Background: Gas exsolution from supersaturated water injection (SWI) into porous media is of primary interest and has important applications (CCS, residual NAPL-remediation, CO2-enhanced oil recovery). Bubble formation and growth kinetics are typically studied in 2D-micro-models (sandstones-analoges; Zuo et al., 2013; Zuo and Benson, 2013). The only 3D-study was conducted by Li et al., 2017, using the NMR-method, and indicated a strong dependency of the exsolution process on the initial CO2-gas phase. However, the NMR-method was not able to attribute these different fluid-fluid-saturations to key parameters of the dissolution process such as gas cluster morphology and gas cluster size distribution. Methods: We conduct a series of column experiments to study the gas exsolution and gas cluster formation in 3D-porous media (natural sands, glass beads) using μ-CT. Based on this high-resolution non-invasive visualization method followed by image processing, we quantify (i) gas-cluster morphology, (ii) gas-cluster size distribution, (iii) correlation between pore structure and bubble formation, and (iv) the impact of surface roughness on exsolution efficiency. Results: We found that CO2-saturated water equilibrated under ambient pressure, pCO2 = 1.013 bar, (no supersaturation was measured and no pressure reduction was applied), already leads to gas exsolution of significant amount (about 10–12% gas saturation) in the presence of untreated SiO2-surfaces (natural sands, glass beads) which exhibit heterogeneous wettability. To the best of our knowledge this exsolution phenomenon was not observed before, and we assume it to be caused by fluid-rock interactions, i.e. by hydrophobic nucleation sites at the siliceous surface. The heterogeneous wettability has a dramatic impact on capillary trapping efficiency and was experimentally observed in Glass-beads monolayer (Geistlinger and Ataei, 2015, Influence of the heterogeneous wettability on capillary trapping in glass-beads monolayers: Comparison between experiments and the invasion percolation theory, J. Colloid Interface Sci., 459, 230 - 240).

We study a large and long-lived earthquakes swarm occurring in 2020-2021 in the Bransfield Basin, south of the South Shetland islands, Antarctica. We make use of local seismological stations to detect and characterize more than 36000 small earthquakes, occurring from the end of August 2020 to June 2021. Together with the occurrence of the ~36000 earthquakes, we observe a significant (up to 8cm) geodetic deformation at nearby GPS stations. By joint interpretation of b-value, spatiotemporal evolution of seismicity and geodetic deformation, we infer a volcanic origin for this swarm, which takes place close to the ridge axis. Our study suggest that a significant amount of extension observed at the Bransfield Basin ridge is occurring in rapid deformation episodes (e.g., 1 year), and is most likely driven by volcanic activity localized at the ridge axial volcanic structure, rather than at the rifting bounding border faults.

Cenozoic strike-slip deformation and associated basin formation in Indochina provide critical clues on crustal response during India-Asia collision. Typically, Indochina is considered a rigid block during continental extrusion. We demonstrate that the Song Ca-Rao Nay Fault System (SCRNFS) in north central Vietnam and its offshore extension, the Hue Sub-basin, subdivided Indochina into discrete blocks. Using an integrated dataset including topographic maps, geologic maps, onshore fieldworks, and offshore seismic and well interpretation, the structural evolution of the SCRNFS and Hue Sub-basin is investigated. During Late Oligocene, the SCRNFS initiated with right-lateral motion, causing pull-apart onshore and Hue Sub-basin opening offshore. The End-Oligocene inversion affecting the northern Song Hong Basin also caused a major NE–SW reverse fault in the Hue Sub-basin. In Early Miocene, rifting resumed in the Hue Sub-basin with accelerated faulting and westward rift migration in the south. This is distinct from the Song Hong Basin, where the main rift period was Eocene(?) – Oligocene, and the Early Miocene only features mild extension. During latest Early Miocene – earliest Middle Miocene, the SCRNFS switched to left-lateral transpression. This caused inversion and prolonged uplift in the northern-most Hue Sub-basin. The inversion associated unconformity can be traced onshore where it separates a compositionally immature conglomerate from an overlying quartz conglomerate. Left-lateral transpression in the Hue Sub-basin coincides with that in the Song Hong Basin and other inversion events across SE Asia. This may have been caused by Australia-SE Asia collision restricting escape movement of Indochina away from the India-Asia collision zone.

