Satellite Radar Interferometry Data Research Articles

The February 6, 2023, Earthquakes in Turkey: A Model of the Rupture Surface Based on Satellite Radar Interferometry

Two strike–slip faults, displacements along which caused the catastrophic earthquakes in Turkey on February 6, 2023, were mapped from satellite radar interferometry data. According to the satellite data, the relative displacements of the sides of the East Anatolian Fault Zone (EAFZ), with which the first event of Mw 7.8 was associated, exceeded 5 m in the central segment. The rupture surface extends from the area of the Doğanyol-Sivris earthquake Mw 6.7 of January 24, 2020, in the north to the Mediterranean coast in the south, where the earthquake Mw 6.3 occurred on February 20, 2023. The second event Mw 7.5 is associated with the Surgü-Çardak fault; the relative displacements of its sides, according to satellite data, exceeded 7 m. The obtained displacement fields of the Earth’s surface were used to construct a model of the seismic rupture. This model was worked out on the basis of the Pollitz, 1996 solution, which defines displacements on the surface of the spherically stratified planet as a result of along dip and strike displacements on a rectangular rupture located inside the sphere. Ignoring the spherical stratification of the planet leads to errors of up to 20%, especially in the presence of a large strike–slip component [5]. Ignoring sphericity also causes an error, when using the solution obtained for an elastic homogeneous half-space, as the US Geological Survey (USGS) has done, in modeling the seismic rupture for earthquakes in Turkey in 2023. Our model differs in the detailed consideration of the fault geometry. For this purpose, the faults were approximated by 19 planes along the strike, divided into two levels along the dip. In our rupture model strike–slip displacements in the central segment of the EAFZ reached 12.7 m. In the southern segment of this rupture, the displacements are much smaller. It should be emphasized that we registered the displacements for the period from January 29, 2023, to February 10, 2023; therefore, together with co-seismic ones, they also include post-seismic displacements for four days after the main seismic events. The displacements on the rupture surface along the Surgü-Çardak Fault, where the Mw 7.5 earthquake occurred, were up to 10 m. The results demonstrate, in particular, the efficiency of application of the satellite radar interferometry in the operative study of catastrophic geodynamic phenomena and processes.

EARTHQUAKES IN TURKEY 06.02.2023: MODEL OF THE RUPTURE SURFACE BASED ON SATELLITE RADAR INTERFEROMETRY

Satellite radar interferometry data made it possible to clearly map two faults, shear displacements along which caused catastrophic earthquakes on February 06, 2023 in Turkey. According to satellite data, the relative displacements of the sides of the East Anatolian Fault Zone (EAFZ), to which the first event with a magnitude of Mw 7.8 was associated, exceeded 5 m in the central segment. The rupture surface extends from the area of the Doğanyol-Sivris of 24.01.2020 Mw 6.7 earthquake in the north to the Mediterranean coast in the south, where the earthquake Mw 6.3 occurred on 20.02.2023. The second event of Mw 7.5 is associated with the Surgü-Çardak fault, and the relative displacements of its sides, according to satellite data, exceeded 7 m. The obtained displacement fields of the Earth’s surface were used to construct a model of the seismic rupture. The model is based on the solution [5], which defines displacements on the surface of a spherically stratified planet as a result of dip and strike displacements on a rectangular rupture located inside the sphere. Ignoring the spherical stratification of the planet leads to errors of up to 20%, especially in the presence of a large shear component [5]. Also, an error is introduced by ignoring sphericity when using the solution obtained for an elastic homogeneous half-space [6], as the US Geological Survey (USGS) did when building seismic rupture models for earthquakes in Turkey in 2023. The difference of our model is the detailed consideration of the fault geometry. For this purpose, the faults were approximated by 19 planes along the strike, divided into two levels along the dip. In the built model, shear displacements in the central segment of the EAFZ reached 12.7 m. In the southern segment of this rupture, the displacements are substantially smaller. It should be emphasized that we registered the displacements for the period from January 29 to February 10, 2023, i.e. together with coseismic ones, they also include postseismic displacements for 4 days after the main seismic events. The displacements on the rupture surface along the Surgü-Çardak fault, where an Mw 7.5 earthquake occurred, reached 10 m. The obtained results demonstrate, in particular, the efficiency of application of satellite radar interferometry in the operative study of catastrophic geodynamic phenomena and processes.

