GNSS Velocity Research Articles

Reconciling the conflicting extent of overriding plate deformation before and during megathrust earthquakes in South America, Sunda and northeast Japan

SUMMARYWe aim to better understand the overriding plate deformation during the megathrust earthquake cycle. We estimate the spatial patterns of interseismic GNSS velocities in South America, Southeast Asia and northern Japan and the associated uncertainties due to variations in network density and observation uncertainties. Interseismic velocities with respect to the overriding plate generally decrease with distance from the trench with a steep gradient up to a ‘hurdle’, beyond which the gradient is distinctly lower and velocities are small. The hurdle is located 500–1000 km away from the trench for the trench-perpendicular velocity component, and either at the same distance or closer for the trench-parallel component. Significant coseismic displacements were observed beyond these hurdles during the 2010 Maule, 2004 Sumatra–Andaman, and 2011 Tohoku earthquakes. We hypothesize that both the interseismic hurdle and the coseismic response result from a mechanical contrast in the overriding plate. We test our hypothesis using physically consistent, generic, 3-D finite element models of the earthquake cycle. Our models show a response similar to the interseismic and coseismic observations for a compliant near-trench overriding plate and an at least five times stiffer overriding plate beyond the contrast. The model results suggest that hurdles are more prominently expressed in observations near strongly locked megathrusts. Previous studies inferred major tectonic or geological boundaries and seismological contrasts located close to the observed hurdles in the studied overriding plates. The compliance contrast probably results from thermal, compositional and thickness contrasts and might cause the observed focusing of smaller-scale deformation like backthrusting.

Present-day Crustal Deformation in West Sumatra After Series of Sumatran Great Earthquake from 2004-2010

Present-day crustal deformation was an attempt to estimate earthquake potential, yet the presence of postseismic deformation should be carefully identified. Studying crustal deformation in West Sumatra has been important for this purpose since the series of Sumatran Great Earthquake from 2004-2010. This study utilized present-day GNSS data (2017-2021) and pre-2004 GNSS velocities to understand the present-day crustal deformation. Bernese 5.2 was used to process the GNSS data and linear regression was used to calculate present-day velocities. These velocities were transformed into an ITRF2000-based Sundaland plate reference frame and then the velocities were compared to pre-2004 velocities in the same reference frame. The present-day velocities were ranging from 28.4 mm/yr to 58.3 mm/yr in ITRF2014 and from 8.8 to 44.8 mm/yr in the Sundaland plate reference frame. This suggests West Sumatra was located on the Sumatra block of the Sundaland plate. The low velocity difference ( 11.7 mm/yr) with the random vector direction between present-day velocities and pre-2004 velocities shows that there is no postseismic deformation affecting West Sumatra. This proposes the utilization of present-day velocities for earthquake potential estimation in West Sumatra.

Geodetic and seismic constraints on contemporary deformation on the northeastern Tibetan plateau: Velocity and strain rate tensor analysis

The study of the velocity and strain rate of the northeastern Tibetan Plateau can explain its crustal deformation characteristics. Previous investigations have relied on mathematical interpolation in GPS velocity to obtain a continuous strain field; these approaches can be applied well to regions where the deformation is relatively smooth and are not entirely suitable for the northeastern Tibetan Plateau that is cut by several large strike-slip faults. Thus, this study incorporates seismic constraints into the GNSS velocity and strain analysis to obtain a more realistic deformation field and compares it with the uplift rate and the stress results in depth, it will provide a comprehensive view of contemporary deformation on the northeastern Tibetan Plateau. It shows that there are two prominent deforming zones localized on the middle segments of the Haiyuan and East Kunlun faults, which may result from the different strengths in fault segmentation. The velocity and strain rate in the four profiles show that the convergence strain obviously decay from ∼15.5 mm/yr and ∼ 15.48 nstrain/yr in the western Qilian Mountains to ∼5.73 mm/yr and ∼ 5.76 nstrain/yr in the eastern Long Zhong Basin, respectively. The comparison between the vertical uplift rate, SKS result, and strain rate field indicates that the northeastern Tibetan Plateau is not only dominated by crustal shortening corresponding to the topography and surface fault geometry, but also by the strain transfer of motion along these significant strike-slip faults accounting for the extrusion and growth of the Tibetan Plateau. Combined with recent seismological results, our results indicate that the deformation of the study region resembles that of the Tibetan Plateau and can be viewed as a combined process linking both NE- or NEE-directed crustal shortening, vertical uplift, lateral extrusion along strike-slip faults and partial melting or mantle upwelling at depth.