We explore the impact of roughness in crack walls on the P-wave modulus dispersion and attenuation caused by squirt flow. For that, we numerically simulate oscillatory relaxation tests on models having interconnected cracks with both simple and intricate aperture distributions. Their viscoelastic responses are compared with those of models containing planar cracks but having the same hydraulic aperture as the rough wall cracks. In the absence of contact areas between crack walls, we found that three apertures affect the P-wave modulus dispersion and attenuation: the arithmetic mean, minimum and hydraulic apertures. We show that the arithmetic mean of the crack apertures controls the effective P-wave modulus at the low- and high-frequency limits, thus representing the mechanical aperture. The minimum aperture of the cracks tends to dominate the energy dissipation process, and consequently, the characteristic frequency. An increase in the confining pressure is emulated by uniformly reducing the crack apertures, which allows for the occurrence of contact areas. The contact area density and distribution play a dominant role in the stiffness of the model and, in this scenario, the arithmetic mean is not representative of the mechanical aperture. On the other hand, for a low percentage of minimum aperture or in presence of contact areas, the hydraulic aperture tends to control de characteristic frequency. Analysing the local energy dissipation, we can more specifically visualise that a different aperture controls the energy dissipation process at each frequency, which means that a frequency-dependent hydraulic aperture might describe the squirt flow process in cracks with rough walls.

Introduction: Ocean Worlds are of high interest to the planetary community [1, 2] due to the potential habitability of their subsurface oceans [3–5]. Over the next few decades several missions will be sent to ocean worlds including the Europa Clipper [6], Dragonfly [7], and possibly a Europa lander [8]. The Dragonfly and Europa lander missions will carry seismic payloads tasked with detecting and locating seismic sources. The Seismometer to Investigate Ice and Ocean Structure (SIIOS) is a NASA PSTAR funded project that investigates ocean world seismology using terrestrial analogs. One goal of the SIIOS experiment is characterizing the local seismic environment of our field sites. Here we present an analysis of detected local events at our field sites at Gulkana Glacier in Alaska and in Northwest Greenland approximately 80 km North of Qaanaaq, Greenland (Fig. 1a). Both field sites passively recorded data for about two weeks. We deployed our experiment on Gulkana Glacier in September 2017 (Fig. 1b) and in Greenland in June 2018 (Fig. 1c). At Gulkana there was a nearby USGS weather station [9] which recorded wind data. Temperature data was collected using the MERRA satellite [10]. In Greenland we deployed our own weather station to collect temperature and wind data. Gulkana represents a noisier and more active environment: Temperatures fluctuated around 0C, allowing for surface runoff to occur during the day. The glacier had several moulins, and during deployment we heard several rockfalls from nearby mountains. In addition to the local environment, Gulkana is located close to an active plate boundary (relative to Greenland). This meant that there were more regional events recorded over two weeks, than in Greenland. Greenland’s local environment was also quieter, and less active: Temperatures remained below freezing. The Greenland ice was much thicker than Gulkana (~850 m [11] versus ~100 m [12, 13]) and our stations were above a subglacial lake. Both conditions can reduce event detections from basal motion. Lastly, we encased our Greenland array in an aluminum vault and buried it beneath the surface unlike our array in Gulkana where the instruments were at the surface and covered with plastic bins. The vault further insulated the array from thermal and atmospheric events. Event Detection and Clustering: To detect local events we filtered the data between 5-20 Hz. Using the Obspy module in python [14], we performed a short-term average/long-term average (STA/LTA) approach to determine where amplitudes spiked. For short term we used 1.5 seconds and 40 seconds and a ratio of 20 to detect events [15]. Through this approach we detect-ed 104 events at our Greenland site and 2252 events at our Gulkana site. The Gulkana site showed a strong correlation with both temperature and changes in temperature, while Greenland did not show this relationship [16]. Once we had a catalog of events, we performed a hierarchal cluster analysis to cluster events.

The amount and quality of land, water and atmospheric information is critical to plan, monitor, predict and mitigate the impacts of climate change, urbanization and population growth. To get reasonably accurate regional information, Ethiopia launched its first Earth Observing satellite on the 20thof December 2019 in collaboration with the government of China. The 65-kg Ethiopian Remote Sensing Satellite (ETRSS-1) carries one earth observing multispectral camera to measure many aspects of land, water and biosphere. It was placed on sun-synchronous orbit at an altitude of 628.61km and collects images at a Ground Sampling Distance (GSD) of 13.75-m within a revisit period of 4 days. Currently, all the instruments are operating as intended and the early-stage images captured by ETRSS-1 are within sensible and acceptable range. This indicates that it can serve as a supplementary and alternative data source to operational and research services.

