Active Region Research Articles

Dynamically Triggered Tectonic Tremors and Earthquakes in the Caucasian Region Following the 2023 Kahramanmaraş, Türkiye, Earthquake Sequence

AbstractDeep tectonic tremor has been observed along major subduction zones and several continental strike‐slip faults around the Pacific Rim and the Caribbean. However, it has not be widely identified in other tectonically active regions such as the Alpine‐Himalayan orogenic belt yet. Here we present dynamically triggered tremors and microearthquakes in the Caucasian Region following the 2023 Mw 7.8 and Mw 7.5 mainshocks in the 2023 Kahramanmaraş, Türkiye, earthquake sequence. We observe triggered deep tectonic tremors within Azerbaijan, where seismological evidences suggest pre‐existing subduction slabs. Meanwhile, we document cases of triggered earthquakes in Azerbaijan and Georgia, and Javakheti highland near the border of Georgia and Armenia. These triggered earthquakes are either associated with mud volcanism or volcanic formations. Our results highlight a variety of responses to dynamic stress perturbations, suggesting high susceptibility to dynamic stress perturbations and a broad spectrum of slip behaviors for critically stressed faults in the Caucasian region.

Generating X-Ray Transit Profiles with Batman

We present an adaptation of the exoplanet transit model code batman, in order to permit the generation of X-ray transits. Our underlying extended coronal model assumes an isothermal plasma that is radially symmetric. While this ignores the effect of bright, active regions, observations of transits in X-rays will require averaging across multiple epochs of data for the foreseeable future, significantly reducing the importance of more complex modeling. Our publicly available code successfully generates the predicted W-shaped transit profile in X-rays due to the optically thin nature of the emission, which concentrates the expected observational emission around the limb of the photospheric stellar disk. We provide some examples based on the best known X-ray transit target, HD 189733 b, and examine the effect of varying the planet size, coronal temperature, and impact parameter on the resulting transit profile. We also derived scaling relationships for how the overall transit detectability is affected by changing these parameters. Over most of the parameter space, we find that the detectability scales linearly with the cross-sectional area of the planet in X-rays. The relationship with increasing coronal temperature is less fixed, but averages out to a power law with slope −1/4 except when the impact parameter is high. Indeed, varying impact parameter has little effect on detectability at all until it approaches unity.

Unveiling key factors in solar eruptions leading to the solar superstorm in 2024 May

NOAA active region (AR) 13664/8 produced the most intense geomagnetic effects since the Halloween event of 2003. The resulting extreme solar storm is thought to be the consequence of multiple interacting coronal mass ejections (CMEs). Notably, this AR exhibits exceptionally rapid magnetic flux emergence. The eruptions on which we focus all occurred along collisional polarity inversion lines (PILs) through collisional shearing during a three-day period of extraordinarily high flux emergence (sim 1021 Mx hr$^ $). Our key findings reveal how photospheric magnetic configurations in eruption sources influence solar superstorm formation and geomagnetic responses, and link exceptionally strong flux emergence to sequential homologous eruptions: (1) We identified the source regions of seven halo CMEs that were distributed primarily along two distinct PILs. This distribution suggests two groups of homologous CMEs. (2) The variations in the magnetic flux emergence rates in the source regions are correlated with the CME intensities. This might explain the two contrasting cases of complex ejecta that are observed at Earth. (3) Our calculations of the magnetic field gradients around the CME source regions show strong correlations with eruptions. This provides crucial insights into solar eruption mechanisms and enhances our prediction capabilities for future events.

Comparison between InAs-based and GaSb-based interband cascade lasers with hybrid superlattice plasmon-enhanced claddings

