pure and applied geophysics最新文献

We conducted a magnetovariational field investigation at Lampedusa island (Italy), in the proximity to the geomagnetic observatory of Lampedusa. Data were collected from March 19 to March 23, 2022, using vector fluxgate magnetometers, configured in different spatial arrangements for two main purposes: (a) estimating the spatial distribution of potential anthropogenic noise; (b) identifying different conductivity structures beneath the observatory’s surroundings. The results obtained by means of the 1-D gradient method on simultaneous measurements indicate a very low ambient noise level, likely originating north of the geomagnetic observatory. Hypothetical event analysis, combining data from eleven sites with temporary magnetometer installations, reveals the presence of at least three distinct strata in the crust: a highly conductive layer positioned between two more resistive layers, located west of the observatory.

Understanding deep coal rock’s dynamic mechanical characteristics is crucial for safe design and assessment of coal rock engineering. This article tested triaxial coal samples with SHPB on deep Test coal samples and equipment using the split Hopkinson pressure bar in different conditions. Coal stress–strain curves under combined triaxial dynamic-static loading show a consistent pattern. The first axial prestress prevented compaction in the stress–strain curves. The dynamic peak stress and secant modulus of deep coal samples rose linearly with constraint pressure and strain and decreased with axial prestress. Axial prestress changes occur at 8 MPa (44% of compressive strength). The amount of energy deep coal samples absorb during impact loading varies with axial static prestress at the same strain rate and confining pressure. It rises then falls. Coal samples went from shear damage to shear and tension damage as axial static tension rose. This research helps avoid coal rock dynamic catastrophes and evaluate mining engineering stability.

Graphical Abstract

We study coastal storm risk reduction using a steel mesh revetment system known as Tecco Cell (TC). This system consists of high-tensile stainless steel mesh filled with rock and securely fastened with tension rods. This coastal defence system is implemented in Beesands (UK), and its performance is studied here through preliminary laboratory physical modelling. The TC revetment in Beesands was installed in 2016 and has effectively protected the coast since then. We conducted 32 physical tests to assess performance criteria of a TC model in comparison to a rock armour (RA) model. Wave runup is used as the performance criterion in this study, as it is one of the key factors in coastal risk reduction research. Results showed that the TC model consistently yielded smaller runup than the RA model, with an average runup reduction of 15%. The mean spectral ratio index was employed as a measure of wave reflection and oscillations. Results indicated a mean index of 20.5 for the RA model and 3.8 for the TC model, demonstrating the potential for higher stability with the TC revetment. We established relationships between dimensionless runup and surf similarity and formulated a runup law.

The mechanical properties of red-bed soft rock, commonly encountered in the Central Yunnan Water Diversion Project, deteriorate significantly upon contact with water, impacting the project’s safety. This study investigates the effects of moisture content on the mechanical properties of red-bed soft rock by conducting triaxial compression tests under varying confining pressure. Degradation mechanisms associated with different moisture content levels are identified, and deformation and deterioration mechanisms are examined through mineral compositions using X-ray diffraction. Modifications to the Drucker-Prager criterion are explored to incorporate the Lode parameter. Using the Weibull distribution, a statistical damage constitutive model for red-bed soft rock is established. The triaxial compression test results of red-bed soft rock are used for model validation, demonstrating a strong agreement between the theoretical model and empirical findings, confirming its suitability for analyzing the mechanical behavior of red-bed soft rock under varying moisture content. The findings of this paper provide valuable insights for investigating large deformations in red-bed soft rocks within the context of Central Yunnan Water Diversion Project.

This work presents a method for the analytical solution of the fractal advection-diffusion equation, considering the Hausdorff derivative to maintain dimensional consistency, so that is possible to simulate the atmospheric pollutant dispersion in the Planetary Boundary Layer (PBL). The results show that the fractal parameter is a function of atmospheric stability, explicitly depending on the relationship between friction velocity and convective velocity (({{u_{*} } mathord{left/ {vphantom {{u_{*} } {w_{*} }}} right. kern-0pt} {w_{*} }})), and the inclusion of fractal derivative in the atmospheric dispersion equation improves the description of the turbulent transport process in the near-field region.

This paper describes the results of modifying the parametrization of subgrid stationary orographic gravity waves (OGWs) in the chemistry-climate model SOCOL, version 3. The originally used OGW parameterization is modified using polarization relations for stationary waves in the rotating atmosphere. Parameterizing the OGW generation by the Earth’s topography at subgrid scales follows the widely used Lott and Miller scheme, but the expressions for calculating the vertical profiles of OGW amplitudes, wave drag and heat influx, are modified. Test simulations of the general atmospheric circulation for 10 years (from 2009 to 2018) have been launched with the SOCOL model involving the modified OGW parameterization. Using the realistic profiles of the background wind and temperature, characteristics of OGWs propagating in the atmosphere from the Earth’s surface to the heights of about 80 km are simulated for different locations in the Northern and Southern Hemispheres. Comparisons with the MERRA2 reanalysis data show that the modified OGW parameterization provides better agreement of simulated and observed multiyear-mean zonal wind and temperature in the mesosphere and lower thermosphere region. The modified parameterization can be used in other atmospheric circulation models.