Mapping fluid accumulation in the crust is pertinent for numerous applications including volcanic hazard assessment, geothermal energy generation and mineral exploration. Here, we use seismic attenuation tomography to map the distribution of fluids in the crust below Uturuncu volcano, Bolivia. Seismic P-wave and S-wave attenuation, as well as their ratio (QP/QS), constrain where the crust is partially and fully fluid-saturated. Seismic anisotropy observations further constrain the mechanism by which the fluids accumulate, predominantly along aligned faults and fractures in this case. Furthermore, subsurface pressure-temperature profiles and conductivity data allow us to identify the most likely fluid composition. We identify shallow regions of both dry and H2O/brine-saturated crust, as well as a deeper supercritical H2O/brine column directly beneath Uturuncu. Our observations provide a greater understanding of Uturuncu’s transcrustal hydrothermal system, and act as an example of how such methods could be applied to map crustal fluid pathways and hydrothermal/geothermal systems elsewhere.

The Transantarctic Mountains (TAM) separate the warmer lithosphere of the West Antarctic rift system and the colder East Antarctic craton. Low velocity zones beneath the TAM imaged in recent seismological studies have been interpreted as warm low-density mantle material, suggesting a strong contribution of thermal support to the uplift of the TAM. We present new Curie Depth Point (CDP) and geothermal heat flow (GHF) maps of the northern TAM and adjacent Wilkes Subglacial Basin (WSB) based on high resolution magnetic airborne measurements. We find shallow CDP and high GHF, beneath the northern TAM reinforcing the idea of thermal support of the topography of the mountain range. Additionally, locally high GHF is observed in the Central Basin of the WSB and the Rennick Graben, which has not been resolved previously, while the broader WSB show lower GHF. Across the study area the GHF values range from 30 to 110 mW/m2. Lastly, we compare our CDP estimates to recent Moho depth estimates and our GHF estimates to sparse in situ GHF measurements as well as to existing continent-wide GHF estimates, which shows closed agreement to previous seismic estimates.

Copper-Au magmatic-hydrothermal systems dominate in the Chibougamau area of the Neoarchean Abitibi subprovince (greenstone belt) of the Superior Province (craton), whereas orogenic gold mineralization is more common in the rest of the Abitibi. Understanding differences in metal endowment within the Abitibi greenstone belt requires insights into the geodynamic evolution of the Chibougamau area. This was addressed by imaging the crust using seismic reflection profiling acquired as part of the Metal Earth project. Seismic reflection sections display shallowly south-dipping reflectors located within the upper-crust (e.g., deep continuation of the Barlow fault) and a northward-dipping mid-crust imbricated with older crust (Opatica subprovince) to the north. Multiple reflectors characterize the upper part of the mid-crust, interpreted as faults superimposed on a major lithological boundary. These structures likely formed during terrane accretion prior to craton stabilization. Combining the new seismic data with known stratigraphic, structural and magmatic records, we propose that the study area was initially a normal (i.e., thick) Archean oceanic crust that formed at or before 2.80 Ga and that evolved through terrane imbrication at 2.73-2.70 Ga. Shortening caused rapid burial, devolatilization and partial melting of hydrated mafic rocks to produce tonalite magmas that may have mixed with mantle-derived melts to produce the diorite-tonalite suite associated with observed Cu-Au magmatic-hydrothermal mineralization.

