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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...

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.

Abstract

Partial ambiguity resolution (PAR) has been widely adopted in real-time kinematic (RTK) and precise point positioning with augmentation from continuously operating reference station (PPP-RTK). However, current PAR methods, either in the position domain or the ambiguity domain, suffer from high false alarm and miss detection, particularly in challenging environments with poor satellite geometry and observations contaminated by non-line-of-sight (NLOS) effects, gross errors, biases, and high observation noise. To address these issues, a PAR method based on machine learning is proposed to significantly improve the correct fix rate and positioning accuracy of PAR in challenging environments. This method combines two support vector machine (SVM) classifiers to effectively identify and exclude ambiguities those are contaminated by bias sources from PAR without relying on satellite geometry. The proposed method is validated with three vehicle-based field tests covering open sky, suburban, and dense urban environments, and the results show significant improvements in terms of correct fix rate and positioning accuracy over the traditional PAR method that only utilizes ambiguity covariances. The fix rates achieved with the proposed method are 93.9%, 81.9%, and 93.1% with the three respective field tests, with no wrong fixes, compared to 72.8%, 20.9%, and 16.0% correct fix rates using the traditional method. The positioning error root mean square (RMS) is 0.020 m, 0.035 m, and 0.056 m in the east, north, and up directions for the first field test, 0.027 m, 0.080 m, and 0.126 m for the second field test, and 0.035 m, 0.042 m, and 0.071 m for the third field test. In contrast, only decimeter- to meter-level accuracy was obtainable with these datasets using the traditional method due to the high wrong fix rate. The proposed method provides a correct and fast time-to-first-fix (TTFF) of 3–5 s, even in challenging environments. Overall, the proposed method offers significant improvements in positioning accuracy and ambiguity fix rate with high reliability, making it a promising solution for PAR in challenging environments.

Nature Geoscience, Published online: 16 January 2025; doi:10.1038/s41561-025-01643-1

Author Correction: Recent uplift of Chomolungma enhanced by river drainage piracy

Abstract

Tidal interactions play a key role in the dynamics and evolution of icy worlds. The intense tectonic activity of Europa and the eruption activity on Enceladus are clear examples of the manifestation of tidal deformation and associated dissipation. While tidal heating has long been recognized as a major driver in the activity of these icy worlds, the mechanism controlling how tidal forces deform the different internal layers and produce heat by tidal friction still remains poorly constrained. As tidal forcing varies with orbital characteristics (distance to the central planet, eccentricity, obliquity), the contribution of tidal heating to the internal heat budget can strongly change over geological timescales. In some circumstances, the tidally-produced heat can result in internal melting and surface activity taking various forms. Even in the absence of significant heat production, tidal deformation can be used to probe the interior structure, the tidal response of icy moons being strongly sensitive to their hydrosphere structure. In the present paper, we review the methods to compute tidal deformation and dissipation in the different layers composing icy worlds. After summarizing the main principle of tidal deformation and the different rheological models used to model visco-elastic tidal response, we describe the dissipation processes expected in rock-dominated cores, subsurface oceans and icy shells and highlight the potential effects of tidal heating in terms of thermal evolution and activity. We finally anticipate how data collected by future missions to Jupiter’s and Saturn’s moons could be used to constrain their tidal response and the consequences for past and present activities.

Abstract

This study addresses the frequent convergence issues of satellite clocks within regional network, with a particular focus on the multifrequency advantages using data from 25 uniformly distributed reference stations across China. Experimental results demonstrate that incorporating the third frequency significantly enhances the accuracy of BDS-3 clock solutions, reducing the root mean square (RMS) by 44.5%. Additionally, employing a 2-min smoothing interval, multifrequency inclusion increases the wide-lane (WL) fixing rate by 30.4% at low elevation angles, which in turn leads to a marked improvement in narrow-lane (NL) ambiguity resolution. By leveraging phase-wide-lane observations, the stable wide-lane phase bias enables the continuous generation of inter-frequency clock bias (IFCB), ensuring reliable cyclic sequence construction even when satellites exit the observed region. The effectiveness of regional observable specific bias (OSB) on ambiguity resolution at the user level is highlighted, and over 95% of GPS, BDS-3, and Galileo NL fractional biases below 0.15 cycles could be achieved. Furthermore, the single-epoch convergence rates of multi-constellation precise point positioning (PPP) reach horizontal 91.9% and vertical 84.5% for multifrequency, a substantial improvement over the dual-frequency, which does not exceed 25%.

Nature Geoscience, Published online: 15 January 2025; doi:10.1038/s41561-025-01641-3

Author Correction: An ongoing satellite–ring cycle of Mars and the origins of Phobos and Deimos

Nature Geoscience, Published online: 15 January 2025; doi:10.1038/s41561-024-01626-8

Photochemical modelling suggests that H2 outgassing from crustal hydration could have supported transient warming episodes on early Mars in a CO2-rich atmosphere with abrupt transitions to cold climate states in a CO-rich atmosphere.