Mosaicking Andean morphostructure and seismic cycle crustal deformation patterns using GNSS velocities and machine learning

We use unsupervised machine learning techniques to analyze continental-scale crustal motions in areas affected by the seismic cycle of large subduction earthquakes along the Chilean Trench. Specifically, we use the agglomerative clustering algorithm as an exploratory tool to investigate spatial patterns in GNSS regional velocities without the complexity of modeling a physical source. We present a continental-scale velocity field including all available GNSS data for two-time windows (pre-2014, 2018–2021) that represents two periods with different deformation patterns of the seismic cycle. We test two different pre-processing methodologies for the design of machine learning features from the GNSS-derived velocities. The first method uses the direction and magnitude of the secular rates as input features to the clustering algorithm. These results show a clustering spatially related to seismic cycle deformation, separating latitudinal segments with different velocities in the fore-arc and back-arc, as well as regions affected by postseismic relaxation. Thus, highlighting the effectiveness of this method for mapping first-order patterns of active deformation in a subduction zone, that are particularly related to variations on interplate coupling and postseismic transient deformation. In a more sophisticated approach, we use surface strain and rotational rates from GNSS velocities as features in the second methodology. Here, we develop a novel methodology to estimate strain and rotation rates accounting for the spatial heterogeneity of the GNSS-network. We determine the spatial scale at which these features are estimated by least squares inversions, by using a Bayesian model class selection method. The distribution of stations allows to identify heterogeneities in strain and rotation rates at spatial scales larger than 50 km, being particularly notorious the main features of regional deformation at scales > 100 km. Interestingly, the results show a spatial correlation between seismic segmentation in the fore-arc and geologic and structural domains in the arc and back-arc. Our results demonstrate the ability of the combination of inverse and machine learning methods to efficiently identify active deformation patterns and their relationship to the subduction seismic cycle and regional-scale geological structures. Furthermore, our analysis suggests that Andean geological structures influence the observed deformation field.

Present-Day Surface Deformation in North-East Italy Using InSAR and GNSS Data

Geodetic data can detect and estimate deformation signals and rates due to natural and anthropogenic phenomena. In the present study, we focus on northeastern Italy, an area characterized by ~1.5–3 mm/yr of convergence rates due to the collision of Adria-Eurasia plates and active subsidence along the coasts. To define the rates and trends of tectonic and subsidence signals, we use a Multi-Temporal InSAR (MT-InSAR) approach called the Stanford Method for Persistent Scatterers (StaMPS), which is based on the detection of coherent and temporally stable pixels in a stack of single-master differential interferograms. We use Sentinel-1 SAR images along ascending and descending orbits spanning the 2015–2019 temporal interval as inputs for Persistent Scatterers InSAR (PSI) processing. We apply spatial-temporal filters and post-processing steps to reduce unrealistic results. Finally, we calibrate InSAR measurements using GNSS velocities derived from permanent stations available in the study area. Our results consist of mean ground velocity maps showing the displacement rates along the radar Line-Of-Sight for each satellite track, from which we estimate the east–west and vertical velocity components. Our results provide a detailed and original view of active vertical and horizontal displacement rates over the whole region, allowing the detection of spatial velocity gradients, which are particularly relevant to a better understanding of the seismogenic potential of the area. As regards the subsidence along the coasts, our measurements confirm the correlation between subsidence and the geological setting of the study area, with rates of ~2–4 mm/yr between the Venezia and Marano lagoons, and lower than 1 mm/yr near Grado.