The digital zenith camera VESTA (VErtical by STArs) was designed by the Institute of Geodesy and Geoinformatics (GGI) of the University of Latvia and completed in 2016. Since that more than 300 terrestrial vertical deflection measurements were observed in the territory of Latvia. These observations were post-processed by the GGI developed software and the accuracy was evaluated at 0.1 arc seconds. Terrestrial observations were compared with global geopotential models, e.g. GGM+ and EGM2008. The results show a better correspondence with GGM+ model by evaluating the standard deviation: 0.314 and 0.307 arcseconds for ξ and η components respectively in comparison to 0.346 and 0.358 arcseconds for ξ and η components for EGM2008 model. The comparisons of average and minimum/maximum differences are introduced in this study for better evaluation of the results. Moreover, vertical deflections have been used as additional terrestrial data in DFHRS (Digital Finite-element Height Reference Surface) software v. 4.3 in combination with GNSS/levelling data (B, L, h|H) and global geopotential model EGM2008 for gravity field and quasi-geoid improvement (www.dfhbf.de). The results of the computed quasi-geoid models using different types of data are introduced in this research, representing several solutions, as well as these solutions are compared with the national quasi-geoid model LV’14. In the middle of 2019, the new upgraded version of digital zenith camera was developed by the scientific staff and the accuracy of the measurements of improved camera was evaluated at 0.05 arcseconds, which is two times better than previous one. The improvements of new digital zenith camera are also discussed in this research. It is important to point out that according to our observations the application of digital zenith camera reveals a new capabilities for studies of mass distribution beneath earth.

Recent fast developments of satellite magnetic observations facilitate global Lithospheric Magnetic Field (LMF) modelling and their applications to subsurface tectonics. Here, the vertical component (Bz) of LMF at an altitude of 200km in Mainland China and surroundings is calculated from two global LMF models NGDC-720 and EMM2017. Next, Bz is used to invert the Curie Point Depth (CPD) by Equivalent Source Dipole (ESD) forward and Nonlinear Conjugate Gradient Method (NCGM) inversion scheme. Then, the surficial Heat Flux (HF) is derived by a simple one-dimensional steady heat conduction equation from the CPD distribution. At last, the continental seismicity is compared statistically to Bz, CPD and HF. Our essential conclusions are as follow: 1) Histograms and boxplots show that most (81.8%) earthquakes (EQs, Ms≥5.0) occurred in negative Bz areas, and more than a half (53.2%) number of EQs (corresponding to an energy percent of 94.6%) occurred inside areas with Bz between -5 and -3nT, in a period between 2004 and 2007, which is the same with the satellite data collection. When the time span is extended (most to 110 years), these phenomena maintain while weaken; 2) Most (88%) EQs occurred in areas with CPD between 10 and 30km, while only a few (7% and 5%) occurred in shallow (<10km) and deep (>30km) CPD areas, in a period between 2000 and 2010; 3) EQs seldom occurred inside cold areas (HF<50mW/m2), and are prone to occur in warm areas (HF>120mW/m2). EQs are also prone to occur along the boundaries of warm or cold areas. The mechanism of the correlations between EQs and Bz, CPD and HF maybe the lithospheric strength jumps caused by the temperature variations at boundaries between blocks with different CPDs.

Old abandoned coal working create major hazards in the form of subsidence of the coalfields. To avoid such hazards, there is need to detect these cavities prior to start of deeper seam mining. There are number of geophysical techniques available for detecting subsurface cavity. High-resolution seismic survey is one such technique which provides accurate results as compared to others. Usually, most of the seismic processing and interpretation of these cavity detection was performed based on stacked data only. To understand these signatures more precisely, in our study, an attempt has been made to image these cavities with the help of Reverse Time Migration (RTM) combined with Full Waveform Inversion (FWI). RTM mostly used for hydrocarbon exploration targets with low central frequency as source. Application of this method to shallow subsurface exploration is still in research stage. Like the same way for velocity model updating, FWI gives mostly appropriate optimization results as compare to other techniques, but it also has the limitation to application of low frequency only. In this paper we first develop a 2D realistic Water Filled Cavity (WFC) model with a work flow of RTM combined with FWI in a high-frequency Ricker source wavelet as 100 Hz. In order to provide a velocity model with high accuracy for RTM, we apply FWI to estimate the subsurface velocity by considering an initial smooth velocity model with addition of 30 % Gaussian noise. The conventional RTM fails to image the cavities and yield a large amount of low frequency back scattered noise at shallow depth during the time of cross correlation due to time/space lag. To avoid these situation, we introduced an automatic shift operator at the time of imaging condition that operates automatically both in time or space. It leads to reduce the lag and improve the results by minimizing the noises at shallow subsurface. By comparing both the results it is observed that most of the noises in the migrated section of conventional method were eliminated by the improved form of RTM with the help of FWI velocity model estimation.