We compare InAs-based and GaSb-based interband cascade lasers (ICLs) with the same 12-stage active region designed to emit at a wavelength of 4.6 µm. They employ a hybrid cladding architecture with the same geometry and inner claddings consisting of InAs/AlSb superlattices but different outer claddings: The InAs-based ICL employs plasmon enhanced n-type doped InAs layers while the GaSb-based ICL employs plasmon-enhanced n-type doped InAs0.915Sb0.085 claddings lattice matched to GaSb. Due to the lower refractive index of n + -InAsSb (n = 2.88) compared to n+ -InAs (n = 3.10) and higher refractive index of separate confinement layers, the GaSb-based ICL shows a 3.8% higher optical mode confinement in the active region compared to the InAs-based ICL. However, the InAs-based ICL has 15.3% lower free carrier absorption losses than the GaSb-based ICL, resulting in approximately equal threshold gains. Experimentally operated in pulsed mode and at room temperature, the GaSb-based ICL shows a 15.3% lower threshold current density, but also 12.8% higher threshold voltage resulting in comparable threshold power densities. Also presented is the influence of geometry and doping variation on confinement factors and calculated free carrier absorption losses in the GaSb-based ICL.

Investigation of the Effective Numerical Model for Seismic Response Analysis of Concrete-Faced Rockfill Dam on Deep Overburden

The construction of high rockfill dams on deep overburden in seismically active regions poses significant challenges. Currently, there are no standardized guidelines for defining the computational domain range in seismic analysis, necessitating the establishment of a universally applicable computational domain range that optimizes the balance between computational accuracy and efficiency. This has critical engineering implications for the seismic analysis of rockfill dams on deep overburden. This study employed the seismic wave input method to consider the dynamic interaction between the dam, overburden, and infinite domain. A systematic investigation was conducted on a concrete-faced rockfill dam (CFRD) constructed on deep overburden, considering the influences of overburden thickness, dam height, overburden properties, soil layer configuration, ground motion intensity, and the frequency content of the seismic waves. The acceleration response and seismic deformation of the dam were analyzed. Subsequently, the computational domain range corresponding to various levels of acceptable engineering precision was established. The results indicated that the lateral boundary length should extend a minimum distance equal to the sum of 3 times the overburden depth and 1.2 times the maximum dam height. Additionally, the depth below the overburden–bedrock interface should extend at least 1.2 times the maximum dam height. This study provides a crucial foundation for determining the optimal computational domain range in the seismic analysis of rockfill dams constructed on deep overburden.

Convergent degenerated regulatory elements associated with limb loss in limbless amphibians and reptiles.

Limbs are a defining characteristic of tetrapods, yet numerous taxa, primarily among amphibians and reptiles, have independently lost limbs as an adaptation to new ecological niches. To elucidate the genetic factors contributing to this convergent limb loss, we present a 12 Gb chromosome-level assembly of the Banna caecilian (Ichthyophis bannanicus), a limbless amphibian. Our comparative analysis, which includes the reconstruction of amphibian karyotype evolution, reveals constrained gene length evolution in a subset of developmental genes across three large genomes. Investigation of limb development genes uncovered the loss of Grem1 in caecilians and Tulp3 in snakes. Interestingly, caecilians and snakes share a significantly larger number of convergent degenerated conserved non-coding elements (dCNEs) than limbless lizards, which have a shorter evolutionary history of limb loss. These convergent dCNEs overlap significantly with active genomic regions during mouse limb development and are conserved in limbed species, suggesting their essential role in limb patterning in the tetrapod common ancestor. While most convergent dCNEs emerged in the jawed vertebrate ancestor, coinciding with the origin of paired appendage, more recent dCNEs also contribute to limb development, as demonstrated through functional experiments. Our study provides novel insights into the regulatory elements associated with limb development and loss, offering an evolutionary perspective on the genetic basis of morphological specialization.

Improved hole injection for AlGaN-based DUV LEDs with graded-composition multiple quantum barrier insertion layers

The primary impediments to achieving high external quantum efficiency (EQE) and light output power (LOP) in AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) are inadequate hole injection efficiency and pronounced electron leakage. The significant polarization-induced positive charges, originating from the discontinuity in the Al composition between the last quantum barrier (LQB) and electron-blocking layer (EBL), attract electrons, consume holes, and reflect holes back into the p-type region, leading to severe electron leakage and low hole injection efficiency. In this paper, we introduce a graded-composition multiple quantum barrier (GQB) structure at the LQB/EBL interface. We adjust the Al composition in the insertion layer to alter the electrical polarity of the polarization-induced sheet charges, thereby modifying the electric field distribution in the EBL, LQB, and inserted GQB structure. Consequently, holes acquire boosted energy during their migration towards the active region. In addition, we enhance the hole injection and electron confinement ability via reducing the effective valence band barrier height and increasing the effective conduction band barrier height, thus diminishing the possibility of electron leakage from the active region into the p-type region. Therefore, the GQB structure proposed in this study provides a promising approach to improving the optical and electrical performance of DUV LEDs.