Present-Day Crustal Velocity Field in Ecuador from cGPS Position Time Series

The present study analyzes the GNSS time series obtained between the years 2017 and 2022 for the calculation of absolute and residual rates of Ecuador in 10 stations (ABEC, CUEC, ECEC, EPEC, FOEC, GZEC, MUEC, PLEC, RIOP, SEEC, TPC) of the continuous monitoring REGME network. Considering that the latest studies refer to periods 2012-2014 and Ecuador is located in an area of high seismic activity, it is important to update the GNSS rates. The RINEX data were provided by the Military Geographic Institute of Ecuador, the governing institution of geoinformation in that country; for processing, GipsyX scientific software was used with a PPP mode, considering 24 h sessions, and high precision was achieved. For the analysis of time series, the SARI platform was used. The series was modeled using a least-squares adjustment, which delivered the velocities for each station in the three local topocentric components. The results were contrasted with other studies, obtaining interesting conclusions as the presence of abnormal post-seismic rates stands out due to the high rate of seismic occurrence in Ecuador, and reaffirms the idea of a constant update of velocities for the Ecuadorian territory and the inclusion of the stochastic factor in the analysis of GNSS time series, since it can affect the ability to obtain the final GNSS velocities.

Fault locking behavior of the Longmenshan Thrust Belt preceding the 2008 Wenchuan earthquake

Fault locking inversion can clarify the occurrence mechanisms of large earthquakes and the seismic hazards of future earthquakes. Due to limited observations in mainland China, fault locking inversions have typically been unstable. To investigate a more suitable fault locking behavior of the Longmenshan Thrust Belt (LTB) preceding the 2008 Wenchuan earthquake, GNSS velocity field data during 1999–2007 and the least-squares collocation method (LSCM) are used in this study. Despite the limited stations, after interpolating the GNSS velocity with the LSCM, uncertainties are reduced to some extent during the inversion. Based on the interpolation data, the inversion shows two locked areas that are consistent with the coseismic slip distribution of the Wenchuan earthquake. The third locked area is located on the southern LTB. A checkerboard scheme is proposed, and historic earthquakes larger than M 3.0 since 1950 are analyzed to recheck our inversion. According to the inverted result, the Wenchuan and Lushan earthquakes are two independent events. Additionally, we propose that future destructive earthquakes may occur on the southern segment of the LTB. The maximum magnitude of a future possible earthquake is Mw 8.2.

Fine divided method of active tectonic blocks based on adaptive density peak clustering and improved Euler model, revealed by GNSS velocities in Southwest Japan

The rational division of active tectonic blocks is an important premise for distinguishing active faults, discovering hidden faults, and an in-depth understanding of regional crustal deformation characteristics, seismicity, and tectonic dynamics. In recent years, clustering algorithms have been widely used in active block division owing to their high efficiency and reliability. However, the classical clustering algorithm sensitivity to the block boundary under different conditions is inconsistent. Additionally, the Euler model constraint (EMC) process involved in the classical clustering algorithm ignores the influence of the boundary points and gross error points of the active block. Therefore, in this study, a new active block division method based on adaptive density peak clustering (ADPC) and an improved Euler model constraint (IEMC) is proposed. The simulation test results show that compared with the traditional clustering algorithm, the mean error rate of the new method can be reduced by up to 40% in the simple single-fault model and by 10% in the complex three-segment model. The new method was further applied to an actual case of an active block division in southwest Japan. The results further show that the new method is less affected by the regional environmental conditions. Compared with previous results in southwest Japan, the proposed method has higher accuracy and higher reliability of the active block division results. The new method for active block division proposed in this study can be used to accurately explore the location and quantity of block boundaries.

Spatial outlier detection on discrete GNSS velocity fields using robust Mahalanobis-distance-based unsupervised classification

GNSS velocity field filtering can be identified as a multidimensional unsupervised spatial outlier detection problem. To detect and classify the spatial outliers, we jointly interpret the horizontal and vertical velocity fields with the related standard deviations. We also describe the applied feature engineering process, which represents the underlying problem better than the initial attributes. According to this, we discuss the utilized algorithms and techniques, like the spatial- and non-spatial mapping functions, the k-nearest neighborhood (kNN) technique to retrieve the local environment of each GNSS station, as well as the principal component analysis (PCA) as a dimensionality reduction technique. We also assume that regular velocity field samples containing no outliers come from an approximate multivariate normal distribution (MVN) at the local scale. Regarding this, we evaluate the corresponding sample-wise distance related to model distribution, namely the Mahalanobis distance, with the estimation of the robust covariance matrix derived by the minimum covariant determinant (MCD) algorithm. Subsequently, we introduce the applied binary classification on the values of the derived robust Mahalanobis distances (RMD) which follows the χ2distribution. We also present three cases of artificially generated, pre-labeled synthetic velocity field datasets to perform cross-validation and comparison of the proposed RMD approach to other classification techniques. According to this, we found that k = 12 yields > 95% classification accuracy. While the compared methods have a mean classification accuracy of 96.2–99.8%, the advantage of the RMD approach is that it does not require pre-defined labels to indicate regular and outlier samples. We also demonstrate the proposed RMD based filtering process on a real dataset of the EUREF Permanent Network Densification velocity products. The RMD-based approach has been integrated into the EPN Densification as a quality checking algorithm. According to this, we also introduce a co-developed and regularly updated interactive webpage to disseminate the corresponding results.

