pure and applied geophysics最新文献

The study proposes a comprehensive Bayesian framework that integrates spatial clustering with binary copulas and zero-inflated binary logistic regression to model complex, non-linear dependencies between seasonal drought conditions and inter-seasonal drought persistence. Bayesian inference was performed via the RStan package, with model performance evaluated based on convergence diagnostics (R-hat, effective sample size), model fit (log posterior density, AIC, BIC), and predictive accuracy (posterior predictive checks, AUC/ROC curves, confusion matrix). Clustering analysis using the Elbow Method and Silhouette Score revealed that 4 clusters optimally capture the drought patterns across the stations. K-means clustering found most appropriate choice in term of higher Silhouette Score (winter-spring = 0.332, spring–summer = 0.391, autumn–winter = 0.363 and higher Dunn Index (winter-spring = 0.260, spring–summer = 0.260, autumn–winter = 0.181) for all seasonal transitions except summer-autumn. Medoid-Based Selection proved to be the most reliable method for selecting representative stations across all seasonal transitions with the lowest Davies–Bouldin Index (DB Index) (1.38, 1.091, 0.992, and 1.163) and highest Silhouette Score (0.273, 0.345, 0.411, and 0.348), ensuring comprehensive coverage of climatic conditions within each cluster. Archimedean copulas and Farlie–Gumbel–Morgenstern (FGM) copulas captured most seasonal transitions, while Plackett and Gumbel copulas were better for autumn–winter cases. Building on the dependence captured by the copulas, Bayesian zero-inflated binary logistic regression (ZIBLR) indicated strong effects of seasonal drought conditions on drought persistence. These models examine how drought conditions in one season influence persistence into the subsequent season, offering valuable insights into the drivers of drought dynamics in Punjab. ZIBLR parameters, across all clusters and seasonal transitions, showed statistically sound convergence with R-hat values of 1.00 and sufficient posterior sampling with high effective sample sizes (n_eff > 12,000). The confusion matrices illustrates the superior predictive accuracy and stable model performance, with high sensitivity and specificity. The ROC curves corroborate this, as evidenced by the shape of the curve, with a sharp rise towards the top-left corner of the plots. The AUC values, appear to be 1, confirming strong classification accuracy, and validating the model’s reliability in capturing drought persistence dynamics. The study contributes a novel methodological framework for understanding regional drought dynamics and provides policymakers with data driven insights to develop targeted mitigation and adaptation strategies, particularly in arid and semi-arid environments, for effective risk management.

Annual deformation signals recorded by vault-housed extensometers remain poorly understood despite their prevalence in crustal dynamics research. Many observatories in mainland China report pronounced annual strain variations, yet their physical origin has rarely been quantified. Here this study systematically analyzes data from the Kuancheng Geodynamic Observatory (KGO), North China, to test whether annual air temperature variations drive these signals. Using a half-space thermoelastic model overlain by a thin unconsolidated layer, we show that the observed annual temperature cycle (amplitude 16.8 °C) can generate thermoelastic strains on the order of 10⁻⁷ at 30 m depth. Modeled amplitudes and phases agree closely with observed North–South and East–West strain components, strongly indicating that temperature-induced thermoelastic deformation is the primary source of annual strain at KGO. These findings provide a quantitative framework for interpreting annual signals in China’s extensometer network and highlight the need to separate temperature-driven annual strain variations from potential earthquake precursor signals.

On January 15, 2022 the great volcanic explosion at the Hunga-Tonga–Hunga-Hua’apai Island in the South Pacific sent atmospheric Lamb waves (A_n) around the Earth in all directions. The Lamb wave (A_1) caused clearly observable disturbances on barometers, seismic sensors, and also gravimeters. We show these disturbances on barometers (with a peak-to-peak amplitude of 2.3 hPa) and the superconducting gravimeters (SG) iOSG-023 and OSG-056 at the stations J9 and BFO (57 km to the east), respectively. We subsequently model these disturbances in gravity using very simple physics-based models. It turns out that the inertial accelerations due to ground displacement by the pressure loading are very important in this case as already shown by Imanishi (Earth Planets Space 74:54, 2022 https://doi.org/10.1186/s40623-022-01615-4) for the SG in Matsushiro, Japan. This inertial effect is almost twice as large at J9 than at BFO, while the pressure pulses have about equal amplitudes. This must with high probability be blamed to the higher deformability of the upper layers of the crust at J9 with soft fluvial sediments on the top compared to BFO where granites and gneisses make up the rocks near the surface.