Robust seismic fragility curves for concrete gravity dams incorporating aleatory, epistemic, and fuzzy uncertainties

Concrete gravity dams are critical infrastructure assets, and their failure in seismically active regions poses significant risks. The primary problem addressed in this research is the need for a reliable assessment of the seismic fragility of these dams to ensure safety in such areas. The research aims to develop a comprehensive methodology for seismic fragility analysis that accounts for various uncertainties affecting dam performance, including uncertainties in material properties and seismic characteristics and the fuzziness of damage state thresholds through the Latin Hypercube Sampling method. The methodology involves a three-stage approach: first, a finite element model is created using Abaqus software, incorporating uncertainties in material properties and earthquake characteristics using the Latin Hypercube Sampling method (LHS). Second, incremental dynamic analysis (IDA) defines damage states based on concrete cracking severity and overall stability, utilizing four performance categories of limit states (minor, moderate, extensive, and heavy). Finally, a mathematical model is introduced to characterize the ambiguity in damage state thresholds, recognizing the gradual nature of damage evolution. The primary findings demonstrate that fuzziness substantially influences the probability of exceedance across all damage states, with varying effects on different damage indices because of their differing frequency distributions. This research enhances the reliability and accuracy of seismic fragility assessments, contributing to more robust design guidelines and effective risk mitigation strategies for concrete gravity dams.

Evaluation of liquefaction potential in central Taiwan using random forest method

AbstractLiquefaction is a significant geotechnical hazard in seismically active regions like Taiwan, threatening infrastructure and public safety. Accurate prediction models are essential for assessing soil susceptibility to liquefaction during seismic events. This study evaluates liquefaction potential in central Taiwan using the random forest (RF) method. The RF models were developed with a dataset of 540 soil and seismic parameter sets, including depth, effective and total overburden stresses, SPT-N values, fine soil content, earthquake magnitude, peak ground acceleration, and historical liquefaction occurrences. Rigorous validation techniques, such as cross-validation and comparisons with observed liquefaction events, confirm the RF model’s effectiveness, achieving an accuracy of 98.89%. The model also quantifies predictor importance, revealing that the SPT-N value is the most critical soil factor, while peak ground acceleration is the key seismic factor for liquefaction prediction. Notably, the RF model outperforms simplified procedures in accuracy, even with fewer input factors. Our case studies show that an accuracy of over 95% can still be achieved, highlighting the RF model’s superior performance compared to conventional methods, which struggle to reach similar levels.

A Quad‐Port MIMO Antenna With Improved Isolation Developed by Colored Resin Fiber Material for Wideband Applications

ABSTRACTThe article explores a quad‐port compact (56 × 56 × 1.5 mm3) multiple‐input multiple‐output (MIMO) antenna developed on a colored resin fiber material encompassing enhanced isolation for wideband applications. The design antenna configuration incorporates four ground stubs positioned among antenna pairs on the upper section of the substrate and eight rectangular‐shaped ground slots to enhance antenna isolation. The antenna functions over a broad spectral range from 4.21 to 10.95 GHz, providing coverage for WLAN (5.15–5.35 GHz/5.725–5.825 GHz), C band uplink (5.925–6.425 GHz), downlink defense (7.2–7.7 GHz), and ITU band (8–8.5 GHz), with 88.91% fractional bandwidth. The antenna design ensures exceptional isolation, exceeding 21 dB among orthogonal antennas and 25 dB between oppositely placed antennas across the entire functioning bandwidth. Across the working band, the antenna showcases favorable diversity characteristics, including a lower envelope correlation coefficient (ECC < 0.085), higher diversity gain (DG > 9.95 dB), minimal channel capacity loss (< 0.39 bits/s/Hz), and negligible magnitude variation in mean effective gain among the antenna ports (< 0.1 dB). The acquired total active reflection (TARC) curve exhibits the antenna's robust resonance features over the application band and commendable time domain properties in the active spectral region. The findings of the simulation and measurements revealed a close alignment.