Deformation mechanisms of glaciers are highly sensitive to basal temperature; the motion of temperate glaciers is dominated by basal slip while cold-based glaciers deform mainly by internal creep. While basal slip is usually aseismic, unstable slip sometimes occurs and can be detected by seismometers. I have detected clusters of repeating low-frequency icequakes (LFIs) in the Mont-Blanc massif. Some properties of LFIs are similar to the high-frequency icequakes (HFIs) located at the base of Argenti\‘ere glacier (Helmstetter et al., 2015). Both HFIs and LFIs occur as bursts of tens to several thousand events lasting for days or weeks, with typical inter-event times of several minutes during bursts. Unlike HFIs that have a broad spectra, LFIs have a characteristic frequency of about 5 Hz at all stations, suggesting a rupture length of about 100 m. Seismic amplitudes and seismic waveforms of LFIs progressively evolve with time within each cluster, suggesting changes in either rupture length or rupture velocity. Most LFIs are detected during snowfall episodes while HFIs are not correlated with snowfall episodes. In this study, I used all available seismic stations within or around the Mont-Blanc massif between 2017 and 2022. I found LFIs located all over the massif but mainly above 3000 m. Some clusters are clearly associated with cold basal ice (near Mont-Blanc summit) while others below 2700 m a.s.l. are likely located under temperate glaciers and two clusters could be associated with landslides. This observation of LFIs on cold glaciers is consistent with laboratory friction experiments suggesting that cold ice promotes unstable slip.

To understand the causes of climate change, it is necessary to consider the relationship between the various physical fields of our planet. The relationship between variations in atmospheric circulation and the magnetic field has received little attention.We studied changes of atmospheric circulation in the lower troposphere and geomagnetic field in the Northern Hemisphere during the 20th and beginning of the 21th centuries to determine spatial-temporal relations between variations of these fields . Integral characteristics of atmospheric circulation and geomagnetic field have been investigated in the latitudinal band 40-70o N , applying the same approach. In the indicated latitudinal range, the main centers of action of the atmosphere in the Northern Hemisphere are located (Canadian and Siberian anticyclones, North Atlantic ridge, and Icelandic and Aleutian depressions and European trough), as well as global geomagnetic anomalies (Canadian and Siberian). For the analyzed time period there is the most complete set of observational data, which ensures high reliability of the results obtained. The time diagrams were plotted for atmospheric circulation and magnetic field by their integral characteristics. Their comparison showed that the minima and maxima of the pressure field and the full vector of the geomagnetic field coincide quite well. This allows to assume that trends in changes in the geomagnetic field and atmospheric circulation, which were outlined at the beginning of this millennium, will continue in the coming decades. For prediction of global changes of the air pressure and geomagnetic fields in the future it is possible using the same methodology.

In this study, we for the first time applied a joint geodynamic-geophysical inversion (JGGI) approach to oceanic plateau subduction models, and compared the subduction style and corresponding topography and Bouguer gravity of two representative subduction scenarios with passive or active collision. We showed that the case of passive collision of the Ontong Java Plateau (OJP) crust better explains the topography, gravity, and seismic data than the active collision scenario. This implies that the OJP did not control the regional dynamics during the collisional process. We conclude that previous studies may have overestimated the role of the OJP in triggering subduction initiation, subduction polarity reversal, and even Pacific Plate rotation.

We propose a novel scheme that applies a multitasking convolutional neural network to learn the back azimuthal behavior from receiver function seismograms, which can effectively predict the depth and occurrence of the Moho beneath a single seismic station. Our scheme consists of three main steps: 1. Based on the style transfer technique, we generate 9000 synthetic receiver function seismograms blended by realistic noise as training data sets. 2. A multitasking convolutional neural network is trained to predict the depth and occurrence of the Moho. 3. All real receiver function seismograms are reconstructed by the accelerated joint iterative method before prediction. We apply the scheme to study the middle-southern of the Tanlu fault zone and adjacent regions and successfully achieve the depth and occurrence of the Moho beneath 10 permanent seismic stations. The predicted depths are in agreement with the results computed by conventional methods, and the predicted strikes and dip angles present an undulating Moho with near NE-striking. Moreover, the predicted strikes are nearly consistent with the strikes of the normal faults in the upper crust, which implies that intense continental extension in the Cretaceous play a prominent role in the tectonic deformation of the brittle upper crust and the ductile lower crust simultaneously. Besides, it helps to illustrate that the stress field orientation of the major geological event can be recorded and preserved in the lower crust.