Nature Geoscience, Published online: 14 January 2025; doi:10.1038/s41561-024-01624-w

Near-daily sampling of volcanic ash during a three-month eruption reveals shifts in mantle-derived liquid magma (melt) composition, highlighting its potential as a monitoring and forecasting tool. These shifts align with the amplitude of volcanic tremor, a persistent seismic signal, suggesting a link between magma viscosity, shallow bubble escape dynamics, and tremor changes.

Abstract

In this paper, we propose a novel algorithm for fast frequency and phase synchronization of high-stability oscillators synchronized with 1 PPS signal from satellite navigation systems. The algorithm uses a model of a control object in the space of state variables and controls the frequency of an oscillator operating in a phase-locked loop. A new element is the introduction to the theoretical analysis and the design process, the time of entering synchronization. Currently, the literature lacks theoretical analysis and design methodology that considers the impact of the synchronization time on the choice of the steering algorithm and its parameters. All the data needed to determine the numerical values of the model were found experimentally for three different classes of control objects. Short synchronization times, a detailed description of the design methodology, and the use of values measured in the real system distinguish the proposed algorithm from the solutions described in the literature. The effect of optimization was achieved thanks to the algorithm’s two-stage operation. In the first stage, the algorithm aims to minimize the phase error quickly. The best solution for this stage is Sliding Mode Control (SMC). In the second stage, the algorithm strives to maximize the control quality, understood as minimizing the values of Maximum Time Interval Error (MTIE) and Time Deviation (TDEV). The Model Predictive Control (MPC) and Linear-Quadratic Regulator (LQR) optimal control algorithms were used at this stage. The paper also investigated the influence of the tuning parameters of these algorithms (weights as a function of cost) on the long-term behavior of the control system.

Nature Geoscience, Published online: 13 January 2025; doi:10.1038/s41561-024-01627-7

Space exploration has expanded the realm of geoscience to the outermost Solar System. A new generation of missions shines the way.

The micromechanics of friction has been investigated from the viewpoint of the healing of real contacts. In this study, the underlying processes of friction are discussed from the viewpoint of the contact junc...

Constraining the effective rheology of major faults contributes to improving our understanding of the physics of plate boundary deformation. Geodetic observations over the earthquake cycle are often used to e...

On February 8, 2022, approximately 40 of the 49 Starlink satellites were reported to have lost altitude, leading to atmospheric re-entry. SpaceX reported that the orbital decay on Starlink satellites was consi...

Nature Geoscience, Published online: 10 January 2025; doi:10.1038/s41561-024-01623-x

The SiO2 contents of erupted volcanic melts are correlated with persistent seismic signals that accompany eruptions—volcanic tremor—and may represent an eruption monitoring tool, according to a study of volcanic ash glasses from Cumbre Vieja volcano.

Abstract

In order to further improve the convergence rate and positioning accuracy of multi-frequency multi-system precise point positioning (PPP), an open-sourced software for fractional cycle bias (FCB) estimation (M_FCB) was produced based on MATLAB 2016a for GPS, BDS-2, Galileo, and BDS-3 satellite users. Based on raw frequency float ambiguity, the software can estimate ultra-wide-lane, wide-lane, narrow-lane combined FCB and raw frequency FCB. To validate the usability of the M_FCB software, 180 and 24 globally uniformly distributed multi-GNSS experiment stations were used to perform FCB estimation and triple-frequency uncombined PPP ambiguity resolution performance evaluation. The results show that the M_FCB software can generate stable and reliable FCB products. Particularly, Galileo satellites presented the best FCB stability. In addition, taking GPS/Galileo/BDS-2/BDS-3 fusion positioning as an example, the kinematic PPP after ambiguity resolution was significantly improved in terms of three-dimensional coordinate accuracy and positioning stability. Relative to the float solution, the average root mean square of the fixed-solution coordinate residuals in the east, north and vertical directions decreased by 30.3%, 12.5% and 16.0%, respectively.

Nature Geoscience, Published online: 09 January 2025; doi:10.1038/s41561-024-01618-8

This study examines the influence of agricultural irrigation on heat stress and contrasts it against local impacts of urbanization in North American cities using regional climate model simulations. The results indicate that irrigation decreases air temperature and increases relative humidity, with daytime urban moist heat stress reduced according to most indices.

Nature Geoscience, Published online: 09 January 2025; doi:10.1038/s41561-024-01613-z

Convection-permitting regional climate simulations suggest that irrigation reduces daytime urban heat stress in North America.

Abstract

In this paper, we studied the impact of solar activity, especially proton density, He++/H+ ratio and temperature of solar wind, on the geomagnetic field and thereby on earth’s climate. The verified data of these indices are collected from the official websites: wdc.kugi.kyoto-u.ac.jp and www.srl.caltech.edu/ace. Using the data values, both the indices are analyzed and studied to explore the link between solar activity and geomagnetic field. The magnetic field is irregular with negative and positive peaks and at the same time it shows the uniformity with the irregularities of solar wind plasma parameters. It has been observed that solar wind plasma has a significant influence on the intensity of magnetic field of earth and this correlation can be used for weather forecasts and climatic studies in the future.