Elimination of dead layer in silicon particle detectors via induced electric field based charge collection

The front surface of semiconductor particle detectors typically contains undepleted recombination active regions that the impinging particles pass through before reaching the sensitive area of the device. These so-called dead layers pose a fundamental limitation for achievable energy resolutions and are unavoidable in externally doped pn-junction detectors. Here, we fabricate a silicon particle detector using an alternative method for charge collection that extends the sensitive region to the front surface of the device and minimizes the dead layer. The junction is realized by inducing an electric field at the surface of the detector using a charged thin film. Such an approach has previously been implemented in photodiodes, which have demonstrated effective collection of charge carriers from the very surface of the devices. Our detector displays low leakage currents and recombination, which allow efficient charge collection throughout the device, as demonstrated by excellent internal quantum efficiency of the device. The detector is further characterized using detection of alpha particles as a case example. We achieve 20 keV energy resolutions that are, already without extensive device optimization, on the same level with commercial externally doped silicon particle detectors. Notably, the design shows promise for detection of shallow penetrating charged particles, which is very sensitive to dead layers.

Analysis of SiNx Waveguide-Integrated Liquid Crystal Platform for Wideband Optical Phase Shifters and Modulators

In this study, the potential of employing SiNx (silicon nitride) waveguide platforms to enable the use of liquid-crystal-based phase shifters for on-chip optical modulators was thoroughly investigated using 3D-FDTD (3D finite-difference time-domain) simulations. The entire structure of liquid-crystal-based Mach–Zehnder interferometer (MZI) optical modulators, consisting of multi-mode interferometer splitters, different tapering sections, and liquid-crystal-based phase shifters, was systematically and holistically investigated with a view to developing a compact, wideband, and CMOS-compatible (complementary metal-oxide semiconductor) bias voltage optical modulator with competitive modulation efficiency, good fabrication tolerance, and single-mode operation using the same SiNx waveguide layer for the entire device. The trade-off between several important parameters is critically discussed in order to reach a conclusion on the possible optimized parameter sets. Contrary to previous demonstrations, this investigation focused on the potential of achieving such an optical device using the same SiNx waveguide layer for the entire device, including both the passive and active regions. Significantly, we show that it is necessary to carefully select the phase shifter length of the LC-based (liquid crystal) MZI optical modulator, as the phase shifter length required to obtain a π phase shift could be as low as a few tens of microns; therefore, a phase shifter length that is too long can contradictorily worsen the optical modulation.

Hybrid poly(lactide-co-glycolide) membranes incorporated with doxycycline-loaded copper-based metal-organic nanosheets as antibacterial platforms.

The rise of antimicrobial resistance necessitates innovative strategies to combat persistent infections. Metal-Organic Frameworks (MOFs) have attracted significant attention as antibiotic carriers due to their high drug loading capacity and structural adaptability. In particular, 2D MOF nanosheets are emerging as a notable alternative to their traditional 3D relatives due to their remarkable advantages in enhanced surface area, flexibility and exposed active region properties. Herein, we synthesized 2D Copper 1,4-benzendicarboxylate (CuBDC) nanosheets and utilized them as a carrier and controlled release system for Doxycycline (Doxy@CuBDC), for the first time. The Doxy@CuBDC nanosheets were subsequently incorporated into poly (DL-lactide-co-glycolide) (PLGA) electrospun membranes (Doxy@CuBDC/PLGA). The resultant bioactive fibrous membranes exhibited double-barrier controlled release properties, extending the Doxy release up to ∼9 days at pH 7.4 and 5.5. Significant inhibitory effects against Staphylococcus aureus and Escherichia coli were observed. The morphological analyses revealed the deformed bacterial cell structures on Doxy@CuBDC/PLGA membranes that indicates potent bactericidal activity. Furthermore, cytotoxicity assays demonstrated the non-toxic nature of the fabricated membranes, underscoring their potential use for biomedical applications. Overall, the hybrid antibacterial PLGA membranes present a promising strategy for combating microbial infections while maintaining biocompatibility and offer a versatile approach for biomedical material design and surface coatings (e.g., wound dressings, implants).&#xD.