Strain Partitioning Among Forearc Faults in Southern Cascadia Inferred From GNSS

AbstractCrustal faults in the southern Cascadia forearc help to accommodate strains related to plate interactions near the Mendocino triple junction (MTJ). Geologic work has identified the Little Salmon fault, Mad River fault zone (MRFZ), and Grogan fault as Quaternary‐active structures; however, the slip rates on these major fault systems are poorly constrained. This work constructs elastic block models of the MTJ region and leverages GNSS velocity data to better understand how strain is partitioned among these three faults. We evaluate models with various forearc fault structures and apply a bootstrap analysis to provide independent slip rate distributions for each fault. Model results indicate that the Little Salmon fault zone is an important structure that accommodates both thrust and right‐lateral shear motion in the forearc. Appreciable right‐lateral slip rates on the MRFZ indicate that this system plays an important role in facilitating translation of the forearc and may serve as an extension of the northern San Andreas fault system. In contrast, the models place very little strike‐slip motion on the Grogan fault and prefer this structure to mainly host reverse slip. We observe the highest slip rates on the Bear River fault zone, indicating significant strain to the north of the MTJ.

Elusive active faults in a low strain rate region (Sicily, Italy): Hints from a multidisciplinary land-to-sea approach

Low Strain Rate regions (LSRrs), i.e., areas undergoing tectonic deformation at rates of 1 mm/yr or less, often host important cities and highly vulnerable anthropogenic assets, and due to their subdued topography and relatively infrequent seismicity, are often considered low seismic hazard areas. Despite this, infrequent but high-magnitude earthquakes in such regions suggest that identifying active structures in the LSRr is one of the primary challenges for both the scientific community and modern societies. In such regions, one of the main issues in identifying active faults is the lack of valuable outcrop data due to erosional/sedimentation rates overwhelming the fault deformation, causing the hidden morphological signature of the tectonic structures.This work proposes a multidisciplinary approach designed to detect active geological structures and their related deformation in such areas. Our approach consists of quantitative morphotectonic, offshore and onshore tectonostratigraphic and GNSS joint analyses. To test this approach, we selected as a natural laboratory the partially offshore northern Sicilian LSRr (southern Italy) in the coastal sector located between the two major cities of Palermo and Termini Imerese. This area includes the compressional structures of the northern sector of the Apennine-Maghrebian fold and thrust belt, presently accommodating the slow Africa-Europe plate convergence.The main results we achieved are 1) new evidence of active tectonic deformation in this region; 2) the 3D modelling of two NNW-trending active faults; 3) the slip rate of a segment of the westernmost of the two detected faults; 4) a newly recorded relative GNSS velocity field; 5) a new morphotectonic map and morphotectonic evolution model of the study area. Our multidisciplinary approach allowed us to shed new light on the active tectonic framework of a slowly deforming area that crosses the physical limit of the coastline.

3D GNSS Velocity Field Sheds Light on the Deformation Mechanisms in Europe: Effects of the Vertical Crustal Motion on the Distribution of Seismicity