The three-dimensional attenuation structure and frequency-dependent attenuation layered model are proposed for constraining seismic hazards and exploring the presence of an intra-crustal high conductive (ICHC) layer in the Himachal Himalaya, India. Using acceleration data recorded in the Himachal Himalaya, this work quantifies the attenuation characteristics in the form of shear-wave quality factor (Q_β). The low Q_β values (ranging 10–60) depict an aqueous fluid zone starting from a depth of ~ 11 km. This aqueous fluid identified in the study region closely resembles the ICHC layer identified by other researchers in its adjacent area. The geometry of the Main Himalayan Thrust (MHT) is explored in terms of the obtained attenuation model, which suggests the absence of a ramp structure of MHT below the Main Central Thrust (MCT) in the study region. The presence of an aqueous fluid zone identified at 11–20 km depth may be one of the possible reasons for high seismicity in the Himalayan seismic belt. This work also suggests a frequency-dependent shear wave attenuation (Q_β(f)) model of the form Q_of ⁿ for six different layers of 5 km thickness each. The obtained layered model suggests low Q values, i.e., (49 ± 16) f ^(0.60±0.12) for layer 3 (10–15 km) and (27 ± 11) f ^(0.99±0.18) for layer 4 (15–20 km), corresponding to the aqueous fluid in the study region. The obtained Q_β(f) model appraises the region’s seismic hazard by describing the heterogeneity and tectonic activity level in the present study region.

This study mainly focuses on the relationship between Total Totals index (TTI) and other thunderstorm related parameters over Kerala region, India. This study has been carried out on thunderstorm days for the pre-monsoon season during the time period 2017–2022. The thunderstorm related parameters such as lightning, K Index (KI), Humidity Index (HI), Total precipitable water (TPW), Rainfall to Lightning Ratio (RLR), Maximum updraft speed (MUS), Lifted Index (LI), Convective available potential energy (CAPE), Dew point depression (DPD), Cloud fraction (CF) and Temperature Difference (TempDiff) have been considered for the analysis. For a better understanding between TTI and thunderstorm indices, two distinct regions D1 (10.8°-12.4° N, 75.2°-76.8° E) and D2 (9.2°-10.8° N, 76.2°-77.8° E) of Kerala state were selected as the study region. The results reveal that D2 region (135 days) showed more lightning activity than D1 region (88 days). A significant positive trend has been seen between TTI and KI parameters. RLR & TPW parameters showed a significant negative trend with TTI parameter. MUS exhibits positive trend whereas LI showed negative trends with TTI on lightning days over both regions. This study also shows that the CAPE and DPD showed an increasing trend with TTI during lightning days. We also utilized Random forest technique to study the relationship between various thunderstorm related parameters.

Curie depth plays an important role in the study of geological structures and resource exploration. Conventional methods usually employ a fixed window size for estimation, often resulting in significant inaccuracies. To overcome this deficiency, a new adaptive window Curie depth calculation approach is proposed, which can automatically select the optimal window size across a range of diverse geological conditions to achieve a more precise Curie depth. We validated the new approach using synthetic data, demonstrating that the average error of the bottom depth of the model was reduced compared to traditional methods. Subsequently, we applied the new method to real magnetic data from the South China Block, and a new Curie depth result was obtained and verified using measured ground heat flow data. The mean square error between the derived results and the measured ground heat flow was found to be lower than that of the Curie depth inversed by previous researchers. The adaptive window Curie depth calculation method presented herein exhibited high adaptability and accommodated various geological features. For the South China Block, the Curie depths exhibited a smooth and continuous pattern in stable regions such as cratons, while displaying a distinct uplift in the junction region between fault zones and blocks. This method can not only accurately capture the Curie depth variations across large areas, but also vividly highlight subtle changes in the Curie depth within smaller regions, demonstrating the superiority of this new approach.

This study examines the structure of the Lofoten Anticyclone, located in the Lofoten Basin of the Norwegian Sea. The high-resolution ROMS model is used for hydrodynamic modeling of the Lofoten Basin circulation. The dynamics of the Lofoten Vortex are investigated using the Lagrangian methods, where trajectories of passive tracers advected by the model velocity field are calculated, and Lagrangian indicators are computed for the studied region. Lagrangian markers initially located both in the core and on the periphery of the Lofoten Vortex are considered, showing different behaviors. Lagrangian markers in the core move along closed trajectories with angular velocities depending on their distance from the eddy's center. Those initially on the periphery form a series of S-shaped folds and twists, entering and exiting the eddy. We refer to this process as “ventilation of the vortex periphery”. We demonstrated that particles leave the core and periphery of the eddy intermittently rather than uniformly over time, and the statistics of this process are analyzed. Additionally, it was found that the center of the Lofoten Vortex not only drifts cyclonically at an average speed of 3.8 cm/s but also oscillates in the horizontal plane, with the amplitude increasing in the eastern part of the Vortex’s movement area.