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Abstract   Using a NDJ-1 rotational viscometer and an AR500 rheometer, both static and dynamic viscosities of sodium silicate solutions were measured with changes of concentration, temperature, modulus (molar ratio of SiO2 to Na2O), shear rate and chemical additives. Static results show that viscosity increases monotonously with concentration varying from 15 to 55%, decreases with temperature rising from 15 to 70 °C, and has a minimum value at a modulus of about 1.8. Measured data can be fitted quantitatively either by the Krieger-Dougherty expression or the Arrhenius equation with good agreement. This fact suggests that the sodium silicate solutions exhibit the properties of a suspension, in which the silicate anions, mainly constructed of Q 1 and Q 2 groups, act as a binder; the colloidal particles mainly constructed of Q 3 and Q 4 groups and small cations, act as effective rigid particles. Dynamic results show a shear thickening property in the high shear-rate regime, and a Newtonian property in the low shear-rate regime. [ABSTRACT FROM AUTHOR]

Largescale volcanic eruptions and earthquakes are occurring frequently in the Philippines, and research has shown that slab metamorphism and diversity alter the impacts of subducted oceanic plates by changing water‒carbon productivity and interplate stability. Within the framework of the thermal evolution history of subducting slabs, the relationships between subduction zone seismicity characterized by both regular megathrust earthquakes and slow slip events of various magnitudes and long-term slab dehydration–decarbonation evolution in the Philippines remain poorly understood. Here, we constructed a comprehensive thermal model incorporating 3-D slab geometric data for the incoming plate and a 3-D subduction velocity field based on the MORVEL plate motion dataset for the Philippine subduction zone with high spatial and temporal resolutions. Our findings reveal that subduction seismicity and arc volcanism are prominent in belt-shaped regions with high thermal gradients (> 5 °C/km) and large-scale slab dehydration (> 0.05 wt%/km). Dehydration of serpentinite in ultramafic rocks in the subducting slab and decarbonation of carbonate minerals preferentially contribute to the generation and transport of fluids and carbonate melts, thus facilitating seismicity and carbon-rich magmatism. Our results suggest that slab geometry diversity-induced juxtaposed slab dehydration-decarbonation processes play a vital role in the generation of megathrust earthquakes below the forearc. [ABSTRACT FROM AUTHOR]

Compelling evidence has shown that geomagnetic disturbances in vertical intensity polarization before great earthquakes are promising precursors across diverse rupture conditions. However, the geomagnetic vertical intensity polarization method uses the spectrum of smooth signals, and the anomalous waveforms of seismic electromagnetic radiation, which are basically nonstationary, have not been adequately considered. By combining pulse amplitude analysis and an experimental study of the cumulative frequency of anomalies, we found that the pulse amplitudes before the 2022 Luding M6.8 earthquake show characteristics of multiple synchronous anomalies, with the highest (or higher) values occurring during the analyzed period. Similar synchronous anomalies were observed before the 2021 Yangbi M6.4 earthquake, the 2022 Lushan M6.1 earthquake and the 2022 Malcolm M6.0 earthquake, and these anomalies indicate migration from the periphery toward the epicenters over time. The synchronous changes are in line with the recognition of previous geomagnetic anomalies with characteristics of high values before an earthquake and gradual recovery after the earthquake. Our study suggests that the pulse amplitude is effective for extracting anomalies in geomagnetic vertical intensity polarization, especially in the presence of nonstationary signals when utilizing observations from multiple station arrays. Our findings highlight the importance of incorporating pulse amplitude analysis into earthquake prediction research on geomagnetic disturbances. [ABSTRACT FROM AUTHOR]

Electromagnetic indices play a potential role in the forecast of short-term to imminent M ≥ 5.5 earthquakes and have good application prospects. However, despite possible progress in earthquake forecasting, concerns remain because it is difficult to obtain accurate epicenter forecasts based on different forecast indices, and the forecast time span is as large as months in areas with multiple earthquakes. In this study, based on the actual demand for short-term earthquake forecasts in the Gansu–Qinghai–Sichuan region of western China, we refined the construction of earthquake forecast indicators in view of the abundant electromagnetic anomalies before moderate and strong earthquakes. We revealed the advantageous forecast indicators of each method for the three primary earthquake elements (time, epicenter, magnitude) and the spatiotemporal evolution characteristics of the anomalies. The correlations between the magnitude, time, intensity, and electromagnetic anomalies of different M ≥ 5.5 earthquakes indicate that the combination of short-term electromagnetic indices is pivotal in earthquake forecasting. [ABSTRACT FROM AUTHOR]

