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SummaryDispersion curves of surface waves are widely used for the inversion of subsurface structures. To extract dispersion curves, many methods have been developed. Among them, multichannel analysis of surface waves such as slant stack and frequency-Bessel transform can extract not only the fundamental mode but also overtones. Inversion with overtones is proven to be more stable and has better resolution at greater depths. However, with a limited number of array receivers, artifacts and misfits due to array-layout effects arise in the dispersion spectra and impede the identification of dispersion curves. We evaluate the array-layout effects in the frequency-Bessel transform and calculate the array response functions which can help to mitigate artifacts and calibrate dispersion curves. We apply this technique to synthetic simulated, active source and ambient noise data. The artifacts caused by array-layout effects can be mitigated, which helps the identification of dispersion curves. We further calculate the Pearson correlation coefficient between the array response function and the dispersion spectrum section. It is used to calibrate the biases produced by the array-layout effects if we select dispersion curves by maximum values. The confidence intervals of the dispersion curves are then determined based on the correlation coefficients. It is helpful for the design of array layouts according to the investigation depths of interest.

SummaryPowerful infrasound (acoustic waves <20 Hz) can be produced by explosive volcanic eruptions. The long-range propagation capability, over hundreds to thousands of kilometers, of atmospheric infrasound motivates the development of regional or even global scale volcano-infrasound monitoring systems. Infrasound propagation paths are subject to spatiotemporal atmospheric dynamics, which lead to deviations in the direction-of-arrival (back-azimuth) observed at sensor arrays and contribute to source location uncertainty. Here we further investigate the utility of empirical climatologies combined with 3-dimensional ray-tracing for providing first-order estimates of infrasound propagation paths and back-azimuth deviation corrections. The intended application is in scenarios requiring rapid or precomputed infrasound propagation calculations, such as for a volcano-infrasound monitoring system. Empirical climatologies are global observationally based function fitting models of the atmosphere, representing robust predictors of the bulk diurnal to seasonal atmospheric variability. Infrasound propagation characteristics have previously been shown to have strong seasonal and diurnal components. At the International Monitoring System (IMS) infrasound station IS22, New Caledonia, quasi-continuous multi-year infrasound array detections show oscillating azimuthal variations for arrivals from volcanoes in Vanuatu, including Yasur (∼400 km range), Ambrym (∼670 km range), and Lopevi (∼650 km range). We perform 3-dimensional ray-tracing to model infrasound propagation from the Ambrym and Yasur volcano locations to IS22 every six hours (00:00, 06:00, 12:00, and 18:00 UTC) for every day of 2004 and 2019 for Ambrym and Yasur, respectively and evaluate the results as compared to the multi-year observations. We assess a variety of models and parameterizations, including both empirical climatologies and hybrid descriptions; range-independent and range dependent atmospheric discretizations; and unperturbed and perturbed range-independent empirical climatologies. The hybrid atmospheric descriptions are composed of ERA 5 reanalysis descriptions from the European Centre for Medium-Range Weather Forecasts (ECMWF) below ∼80 km altitude combined with empirical climatologies above. We propose and employ simple parametric perturbations to the empirical climatologies, which are designed to enhance the stratospheric duct and compensate for missing gravity wave perturbations not included in the climatologies, and thereby better match observations. We build year-long back-azimuth deviation interpolations from the simulations and compare them with three different multi-year array detection datasets from IS22 covering from 2003 up to 2022. Through a systematic comparison, we find that the range-independent empirical climatologies can capture bulk azimuth deviation variability and could thus be useful for rapid infrasound propagation calculation scenarios, particularly during favorable sustained propagation ducting conditions. We show that the hybrid models better describe infrasound propagation during periods of weak stratospheric ducting and during transient atmospheric changes such as stratospheric wind reversals. Overall, our results support the notion that climatologies, if perturbed to compensate for missing gravity wave structure, can improve rapid low-latency and precomputed infrasound source discrimination and location procedures.

Abstract

The Rashid-1 lunar rover represented the first attempt by the United Arab Emirates to explore the surface of the Moon. The mission of Rashid-1 was supposed to begin only a few hours following the planned landing by the iSpace Hakuto-R M1 lunar lander inside the Atlas crater of the Moon. Unfortunately, the lander was unable to successfully complete the landing maneuver and it crashed on the surface of the Moon destroying both itself and its payloads in the process. In this paper, we present the characterization of the optical image acquisition systems onboard the Rashid-1 rover which consisted of two wide-field ( \(82^{\circ } \times 82^{\circ }\) ) identical cameras aptly named CAM-1 and CAM-2 and mounted on the front and back of the rover respectively. Additionally, a third high resolution optical imager (CAM-M) with a spatial resolution of approximately 27 μm/pixel was placed on the front of the rover and was tasked with obtaining what would have been, at that time, the highest resolution in-situ images ever taken of the lunar regolith. We discuss the basic calibration processes such as the thermal, radiometric, color, distortion and perspective corrections of the three optical systems. We also provide an overview of both the onboard as well as the ground processing steps that were set up to receive and examine the images the rover would have sent from the lunar surface.

