, and the lack of ice–ocean coupling.</p>

J. Wheeler

T. Kenkmann, M. Poelchau, G. Wulf

Xiang Li, Sai Xu, Youzhi Hao et al.

Based on the results of molecular dynamics simulation, in a gas-water miscible zone, the velocity profiles of the flowing water film do not increase monotonously but increase first and then decrease, which is due to the interaction between water and gas molecules. This exhibits a new physical mechanism. In this paper, we firstly propose a gas-water flow model that takes into account the new physical phenomena and describes the distribution of gas-water velocity in the whole pore more accurately. In this model, a decreasing factor for water film in the gas-water miscible zone is used to describe the decrease of water velocity in the gas-water miscible zone, which leads to the gas velocity decrease correspondingly. The new flow model considers the interaction among gas and water molecules in the miscible zone and can provide more accurate velocity profiles compared with the flow models not considering the miscible region. Comparison calculation shows that the previous model overestimates the flow velocity, and the overestimation increases with the decrease of the pore radius. Based on the new gas-water flow model, a new permeability correction factor is deduced to consider the interaction among gas and water molecules.

Sang Whan Han, Hyun Woo Jee

Ground motions are used as input for the response history analyses of a structure. However, the number of ground motions recorded at a site located in low-to-moderate seismic regions such as the Korean Peninsula is few. In this case, artificial ground motions need to be used, which can reflect the characteristics of source mechanism, travel path, and site geology. On 15 November, 2017, the Pohang earthquake, with a magnitude of 5.4 and a focal depth of 9 km, occurred near the city of Pohang. This earthquake caused the most significant economic loss among the earthquakes that occurred in the Korean Peninsula. During the Pohang earthquake, valuable ground motions were recorded at stations distributed in the Korean Peninsula. In this study, a ground motion model is proposed based on ground motions recorded during the 2017 Pohang earthquake. The accuracy of the proposed model is verified by comparing measured and simulated ground motions at 111 recording stations.

Skuodis Šarūnas, Dirgėlienė Neringa, Medzvieckas Jurgis

Geogrids are widely used in civil engineering projects to reinforce road and railway structures. This paper presents research on the shearing strength of soil samples that have been reinforced with geogrids. The relationship between soil and geogrids is explored and evaluated by modeling the mechanical behavior of heterogeneous materials. For the purposes of this research, data obtained from tests of unreinforced sand samples with triaxial cells were compared with the data obtained from tests of reinforced sand samples. It was found that the shearing strength for reinforced samples was higher (from 9% to 49%) compared to unreinforced samples. Some damage to the geogrid was detected during the experiment, and for this reason, the same tests were numerically simulated for both unreinforced samples and samples reinforced with geogrids. Numerical simulations revealed the main reasons for damage to the geogrids during triaxial testing.

A. Aitken, D. Young, F. Ferraccioli et al.

Ruth Durán, Francisco José Lobo, Marta Ribó et al.

Clinoform depositional features along the Iberian Mediterranean margin are investigated in this study, with the aim of establishing the causes of their varied shapes and other characteristics. We have analyzed the broad-scale margin physiography and seismic stratigraphic patterns based on high-resolution bathymetric data and previously interpreted seismic data. In addition, we have evaluated regional supply conditions and the uplift-subsidence regime of the different shelf sectors. The upper Quaternary record is strongly dominated by shelf-margin regressive wedges affected by the prevailing 100 ka cyclicity. However, the margins exhibit considerable lateral variability, as the result of the balance between the amount of sediment supply and the uplift-subsidence relationship. Three major shelf sectors with distinct morpho-sedimentary features have been defined. The relatively narrow northern shelves (Roses, La Planassa and Barcelona) are supplied by discrete river outlets that collectively constitute a linear source and are mainly affected by tectonic tilting. The wide middle shelves (Ebro Shelf, the Gulf of Valencia, and the Northern Arc) receive the sediment supply from the large Ebro River and other medium rivers. Although the tectonic regime changes laterally (strong subsidence in the north and uplift in the south), shelf growth is maintained by lateral advection of sediments. The southern shelves (the Southern Arc and the northern Alboran Shelf) are very abrupt and narrow because of the uplifting Betic Cordillera, and the torrential fluvial regimes that determine a very efficient sediment by-pass toward the deep basin. Submarine canyons deeply incised in the continental margin constitute a key physiographic feature that may enhance the transport of sediment to the deep sea or individualize shelf sectors with specific sedimentation patterns, as occurs in the Catalan margin.

Kun-Sung Liu

The purpose of this study is to estimate maximum ground motions in southern Taiwan as well as to assess potential human fatalities from scenario earthquakes on the Chishan active faults in this area. The resultant Shake Map patterns of maximum ground motion in a case of Mw 7.2 show the areas of PGA above 400 gals are located in the northeastern, central and northern parts of southwestern Kaohsiung as well as the southern part of central Tainan, as shown in the regions inside the yellow lines in the corresponding figure. Comparing cities with similar distances located in Tainan, Kaohsiung, and Pingtung to the Chishan fault, the cities in Tainan area have relatively greater PGA and PGV, due to large site response factors in Tainan area. Furthermore, seismic hazards in terms of PGA and PGV in the vicinity of the Chishan fault are not completely dominated by the Chishan fault. The main reason is that some areas located in the vicinity of the Chishan fault are marked with low site response amplification values from 0.55 - 1.1 and 0.67 - 1.22 for PGA and PGV, respectively. Finally, from estimation of potential human fatalities from scenario earthquakes on the Chishan active fault, it is noted that potential fatalities increase rapidly in people above age 45. Total fatalities reach a high peak in age groups of 55 - 64. Another to pay special attention is Kaohsiung City has more than 540 thousand households whose residences over 50 years old. In light of the results of this study, I urge both the municipal and central governments to take effective seismic hazard mitigation measures in the highly urbanized areas with a large number of old buildings in southern Taiwan.