AbstractCrustal deformation and seismicity in Europe are still poorly understood. Seismic activity is classically ascribed to crustal strain rates generated by edge‐driven tectonic forces. However, crustal deformation is not only due to tectonic loading, but can also be related to isostatic and mantellic processes that induce additional stress and strain on the crust by flexure. The influence that those processes have on seismic activity, as well their interaction, is still controversial. The main limitation to study it is because the deformation and its causal mechanisms are usually analyzed separately in small regions. We present here a 3D secular velocity field that covers Eurasia and its plate boundaries including 4,863 Global Navigation Satellite System stations obtained by combining 10 different datasets. We have developed a method based on spatial filtering to identify outliers and smooth the velocity field, and have computed both strain and uplift rate maps that are interpreted in the light of the different driving processes that contribute to the 3D deformation in Europe. The vertical and horizontal deformation features are compared with seismic rates obtained from the spatial and temporal distribution of the seismicity in Europe. Our results suggest that is not possible to explain the seismicity in Europe with edge‐driven horizontal tectonic forces only. In some areas markers of the crustal flexure such as the vertical velocity field and its derivative, resulting from buoyancy‐driven processes, may help to interpret earthquake distribution.

Ongoing tectonic subsidence in the Lesser Antilles subduction zone

SUMMARYGeological estimates of vertical motions in the central part of the Lesser Antilles show subsidence on timescales ranging from 125.000 to 100 yr, which has been interpreted to be caused by interseismic locking along the subduction megathrust. However, horizontal GNSS velocities show that the Lesser Antilles subduction interface is currently building up little to no elastic strain. Here, we present new present-day vertical velocities for the Lesser Antilles islands and explore the link between short- and long-term vertical motions and their underlying processes. We find a geodetic subsidence of the Lesser Antilles island arc at 1–2 mm yr−1, consistent with the ∼100-yr trend derived from coral micro-atolls. Using elastic dislocation models, we show that a locked or partially locked subduction interface would produce uplift of the island arc, opposite to the observations, hence supporting a poorly coupled subduction. We propose that this long-term, margin-wide subsidence is controlled by slab dynamic processes, such as slab rollback. Such processes could also be responsible for the aseismic character of the subduction megathrust.

Model Optimization of Agricultural Machinery Information Control System Based on Artificial Intelligence

Agricultural mechanization information in our country has the main problems existing in the management and utilization. The analysis of China’s agricultural mechanization management model and related software is presented based on combining modern science and technology as well as the development of agricultural mechanization management information system based on network software to standardize the management information collection, processing, storage and transmission, agricultural mechanization management information science, standardization, automation, etc. According to the analysis, the output target speed after fusion is more stable, and the stability is increased by 59.59% compared with the single-point GNSS velocity measurement data, and by 18.32% compared with the data measured by the binocular vision velocity measurement system. It has realized the goal of accurate speed measurement from low speed to high speed. In particular, it has solved the problems such as vehicles unable to complete positioning and vehicle skidding caused by trees blocking GNSS satellite signals during field operations.

ACCURACY EVALUATION OF MULTI-GNSS DOPPLER VELOCITY ESTIMATION USING ANDROID SMARTPHONES

Abstract. The number of smartphone users has increased dramatically as smartphones have become more widely available. The mass-market urgently requires the deployment of low-cost GNSS chips in smartphones to achieve continuous, high-precision velocity and location services. Currently, most GNSS velocity determination research relies on traditional geodetic receivers and focuses on comparing velocity determination methods and analyzing velocity determination influencing factors, while research into the direction of multi-GNSS velocity determination for smartphones is insufficient. To solve this problem, we study the differences in velocity determination accuracy of Android smartphones with single-constellation, dual-constellation and multi-constellation focusing on BDS-2 and BDS-3. The results show that the accuracy of velocity determination differs significantly between different mobile phone models. The velocity determination accuracy of BDS is the highest in all single constellations, and the accuracy of BDS-2, BDS-3 and GPS are not much different. The velocity determination accuracy of dual-constellation and multi-constellation is better than single-constellation. In static velocity determination, the Huawei nova5 quad-constellation velocity determination error is in the cm/s level, while the Redmi K40 error is in the dm/s level. In kinematic velocity determination, the Huawei nova5’s quad-constellation velocity determination error in horizontal and vertical directions is 1.06 dm/s and 1.77 dm/s respectively; The Redmi’s quad-constellation velocity determination error in horizontal and vertical directions is 3.76 dm/s and 4.59 dm/s respectively.