Geomagnetic vertical intensity polarization is a method with a clear mechanism, mature processing methods, and a strong ability to extract anomalous information in the quantitative analysis of seismogenic geomagnetic disturbances. The existing analyses of geomagnetic vertical intensity polarization are all based on the 5~100 s frequency band without refinement of the partitioning process. Although many successful results have been obtained, there are still two problems in the process of extracting anomalies: the geomagnetic anomalies that satisfy the determination criteria are still high in occurrence frequency; and the anomalies are distributed over too large an area in space, which leads to difficulties in determining the location of the epicenter. In this study, based on observations from western China, where fluxgate observation points are positioned in areas with frequent, densely distributed medium-strength earthquakes, we refined the frequency bands of geomagnetic vertical intensity polarization, recalculated the spatial and temporal evolution characteristics of geomagnetic disturbances before earthquakes, and improved the crossover frequency anomaly prediction index while promoting the application of the method in earthquake forecasting. [ABSTRACT FROM AUTHOR]

Geochemistry, Geophysics, Geosystems (G‐Cubed) is a respected Earth science journal that publishes research papers, methods, and coding applications. In 2023, the journal received 485 manuscripts and published 244 of them. The journal credits its success to the voluntary contributions of over 764 reviewers who provided more than 937 reviews. The journal expresses gratitude to the reviewers for their time and expertise, as their efforts ensure that the published papers meet the high standards expected by the research community. The journal welcomes feedback on its peer review process and anticipates exciting advancements in the field. Additionally, the document is a list of names of individuals who have contributed to a report or study, organized alphabetically. The purpose of the document is to acknowledge the participation of these individuals, who come from diverse fields, in the research or study. [Extracted from the article]

B Monolayer Silicon Monochalcogenides b The polarization electric field induced by the dipole moment in monolayer silicon monochalcogenides is suitable to separate photo-generated carriers swiftly. The 2D polar monolayer silicon monochalcogenides with the polarization electric field would be potential catalysts for photocatalytic water splitting. Polarization Electric Field in 2D Polar Monolayer Silicon Monochalcogenides SiX (X = S, Se) as Potential Photocatalysts for Water Splitting. [Extracted from the article]

In this paper, different Mn content doped potassium sodium niobate (KNMN) coatings were prepared by plasma spraying technology, and the effects of different Mn content doping on the microstructure and electrical properties of the coatings were investigated. The results showed that the mechanical and electrical properties of the coatings showed a trend of increasing and then decreasing with the increase of Mn doping content, and the best mechanical and electrical properties of the coatings were obtained when the Mn doping content was 2 mol%. [ABSTRACT FROM AUTHOR]

Changing thermal regime is one of the key mechanisms driving seismogenic behaviors at cold megathrusts, but it is difficult to interpret warm subduction zones such as Vanuatu for the temperatures are higher than that accommodates shallow brittle failures. We construct a 3-D thermomechanical model to clarify the thermal structure that controls tectonic seismicity in Vanuatu and predict a warm circumstance associated with abundant seismicity. Results reveal a heterogeneous slab ranging from 300 °C to over 900 °C from the Moho to subvolcanic depth. The subduction seismicity corresponds well to the plate interface where dynamic thermal dehydration is focused. The transformation from hydrated basalts to eclogites along the slab facilitates the occurrence of intense earthquakes and slips. Multistage mineralogical metamorphism affects the dynamic stability of megathrusts and favors the generation of active interplate large events. Therefore, slab thermal dehydration plays a greater role than slab temperature condition in influencing the subduction earthquake distribution in warm subduction systems. [ABSTRACT FROM AUTHOR]