Comparative Proteomic Analysis of Cell Wall Proteins of Aminoglycosides Resistant and Sensitive Mycobacterium tuberculosis Clinical Isolates.

The rising prevalence of Mycobacterium tuberculosis (M.tb) strains resistant to aminoglycosides (amikacin and kanamycin) challenges effective TB control and treatment. Understanding the mechanisms behind this resistance is crucial since aminoglycosides are a mainstay of TB therapy. The study aimed to analyze the cell wall proteins overexpressed in aminoglycoside-resistant isolates of Mycobacterium tuberculosis using proteomics approaches. We used two-dimensional electrophoresis and mass spectrometry to compare the cell wall proteomes of aminoglycosides-resistant and susceptible clinical isolates. The overexpressed protein spots were excised and identified using liquid chromatography-mass spectrometry (LC/MS). The identified proteins were subsequently analyzed for molecular docking, pupylation site identification, and STRING analysis. We found a total of nine significantly upregulated proteins in aminoglycosides-resistant isolates. Three of these proteins were the same (isoform), resulting in the identification of seven unique proteins. Specifically, Rv3841 and Rv1308 belonged to intermediary metabolism and respiration; Rv2115c to the cell wall and cell processes; Rv2501c, Rv2247 and Rv0295c to lipid metabolism; and Rv2416c to virulence, detoxification/adaptation. Notably, variations in these proteins support cell wall integrity, aiding mycobacteria's establishment and proliferation. Molecular docking study revealed that both drugs bind strongly to the proteins' active site regions. Additionally, the GPS-PUP algorithm successfully identified possible pupylation sites within these proteins, except Rv0295c. Based on interactome analysis using the STRING 12.0 database, we have identified potential interactive partners suggesting their role in aminoglycosides resistance. Overexpressed proteins not only act to counteract or regulate drug effects but also have a role in protein dynamics that allow for resistance. Some of these identified proteins may serve as innovative drug targets and biomarkers for the early detection of drug-specific resistance in M.tb. Further research is needed to elucidate the mechanisms by which these potential protein targets contribute to resistance in AK and KM M.tb isolates.

Constructing a 22-year internal wave dataset for the northern South China Sea: spatiotemporal analysis using MODIS imagery and deep learning

Abstract. Internal waves (IWs) are an important ocean phenomenon facilitating energy transfer between multiscale ocean processes. Understanding such processes necessitates the collection and analysis of extensive observational data. IWs predominantly occur in marginal seas, with the South China Sea (SCS) being one of the most active regions, characterized by frequent and large-amplitude IW activities. In this study, we present a comprehensive IW dataset for the northern SCS (https://doi.org/10.12157/IOCAS.20240409.001, Zhang and Li, 2024), covering the area from 112.40 to 121.32° E and from 18.32 to 23.19° N, spanning the period from 2000 to 2022 with a 250 m spatial resolution. During the 22 years, a total of 15 830 MODIS images were downloaded for further processing. Out of these, 3085 high-resolution MODIS true-color images were identified to contain IW information and were included in the dataset with precise IW positions extracted using advanced deep learning techniques. IWs in the northern SCS are categorized into four regions based on extracted IW spatial distributions. This classification enables detailed analyses of IW characteristics, including their spatial and temporal distributions across the entire northern SCS and its specific sub-regions. Interestingly, our temporal analysis reveals characteristic “double-peak” patterns aligned with the lunar day, highlighting the strong connection between IWs and tidal cycles. Furthermore, our spatial analysis identifies two IW quiescent zones within the IW clusters influenced by underwater topography, highlighting regional variations in IW characteristics and suggesting underlying mechanisms which merit further investigation. There are also three gap regions between distinct IW clusters, which may indicate different IW sources. The constructed dataset holds significant potential for studying IW–environment interactions, developing monitoring and prediction models, validating numerical simulations, and serving as an educational resource to promote awareness and interest in IW research.

The effect of data-driving and relaxation models on magnetic flux rope evolution and stability

Understanding the flux rope eruptivity and effects of data driving in modelling solar eruptions is crucial for correctly applying different models and interpreting their results. We aim to investigate these by analysing the fully data-driven modelled eruption of the active regions (ARs) 12473 and AR11176, as well as preforming relaxation runs for AR12473 (found to be eruptive) where the driving is switched off systematically at different time steps. We intend to analyse the behaviour and evolution of fundamental quantities that are essential for understanding the eruptivity of magnetic flux ropes (MFRs). The data-driven simulations were carried out with the time-dependent magnetofrictional model (TMFM) for AR12473 and AR11176. For the relaxation runs, we employed the magnetofrictional method (MFM) and a zero-beta magnetohydrodynamic (MHD) model to investigate how significant the differences between the two relaxation procedures are when started from the same initial conditions. In total, 22 simulations were studied. To determine the eruptivity of the MFRs, we calculated and analysed characteristic geometric properties such as the cross-section, MFR height, and physical stability parameters such as MFR twist and the decay index. Furthermore, for the eruptive cases, we investigated the effect of sustained driving beyond the point of eruptivity on the MFR properties and evolution. We find that the fully driven AR12473 MFR is eruptive, while the AR11176 MFR is not. For the relaxation runs, we find that the MFM MFRs are eruptive when the driving is stopped around the flare time or later, while the MHD MFRs show eruptive behaviour even if the driving is switched off one and a half days before the flare occurs. We also find that characteristic MFR properties can vary greatly even for the eruptive cases of different relaxation simulations. The results suggest that data driving can significantly influence the evolution of the eruption, with differences appearing even when the relaxation time is set to later stages of the simulation when the MFRs have already entered an eruptive phase. Moreover, the relaxation model affects the results significantly, as highlighted by the differences between the MFM and MHD MFRs, showing that eruptivity in MHD does not directly translate to eruptivity in the MFM, despite the same initial conditions. Finally, if the exact critical values of instability parameters are unknown, tracking the evolution of typical MFR properties can be a powerful tool for determining MFR eruptivity.

2023 Jishishan Earthquake-triggered river terrace landslide enabled by tectonic and human activities

The continued increase in demand for food is such that flood-irrigation-based agricultural techniques are not expected to change in the future. Consequently, in cultivated areas dominated by river terraces that experience neotectonic movements, catastrophes caused by earthquakes that trigger material liquefaction may continue to occur. Among such catastrophes, low-angle, ultra-long-distance landslides induced by synergistic effects of tectonic and human activities are events that are not fully understood but can potentially be mitigated. A landslide-mudflow that occurred on December 18, 2023, during an Ms 6.2 earthquake in Jishishan, China, on the tertiary terrace of the Yellow River. We reveal the causal mechanisms by which geomorphology, tectonics, and human activities controlled the landslide-mudflow, and outline a new, potentially widespread, dual liquefaction layer-dominated failure mode for earthquake-induced landslides on river terraces. Our findings serve as a warning that urgent landslide-potential assessments should be conducted across river terrace irrigation areas in tectonically active regions.

Source mechanism of the 2023 Ms 5.5 earthquake in Subei, Gansu Province revealed by relocated aftershocks and InSAR: complement to the ‘shallow slip deficit’ of the eastern boundary of the Altyn Tagh fault

The Ms 5.5 earthquake struck on 24 October 2023, in Subei County, Gansu Province, China, occurring along the eastern segment of the Altyn Tagh fault. It raises the question of whether this earthquake is linked to the ongoing shortening slip rate along this segment or triggered by other seismic events. Analyzing the fault geometry of the Subei earthquake and understanding the significance of the weakening activity rate for seismic hazards in neighboring regions is crucial. The surface deformation from small- and medium-sized earthquakes (magnitudes less than Mw5.5) is often subtle, and the coseismic deformation detected by interferometric synthetic aperture radar (InSAR) is vulnerable to atmospheric disturbances, leading to significant measurement errors. Moreover, inaccuracies in the regional crustal velocity structure can cause errors in earthquake localization based on seismic data. These challenges complicate the establishment of a rupture model for seismogenic faults and hinder the inversion of fault slip models. To overcome these limitations, we employed the time-series InSAR stacking method and aftershock relocation to determine the fault geometry of the Subei earthquake. A two-step inversion method was utilized to ascertain both the fault geometry and slip distribution. Our modeling indicates that the 2023 Subei earthquake had a thrust mechanism with a component of strike-slip. The rupture did not reach the surface, with the maximum fault slip measuring 0.45 m at a depth of 2.5–3.5 km. The fault dips westward, and the moment magnitude is calculated at 5.4. This earthquake is associated with the ongoing weakening of the left-lateral strike-slip rupture along the Altyn Tagh fault in the Subei region. Furthermore, retrograde thrust tectonics significantly contribute to the absorption of accumulated stress during this process.Our findings highlight the potential of utilizing time-series InSAR images to enhance earthquake catalogs with geodetic observations, offering valuable data for further studies of the earthquake cycle and active tectonics. This approach is also applicable in other tectonically active regions, enhancing understanding of seismic hazards and risk assessment.

Nested active regions anchor the heliospheric current sheet and stall the reversal of the coronal magnetic field

During the solar cycle, the Sun's magnetic field polarity reverses due to the emergence, cancellation, and advection of magnetic flux towards the rotational poles. Flux emergence events occasionally cluster together, although it is unclear if this is due to the underlying solar dynamo or simply by chance. Regardless of the cause, we aim to characterise how the reversal of the Sun's magnetic field and the structure of the solar corona are influenced by nested flux emergence. From the spherical harmonic decomposition of the Sun's photospheric magnetic field, we identified times when the reversal of the dipole component stalls for several solar rotations. Using observations from sunspot cycle 23 to present, we located the nested active regions responsible for each stalling and explored their impact on the coronal magnetic field using potential field source surface extrapolations. Nested flux emergence has a more significant impact on the topology of the coronal magnetic field than isolated emergences as it produces a coherent (low spherical harmonic order) contribution to the photospheric magnetic field. The heliospheric current sheet, which separates oppositely directed coronal magnetic fields, can become anchored above nested active regions due to the formation of strong opposing magnetic fluxes. Further flux emergence, cancellation, differential rotation, and diffusion, then effectively advects the heliospheric current sheet and shifts the dipole axis. Nested flux emergence can restrict the evolution of the heliospheric current sheet and impede the reversal of the coronal magnetic field. The sources of the solar wind can be more consistently identified around nested active regions because the magnetic field topology remains self-similar for multiple solar rotations. This highlights the importance of identifying and tracking nested active regions to guide the remote-sensing observations of modern heliophysics missions.

InSAR phase gradient reveals fault‐zone controls on the spatial distribution of slow‐moving landslides in the active orogenic region of Hazara‐Kashmir, Pakistan

AbstractSlow‐moving landslides play important roles in the landscape evolution and hazards planning. Studies along some strike‐slip faults have shown that the geological structures and bed‐rock lithology significantly contribute the distribution of slow‐moving landslides. However, controls on the distribution of slow‐moving landslides are poorly constrained in active orogenic regions, hindering our understanding of its role in the rapid orogenic process. The Hazara Kashmir Syntaxis in Pakistan is such a prominent geological structure of lesser Himalaya, where the inventory of slow‐moving landslides is scarce. Here, we attempt the interferometric synthetic aperture radar phase‐gradient stacking coupled with a deep‐learning system to provide the first slow‐moving landslides inventory (1066 presently active landslides, 2016–2023) in the Hazara‐Kashmir region. Along with optical imagery and field investigations, we analyse the impacts of fault structures, bed‐rock lithology, topography along with spatial distribution of earthquake and precipitation on the distribution of these slow‐moving landslides. We find that 33% of the detected slow‐moving landslides are distributed within 1000 m to active faults, and show a decreasing trend moving away from fault zones. This pattern strongly suggests that the active thrusting faults in this region significantly controls the distribution of slow‐moving landslides, while topography and precipitation show less impacts. Our study reveals the spatial distribution of slow‐moving landslides in a tectonic complex region with rapid orogenic process, and thus shows potential implications in geomorphology modelling and hazards evaluation for many less‐monitored, contemporary uplifting high‐mountain regions.