Abstract

Metasomatism refers to the process during which a pre-existing rock undergoes compositional and mineralogical transformations associated with chemical reactions triggered by the reaction of fluids which invade the protolith. It changes chemical compositions of minerals, promotes their dissolution and precipitation of new minerals. In this paper, we review metasomatic alteration of type 3 ordinary (H, L, LL) and carbonaceous (CV, CO, CK) chondrites, including (i) secondary mineralization, (ii) physicochemical conditions, (iii) chronology (53Mn-53Cr, 26Al-26Mg, 129I-129Xe) of metasomatic alteration, (iv) records of metasomatic alteration in H, O, N, C, S, and Cl isotopic systematics, (v) effects of metasomatic alteration on O- and Al-Mg-isotope systematics of primary minerals in chondrules and refractory inclusions, and (vi) sources of water ices in metasomatically altered CV, CO, and ordinary chondrites, and outline future studies.

In this paper, we augment airborne gravity anomaly data from Antarctica, expanding the coverage area by 10.4% based on the existing data set. These data are combined with a gravity field model to establish a m...

Carbon dioxide in the atmosphere is increasing at rates that are incompatible with staying below 1.5 degrees Celsius (2.7 degrees Fahrenheit) of global warming, a Met Office study warns.

Abstract

Latest harmonic developments of the Earth tide-generating potential (TGP), e.g., HW95 (Hartmann and Wenzel in Geoph Res Lett 22:3553, 1995), RATGP95 (Roosbeek in Geophys J Int 126:197, 1996), KSM03 (Kudryavtsev in J Geodesy 77:829, 2004), include a number of terms caused by the joint effect of the Earth’s polar flattening (that can be numerically described by the \({J}_{2}\) geopotential coefficient) and the Moon/the Sun gravitational attraction. In the present study, we additionally consider the effect of the Earth’s equatorial flattening due to the Earth’s triaxiality. Explicit analytical expressions for the relevant part of the TGP are derived. New terms of the TGP development due to the Earth’s triaxial figure are found. Amplitudes of nineteen of them exceed the threshold level of 10–8 m2s−2 used by the modern tidal potential catalogs. Three of the new terms have the frequency sign opposite to that of the Earth rotation. It is not the case for any previously known term of the Earth TGP development. Every term has a new feature that an integer multiplier of the mean local lunar time used in its argument is not equal to the order of the spherical harmonic associated with the term. It necessitates a relevant modification of the standard HW95 format for representing the Earth TGP. The new terms are suggested for including in the current and future tidal potential catalogs.

Abstract

On February 6, 2023 the Kahramanmaraş Earthquake Sequence caused significant ground shaking and catastrophic losses across south-central Türkiye and northwest Syria. These seismic events produced ionospheric perturbations detectable in Global Navigation Satellite System (GNSS) total electron content (TEC) measurements. This work aims to develop and incorporate a near-real-time (NRT) ionospheric disturbance detection method into JPL’s GUARDIAN system. Our method uses a Long Short-Term Memory (LSTM) neural network to detect anomalous ionospheric behavior, such as co-seismic ionospheric disturbances among others. Our method detected an anomalous signature after the second \(M_w\)  7.5 earthquake at 10:24:48 UTC (13:24 local time) but did not alert after the first \(M_w\)  7.8 earthquake at 01:17:34 UTC (04:17 local time), which had a visible disturbance of smaller amplitude likely due to lower ionization levels at night and potentially the multi-source mechanism of the slip.

Plain Language Summary Seismic activity, including the destructive Kahramanmaraş Earthquake Sequence on February 6, 2023 in the Republic of Türkiye, result in vertical ground displacement that cause atmospheric waves. These waves propagate upwards to the outer atmosphere, disturbing the ionospheric electron content. This disturbance impacts the signals broadcast by positioning satellites (such as GPS) and received by ground-based receivers. If the receiver position is known, the impact to these signals can be used to measure the electron density disturbance caused by these seismically-induced atmospheric waves. Such studies usually rely on being aware of the event a priori. Using deep learning neural networks, we instead aim to detect anomalous signals automatically. We propose to utilise this method to detect seismically-induced disturbances over a large geographical area. The detection method proposed in this paper successfully detected an anomalous event in the ionosphere approximately ten minutes after the second earthquake in the Kahramanmaraş Earthquake Sequence.