Melt rates in the kilometer-size grounding zone of Petermann Glacier, Greenland, before and during a retreat

Warming of the ocean waters surrounding Greenland plays a major role in driving glacier retreat and the contribution of glaciers to sea level rise. The melt rate at the junction of the ocean with grounded ice-or grounding line-is, however, not well known. Here, we employ a time series of satellite radar interferometry data from the German TanDEM-X mission, the Italian COSMO-SkyMed constellation, and the Finnish ICEYE constellation to document the grounding line migration and basal melt rates of Petermann Glacier, a major marine-based glacier of Northwest Greenland. We find that the grounding line migrates at tidal frequencies over a kilometer-wide (2 to 6 km) grounding zone, which is one order of magnitude larger than expected for grounding lines on a rigid bed. The highest ice shelf melt rates are recorded within the grounding zone with values from 60 ± 13 to 80 ± 15 m/y along laterally confined channels. As the grounding line retreated by 3.8 km in 2016 to 2022, it carved a cavity about 204 m in height where melt rates increased from 40 ± 11 m/y in 2016 to 2019 to 60 ± 15 m/y in 2020 to 2021. In 2022, the cavity remained open during the entire tidal cycle. Such high melt rates concentrated in kilometer-wide grounding zones contrast with the traditional plume model of grounding line melt which predicts zero melt. High rates of simulated basal melting in grounded glacier ice in numerical models will increase the glacier sensitivity to ocean warming and potentially double projections of sea level rise.

Application of Sntinel-1 radar interferometric images for the monitoring of vertical displacements of the earth’s surface affected by non-tidal atmospheric loading

The vertical movements of the Earth’s surface affected by non-tidal atmospheric loading (NTAL) are analyzed using satellite radar interferometry data. A clear relationship between deformation maps data derived from radar interferometry data and the GNSS time series of permanent stations has been established. The object of the study was the areas around the GNSS stations BYCH (Buchach), GORD (Horodok), CRNT (Chernivtsi). The input data were four pairs of radar interferometric images for the specified areas.Radar satellite images were obtained from the Sentinel-1A spacecraft. Data type — SLC (Single Look Complex) with vertical polarization. Acquisition mode — wideband interferometric IW (Interferometric Wide Swath). Data were processed using SNAP (Sentinel Application Platform) software. The processing yileded maps of vertical displacement of the specified territories where the earth’s surface displacement caused by influence of non-tidal atmospheric loading had taken place. The values obtained on the basis of vertical displacement maps have a high agreement with the results of time series of changes in the altitude position of permanent GNSS stations. The results obtained in the article are of both scientific and practical importance for studying the impact of non-tidal atmospheric loading in large areas. The practical significance is in improving the accuracy of terrestrial geodetic measurements’ processing, in particular high-precision levelling. The research data allow to make corrections of the results of levelling for short-period displacements affected by the influence of non-tidal atmospheric loading (NTAL).

Seasonal Acceleration of Petermann Glacier, Greenland, From Changes in Subglacial Hydrology

AbstractPetermann Glacier is a major outlet glacier of northern Greenland that drains a marine‐based basin vulnerable to destabilization from enhanced oceanic and atmospheric forcings. Using satellite radar interferometry data from the Sentinel‐1a/b missions, we observe a seasonal glacier acceleration of 15% in the summer, from 1,250 to 1,500 m/yr near the grounding line, but the physical drivers of this seasonality have not been elucidated. Here, we use a subglacial hydrology model coupled one‐way to an ice sheet model to evaluate the role of subglacial hydrology as a physical mechanism explaining the seasonal acceleration. We find excellent agreement between the observed and predicted velocity in terms of timing and magnitude with the addition of an applied lower limit on effective pressure of 6% of ice overburden pressure. We conclude that seasonal changes in subglacial hydrology are sufficient to explain the observed seasonal speed up of Petermann Glacier.

