The Cluster mission will always be the first ever multi-spacecraft mission mapping the Earth magnetosphere in three dimensions. Launched in 2000 and originally planned to operate for two years, it has been orb...
Anisotropic structures within the crust are frequently perceived to originate from stress-induced cracks, which have been mainly estimated on land through different wave speeds of orthogonally polarized S wave...
SummaryThe left-lateral Xianshuihe fault is a seismically active fault system located at the eastern boundary of the Tibetan Plateau. We analyzed the Sentinel InSAR data from 2014 to 2021 to study the temporal and spatial variation of fault creep along the Xianshuihe fault. We applied the InSAR stacking method and the coherence-based SBAS method to derive the Line-Of-Sight (LOS) velocity map and time-series from both the ascending and descending orbits. We studied both the secular component and the time-dependent component of surface deformation from InSAR. We compare the InSAR-derived velocity maps with the GPS-derived velocity field and found that these two independent measurements are consistent. A 200 km long creeping section is identified along the central segment of the Xianshuihe fault. The surface creep rate is measured to be ranging from 0 to 6 mm yr−1. We combined the elastic dislocation model and the InSAR velocity maps to invert for the geodetic fault slip rate and the aseismic slip distribution in the upper crust. The secular fault creep model shows that most of the Xianshuihe fault is creeping at depth. The time-dependent fault creep model indicates that the maximum aseismic slip rate from Bamei to Kangding accelerated from 30 mm yr−1 to 40 mm yr−1 and then decayed to 5 mm yr−1 from 2014 to 2021. The fully creeping segment of the Xianshuihe fault seems to become a partially locked segment in a short time period (a couple of years). We suspect that the acceleration of fault creep from 2017 to 2019 is linked to dynamic triggering by passing seismic waves or fluid migration. Finally, we compare the temporal variation of fault creep with previous studies and discuss the earthquake hazard implications.
SummaryAntarctica has been proposed as a significant source of the meltwater that entered the oceans during Meltwater Pulse 1B (MWP1B) approximately 11,500 years ago. Support for this scenario has been provided by evidence that the deep fjords of coastal Antarctica, which were heavily glaciated at the maximum of glaciation, were deglaciated at this time. Further support for this scenario was provided by the observation that the inter-hemispheric sea level teleconnection associated with significant southern hemisphere deglaciation at this time provided an explanation of the highly non-monotonic relative sea level histories recorded at sites on the coast of Scotland, a region which had also been heavily glaciated at the last glacial maximum. Furthermore, it has been argued that a significant contribution to MWP1B must have also been delivered to the oceans by the abrupt northern hemisphere warming that occurred at the end of the Younger Dryas (YD) cold reversal, which also occurred approximately 11,500 years ago. Our focus in the present paper is to distinguish between these two possible primary sources of MWP1B. The investigation of how local alterations to ice thicknesses are able to explain evidence which has previously been used to argue for an Antarctic dominant MWP1B will lead us to the conclusion that the Laurentide may be primary source of MWP1B.
SummaryThe complete catalog of moment tensor (MT) solutions is essential for a wide range of research in solid earth science. However, the number of reliable MT solutions for small to moderate earthquakes (3.0 ≤ M ≤ 5.5) is limited due to uncertainties arising from data and theoretical errors. In this study, we develop a new procedure to enhance the resolvability of MT solutions and provide more reliable uncertainty estimates for these smaller to moderate earthquakes. This procedure is fully automatic and efficiently accounts for both data and theoretical errors through two sets of hybrid linear-nonlinear Bayesian inversions. In the inversion process, the covariance matrix is estimated using an empirical approach: the data covariance matrix is derived from the pre-event noise and the theoretical covariance matrix is derived from the residuals of the initial solution. We conducted tests using synthetic data generated from the 3D velocity model and interference from background seismic noise. The tests found that using a combination of the non-Toeplitz data covariance matrix and the Toeplitz theoretical covariance matrix improves the solution and its uncertainties. Test results also suggest that including a theoretical covariance matrix when analyzing MT in complex tectonic regions is essential, even if we have the best 1D velocity model. The application to earthquakes in the northern region of the Banda Arc resulted in the first published Regional Moment Tensor (RMT) catalog, containing more than three times the number of trusted solutions compared to the Global Centroid Moment Tensor (GCMT) and the Indonesian Agency for Meteorology Climatology and Geophysics Moment Tensor (BMKG-MT) catalog. The comparison shows that the trusted solutions align well with the focal mechanism of the GCMT and BMKG-MT, as well as with the maximum horizontal stress of the World Stress Map, and tectonic conditions in the study area. The newly obtained focal mechanisms provide several key findings: (i) They confirm that the deformation in the northern and eastern parts of Seram Island is influenced by oblique intraplate convergence rather than by the subduction process; (ii) They validate the newly identified Amahai Fault with a greater number of focal mechanisms; (iii) They reveal an earthquake Mw 4.7 with the same location and source mechanism six years before the 2019 Ambon-Kairatu earthquake (Mw 6.5) which occurred on a previously unidentified fault.