Publication date: Available online 2 December 2024

Source: Earth and Planetary Science Letters

Author(s): Shuo Chen, Pu Sun, Yaoling Niu, Pengyuan Guo, Tim Elliott, Remco C. Hin

Publication date: Available online 2 January 2025

Source: Advances in Space Research

Author(s): Bo Meng, Leyu Chen, Haichao Gui, Rui Zhong

Publication date: Available online 2 January 2025

Source: Advances in Space Research

Author(s): XiaoMing Li, HaoJun Li, Zhicheng Li

Publication date: Available online 2 January 2025

Source: Advances in Space Research

Author(s): L.F. Chernogor

Publication date: Available online 2 January 2025

Source: Advances in Space Research

Author(s): K.V. Beluchenko, M.V. Klimenko, V.V. Klimenko, K.G. Ratovsky, A.M. Vesnin

Publication date: 1 January 2025

Source: Advances in Space Research, Volume 75, Issue 1

Author(s): D. Sierra-Porta

Publication date: 1 January 2025

Source: Advances in Space Research, Volume 75, Issue 1

Author(s): Yuqing Liu, Hu Wang, Lina He, Hongyang Ma, Yingying Ren, Yafeng Wang, Jing Jiao, Yamin Dang

Publication date: 1 January 2025

Source: Advances in Space Research, Volume 75, Issue 1

Author(s): Ehsan Abbasali, Amirreza Kosari, Majid Bakhtiari

Extreme climate events endanger groundwater quality and stability when rain water evades natural purification processes in the soil. This was demonstrated in long-term groundwater analyses using new analytical methods, as described in a recent study in Nature Communications. As billions of people rely on sufficient and clean groundwater for drinking, understanding the impacts of climate extremes on future water security is crucial.

Directly measuring soil carbon rather than relying on predictive models can provide hard evidence of how much carbon is being stored, allowing for better assessments of confidence in carbon markets for croplands, according to a study co-authored by Yale School of the Environment scientists and recently published in Environmental Research Letters.

The Arctic is heating up particularly fast as a result of global warming—with serious consequences. The widespread permafrost in this region, where soils currently store twice as much carbon as the atmosphere, is thawing. Scientists are using increasingly detailed climate models to investigate what this means for the global climate and which striking feedbacks need to be taken into account.

SummaryStress accumulation on the plate interface of subduction zones is a key parameter that controls the location, timing and rupture characteristics of earthquakes. The diversity of slip processes occurring in the megathrust indicates that stress is highly variable in space and time. Based on GNSS and InSAR data, we study the evolution of the interplate slip-rate along the Oaxaca subduction zone, Mexico, from October 2016 through October 2020, with particular emphasis on the pre-seismic, coseismic and post-seismic phases associated with the June 23, 2020 Mw 7.4 Huatulco earthquake (also known as La Crucecita earthquake), to understand how different slip regimes contribute to the stress accumulation in the region. Our results show that continuous changes in both the aseismic stress-releasing slip and the coupling produced a high stress concentration (i.e., Coulomb Failure Stress (CFS) of 80 kPa) prior to the event on the region with the highest moment release of the Huatulco earthquake (between 17 and 30 km depth) and a stress deficit zone in the adjacent updip region (i.e., shallower than 17 km depth with CFS around -90 kPa). This region under negative stress accumulation can be explained by possible recurrent shallow Slow Slip Events (SSE) offshore Huatulco as well as by the stress shadow from adjacent locked segments. Absent in the literature, the shallow rupture is characterized by a secondary slip patch (between 7 and 14 km depth) that overlaps with the highest concentration of aftershocks. Two months prior to the event, a Mw 6.6 long-term SSE also occurred about 80 km northwest from the hypocenter, between 25 and 55 km depth. Transient increments of the interplate coupling around the adjacent 1978 (Mw 7.8) Puerto Escondido rupture zone correlate with the occurrence of the last three SSEs in Oaxaca far downdip of this zone, possibly associated with along-dip fluid diffusion at the subduction interface. Throughout the four-year period analyzed, the interface region of the 1978 event experienced a high CFS build up of 80-150 kPa, primarily attributable to both the co-seismic and early post-seismic slip of the Huatulco rupture, that, considering the 55 year average return period of the region, indicates large earthquake potential near Puerto Escondido. Continuous monitoring of the interplate slip-rate thus provides a better estimation of the stress accumulation in seismogenic regions than those given by long-term, time-invariant coupling models, and improves our understanding of the megathrust mechanics where future earthquakes are likely to occur.