Feed aggregator

On Friday 23 August, a magnitude 4.8 earthquake near Muswellbrook, New South Wales, shook the state. The earthquake caused local damage and Geoscience Australia received more than 3,600 felt reports, including from Sydney and Canberra, up to 360 kilometers away.

Abstract

Mafic magma recharge of crustal reservoirs and subsequent magma mixing has been considered a direct trigger of volcanic eruptions. However, although recharge frequently occurs in many active volcanoes, it rarely leads to an eruption immediately, making its role as a trigger ambiguous. Sakurajima volcano, Japan, has vigorously erupted three times since the 15th century following a common process; mixed magmas after recharge were once stored in a shallow, thick conduit before each eruption (conduit pre-charge). We reconstructed the magma migration with a high time resolution by diffusion modeling on orthopyroxene and magnetite. Orthopyroxene phenocrysts recorded prolonged diffusive re-equilibration timescales of years or more after recharge-and-mixing. Magnetite, which has the fastest elemental diffusivity among the phenocrysts examined, predominantly lacks zoning. This demonstrates that the mineral phase was re-equilibrated with surrounding magma and homogenized via elemental diffusion after the final magmatic perturbation, implying the final repose of the shallow pre-charged magma body for more than several tens of days. After this shallow stagnation period, the Plinian magmas began to ascend and reached the surface within 55 hr. Mass balance calculations show that crystallization-driven vesiculation upon pre-charge can produce overpressure sufficient to cause an eruption. The Sakurajima cases demonstrate the hierarchical timescales of trigger processes leading to the explosive eruptions.

Abstract

Simulating dynamic rupture of fault systems can be computationally demanding, as it requires reproducing complex fault geometry and accurately capturing waves propagating away from the rupture front. It is in particular challenging to predict an initial stress state consistent with fault geometries, heterogeneous distribution of surrounding materials, and far-field tectonic loading. While standard techniques such as contact analysis and Lagrangian multipliers can be used to model the fault, it can lead to significant computational overhead in FEM. We extended Particle Discretization Scheme-FEM, which provides numerically efficient crack treatment, without requiring contact analysis, to simulate dynamic fault rupture as a frictional crack propagating along a pre-existing shear crack surface. Initial stress, which is consistent with initial frictional forces, material distribution and fault geometry, is derived using Coulomb friction and far-field boundary conditions. The study first demonstrates the ability of the numerical method to reproduce a 2D ideal supershear scenario, and the underlying Burridge-Andrew rupture mechanism. The methodology is then applied to the large scale simulation of the 2018 Palu earthquake on the Palu-Koro fault. The simulation successfully reproduces the early and sustained supershear rupture which was observed for the Palu earthquake. Also, it indicates that the presence of an off-fault damage zone can contribute to the low rupture velocity measured during the earthquake. Unlike sub-Rayleigh earthquakes, the shockwave propagation was observed to lead to significant amplitudes of the ground motion even far from the fault.

No abstract is available for this article.

Author(s): Rune Højlund Marholt, Mads Givskov Senstius, and Stefan Kragh Nielsen

The Wentzel, Kramers, and Brillouin (WKB) approximation of geometrical optics is widely used in plasma physics, quantum mechanics, and reduced wave modeling, in general. However, it is well-known that the approximation breaks down at focal and turning points. In this paper, we present an unsupervise…

[Phys. Rev. E 110, 025208] Published Tue Aug 27, 2024

Comparison of Inductive and Capacitive End Couplings in the Design of a Combline Microwave Cavity Filter for the E1 Galileo Band
Enrico Boni, Giacomo Giannetti, Stefano Maddio, and Giuseppe Pelosi
Adv. Radio Sci., 22, 1–8, https://doi.org/10.5194/ars-22-1-2024, 2024
The manuscript is about the design and experimental characterization of microwave filters to be used for satellite communication, especially for the E1 Galileo band. To feed the filter with microwave power, inductive and capacitive coupling schemes are adopted and compared. The measurement results show a good agreement with simulated ones. The outcome of this research is to compare the inductive and capacitive coupling schemes in the design of combline cavity filters.