Synthetic aperture radar (SAR) multi-temporal techniques have been proposed to improve image resolution, persistent-scatterer detection, and damage-map generation (Bujor et al., 2004; Hooper, 2008; Yun et al., 2012). The usage of multiple scenes diminishes the speckle noise commonly present in a SAR image and increases the overall signal-to-noise ratio (SNR) of dominant radar scatterers. Following the same idea, we propose a new SAR processing workflow based on the back-projection algorithm (Cafforio et al., 1991). We employ the back-projection method’s flexibility to focus the radar pulses at multiple depths shifted with respect to the reference digital elevation model (DEM), yielding a volume of SLCs discretely sampled over a range of elevations/depths. These scenes are then combined to produce a single-look complex (SLC) image, which presents increased SNR and effective resolution. Similar image improvements can be achieved by spatially averaging a SLC image generated at high spatial sampling. However, the proposed method requires a fraction of the processing time of the fine-spatial SLC formation. The proposed approach retains the same benefits of any back-projection algorithm and enables the formation of SLC images corresponding to large Earth surface extents.

In the last 20 years, there has been an international effort to develop approaches to experimentally measure the petrophysical and geomechanical properties of hydrate-bearing core samples. The measurements are extremely challenging because sub-sampling, sample preparation, and testing must be conducted at high pressure and low temperature. Despite these challenges, multiple laboratories are now measuring the geotechnical properties of hydrate-bearing sediments. However, there have been relatively few attempts to validate these measurements. We developed experimental protocols to accurately conduct zero-lateral strain tests at effective stresses up to 20 MPa using a pressure core triaxial device. We directly measure displacement during compression through periodic instantaneous undrained loading. To evaluate the accuracy of our measurement system, we conducted a benchmark study to compare properties obtained in our pressure core test chamber against classical geotechnical devices. We prepared a Boston Blue Clay specimen through re-sedimentation. Comprehensive properties databases favor the use of this material for comparison analyses. A compression test to 20 MPa accurately reproduced the compression, lateral stress, and permeability behavior demonstrated in previous testing programs. This experimental procedure provides a convenient framework for future validation studies in a broad range of pressure core laboratory devices.

The Schumann resonance (SR), the source of which is the global thunderstorm activity is constantly observed in the Earth-ionosphere waveguide. Changes in the parameters of SR signals caused by geophysical disturbances make it possible to study the state and dynamics of the lower ionosphere. When calculating the SR parameters, there are problems associated with the impact of electromagnetic interference of natural and anthropogenic origin. The main natural sources of interference are signals associated with the radiation of nearby lightning discharges, as well as the influence of the Alfvén ionospheric resonator. The paper presents a new method for calculating the SR parameters,which significantly reduces the impact of these interferences. The developed technique significantly increased the temporal resolution of the obtained data on the frequency and amplitude of the SR. Due to this, it became possible to study the influence of fast heliogeophysical disturbances (such as solar X-ray flares) on the lower ionosphere and, as a consequence, on the parameters of the SR. An analysis of the experimental data made it possible to establish a linear dependence of the SR frequency on the logarithm of the X-ray flux in the range up to 0.2 nm during a class X solar flare.

InSAR measurements of ground displacement are relative, due to unknown integer ambiguities introduced during propagation of the signal through the atmosphere. However, these ambiguities mostly cancel when using spectral diversity to estimate along-track (azimuth) velocities allowing measurements to be made with respect to a terrestrial reference frame. Here, we calculate along-track velocities for a partial global dataset of Sentinel-1 acquisitions as processed by the COMET LiCSAR system, and find good agreement with model values from ITRF2014 plate motion model. We include corrections for solid-Earth tides and gradients of ionospheric total electron content based on a moderate resolution model IRI2016. Application of tidal corrections improves the average velocity precision from 23 to 11 mm/yr. Ionospheric corrections, however, have significant effect only in near-equatorial regions. The median difference between along-track velocities and values predicted by ITRF2014 is 3 mm/yr. A preliminary study using reprocessed precise orbit determination products in a limited dataset shows significant improvement in both precision and accuracy. By combining data from ascending and descending orbits we are able to estimate north-south (N-S) and east-west (E-W) velocities with an average precision of 3 and 16 mm/yr, respectively. Although we have calculated these estimates over large 250 x 250 km areas, such measurements can also be made at much higher resolution, albeit with lower precision. These “absolute” measurements can be particularly useful for global velocity and strain rate estimation, where GNSS measurements are sparse. We will also investigate large-scale averages of across-track (range) pixel offsets, which are most sensitive to E-W and vertical displacements, and perform a comparison to a GNSS network in selected areas.