Landslide Sensitivity and Response to Precipitation Changes in Wet and Dry Climates.

Slow‐moving landslides are hydrologically driven. Yet, landslide sensitivity to precipitation, and in particular, precipitation extremes, is difficult to constrain because landslides occur under diverse hydroclimatological conditions. Here we use standardized open‐access satellite radar interferometry data to quantify the sensitivity of 38 landslides to both a record drought and extreme rainfall that occurred in California between 2015 and 2020. These landslides are hosted in similar rock types, but span more than ∼2 m/yr in mean annual rainfall. Despite the large differences in hydroclimate, we found these landslides exhibited surprisingly similar behaviors and hydrologic sensitivity, which was characterized by faster (slower) than average velocities during wetter (drier) than average years, once the impact of the drought diminished. Our findings may be representative of future landslide behaviors in California where precipitation extremes are predicted to become more frequent with climate change.

Satellite radar interferometry: Potential and limitations for structural assessment and monitoring

The present paper analyzes potential and limitations of multi-temporal Differential Synthetic Aperture Radar Interferometry (DInSAR) techniques applied for the structural monitoring and assessment of constructions affected by different external actions. A comprehensive approach for the processing, interpretation and proper use of satellite radar interferometry data for structural analyses at urban and single-construction scales is proposed. Following a brief literature review, highlighting the most relevant applications in this field, some aspects concerning DInSAR techniques are shortly summarized, particularly focusing on the Small BAseline Subset (SBAS) approach applied to perform advanced analyses at structural level. Then, the main issues of the DInSAR measurements exploitation for structural applications are discussed, focusing on the use of both one or two datasets relevant to ascending and descending satellite passes. Analysis at the scale of single construction (i.e., building, bridge, etc.) of displacements time series and mean deformation velocities is discussed, in order to identify scenarios that may become potentially critical for the structures. Some application examples are provided, employing COSMO-SkyMed (CSK) datasets relative to the urban area of Rome (Italy), acquired during the 2011–2019 time interval and processed through the SBAS algorithm. Specific considerations related to the use of DInSAR measurements for structural monitoring and assessment are then proposed, also discussing possible approaches for preliminary and detailed evaluation of structural damages.

Integrated Procedure for Monitoring and Assessment of Linear Infrastructures Safety (I-Pro MONALISA) Affected by Slope Instability

The occurrence of geological events such as landslides is one of the main causes of damage along linear infrastructures: Damage to transport infrastructures, as roads, bridges, and railways, can restrict their optimal functions and contribute to traffic accidents. The frequent and accurate monitoring of slope instability phenomena and of their interaction with existing man-made infrastructures plays a key role in risk prevention and mitigation activities. In this way, the use of high-resolution X-band synthetic aperture radar (SAR) data, characterized by short revisiting times, has demonstrated to be a powerful tool for a periodical noninvasive monitoring of ground motion and superstructure stability, aimed at improving the efficiency of inspection, repairing, and rehabilitation efforts. In the present work, we suggest a semiautomatic GIS approach, which, by using satellite radar interferometry data and results of geomorphological field survey integrated in a qualitative vulnerability matrix, allows to identify sections with different levels of damage susceptibility, where detailed conventional in situ measurements are required for further analysis. The procedure has been tested to investigate landslide-induced effects on a linear infrastructure in Campania Region (Italy), the Provincial Road “P.R. 264”, which is affected, along its linear development, by several slope instabilities. COSMO-SkyMed interferometric products, as indicator of ground kinematics, and results of in situ damage survey, as indicator of consequences, have been merged in a qualitative 4 × 4 matrix, thus obtaining a vulnerability zoning map along a linear infrastructure in January 2015. Furthermore, an updating of landslide inventory map is provided: In addition to 24 official landslides pre-mapped in 2012, 30 new events have been identified, and corresponding intensity and state of activity has been detected.