This research investigates how lateral near-surface inhomogeneity affects three-dimensional (3D) electrical resistivity tomography (ERT) in terms of resolution and resolvability for Dipole–Dipole, Wenner-Schlumberger, and Joint arrays. Data from an archaeological site in Iraq, along with synthetic models, are used to evaluate the ability of these arrays in resolving underground-buried structures. The presence of lateral near-surface inhomogeneity (characterized by High-Low–High resistivity values) in the upper layer significantly impacts the measured apparent resistivity data. It tends to reduce the resolution and resolvability of the arrays and increase misfit error ratios, which can lead to serious interpretation issues for the 3D resistivity maps. This can lead to partial identification of underground structures. Under these conditions, both Dipole–Dipole and Joint arrays produce similar images, with a slight advantage to Dipole–Dipole as it provides the best resolution. Joint array exhibits a slight reduction in resolution, despite having higher data coverage and quality. Wenner-Schlumberger array provides the poorest resolution. When the upper layer is dominated only by high resistivity values, the resolution and resolvability of these arrays are significantly improved.

During open-pit mining, the geotechnical strength and geological structure of the slope are rather complicated. Varying geological structures and rock mass strengths can lead to diverse failure modes of slopes. Particularly, fault-containing geological structures can exert a pivotal influence on the slope stability and ultimately affect the safe production of open-pit mines. This paper focuses on the K5-K6-K7 convex slope formed from the top to the bottom in the eastern mining area of Kangcheng Stone Mine. Through similarity simulation, the failure modes and deformation characteristics of the convex slope under two conditions, namely with and without a fault tectonic alteration zone, were analyzed. Furthermore, the results of similarity simulation experiments were verified with the aid of FLAC^3D based on the strength reduction method. The key findings are as follows: (1) The failure mode of the K5-K6-K7 slope and similar convex slopes in Kangcheng Stone Mine is overall arc-shaped sliding. The horizontal displacement of the convex slope surface mainly occurs on both sides of the convex surface. (2) The displacement process of the slope can be divided into three stages. In Stage I, i.e., the stable deformation stage, the displacement is relatively mild, accompanied by the emergence of small cracks. In Stage II, i.e., the local failure stage, the displacement changes increasingly noticeably, and small cracks keep expanding into large ones in the upper left, upper middle, and lower middle parts of the slope. Besides, these cracks penetrate the inner part of the slope, ultimately inducing plastic failure and slope sliding. In Stage III, i.e., the failure stage, the deformation and displacement continue at an accelerated rate. Moreover, cracks extend from the upper part to the bottom of the slope and penetrate the inner part of the slope, resulting in damage and sliding. At this time, the displacement distance reaches the maximum. (3) Due to its low strength, the rock mass in the FTA zone exerts a relatively strong influence on the intact surrounding rock mass. During slope failure, the displacement is mainly concentrated on the midline of the convex slope ridge and in the upper part on both sides are relatively large. The stability of the slope with a FTA zone is 0.067 less than that of the slope without a FTA zone, as calculated by the strength reduction method.