A reappraisal of active tectonics along the Fethiye–Burdur trend, southwestern Turkey

SUMMARYWe investigate active tectonics in southwestern Turkey along the trend between Fethiye, near the eastern end of the Hellenic subduction zone, and Burdur, on the Anatolian plateau. Previously, regional GNSS velocities have been used to propose either (1) a NE-trending zone of strike-slip faulting coined the Fethiye–Burdur Fault Zone, or (2) a mix of uniaxial and radial extension accommodated by normal faults with diverse orientations. We test these models against the available earthquake data, updated in light of recent earthquakes at Arıcılar (24 November 2017, Mw 5.3), Acıpayam (20 March 2019, Mw 5.6) and Bozkurt (8 August 2019, Mw 5.9), the largest in this region in the last two decades. Using Sentinel-1 InSAR and seismic waveforms and arrival times, we show that the Arıcılar, Acıpayam and Bozkurt earthquakes were partially or fully buried ruptures on pure normal faults with subtle or indistinct topographic expressions. By exploiting ray paths shared with these well-recorded modern events, we relocate earlier instrumental seismicity throughout southwestern Turkey and incorporate these improved hypocentres in an updated focal mechanism compilation. The southwestern Fethiye–Burdur trend is dominated by ESE–WNW trending normal faulting, even though most faults evident in the topography strike NE–SW. This hints at a recent change in regional strain, perhaps related to eastward propagation of the Gökova graben into the area or to rapid subsidence of the Rhodes basin. The northeastern Fethiye–Burdur trend is characterized by orthogonal normal faulting, consistent with radial extension and likely responsible for the distinct physiography of Turkey’s Lake District. We find that the 1971 Mw 6.0 Burdur earthquake likely ruptured a NW-dipping normal fault in an area of indistinct geomorphology near Salda Lake, contradicting earlier studies that place it on well-expressed faults bounding the Burdur basin, and further highlighting how damaging earthquakes are possible on faults that would prove difficult to identify beforehand. Overall, our results support GNSS-derived kinematic models that depict a mix of uniaxial and radial extension throughout southwestern Turkey, with no evidence from focal mechanisms for major, active strike-slip faults anywhere along the Fethiye–Burdur trend. Normal faulting orientations are consistent with a stress field driven primarily by contrasts in gravitational potential energy between the elevated Anatolian plateau and the low-lying Rhodes and Antalya basins.

Present‐Day Surface Deformation of Sicily Derived From Sentinel‐1 InSAR Time‐Series

AbstractThe Quaternary geodynamics of the Central Mediterranean region is controlled by the migration of narrow orogenic belts within the slow Nubia‐Eurasia plate convergence. As testified by the occurrence of major volcanic and seismic events, the Eastern Sicilian Margin is presently one of the most active regions. Using a Permanent‐Scatterer approach, we process Sentinel‐1 satellite images acquired from 2015 to 2020 to provide an island‐wide quantification of surface displacements at a high spatiotemporal resolution. We then convert the calculated mean surface velocities along the ascending and descending satellite line of sight into the ITRF2014 reference frame by using GNSS velocity data derived from regional stations. The resulting pseudo‐3D velocity field mainly highlights a general uplift of about 1.5 ± 0.5 mm/yr of the Nebrodi‐Peloritani range and its differential motion with respect to mainland Sicily along the Cefalù‐Etna seismic zone. Permanent/Persistent‐Scatterer (PS) vertical velocities in the Eastern Hyblean region reveal a long wavelength eastward downbending of the margin, including the inferred epicentral area of the 1693 Noto earthquake. Compared to Quaternary coastal uplift rates, these results confirm the relative low activity of Western Sicily, a potential slow uplift of South‐Central Sicily and a significant discrepancy along the Eastern Hyblean margin were PS‐derived vertical velocities that appear 2–3 mm/yr lower than the Quaternary rates. Over the 2015–2020 timespan, transient processes are also captured, notably on Mount Etna, showing both magmatic pressurization uplift and collapse of the eastern flank, but also all over Sicily where numerous gravitational mass movements and anthropogenic ground subsidence are detected.