State of the undermined Karaganda Coal Basin area by satellite monitoring data

The application of integrated monitoring of ground subsidence, including geotechnical calculations of rock mass movements, leveling and satellite radar interferometry, is considered in terms of the Karaganda Coal Basin. The satellite radar interferometry data show reliable measurement of ground subsidence as a consequence of underground mining.

Grounding line retreat of Pope, Smith, and Kohler Glaciers, West Antarctica, measured with Sentinel‐1a radar interferometry data

AbstractWe employ Sentinel‐1a C band satellite radar interferometry data in Terrain Observation with Progressive Scans mode to map the grounding line and ice velocity of Pope, Smith, and Kohler glaciers, in West Antarctica, for the years 2014–2016 and compare the results with those obtained using Earth Remote Sensing Satellites (ERS‐1/2) in 1992, 1996, and 2011. We observe an ongoing, rapid grounding line retreat of Smith at 2 km/yr (40 km since 1996), an 11 km retreat of Pope (0.5 km/yr), and a 2 km readvance of Kohler since 2011. The variability in glacier retreat is consistent with the distribution of basal slopes, i.e., fast along retrograde beds and slow along prograde beds. We find that several pinning points holding Dotson and Crosson ice shelves disappeared since 1996 due to ice shelf thinning, which signal the ongoing weakening of these ice shelves. Overall, the results indicate that ice shelf and glacier retreat in this sector remain unabated.

Ice flow in Greenland for the International Polar Year 2008–2009

A digital representation of ice surface velocity is essential for a variety of glaciological, geologic and geophysical analyses and modeling. Here, we present a new, reference, comprehensive, high‐resolution, digital mosaic of ice motion in Greenland assembled from satellite radar interferometry data acquired during the International Polar Year 2008 to 2009 by the Envisat Advanced Synthetic‐Aperture Radar (ASAR), the Advanced Land Observation System (ALOS)'s Phase‐Array L‐band SAR (PALSAR) and the RADARSAT‐1 SAR that covers 99% of the ice sheet in area. The best mapping performance is obtained using ALOS PALSAR data due to higher levels of temporal coherence at the L‐band frequency; but C‐band frequency SAR data are less affected by the ionosphere. The ice motion map reveals various flow regimes, ranging from patterned enhanced flow into a few large glaciers in the cold, low precipitation areas of north Greenland; to diffuse, enhanced flow into numerous, narrow, fast‐moving glaciers in the warmer, high precipitation sectors of northwest and southeast Greenland. We find that the 100 fastest glaciers (v> 800 m/yr) drain 66% of the ice sheet in area, marine‐terminating glaciers drain 88% of Greenland, and basal‐sliding motion dominates internal deformation over more than 50% of the ice sheet. This view of ice sheet motion provides significant new constraints on ice flow modeling.

Slow earthquake in Afghanistan detected by InSAR

The Chaman fault system forms a prominent ∼900‐km‐long left‐lateral transform plate boundary between the Indian and Eurasian plates in Afghanistan and Pakistan. Here we show satellite radar interferometry data that revealed an afterslip (or slow earthquake) signal following an earthquake of magnitude 5.0. This slow slip episode lasted for more than a year, and accompanied a widespread creep signal that occurred at least ∼50 km along the fault. We detected no surface slip before the earthquake during the 1.5 years sampled by our data. This finding of long‐lasting widespread afterslip demonstrates that the plate motion along the Chaman Fault is accommodated by slow slip episodes following moderate earthquakes, and suggests that a potential for magnitude 7‐class earthquakes was significantly reduced. The duration and moment release of the detected afterslip do not fit the recently proposed scaling law for slow earthquakes.

Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet

Using time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, we estimate ice mass changes over Greenland during the period April 2002 to November 2005. After correcting for the effects of spatial filtering and limited resolution of GRACE data, the estimated total ice melting rate over Greenland is -239 +/- 23 cubic kilometers per year, mostly from East Greenland. This estimate agrees remarkably well with a recent assessment of -224 +/- 41 cubic kilometers per year, based on satellite radar interferometry data. GRACE estimates in southeast Greenland suggest accelerated melting since the summer of 2004, consistent with the latest remote sensing measurements.

Recent ice loss from the Fleming and other glaciers, Wordie Bay, West Antarctic Peninsula

Satellite radar interferometry data from 1995 to 2004, and airborne ice thickness data from 2002, reveal that the glaciers flowing into former Wordie Ice Shelf, West Antarctic Peninsula, discharge 6.8 ± 0.3 km3/yr of ice, which is 84 ± 30 percent larger than a snow accumulation of 3.7 ± 0.8 km3/yr over a 6,300 km2 drainage basin. Airborne and ICESat laser altimetry elevation data reveal glacier thinning at rates up to 2 m/yr. Fifty km from its ice front, Fleming Glacier flows 50 percent faster than it did in 1974 prior to the main collapse of Wordie Ice Shelf. We conclude that the glaciers accelerated following ice shelf removal, and have been thinning and losing mass to the ocean over the last decade. This and other observations suggest that the mass loss from the northern part of the Peninsula is not negligible at present.

Rheology of the Ronne Ice Shelf, Antarctica, inferred from satellite radar interferometry data using an inverse control method

The Antarctic Ice Sheet is surrounded by large floating ice shelves that spread under their own weight into the ocean. Ice shelf rigidity depends on ice temperature and fabrics, and is influenced by ice flow and the delicate balance between bottom and surface accumulation. Here, we use an inverse control method to infer the rigidity of the Ronne Ice Shelf that best matches observations of ice velocity from satellite radar interferometry. Ice rigidity, or flow law parameter B, is shown to vary between 300 and 900 kPa a1/3. Ice is softer along the side margins due to frictional heating, and harder along the outflow of large glaciers, which advect cold continental ice. Melting at the bottom surface of the ice shelf increases its rigidity, while freezing decreases it. Accurate numerical modelling of ice shelf flow must account for this spatial variability in mechanical characteristics.

Acceleration of Pine Island and Thwaites Glaciers, West Antarctica

AbstractRecent satellite investigations revealed that in the 1990s the grounding line of Pine Island and Thwaites Glaciers, West Antarctica, retreated several km, the ice surface on the interior of the basins lowered 10 cm a–1, and Pine Island Glacier thinned 1.6 ma–1. These observations, however, were not sufficient to determine the cause of the changes. Here, we present satellite radar interferometry data that show the thinning and retreat of Pine Island Glacier are caused by an acceleration of ice flow of about 18 ± 2% in 8 years. Thwaites Glacier maintained a nearly constant flow regime at its center, but widened along the sides, and increased its 30 ± 15% mass deficit by another 4% in 4 years. The combined mass loss from both glaciers, if correct, contributes an estimated 0.08 ± 0.03 mma–1 global sea-level rise in 2000.

A shallow‐dipping dike fed the 1995 flank eruption at Fernandina Volcano, Galápagos, observed by satellite radar interferometry

Satellite radar interferometry data reveal strong localized uplift in a semi‐ circular pattern on the southwest flank of Fernandina volcano, Galápagos, where an eruption took place in January to April, 1995. The observations show a maximum decrease in radar range of 0.75 m, and they are consistent with a model of a shallow‐dipping dike intrusion feeding this fissure eruption. We solve for the best‐fit single rectangular dislocation dike source using non‐linear inversion techniques where simulated annealing searching algorithm is used to avoid local minima. The best‐fit dike is 3.8 km long, 2.3 km high, 0.86 m thick and with a 34° dip. The total dike volume (7.5 × 10−3 km³) is ∼40% of the volume of extrusive materials estimated to have been produced during the eruption. The data do not permit a sub‐vertical dike, implying that the least principal stress direction is not horizontal as is usually assumed.

North and Northeast Greenland Ice Discharge from Satellite Radar Interferometry

Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise.