Search Results (540)

The arcuate tectonic belt in the northeast Tibetan Plateau has been a contentious topic regarding its formation and evolution, owing to its distinctive geological structure as the lateral growth boundary of the plateau. In this research, leveraging geological and geophysical data, a three-dimensional finite element numerical model is employed to explore the impact of lateral and vertical inhomogeneities in lithospheric strength on the northeast Tibetan Plateau’s growth and the arcuate tectonic belt’s formation and alteration. Additionally, the kinematic and deformation traits of the arcuate tectonic belt, such as regional motion velocity, stress, and crustal thickness during shortening and strike-slip deformation, are comparatively analyzed. The findings indicate that the arcuate tectonic belt takes shape when the weakly strengthened Tibetan Plateau is impelled into the Yinchuan Basin after being obstructed by the robust Alax and Ordos blocks during lateral expansion. Intense shear deformation occurs at the block boundaries during the arc tectonic belt’s formation. The weak middle-lower crust, serving as a detachment layer, facilitates the plateau’s lateral growth and crustal shortening and thickening without perturbing the overall deformation characteristics. It is verified that the arcuate tectonic belt was formed during the NE-SW compression phase from around 9.5 to 2.5 Ma, accompanied by significant crustal shortening and thickening. Since 2.5 Ma, within the ENE-WSW compression process, the internal faults of the arcuate tectonic belt are predominantly strike-slip, with no pronounced crustal shortening and thickening. Only local topographical modification is conspicuous. This study will enhance our comprehension of the Tibetan Plateau’s uplift and lateral growth process and furnish a foundation for investigating the formation of arcuate tectonic belts. Full article

Focusing on major earthquakes (EQs; MS ≥ 7) in Western China, this study primarily analyzes the fluctuation in Atmospheric Chemical Potential (ACP) before and after the Wenchuan, Yushu, Lushan, Jiuzhaigou, and Maduo EQs via Climatological Analysis of Seismic Precursors Identification (CAPRI). The distribution of vertical ACP revealed distinct altitude-dependent characteristics. The ACP at lower atmospheric layers (100–2000 m) exhibited a high correlation, and this correlation decreased with increasing altitude. Anomalies were detected within one month prior to each of the five EQs studied, with the majority occurring 14 to 30 days before the events, followed by a few additional anomalies. The spatial distribution of anomalies is consistent with the distribution of fault zones, with noticeable fluctuation in surrounding areas. The ACP at an altitude of 200 m gave a balance between sensitivity to seismic signals and minimal surface interference and proved to be optimal for EQ monitoring in Western China. The results offer a significant reference for remote sensing studies related to EQ monitoring and the Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) model, thereby advancing our understanding of pre-seismic atmospheric variations in Western China. Full article

The simulations presented here are based on the observational data of lightning electric currents associated with the eruption of the Hunga Tonga volcano in January 2022. The response of the lithosphere (Earth)–atmosphere–ionosphere–magnetosphere system to unprecedented lightning currents is theoretically investigated at low frequencies, including ultra low frequency (ULF), extremely low frequency (ELF), and very low frequency (VLF) ranges. The electric current source due to lightning near the location of the Hunga Tonga volcano eruption has a wide-band frequency spectrum determined in this paper based on a data-driven approach. The spectrum is monotonous in the VLF range but has many significant details at the lower frequencies (ULF, ELF). The decreasing amplitude tendency is maintained at frequencies exceeding 0.1 Hz. The density of effective lightning current in the ULF range reaches the value of the order of 10⁻⁷ A/m². A combined dynamic/quasi-stationary method has been developed to simulate ULF penetration through the lithosphere (Earth)–atmosphere–ionosphere–magnetosphere system. This method is suitable for the ULF range down to 10⁻⁴ Hz. The electromagnetic field is determined from the dynamics in the ionosphere and from a quasi-stationary approach in the atmosphere, considering not only the electric component but also the magnetic one. An analytical/numerical method has been developed to investigate the excitation of the global Schumann resonator and the eigenmodes of the coupled Schumann and ionospheric Alfvén resonators in the ELF range and the eigenmodes of the Earth–ionosphere waveguide in the VLF range. A complex dispersion equation for the corresponding disturbances is derived. It is shown that oscillations at the first resonance frequency in the Schumann resonator can simultaneously cause noticeable excitation of the local ionospheric Alfvén resonator, whose parameters depend on the angle between the geomagnetic field and the vertical direction. VLF propagation is possible over distances of 3000–10,000 km in the waveguide Earth–ionosphere. The results of simulations are compared with the published experimental data. Full article

The purpose of this paper is to discuss the effect of earthquake (EQ) preparation on changes in meteorological parameters. The two physical quantities of temperature (T)/relative humidity (Hum) and atmospheric chemical potential (ACP) have been investigated with the use of the Japanese meteorological “open” data of AMeDAS (Automated Meteorological Data Acquisition System), which is a very dense “ground-based” network of meteorological stations with higher temporal and spatial resolutions than the satellite remote sensing open data. In order to obtain a clearer identification of any seismogenic effect, we have used the AMeDAS station data at local midnight (LT = 01 h) and our initial target EQ was chosen to be the famous 1995 Kobe EQ of 17 January 1995 (M = 7.3). Initially, we performed conventional statistical analysis with confidence bounds and it was found that the Kobe station (very close to the EQ epicenter) exhibited conspicuous anomalies in both physical parameters on 10 January 1995, just one week before the EQ, exceeding m (mean) + 3σ (standard deviation) in T/Hum and well above m + 2σ in ACP within the short-term window of one month before and two weeks after an EQ. When looking at the whole period of over one year including the day of the EQ, in the case of T/Hum only we detected three additional extreme anomalies, except in winter, but with unknown origins. On the other hand, the anomalous peak on 10 January 1995 was the largest for ACP. Further, the spatial distributions of the anomaly intensity of the two quantities have been presented using about 40 stations to provide a further support to the close relationship of this peak with the EQ. The above statistical analysis has been compared with an analysis with recent machine/deep learning methods. We have utilized a combinational use of NARX (Nonlinear Autoregressive model with eXogenous inputs) and Long Short-Term Memory (LSTM) models, which was successful in objectively re-confirming the anomalies in both parameters on the same day prior to the EQ. The combination of these analysis results elucidates that the meteorological anomalies on 10 January 1995 are considered to be a notable precursor to the EQ. Finally, we suggest a joint examination of our two meteorological quantities for their potential use in real short-term EQ prediction, as well as in the future lithosphere–atmosphere–ionosphere coupling (LAIC) studies as the information from the bottom part of LAIC. Full article

This study investigates the hypothesis that meteorological anomalies may precede earthquake events. Long-term time series of observations for air temperature, atmospheric pressure and precipitation at a meteorological station in Kamchatka are considered. Time series are subjected to Huang decomposition into sequences of levels of empirical oscillation modes (intrinsic mode functions—IMFs), forming a set of orthogonal components with decreasing average frequency. For each IMF level, the instantaneous amplitudes of envelopes are calculated using the Hilbert transform. A comparison with the earthquake sequence is made using a parametric model of the intensity of two interacting point processes, which allows one to quantitatively estimate the “measure of the lead” of the time instants of the compared sequences. For each IMF level, the number of time moments of the largest local maxima of instantaneous amplitudes which is equal to the number of earthquakes is selected. As a result of the analysis, it turned out that for the sixth IMF level (periods of 8–16 days), the “lead measure” of the instantaneous amplitude maxima of meteorological parameters in comparison with earthquake time moments significantly exceeds the inverse lead, which confirms the existence of prognostic changes in meteorological parameters in the problem of “atmosphere–lithosphere” interaction. This study reveals that certain meteorological anomalies can be a precursor for seismic activity. Full article

In the last decades, the scientific community has been focused on searching earthquake signatures in the Earth’s atmosphere, ionosphere, and magnetosphere. This work investigates an offshore Mw 5.5 earthquake that struck off the Marche region’s coast (Italy) on 9 November 2022, with a focus on the potential coupling between the Earth’s lithosphere, atmosphere, and magnetosphere triggered by the seismic event. Analysis of atmospheric temperature data from ERA5 reveals a significant increase in potential energy (Ep) at the earthquake’s epicenter, consistent with the generation of Atmospheric Gravity Waves (AGWs). This finding is further corroborated by the MILC analytical model, which accurately simulates the observed Ep trends (within 5%), supporting the theory of Lithosphere–Atmosphere–Ionosphere–Magnetosphere coupling. The study also examines the vertical Total Electron Content (vTEC) and finds notable fluctuations at the epicenter, exhibiting periodicities (7–12 min) characteristic of AGWs and traveling ionospheric disturbances. The correlation between ERA5 observations and MILC model predictions, particularly in temperature deviations and Ep distributions, strengthens the hypothesis that earthquake-generated AGWs impact atmospheric conditions at high altitudes, leading to observable ionospheric perturbations. This research contributes to a deeper understanding of Lithosphere–Atmosphere–Ionosphere–Magnetosphere coupling mechanisms and the potential for developing reliable earthquake prediction tools. Full article

This study conducts a comprehensive analysis of observations related to the M_L6.2 Hualien earthquake that struck eastern Taiwan on 6 February 2018, focusing particularly on gamma-ray emissions and total electron content (TEC) as earthquake precursors. Prior research has shown that significant gamma-ray enhancements are frequently detected at the YMSG (Yangmingshan gamma-ray) station prior to major earthquakes in eastern and northeastern Taiwan, suggesting that gamma-ray anomalies may serve as reliable indicators for identifying seismic precursors in this area. Our findings reveal a significant rise in gamma-ray emissions at the YMSG station from 19 January to 4 February 2018, which corresponds to a precursor period of approximately 18 days before the Hualien earthquake. Positive and negative TEC anomalies were observed in Taiwan on 20–21 January and 5 February, respectively, and may be considered as ionospheric precursors to the earthquake. Additionally, deep-learning techniques applied to TEC data facilitate the detection of ionospheric precursors associated with the Hualien earthquake, enabling forecasts of an approaching seismic event. Collectively, these observations indicate that all identified anomalies are regarded as short-term precursors, explicable through the theoretical framework of lithosphere–ionosphere coupling (LIC). Full article

Vegetation, as a fundamental component of terrestrial ecosystems, plays a pivotal role in the flux of water, heat, and nutrients between the lithosphere, biosphere, and atmosphere. Assessing the impacts of climate change and human activities on vegetation dynamics is essential for maintaining the health and stability of fragile ecosystems, such as the Yarlung Zangbo River (YZR) basin of the Tibetan Plateau, the highest-elevation river basin in the world. Vegetation responses to climate change are inherently asymmetric, characterized by distinct temporal effects. However, these temporal effects remain poorly understood, particularly in high-altitude ecosystems. Here, we examine the spatiotemporal changes in leaf area index (LAI) and four climatic factors—air temperature, precipitation, potential evapotranspiration, and solar radiation—in the YZR basin over the period 2000–2019. We further explore the time-lag and time-accumulation impacts of these climatic factors on LAI dynamics and apply an enhanced residual trend analysis to disentangle the relative contributions of climate change and human activities. Results indicated that (1) a modest increase in annual LAI at a rate of 0.02 m² m⁻² dec⁻¹ was detected across the YZR basin. Spatially, LAI increased in 66% of vegetated areas, with significant increases (p < 0.05) in 10% of the basin. (2) Temperature, precipitation, and potential evapotranspiration exhibited minimal time-lag (<0.5 months) but pronounced notable time-accumulation effects on LAI variations, with accumulation periods ranging from 1 to 2 months. In contrast, solar radiation demonstrated significant time-lag impacts, with an average lag period of 2.4 months, while its accumulation effects were relatively weaker. (3) Climate change and human activities contributed 0.023 ± 0.092 and –0.005 ± 0.109 m² m⁻² dec⁻¹ to LAI changes, respectively, accounting for 60% and 40% on the observed variability. Spatially, climate change accounted for 85% of the changes in LAI in the upper YZR basin, while vegetation dynamics in the lower basin was primarily driven by human activities, contributing 63%. In the middle basin, vegetation dynamics were influenced by the combined effects of climate change and human activities. Our findings deepen insights into the drivers of vegetation dynamics and provide critical guidance for formulating adaptive management strategies in alpine ecosystems. Full article

Mineralization processes in the Tell-Atlas of North Africa coincided with magmatism, extension, and lithospheric rejuvenation during the middle to late Miocene. This review examines the lead isotope compositions and Pb-Pb age dating of ore deposits in the region to elucidate the sources and timing of mineralization events. The data reveal a predominantly radiogenic signature in the ores, indicating that the primary component is from a crustal source, with a contribution from the mantle. Pb-Pb age dating suggests the ranges of mineralization ages, with late Miocene events being particularly significant, coinciding with proposed sub-continental mantle delamination following subduction of the African lithosphere. In this context, polymetallic mineralizations formed related to felsic magmatism, hydrothermalism driven by extensional faults, resulting in the formation of Mississippi Valley-Type, and Sedimentary exhalative deposits within associated semi-grabens and diapirism. The correlation between orogenic extensional collapse, magmatism, and mineralization underscores the importance of understanding the specific geological context of ore formation. The detachment of subducted slabs and subsequent influx of hot asthenosphere play pivotal roles in creating conducive conditions for mineralization. This study sheds light on the intricate interplay between tectonic mechanisms, mantle-crust interactions, and mineralization events in the Tell-Atlas, offering insights for further exploration in the region. Full article

Paleozoic igneous rocks exposed in the northern Yili Block are thought to have resulted from the subduction of the North Tianshan oceanic crust. However, the exact timing of the transition of the northern margin of the Yili Block from a passive to an active continental margin remains unknown. In this paper, the petrological and geochemical features, zircon U-Pb chronology, Lu-Hf isotopes, and Sr-Nd isotopes of volcanic rocks in the Nailenggeledaban area on the northern margin of the Yili Block were studied. Zircon U-Pb dating results show that the crystallization ages of the volcanic rocks in the Nailenggeledaban area on the northern margin of the Yili Block are 491 ± 2 Ma and 500 ± 2 Ma, suggesting they were formed during the Late Cambrian. Geochemical features show that the volcanic rocks are alkaline basalts with rare earth and trace element distribution patterns similar to OIB, although they exhibit some degree of Zr and Hf depletion. The ε_Hf(t) values of alkaline basalts in the Nailenggeledaban area at the northern Yili Block range from −3.48 to −1.00, with a T_DM1 age of 1152 to 1263 Ma. The ε_Nd(t) values range from −3.53 to −0.96, with a T_DM1 age of 1471 to 2162 Ma. Combined with geochemical data, the alkaline basalt magma in the Nailenggeledaban area on the northern margin of the Yili Block may be derived from the Mesoproterozoic enriched lithospheric mantle. The composition of the mantle source area is potentially garnet lherzolite, and the magma appears to have been either unaffected or only minimally contaminated by crustal materials during the ascending process. On the basis of the research results of the Early Paleozoic tectonic evolution in the northern margin of the Yili Block, this paper proposes that the volcanic rocks in the Nailenggeledaban area, located on the northern margin of the Yili Block, were formed in a back-arc extensional environment resulting from the subduction of the North Tianshan Ocean (or Junggar Ocean) beneath the northern margin of the Yili Block during the Late Cambrian. Full article

This study demonstrates a rich complexity of the time–frequency ionospheric signal spectrum, dependent on the measurement type and platform. Different phenomena contributing to satellite-derived and ground-derived geophysical data that only selected signal bands can be potentially sensitive to seismicity over time, and they are applicable in lithosphere–atmosphere–ionosphere coupling (LAIC) studies. In this study, satellite-derived and ground-derived ionospheric observations are filtered by a Fourier-based band-pass filter, and an experimental selection of potentially sensitive frequency bands has been carried out. This work focuses on band-pass filtered ionospheric observations and seismic activity in the region of the Aegean Sea over a two-year time period (2020–2021), with particular focus on the entire system of tectonic plate junctions, which are suspected to be a potential source of ionospheric disturbances distributed over hundreds of kilometers. The temporal evolution of seismicity power in the Aegean region is represented by the record of earthquakes characterized by M ≥ 4.5, used for the estimation of cumulative seismic energy. The ionospheric response to LAIC is explored in three data types: short inspections of in situ electron density (Ne) over a tectonic plate boundary by Swarm satellites, stationary determination of three Ne density profile parameters by the Athens Digisonde station AT138 (maximum frequency of the F2 layer: foF2; maximum frequency of the sporadic E layer: foEs; and frequency spread: ff), and stationary measure of vertical total electron content (VTEC) interpolated from a UPC-IonSAT Quarter-of-an-hour time resolution Rapid Global ionospheric map (UQRG) near Athens. The spectrograms are made with the use of short-term Fourier transform (STFT). These frequency bands in the spectrograms, which show a notable coincidence with seismicity, are filtered out and compared to cumulative seismic energy in the Aegean Sea, to the geomagnetic Dst index, to sunspot number (SN), and to the solar radio flux (F10.7). In the case of Swarm, STFT allows for precise removal of long-wavelength Ne signals related to specific latitudes. The application of STFT to time series of ionospheric parameters from the Digisonde station and GIM VTEC is crucial in the removal of seasonal signals and strong diurnal and semi-diurnal signal components. The time series formed from experimentally selected wavebands of different ionospheric observations reveal a moderate but notable correlation with the seismic activity, higher than with any solar radiation parameter in 8 out of 12 cases. The correlation coefficient must be treated relatively and with caution here, as we have not determined the shift between seismic and ionospheric events, as this process requires more data. However, it can be observed from the spectrograms that some weak signals from selected frequencies are candidates to be related to seismic processes. Full article

This study utilized single-channel seismic, multi-channel seismic, and multibeam bathymetric data to examine the distribution and geomorphological background of geological hazards in the Zhongsha Islands region of the South China Sea. We elucidate the regional geological structure and its evolution while focusing on the types and characteristics of submarine hazards since the Quaternary Period. By integrating geomorphological, tectonic, and sedimentary factors, we analyzed the primary drivers of shallow geological hazards in the region. Our findings reveal that seabed topography, tectonic activity, and sedimentary processes critically influence hazard formation, particularly in geomorphic units prone to disasters, such as submarine slopes and canyons. Igneous rocks in the region display medium-acid to medium-basic compositions, with notable developmental stages during the Himalayan and Yanshan periods. From the Paleogene to the Middle Miocene, tectonic activity intensified, significantly thinning the lithosphere. By the Middle Miocene, the crust stabilized into its present configuration, marking the formation of key tectonic units in the region. Multiple phases of sedimentary evolution, influenced by the Cenozoic tectonic movements, further contribute to the region’s susceptibility to geological hazards. Full article

The Central Indian Ocean Basin (CIOB) is distinguished by unusually high tectonic activity, setting it apart from all other passive oceanic basins. Within the interior of the Indo-Australian lithospheric plate lies a unique area of intraplate deformation. This region is characterized by the highest recorded intraplate oceanic seismicity, with earthquake magnitudes reaching up to M = 8, abnormally high heat flow—measured to be two to four times higher than background levels for the ancient oceanic lithosphere of the Cretaceous age—and, most notably, intense folding and faulting of sediments and the basement, which are typically associated only with boundary zones of lithospheric plates. This anomalously tectonically active intraplate area was studied during regular research cruises in the 1970s–1980s, after which new conclusions were mainly drawn from satellite data modeling. Substantially new geophysical data were obtained in 2017 after a long gap. Bathymetric surveys using multibeam echosounders during the 42nd cruise of the R/V (Research Vessel) Akademik Boris Petrov and the SO258/2 cruise of the R/V Sonne provided full coverage of a large portion of the intraplate deformation area in the CIOB. This confirmed the mosaic-block structure of the intraplate deformation zone in the Central Indian Ocean Basin, consisting of numerous isometrically deformed tectonic blocks. A linear block at 0.2–0.6° S, which has a branch-like shape in plain view, is morphologically distinct from these blocks. It represents a system of structural elements of different scales (folds, flexures, ruptures), which constitute a structural paragenesis formed in the mechanical environment of a dextral transpressive tectonic setting. Full article

The Early Cretaceous intermediate intrusive rocks have important significance in understanding the crust–mantle interaction, iron mineralization, and tectonic evolution in the western Shandong Peninsula. In this study, we present new zircon U–Pb ages, and Hf isotope, whole-rock geochemistry, Sr–Nd isotopes, and the mineral chemistry of the diorite-porphyrite in the southern Xintai area, mid-western Shandong Peninsula. The diorite-porphyrite formed at ca. 125 Ma. They have intermediate SiO₂ (59.57–62.29 wt.%) and MgO (2.78–3.58 wt.%) contents, high Mg# values (53–56), high Sr (589–939 ppm) and low Y (9.2–10.8 ppm) contents, and high Sr/Y ratios (54–94), showing adakitic affinity. The diorite-porphyrite exhibits lower zircon ε_Hf(t) values (−30.1 to 7.5) and whole-rock ε_Nd(t) values (−3.5 to −6.0), with (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.70514–0.70567. We suggest that the diorite-porphyrite was derived from the partial melting of the local delamination of lower continental crust and then by the interaction with the enriched lithospheric mantle. The genesis of diorite-porphyrite may be related to the rollback process of the Paleo-Pacific slab in the Early Cretaceous. This geodynamic process induced the melting of the enriched lithospheric mantle, subducted oceanic crust, and local delamination of lower continental crust, which produced different types of adakitic magmatism in the western Shandong Peninsula. Full article

Olivine in deep-seated ultramafic xenoliths beneath the North China Block serves as a crucial proxy for decoding the compositions, properties, and evolution of the lithospheric mantle. Here, we conduct an investigation on olivine (including gem-grade) hosted in ultramafic xenoliths from Damaping basalt in the northern part of the North China Block. This contribution presents the results from petrographic, Raman spectroscopic, and major and trace elemental studies of olivine, with the aim of characterising the formation environment and genetic type of the olivine. The analysed olivine samples are characterised by high Mg# values (close to 91%) possessing refractory to fertile features and doublet bands with unit Raman spectra beams of 822 and 853 cm⁻¹, which are indicative of a forsterite signature. Major and trace geochemistry of olivine indicates the presence of mantle xenolith olivine. All the analytical olivine assays ≤0.1 wt % CaO, ~40 wt % SiO₂, and ≤0.05 wt % Al₂O₃. Furthermore, olivine displays significantly different concentrations of Ti, Y, Sc, V, Co, and Ni. The Ni/Co values in olivine range from 21.21 to 22.98, indicating that the crystallisation differentiation of basic magma relates to oceanic crust recycling. The V/Sc values in mantle/xenolith olivine vary from 0.54 to 2.64, indicating a more oxidised state of the mantle. Rare earth element (REE) patterns show that the LREEs and HREEs of olivine host obviously differentiated characteristics. The HREE enrichments of olivine and the LREE depletion of clinopyroxene further assert that the mantle in the Damaping area underwent partial melting. The wide variations of Mg# values in olivine and the Cr# values in clinopyroxene, along with major element geochemistry indicate transitional characteristics of different peridotite xenoliths. This is possibly indicative of a newly accreted lithospheric mantle interaction with an old lithospheric mantle at the time of the basaltic eruption during the Paleozoic to Cenozoic. Full article