Abstract

The sensitivity of tree growth to precipitation regulates their responses to drought, and is a crucial metric for predicting ecosystem dynamics and vulnerability. Sensitivity may be changing with continuing climate change, yet a comprehensive assessment of its change is still lacking. We utilized tree ring measurements from 3,044 sites, climate data and CO2 concentrations obtained from monitoring stations, combined with dynamic global vegetation models to investigate spatiotemporal changes in the sensitivity over the past century. We observed an increasing sensitivity since around 1950. This increased sensitivity was particularly pronounced in arid biomes due to the combined effect of increased precipitation and elevated CO2. While elevated CO2 reduced the sensitivity of the humid regions, the intensified water pressure caused by decreased precipitation still increased the sensitivity. Our findings suggest an escalating vulnerability of tree growth to precipitation change, which may increase the risk of tree mortality under future intensified drought.

Abstract

Negative Air Ions (NAIs), essential for environmental and human health, facilitate air purification and offer antimicrobial benefits. Our study achieves hourly estimations of NAIs using a machine learning framework, developed from a multi-layer selection pipeline of over 200 variables, to identify the key determinants critical for adapting to high-resolution NAIs dynamics. Addressing site sparsity and NAIs volatility, we introduced a hybrid stacking incorporating pseudo sites generated from Kriging Spatiotemporal Augmentation (KSTA) to mitigate spatial overfitting. Our approach, validated in Zhejiang, China, demonstrates exceptional accuracy, achieving R 2 values of 0.90 (sample-based), 0.85 (temporal-based), and 0.79 (site-based). This work not only sheds light on NAIs behavior in relation to diurnal shifts, land use, and environmental events, but also integrates a health grading system, enhancing public health strategies through precise air quality assessment.

Abstract

In recent years, it has been found that magnetic dip caused by diamagnetic motion of injected plasma can provide an appropriate environment for excitation of electromagnetic ion cyclotron (EMIC) waves. These findings have been widely reported in the Earth's magnetic environment. However, it has rarely been reported in Jupiter's magnetic environment. This paper reports the characteristics of EMIC waves observed by Juno in the magnetic dip of Jupiter. Multiple-band EMIC waves are observed in frequency range from 10−3 Hz to several Hz. The theoretical analysis shows that in this event both He+ band and O+ band EMIC waves can be constrained in the magnetic dip, which is consistent with the wave emissions observed inside the magnetic dip. Our result provides the first evidence that EMIC wave can be ducted inside a magnetic dip in Jupiter's magnetosphere.

Abstract

On 18 November 2023, SpaceX launched the Starship, the tallest and the most powerful rocket ever built. The Super Heavy engine separated from the Starship spacecraft and exploded at 90 km of altitude, while the main core Starship continued to rise up to 149 km and exploded after ∼8 min of flight. In this work, we used data from ground-based GNSS receivers and we analyzed total electron content (TEC) response to the Starship flight and the two explosions. For the first time, we observed large-distance northward propagation of intensive 2,000 km V-shaped ionospheric disturbances from the rocket trajectory. The observed perturbations, most likely, represent shock waves propagating with the cone angle of ∼14° on the North and ∼7° on the South against the flight track that corresponds to the Mach angle of the shock waves in the lower atmosphere. The Starship explosion also produced a non-chemical depletion in the ionospheric TEC.

Abstract

The Arctic rapidly warms and sea ice retreats, a large fraction of organic carbon (OC), currently stored in coastal permafrost will be released into the marine system. Once reintroduced into the active carbon cycle, this material will either be decomposed or buried on the shelf depending on its hydrodynamic and chemical properties. Currently, carbon estimates are based on bulk measurements, which does not take the hydrodynamic pathway of different fractions into account. Therefore, eight coastal permafrost locations have been sampled along the Canadian Beaufort Sea Coast, hydrodynamically fractionated and analyzed for their C, N, 13C and 14C content. We found that the matrix-free fraction (low density <1.8 g/cm3, and high-density >1.8 g/cm3; <38 μm) account for 77%–98% of the OC. By using a coastal classification combined with field data, our results showed that short coastal segments can become key players in delivering matrix-free, easily degradable OC to the marine system.