On 20 July 2017, an Mw6.6 earthquake occurred offshore Kos Island, the largest to occur in the affected area in the instrumental era, and in the past 60 years in the southeastern Aegean Sea. We estimated the aftershocks relative locations by applying the double-difference technique using both differential times from phase-picked data and waveform cross-correlation. The relocated aftershocks are clustered at least in three distinctive patches, creating a zone getting a total length of about 40 km, elongated in a nearly east-west direction, mainly concentrated at depths 8–15 km, with the mainshock hypocenter placed at ~13 km, implying a seismogenic layer of 7 km thickness, indicative for normal faulting earthquakes with Mmax~6.5. The aftershock fault plane solutions are predominantly suggestive of normal faulting in response to the north-south extension of the back-arc Aegean area. We further applied the satellite radar interferometry (InSAR) technique to define the coseismic surface displacements. This field of deformation along with the available vectors of displacement measured by the Global Navigation Satellite System (GNSS) technique was combined with the seismological data to determine the rupture geometry and process, with the coseismic slip ranging between 0.5 and 2.3 m. The peak moment release occurred in the depth interval of 9–11 km, consistent with the depth distribution of seismicity in the study area. We used the variable slip model to calculate Coulomb stress changes and investigate possible triggering due to stress transfer to the nearby fault segments.

We present a fully Bayesian inverse scheme to determine second moments of the stress glut using teleseismic earthquake seismograms. The second moments form a low-dimensional, physically-motivated representation of the rupture process that captures its spatial extent, source duration, and directivity effects. We determine an ensemble of second moment solutions by employing Hamiltonian Monte Carlo and automatic differentiation to efficiently approximate the posterior. This method explicitly constrains the parameter space to be symmetric positive definite, ensuring the derived source properties have physically meaningful values. The framework accounts for the autocorrelation structure of the errors and incorporates hyperpriors on the uncertainty. We validate this methodology using a synthetic test and subsequently apply it to the 2019 Mw7.1 Ridgecrest earthquake using teleseismic data. The distributions of second moments determined for this event provide probabilistic descriptions of low-dimensional rupture characteristics that are generally consistent with results from previous studies. The success of this case study suggests that probabilistic and comparable finite source properties may be discerned for large global events regardless of the quality and coverage of local instrumentation.

The Great Lakes region is usually considered to be seismically inactive. However, earthquakes do occur around this region and may be related to stress changes caused by water level fluctuations. We perform a systematic template matching analysis of regional seismicity in 2013-2020 and calculate the Coulomb stress change caused by water loading. The new catalog reveals 20-40 M>0 earthquakes/year before 2019. The high seismicity rate in 2019 is dominated by active aftershocks following the ML4.0 Ohio earthquake. Given the limited number of earthquakes, neither seasonal pattern nor obvious increasing trend of seismicity with fluctuating water levels can be established. However, we cannot rule out the role of increasing water level in reactivating the faults that host the 2019 Ohio earthquake sequence. The lake loading induced stress change is found to increase with water level at low effective friction coefficient, with maximum positive stress change of ~0.2 KPa (µ = 0.2).

We present a fully Bayesian inverse scheme to determine second moments of the stress glut using teleseismic earthquake seismograms. The second moments form a low-dimensional, physically-motivated representation of the rupture process that captures its spatial extent, source duration, and directivity effects. We determine an ensemble of second moment solutions by employing Hamiltonian Monte Carlo and automatic differentiation to efficiently approximate the posterior. Our method explicitly constrains the parameter space to be symmetric positive definite, ensuring the derived source properties have physically meaningful values. The framework accounts for the autocorrelation structure of the errors and incorporates hyperpriors on the uncertainty. We validate the methodology using a synthetic test and subsequently apply it to the 2020 Mw 7.7 Caribbean earthquake. The second moments determined for this event indicate the rupture was nearly unilateral and relatively compact along-strike. The solutions from this inverse framework can resolve ambiguities between slip distributions with minimal a priori assumptions on the rupture process.