A GNSS velocity field for crustal deformation studies: The influence of glacial isostatic adjustment on plate motion models

SUMMARYThe two main causes of global-scale secular deformation of the Earth are tectonic plate motion and glacial isostatic adjustment (GIA). We create a bespoke global 3D GNSS surface velocity field ‘NCL20’ to investigate tectonic plate motion and the effect of GIA on plate motion models (PMMs), drawing on a set of 1D and 3D GIA model predictions. The main motivation for creating NCL20 is to include a larger number of GNSS sites in the most GIA-affected areas of investigation, namely North America, Europe, and Antarctica. We do this using the IGS repro2 data and other similarly processed GNSS data sets. Our final GNSS velocity field has horizontal uncertainties mostly within ±0.5 mm yr–1 and vertical uncertainties mostly within ±1 mm yr–1 (at 95 per cent confidence), which make it suitable for testing GIA models. We generate a suite of 117 global GIA model predictions by combining three different ice history models (ICE-5G, ICE-6G and W12) with a range of 1D and 3D Earth models. By subtracting this ensemble from the GNSS velocity field, we identify and compare a range of PMMs which are expected to be unaffected by GIA. Our method allows us to include GNSS sites that are typically excluded from PMM estimations due to their location in GIA-affected regions. We demonstrate that significant GIA-related horizontal motion outside of the rapidly uplifting regions may bias PMMs if left uncorrected. Based on their ability to explain the observed surface velocity field, a group of best-performing GIA models is selected for three regions of interest: North America, Europe and Antarctica. The range of GIA predictions in each best-performing group is assumed to represent the uncertainty in regional GIA modelling insofar as it can be constrained by present-day geodetic velocities. In the horizontal component, we note that 3D GIA models show more variation in the direction of predicted velocities than 1D GIA models, confirming that horizontal velocities are strongly sensitive to lateral variations in Earth structure. Furthermore, for Antarctica the variation in predicted GIA vertical velocities suggests that the total GIA contribution to annual gravimetric mass change ranges from –3 to 22 Gt yr–1 depending on which of the best-performing GIA models is used.

A Snapshot of New Zealand's Dynamic Deformation Field From Envisat InSAR and GNSS Observations Between 2003 and 2011

AbstractMeasuring the deformation at the Earth's surface over a range of spatial and temporal scales is vital for understanding seismic hazard, detecting volcanic unrest, and assessing the effects of vertical land movements (VLMs) on sea level rise. Here, we combine ∼10 years of Interferometric Synthetic Aperture Radar (InSAR) observations from Envisat with interseismic campaign and continuous GNSS velocities to build a high‐resolution velocity field of New Zealand. Exploiting the horizontal GNSS observations, we estimate the vertical component of the deformation to provide the VLM for the entire 15,000‐km‐long coastline. The estimated vertical rates show large variability around the country as a result of volcanic, tectonic, and anthropogenic sources. Interseismic subsidence is observed in Kaikoura region supporting models of at least partial locking of the southern Hikurangi subduction interface. Despite data challenges in the mountainous regions from landslides, sediment compaction, and glaciers, InSAR data shows localized uplift of the Southern Alps.

Resilience Monitoring for Multi-Filter All-Source Navigation Framework With Assurance

<h3>Summary</h3> The Autonomous and Resilient Management of All-source Sensors (ARMAS) framework monitors residual-space test statistics across unique sensor-exclusion banks of filters (known as <i>subfilters</i>) to provide a resilient, fault-resistant all-source navigation architecture with assurance. A critical assumption of this architecture, demonstrated in this paper, is fully overlapping state observability across all subfilters. All-source sensors, particularly those that only provide partial state information (altimeters, TDoA, AOB, etc.), do not intrinsically meet this requirement. This paper presents a novel method to monitor real-time overlapping position state observability and introduces an observability bank within the ARMAS framework, known as stable observability monitoring (SOM). SOM uses a monitoring-epoch stability analysis to provide an intrinsic awareness to ARMAS of the capabilities of the fault detection and exclusion (FDE) functionality. We define the ability to maintain consistent all-source FDE to recover failed sensors as <i>navigation resilience</i>. A resilient FDE capability is one that is aware of when it requires more sensor information to protect the consistency of the FDE and integrity functions from corruption. SOM is the first demonstration of such a system for all-source sensors that the authors are aware of. A multi-agent 3D environment simulating both GNSS and position and velocity alternative navigation sensors was created and individual GNSS pseudorange sensor anomalies are utilized to demonstrate the capabilities of the novel algorithm. This paper demonstrates that SOM seamlessly integrates within the ARMAS framework, provides timely prompts to augment new sensor information from other agents, and indicates when framework stability and preservation of all-source navigation integrity are achieved.