Two heavy rainfall episodes occurred during 12–16 May 2022 and 14–18 June 2022 over the southern districts of Assam, namely Dima Hasao, Cachar, Hailakandi, and Karimganj in the northeast region of India (NER). These episodes resulted in two consecutive catastrophic flood events, causing large-scale infrastructure damage and enormous losses of property and human life. Analysis of vertically integrated moisture flux convergence (VIMFC), Vorticity-Budget, vertical motion, and Iso-surface of wind have been carried out to look into the driving mechanism of two heavy rainfall episodes. A sharp rise (> 1 × 10^–5 kg m⁻² s⁻¹) in district-averaged VIMFC at 1000–700 hPa levels was observed between 2100 UTC on 13 May and 0600 UTC on 14 May, with a peak value of 3.05 × 10^–5 kg m⁻² s⁻¹ at 0000 UTC on 14 May over Dima Hasao district during the first episode. During the second episode, an increase in district-averaged VIMFC at 1000–700 hPa levels was noted from 0000 to 0600 UTC on 18 June, peaking at 6.88 × 10^–5 kg m⁻² s⁻¹ at 0600 UTC over Cachar district. These observations indicate that the high VIMFC over the study area was primarily due to the convergence of lower-level southwesterlies from the Bay of Bengal. Common factors for both episodes include strong moisture transport from the Bay of Bengal via southwesterly winds, resulting in increased VIMFC at lower levels. Furthermore, vertical velocity was positive and more pronounced during these episodes. Vorticity budget analysis shows that during both the episodes, the horizontal advection term and convergence term contributed positively at lower levels, while the vertical advection term contributed positively between low and mid-levels. This suggests that the transport of low-level vorticity to upper and middle levels fueled deep convection, which contributed to the heavy rainfall and subsequent flooding.

In seismic waveform inversion, access to low-frequency information is crucial for an accurate reconstruction of the long-wavelength components of the subsurface model, but, unfortunately, seismic data often lack low-frequency information. One way to overcome this deficiency is to transform the seismic data into an envelope format that concentrates the spectral energy at lower frequencies compared to the original data. However, for salt models characterized by strong reflection contrasts and thick layers, the low-frequency content in conventional envelope data may not be low enough to effectively reconstruct the long-wavelength components from an initial linear model. To overcome this limitation, we adaptively select the window sizes for each trace, aiming to achieve much lower frequencies by smoothing the envelope. These window sizes are determined by analyzing the differences between the picked times corresponding to the upper and lower boundaries of impedance structure with large values, such as salt body, in the seismic profiles. With these dynamically selected trace-dependent window sizes, we implement a smoothed envelope waveform inversion procedure to improve the reconstruction of the long-wavelength components of the impedance model. This procedure is applied to three-dimensional seismic data where frequencies below 4 Hz are missing. We then take this inverted impedance model as a starting point for a Fourier-based inversion, which further refines the impedance model. The tests performed on a 3D salt impedance model show good recovery of the salt body and provide evidence for the feasibility and effectiveness of the adaptive window size in the seismic waveform envelope inversion.

The Anti-Atlas fold and thrust belt is considered an important metallogenic province on the northern margin of the West African Craton (WAC). This structural domain is mainly controlled by structural features inherited from many phases of orogenesis. The present paper focuses on the Saghro massif which is a large Precambrian inlier, including the highest peak in the range, Jbel Mansour, reaching 2600 m, along with many other inaccessible areas. This study fulfills an integrated magnetic interpretation aiming to characterize the underlying structures of the Saghro massif in the Eastern Anti-Atlas. The principal purpose consists in subsurface mapping of hidden faults and structures based on magnetic data interpretation in order to image the structural architecture of an inaccessible area (south-east of the Saghro inlier). We particularly focused on determining the local structures and tectonic units by applying many derivative filters to the magnetic data reduced to pole. We define the superposition of all magnetic lineaments obtained from various edge detection techniques. The results outline directions that are the same as the general tectonic structures of the area. NE–SW and E–W directions correspond mainly to Hercynian faults, while the NW–SE to ESE–WNW directions are related to the late Pan-African phase. The analysis of magnetic grids confirmed the geological knowledge about the study area. Thus, the base-cover boundary is well plotted. This boundary is highlighted through the change in signature and magnetic field strength on the map of the magnetic field reduced to the pole of the study area. The Neoproterozoic base is clearly marked by a heterogeneous expression of the magnetic field and very high intensities. However, the Paleozoic cover is distinguished by its homogeneous and low intensity response. The interpreted magnetic lineament maps identified new profound faults in this region, in addition to confirming other structural features already highlighted by previous geophysical investigations. Our synthetic structural map of magnetic lineaments serves as a framework for future mining exploration.