Southern China experienced an extreme drought that persisted from summer to autumn in 2022, ranking as the most severe drought since 1980. The reason for the occurrence of this extreme drought event was investigated. It shows that both the Eurasian warming and the tropical sea surface temperature (SST) played key roles in the occurrence of this event.

At the end of the Paleocene and beginning of the Eocene epochs, between 59 to 51 million years ago, Earth experienced dramatic warming periods, both gradual periods stretching millions of years and sudden warming events known as hyperthermals.

Publication date: Available online 14 August 2024

Source: Advances in Space Research

Author(s): B. Olugbon, E.O. Oyeyemi, A. Kashcheyev, A.B. Rabiu, A.A. Obafaye

Publication date: Available online 14 August 2024

Source: Advances in Space Research

Author(s): Leonid Tkachev, Aleksandr Blinov, Gali Garipov, Andrey Grinyuk, Khussein Karatash, Pavel Klimov, Maria Lavrova, Il H. Park, Oleg Saprykin, Eldos Sholtan, Ivan Yashin

The GEOEO North of Greenland 2024 Expedition, organized by the Swedish Polar Research Secretariat aboard the icebreaker Oden, has made history as the first vessel to reach the remote Victoria Fjord in North Greenland.

High-altitude balloon-launched uncrewed aircraft system measurements of atmospheric turbulence and qualitative comparison with infrasound microphone response
Anisa N. Haghighi, Ryan D. Nolin, Gary D. Pundsack, Nick Craine, Aliaksei Stratsilatau, and Sean C. C. Bailey
Atmos. Meas. Tech., 17, 4863–4889, https://doi.org/10.5194/amt-17-4863-2024, 2024
This work summarizes measurements conducted in June 2021 using a small, uncrewed, stratospheric glider that was launched from a weather balloon to altitudes up to 30 km above sea level. The aircraft conducted measurements of wind speed and direction, pressure, temperature, and humidity during its descent as well as measurements of infrasonic sound levels. These data were used to evaluate the atmospheric turbulence observed during the descent phase of the flight.

Estimating hourly ground-level aerosols using GEMS aerosol optical depth: A machine learning approach
Sungmin O, Ji Won Yoon, and Seon Ki Park
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-142,2024
Preprint under review for AMT (discussion: open, 0 comments)
Air pollutants such as PM10 or PM2.5 can cause adverse public health and environment effects, therefore their regular monitoring is crucial to keep the pollutant concentrations under control. Our study demonstrates the potential of high-resolution aerosol optical depth (AOD) data from the Geostationary Environment Monitoring Spectrometer (GEMS) satellite to estimate ground-level PM concentrations using a machine learning model. 

It took more than 25 years for Rhonda MacDonald and her family to transform their 41-hectare property on the Shackan Indian Band Lands, south of Merritt, BC, into a vibrant business and homestead—but a massive 2022 debris flow changed everything in just 25 minutes.

Abstract

Precipitation δ18O has offered valuable insights into the evolution of the Asian monsoon. Recent researches focusing on precipitation Δ′17O has enhanced our understanding by offering new perspectives beyond those of δ18O, revealing insights into vapor sources and continental recycling. Nevertheless, there remains a lack of interannual triple oxygen isotope data, particularly in the Asian monsoon region. In this study, we analyzed the triple oxygen isotopes and hydrogen isotopes in monthly precipitation samples collected from Chongqing in Southwest China between 2019 and 2022 A.D. Seasonal variations in δD, δ18O, δ17O, and d-excess values were observed, with lower values during the rainy season and higher values during the dry season, highlighting the impact of changes in moisture sources and local meteorological conditions on seasonal shifts in δD, δ18O, and δ17O. While, mean Δ′17O values were higher in rainy season and lower in dry season. Notably, during rainy season, there is a negative correlation between monthly Δ′17O values and the RH of the vapor source area, as well as a positive correlation with d-excess. Recalculated Δ′17O values based on RH of oceanic moisture source, are higher than the measured values for this period, indicating the contribution of terrigenous moisture to precipitation in SW China. Precipitation Δ′17O values provide a more precise reflection of changes in moisture source, continental recycling, and evapotranspiration processes that drive water cycling compared Integrating modeling works in future will facilitate the use of precipitation Δ′17O values to quantify the impact of different moisture source on precipitation.