SummaryWithin the last decade, thin ultra-low velocity zone (ULVZ) layering, sitting directly on top of the core-mantle boundary (CMB), has begun to be investigated using the flip-reverse-stack (FRS) method. In this method, pre- and post-cursor arrivals that are symmetrical in time about the ScS arrival, but with opposite polarities, are stacked. This same methodology has also been applied to high velocity layering, with indications that ultra-high velocity zones (UHVZs) may also exist. Thus far, studies using the FRS technique have relied on 1-D synthetic predictions to infer material properties of ULVZs. 1-D ULVZ models predominantly show a SdS precursor that reflects off the top of the ULVZ and an ScscS reverberation within the ULVZ that arrives as a postcursor. 1-D UHVZ models are more complex and have a different number of arrivals depending on a variety of factors including UHVZ thickness, velocity contrast, and lateral extent. 1-D modeling approaches assume that lower mantle heterogeneity is constant and continuous everywhere across the lower mantle. However, lower mantle features display lateral heterogeneity and are either finite in extent or display local thickness variations. We examine the interaction of the ScS wavefield with ULVZs and UHVZs in 2.5-D geometries of finite extent. We show that multiple additional arrivals exist that are not present in 1-D predictions. In particular, multipath ScS arrivals as well as additional postcursor arrivals are generated. Subsequent processing by the FRS method generates complicated FRS traces with multiple peaks. Furthermore, post-cursor arrivals can be generated even when the ScS ray path does not directly strike the heterogeneity from above. Analyzing these predictions for 2.5-D models using 1-D modeling techniques demonstrates that a cautious approach must be adopted in utilization and interpretion of FRS traces to determine if the ScS wavefield is interacting with a ULVZ or UHVZ through a direct strike on the top of the feature. In particular, travel-time delays or advances of the ScS arrival should be documented and symmetrical opposite polarity arrivals should be demonstrated to exist around ScS. The latter can be quantified by calculation of a time domain multiplication trace. Because multiple postcursor arrivals are generated by finite length heterogeneities, interpretation should be confined to single layer models rather than to interpret the additional peaks as internal layering. Furthermore, strong tradeoffs exist between S-wave velocity perturbation and thickness making estimations of ULVZ or UHVZ elastic parameters highly uncertain. We test our analysis methods using data from an event occurring in the Fiji-Tonga region recorded in North America. The ScS bounce points for this event sample the CMB region to the southeast of Hawaii, in a region where ULVZs have been identified in several recent studies. We see additional evidence for a ULVZ in this region centered at 14° N and 153° W with a lateral scale of at least 250 × 360 km. Assuming a constant S-wave velocity decrease of -10 or -20% with respect to the PREM model implies a ULVZ thickness of up to 16 or 9 km respectively.
Abstract
Precise knowledge of geocenter motion, i.e., the relative motion between the Earth’s center of mass (CM) and the center of figure of the Earth’s surface (CF), is crucial to high-stakes geodetic applications such as sea-level rise monitoring with satellite altimetry or the establishment of regional and global mass budgets with satellite gravimetry. The computation of the latest release of the International Terrestrial Reference Frame, ITRF2020, involved the estimation of a field of seasonal motions for a global network of geodetic stations, expressed with respect to CM, as sensed by satellite laser ranging, from which the translational part represents seasonal geocenter motion. This paper presents two different methods to isolate seasonal geocenter motion from the field of ITRF2020 seasonal station motions, among which a new method based on a direct weighted average of seasonal station motions, with station-specific weights chosen so as to provide a better approximation of CF than the standard network shift approach. The ITRF2020 annual geocenter motion model thus obtained is then compared with other recent geodetic and geophysical estimates. Although different sub-groups of estimates with relatively good internal consistency may be identified, the overall scatter of recent geodetic estimates remains at the level of several mm, i.e., close to the amplitude of annual geocenter motion itself. Efforts toward reconciling seasonal geocenter motion estimates therefore still appear necessary. Meanwhile, it would seem safe to assume that seasonal geocenter motion models, in particular those currently used in satellite altimetry and satellite gravimetry, are still uncertain.