Tectonic extrusion bypassing the eastern Himalayan syntaxis results in a significant increase in regional stress instability and the associated frequent occurrence of earthquakes in southern Yunnan, China. However, the stress field, and the relationship between the focal mechanism of earthquakes and stress evolution in southern Yunnan, remain enigmatic. In this paper, using a modified grid point test method, we calculated the focal mechanism of ML ≥ 2.5 earthquakes in southern Yunnan (22–25° N, 100–104° E) from January 2009 to June 2023. Utilizing the solutions of historical earthquake focal mechanisms, we obtained the present-day regional tectonic stress field in southern Yunnan via inversion. The results indicate complex and diverse seismic focal mechanisms, and the main types of earthquakes are strike-slip events, followed by normal fault and reverse fault events. The orientations of the maximum and minimum principal stress axes rotate in a clockwise direction from northeast to southwest. The internal stress orientation distribution of the rhombic Sichuan–Yunnan block in the study area is consistent, and the block boundary zone is the site where stress deflection occurs, and the regional tectonic stress field is influenced by the interaction among different blocks. The distribution of R-value in the Lamping–Simao block gradually increases from north to south, indicating that the compressive stress required for material transport becomes relatively small. Combined with the geological and tectonic background of the study area, our results suggest that the speed of block movement gradually decreases from north to south; the distribution of R-value in the South China block is significantly smaller than that of the interior of the Sichuan–Yunnan rhombus, and the proportion of compressive stresses is larger, indicating a stronger extrusion in this region, which may be related to the fact that the Sichuan–Yunnan rhombus is strongly resisted by the South China block in the east. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) polar monolayer with a polarization electric field can be used as a potential photocatalyst. In this work, first principle calculations were used to investigate the stability and photocatalytic properties of 2D polar monolayer SiTe as a potential promising catalyst in water-splitting. Our results show that the 2D polar monolayer SiTe possesses an indirect band gap of 2.41 eV, a polarization electric field from the (001) surface to the (00 1 ¯) surface, a wide absorption region, and a suitable band alignment for photocatalytic water-splitting. We also discovered that the photocatalytic activity of 2D polar monolayer SiTe could be effectively tuned through strain engineering. Additionally, strain engineering, particularly compressive strain in the range from −1% to −3%, can enhance the photocatalytic activity of 2D polar monolayer SiTe. Overall, our findings suggest that 2D polar monolayer SiTe has the potential to be a promising catalyst for photocatalytic water-splitting using visible light. [ABSTRACT FROM AUTHOR]

AZO/Ag(Ti)/AZO, AZO/Ti/Ag/AZO, and GAZO/Ti/Ag/GAZO multilayer transparent conductive films were deposited on the glass substrate by magnetron sputtering at room temperature. The effects of different Ti power co-sputtered with Ag and Ti as a seed layer for Ag films on the optical, electronic and structural properties of multilayer films were investigated. In addition, the influences of the oxide layer and Ti/Ag layer thicknesses on the photoelectric properties of multilayer films were further studied. The experimental results show that Ti as a seed layer changes the growth pattern of Ag. AZO/Ti/Ag/AZO and GAZO/Ti/Ag/GAZO films exhibit high photoelectric performance. Multilayer films with 50 nm GAZO and 12 nm Ti/Ag displayer low sheet resistance of 5.88 Ω sq−1, high average light transmittance in the visible range of 94.38%, and the figure of merit is above 1000 Ω−1. The GAZO/Ti/Ag/GAZO films show high transmittance and low resistivity, which can be used in various photoelectronic fields. [ABSTRACT FROM AUTHOR]

Because of the steep subduction of a highly concave slab, researchers have characterized megathrusts under the Marianas as among the coldest and curviest plate coupling interfaces in various circum-Pacific subduction zones. Seismic tomography indicates that the heterogeneous underlying plate varies markedly in its subduction angle, velocity, and flexure along the strike and dip, while their effects on the thermal structure and intraslab earthquake occurrence remain enigmatic. By incorporating the 3-D MORVEL velocity and state-of-the-art slab geometry into thermomechanical modeling, we estimated the 3-D subduction thermal state and hydrothermal regime below the Marianas. We find that (1) the concave slab geometry and the complexity of the intraslab velocity variation in the Marianas are associated with a heterogeneous along-strike thermal regime and a cold mantle wedge beneath the central Marianas; (2) amphibolitization and eclogitization of subducted oceanic crust cause variations in fluid pressure and fluid release from the subduction interface, which may influence the distribution of interface seismicity in the Mariana system; (3) the concentration of active hydrothermal vents in the trench > 8 km deep is accompanied by a large temperature gradient and subsequent remarkable slab dehydration in the southern Marianas; and (4) slab dehydration (> 0.02 wt%/km) from 30 to 80 km indicates notable fluid release and potential fluid migration in subduction channels, which may correspond to the large water flux at depth beneath the Marianas. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. On 12 June 2021, an earthquake with MS 5.0 occurred in Yingjiang, adjacent to eastern Myanmar, where seismic activity is frequent due to plate collision. To explore the mechanism of this earthquake, the regional stress field of the Yingjiang zone was inverted using the focal mechanisms of 187 historical earthquakes in this area. Furthermore, based on the obtained orientation of the principal stress axes and the stress shape ratio, the fault slip tendency (Ts) was also estimated to evaluate fault instability in the study area. The stress variation results show that the diffusion and migration of the aftershocks suggested strike–slip-type stress accumulation in Yingjiang with a principal compressive stress axis direction-oriented NNE–SSW. Fault slip tendency results show that the seismogenic faults feature strikes within the ranges of 40~80° and 110~150° and dips of 60~90° and exhibit enhanced stress coupling. The distribution of the aftershock sequence is conjectured to have a high correlation with local fluid migration and was likely controlled by the hydrated rock-induced ruptures of the stressed fault systems near the source region. This study provides insights into potential earthquake risks in this region. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. Well water levels can reflect the stress placed on a confined subsurface aquifer system in a similar manner to a strain meter. Based on observations of the geophysical field in Lhasa combined with digital data recorded at an underground fluid well at the Lhasa geomagnetic station in recent years, we comprehensively analyzed the characteristics of co-seismic changes caused by 14 different-magnitude M ≥ 5 earthquakes recorded in the well. The results show that (1) the co-seismic changes in water temperature and water level are different; the water level exhibits oscillation-type changes, while the water temperature variations indicate first heating and subsequent recovery. (2) The co-seismic changes are related to the epicentral distance, magnitude and focal depth of the earthquake. The closer the epicenter is to the well, the earlier the co-seismic responses occur, but the time interval between the co-seismic changes in the water level and temperature differs. (3) The co-seismic ratio of the water temperature is higher than that of the water level; this may be related to faulty water level instrumentation or segmented records. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. Fast and slow earthquakes are predominantly generated along faults constituting active plate boundaries. Characterized by repeated devastating earthquakes and frequent slow slip events and tremors, the Alaska megathrust presents a chance to understand the complicated dynamics of a subduction system changing from steep to shallow dips associated with enigmatically abundant fast and slow seismic events. Based on three-dimensional thermal modeling, we find that the downgoing metamorphosed oceanic crust containing bound water releases a large amount of fluid and causes the recurrence of fast and slow earthquakes by elevated pore fluid pressure and hydrofracturing. The seismogenic interface and the slow slip events (SSEs) identified beneath the Upper Cook Inlet coincide well with the slab metamorphic dehydration regions. The observed slow earthquakes with quasi-stable fault slips preferentially occur, accompanied by high dehydration and temperature downdip along the transition zone. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. Long-term stress accumulation influenced by coseismic stress changes and postseismic viscoelastic relaxation is considered critical to triggering giant earthquakes. Nevertheless, how the stress increase is interrupted by aftershocks and how it influences the megaseismic cycle remain enigmatic. In this study, based on the Mohr–Coulomb failure criterion at the nucleated segments of the 2008 great Sichuan earthquake, the stress variation associated with four M > 6 aftershocks was calculated for the period from 2010 to 2017. The results show that (1) the spatial distribution of coseismic stress change is correlated with the rupture pattern of large events and has a fundamental impact on triggering subsequent earthquakes and (2) postseismic viscoelastic relaxation leads to increased Coulomb stress accumulation at the northern and southern edges of the seismogenic Longmenshan fault, which results in enhanced fault instability and the potential for future large events. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. The probabilistic seismic hazard analysis (PSHA) method is effectively used in an earthquake risk probability evaluation in seismogenic regions with active faults. In this study, by focusing on the potential seismic source area in Najin Lhasa, southern Tibet, and by incorporating the PSHA method, we determined the seismic activity parameters and discussed the relationship of ground motion attenuation, the seismic hazard probability, and the horizontal bedrock ground motion acceleration peak value under different transcendence probabilities in this area. The calculation results show that the PSHA method divides the potential source area via specific tectonic scales and detailed tectonic markers, which reduces the scale of the potential source area and better reflects the uneven spatial distribution of seismic activity in the vicinity of Najin. The corrected attenuation relationship is also in line with the actual work requirements and is suitable for earthquake risk analysis. In addition, the major influences on the peak acceleration of ground motion in the study area are mainly in the potential source areas of Qushui (M7.5), Dangxiong (M8.5), and Kangma (M7.5). The peak horizontal ground motion acceleration (PGA) with a transcendence probability of 10% in 50 years is 185.9 cm/s2, and that with a transcendence probability of 2% in 50 years is 265.9 cm/s2. [ABSTRACT FROM AUTHOR]

Single-stationed geomagnetic vertical intensity polarization (GVIP) anomalies have demonstrated good predictions of the occurrence of large earthquakes in Japan. Nonetheless, due to the lack of a previously densified geomagnetic network, how the multistationary GVIP anomaly (MGVIPA) corresponds to impending earthquakes remains poorly understood. Based on the newly constructed geomagnetic network from 2014 in Qinghai, China, which is composed of 23 electromagnetic stations, we suggested an MGVIPA method to analyze the correlation with large earthquakes since 2015. The results show that (1) the occurrence of MGVIPA is characterized by clusters in time that continue in a short period; (2) the spatial distribution of MGVIPA usually occurs with high values synchronously at several places over the same period; and (3) the Mw ≥ 6 earthquakes occurred in the regions indicated by MGVIPA within a period ranging from 3 months to 1 year from 2015 to 2021 in Qinghai, China. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. Precursory earth tidal triggering is believed to influence earthquake timing preferentially when a region is critically stressed. However, whether and how the recurrence of aftershocks after a giant earthquake is affected by tidal triggering remains perplexing. To provide insight into this study, we utilized the Schuster test to explore the tidally induced stress variation correlated with the 2011 Mw 9.0 Tohoku earthquake aftershock sequence by determining the tidal phase angle at the occurrence time of events and the periodic characteristics of the aftershocks. Our results show that the aftershocks were triggered by short-period tides, including semidiurnal and diurnal tides. The rupture associated with the mainshock likely resulted in a critical stress state in the focal region, which is conducive to tidal triggering. We subdivided the aftershock catalog into several subsets, using a depth of 30 km and a magnitude of 5 as discriminators. The analysis of these subsets reveals that weaker and deeper earthquakes are best correlated with Earth tides, which will be helpful to investigate the mechanisms of tidal correlation. [ABSTRACT FROM AUTHOR]

Featured Application: Resource and environmental effects of the Tibetan Plateau. Himalayan orogenesis remains enigmatic in terms of Tibetan Plateau geodynamics originating from the Cenozoic India–Eurasian continental collision. India underthrusts below Tibet to the Yarlung–Tsangpo suture, which has been identified as the northernmost boundary for underplating. However, the way in which the historical evolution of continental subduction induces plateau uplift and the way it controls the variation in uplift between outboard and inboard areas is still unclear. To interpret the evolutionary mechanisms involved in the Himalayan growth history, we constructed different 3-D dynamic models at important stages to address these questions related to the formation of the Himalayas on the basis of paleoenthalpy evidence encoded in fossil leaves from recently documented assemblages in southern Tibet. The results show that (1) the effect of crustal thickening was the predominant factor in the early evolution from the Paleocene to the early Eocene, which resulted in a moderate growth rate. (2) The consecutive slab break-off eastward from the western syntaxis and the associated slab rebound significantly accelerated orogenesis from the late Eocene to the Oligocene. The upwelling asthenospheric flow was a key control of increasing crustal buoyancy, which resulted in the fastest growth of the Himalayas during the early Miocene. (3) Thereafter, the gradually enhanced monsoon and surface erosion during accompanying the increasing mountain height resulted in a slowdown of the orogenic rate, which counterbalanced the buoyant force produced by asthenospheric flow driving continuous Himalayan growth. [ABSTRACT FROM AUTHOR]

The transition from cold forearc to hot arc is considered fundamental to subduction dynamics. However, the range and depth of the cold nose changing significantly along the strike are difficult to constrain. By incorporating the three‐dimensional high‐resolution slab topography and MORVEL plate motion field to constrain thermomechanical modelling, we estimate the subduction thermal state and petrological dehydration in Izu‐Bonin. The multilayered hydrothermal regime gradually transitions from cold to less cold forearc, associated with a large‐scale subduction dewatering process varying along the strike. The dehydration embrittlement resulting from eclogitization and harzburgitization influences the occurrence of fast to slow earthquakes on megathrusts. Impressively, the cold nose is constrained to a depth of 60 km between the arc and Moho‐depth plate interface. The lowered temperature and delay of rock harzburgitization in the cold center of the subducted plate at depth contribute to the occurrence of deep earthquakes below the hot backarc interface. [ABSTRACT FROM AUTHOR]