Abstract
We examine the decadal evolution of GPS, GLONASS, and Galileo satellite orbital elements, including the semi-major axis, inclination, eccentricity, right ascension of the ascending node, and the argument of perigee. We focus on the long-term changes in Keplerian elements by averaging them over several complete revolutions forming mean orbital elements giving an explanation of the main perturbing forces for each Keplerian parameter. The combined International GNSS Service (IGS) orbits are employed which were derived in the framework of IGS Repro3 for ITRF2020 preparation spanning eight years from 2013 to 2021. The semi-major axis for GPS satellites is affected by a strong resonance with Earth’s gravity field resulting in a long-period perturbation similar to a secular drift. The semi-major axes of Galileo and GLONASS do not show any large-scale rates, however, Galileo satellites are affected by the Y-bias resulting in semi-major axis drifts. A significant perturbations due to solar radiation pressure affect the semi-major axis, eccentricity, and the argument of perigee. Notably, for Galileo satellites in eccentric orbits, the signal with a one-draconitic year is evident in the semi-major axis. The evolution of the mean right ascension of the ascending node and argument of perigee is primarily characterized by nearly linear regression mainly due to even zonal harmonics of the Earth’s gravity field. The long-term evolution of eccentricity and inclination does not follow a linear trend but exhibits clear oscillations dependent on the secular drift of the right ascension of the ascending node (for inclination) or the argument of perigee (for eccentricity). Additionally, the long-term perturbation of inclination reaches its maximum when the absolute value of the Sun’s elevation angle above the orbital plane (
\(\beta\)
angle) is at its minimum, while the eccentricity reaches its minimum simultaneously with the minimum of the
\(\beta\)
angle.
An evaluation of atmospheric absorption models at millimetre and sub-millimetre wavelengths using airborne observations
Stuart Fox, Vinia Mattioli, Emma Turner, Alan Vance, Domenico Cimini, and Donatello Gallucci
Atmos. Meas. Tech., 17, 4957–4978, https://doi.org/10.5194/amt-17-4957-2024, 2024
Airborne observations are used to evaluate two models for absorption and emission by atmospheric gases, including water vapour and oxygen, at microwave and sub-millimetre wavelengths. These models are needed for the Ice Cloud Imager (ICI) on the next generation of European polar-orbiting weather satellites, which measures at frequencies up to 664 GHz. Both models can provide a good match to measurements from airborne radiometers and are sufficiently accurate for use with ICI.
AeroMix v1.0.1: a Python package for modeling aerosol optical properties and mixing states
Sam P. Raj, Puna Ram Sinha, Rohit Srivastava, Srinivas Bikkina, and Damu Bala Subrahamanyam
Geosci. Model Dev., 17, 6379–6399, https://doi.org/10.5194/gmd-17-6379-2024, 2024
A Python successor to the aerosol module of the OPAC model, named AeroMix, has been developed, with enhanced capabilities to better represent real atmospheric aerosol mixing scenarios. AeroMix’s performance in modeling aerosol mixing states has been evaluated against field measurements, substantiating its potential as a versatile aerosol optical model framework for next-generation algorithms to infer aerosol mixing states and chemical composition.
Impact of ITCZ width on global climate: ITCZ-MIP
Angeline G. Pendergrass, Michael P. Byrne, Oliver Watt-Meyer, Penelope Maher, and Mark J. Webb
Geosci. Model Dev., 17, 6365–6378, https://doi.org/10.5194/gmd-17-6365-2024, 2024
The width of the tropical rain belt affects many aspects of our climate, yet we do not understand what controls it. To better understand it, we present a method to change it in numerical model experiments. We show that the method works well in four different models. The behavior of the width is unexpectedly simple in some ways, such as how strong the winds are as it changes, but in other ways, it is more complicated, especially how temperature increases with carbon dioxide.
Physics-motivated cell-octree adaptive mesh refinement in the Vlasiator 5.3 global hybrid-Vlasov code
Leo Kotipalo, Markus Battarbee, Yann Pfau-Kempf, and Minna Palmroth
Geosci. Model Dev., 17, 6401–6413, https://doi.org/10.5194/gmd-17-6401-2024, 2024
This paper examines a method called adaptive mesh refinement in optimization of the space plasma simulation model Vlasiator. The method locally adjusts resolution in regions which are most relevant to modelling, based on the properties of the plasma. The runs testing this method show that adaptive refinement manages to highlight the desired regions with manageable performance overhead. Performance in larger-scale production runs and mitigation of overhead are avenues of further research.
A new study paves the way to understanding biotic recovery after an ecological crisis in the Mediterranean Sea about 5.5 million years ago. An international team led by Konstantina Agiadi from the University of Vienna has now been able to quantify how marine biota was impacted by the salinization of the Mediterranean: Only 11% of the endemic species survived the crisis, and the biodiversity did not recover for at least another 1.7 million years.
Three studies conducted with the collaboration of the Helmholtz Institute Freiberg for Resource Technology, an institute of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), show significant progress in monitoring mining areas.
Exploring the sensitivity of extreme event attribution of two recent extreme weather events in Sweden using long-running meteorological observations
Erik Holmgren and Erik Kjellström
Nat. Hazards Earth Syst. Sci., 24, 2875–2893, https://doi.org/10.5194/nhess-24-2875-2024, 2024
Associating extreme weather events with changes in the climate remains difficult. We have explored two ways these relationships can be investigated: one using a more common method and one relying solely on long-running records of meteorological observations.
Our results show that while both methods lead to similar conclusions for two recent weather events in Sweden, the commonly used method risks underestimating the strength of the connection between the event and changes to the climate.
An impact-chain-based exploration of multi-hazard vulnerability dynamics: the multi-hazard of floods and the COVID-19 pandemic in Romania
Andra-Cosmina Albulescu and Iuliana Armaș
Nat. Hazards Earth Syst. Sci., 24, 2895–2922, https://doi.org/10.5194/nhess-24-2895-2024, 2024
This study delves into the dynamics of vulnerability within a multi-hazard context, proposing an enhanced impact-chain-based framework that analyses the augmentation of vulnerability. The case study refers to the flood events and the COVID-19 pandemic that affected Romania (2020–2021). The impact chain shows that (1) the unforeseen implications of impacts, (2) the wrongful action of adaptation options, and (3) inaction can form the basis for increased vulnerability.
Abstract
The 72-foot sailing yacht Eugen Seibold is a new research platform for contamination-free sampling of the water column and atmosphere for biological, chemical, and physical properties, and the exchange processes between the two realms. Ultimate goal of the project is a better understanding of the modern and past ocean and climate. Operations started in 2019 in the Northeast Atlantic, and will focus on the Tropical Eastern Pacific from 2023 until 2025. Laboratories for air and seawater analyses are equipped with down-sized and automated state-of-the-art technology for a comprehensive description of the marine carbon system including CO2 concentration in the air and sea surface, pH, macro-, and micro-nutrient concentration (e.g., Fe, Cd), trace metals, and calcareous plankton. Air samples are obtained from ca. 13 m above sea surface and analyzed for particles (incl. black carbon and aerosols) and greenhouse gases. Plankton nets and seawater probes are deployed over the custom-made A-frame at the stern of the boat. Near Real-Time Transfer of underway data via satellite connection allows dynamic expedition planning to maximize gain of information. Data and samples are analyzed in collaboration with the international expert research community. Quality controlled data are published for open access. The entire suite of data facilitates refined proxy calibration of paleoceanographic and paleoclimate archives at high temporal and spatial resolution in relation to seawater and atmospheric parameters.
Abstract
We apply a template matching method on GNSS data for stations located in Honshu, Japan, to detect slow slip events associated with the subducting Philippine Sea and Pacific plates during the period from 1997 to 2020. A measure of the minimum detectable moment magnitude is proposed, from which we infer that the method could potentially detect SSEs as small as M
w
5.2 on the westernmost part of the Philippine Sea plate and M
w
6 on the Pacific plate below Honshu eastern coastline. We find 12 slow slip events on the Philippine Sea plate, among which eight are located on the known Boso slow slip event asperity and the four others are located offshore north-east relative to the Boso SSEs, at the transition with the Pacific plate. We find 9 SSEs on the Pacific plate, mainly on the northern section, offshore Iwate prefecture. A clear gap with no SSEs coincides with the main asperity that broke during the 2011 Tohoku earthquake. Most event locations correlate with low locking areas. We do not find any clear temporal pattern apart from the regular occurrence of the largest Boso SSEs.
