Search

A devastating tsunami struck Palu Bay in the wake of the 28 September 2018 Mw = 7.5 Palu earthquake (Sulawesi, Indonesia). With a predominantly strike-slip mechanism, the question remains whether this unexpected tsunami was generated by the earthquake itself, or rather by earthquake-induced landslides. In this study we examine the tsunami potential of the co-seismic deformation. To this end, we present a novel geodetic data set of Global Positioning System and multiple Synthetic Aperture Radar-derived displacement fields to estimate a 3D co-seismic surface deformation field. The data reveal a number of fault bends, conforming to our interpretation of the tectonic setting as a transtensional basin. Using a Bayesian framework, we provide robust finite fault solutions of the co-seismic slip distribution, incorporating several scenarios of tectonically feasible fault orientations below the bay. These finite fault scenarios involve large co-seismic uplift (>2 m) below the bay due to thrusting on a restraining fault bend that connects the offshore continuation of two parallel onshore fault segments. With the co-seismic displacement estimates as input we simulate a number of tsunami cases. For most locations for which video-derived tsunami waveforms are available our models provide a qualitative fit to leading wave arrival times and polarity. The modeled tsunamis explain most of the observed runup. We conclude that co-seismic deformation was the main driver behind the tsunami that followed the Palu earthquake. Our unique geodetic data set constrains vertical motions of the sea floor, and sheds new light on the tsunamigenesis of strike-slip faults in transtensional basins.

Geodetic measurements of crustal deformation rates provide important information on earthquake hazard, indicating that strain is accumulating either faster or slower than the rate suggested by known earthquakes. With the COMET-LiCSAR InSAR processing system, which performs large-scale automated processing and timeseries analysis of Sentinel-1 data, we aim to generate strain rate maps for the entire Alpine-Himalayan Belt, and use these to investigate seismic hazard. In this paper we will present results for Anatolia. Deformation is also a key indicator of volcanic unrest, and is often associated with the flow of magma to shallower depths. The operational nature of Sentinel-1, with frequent revisits and rapid data delivery, makes it suitable for monitoring subaerial volcanoes globally. In order to deal with the large quantity of new data that is continuously being generated, we have developed machine learning approaches to flag when either a new deformation pattern emerges, or an existing deformation pattern changes rate.

Induced seismicity is often associated with fluid injection but only rarely linked to surface deformation. At the Hellisheidi geothermal power plant in south-west Iceland we observe up to 2 cm of surface displacements during 2011–2012, indicating expansion of the crust. The displacements occurred at the same time as a strong increase in seismicity was detected and coincide with the initial phase of geothermal wastewater reinjection at Hellisheidi. Reinjection started on September 1, 2011 with a flow rate of around 500 kg/s. Micro-seismicity increased immediately in the area north of the injection sites, with the largest seismic events in the sequence being two M4 earthquakes on October 15, 2011. Semi-continuous GPS sites installed on October 15 and 17, and on November 2, 2011 reveal a transient signal which indicates that most of the deformation occurred in the first months after the start of the injection. The surface deformation is evident in ascending TerraSAR-X data covering June 2011 to May 2012 as well. We use an inverse modeling approach and simulate both the InSAR and GPS data to find the most plausible cause of the deformation signal, investigating how surface deformation, seismicity and fluid injection may be connected to each other. We argue that fluid injection caused an increase in pore pressure which resulted in increased seismicity and fault slip. Both pore pressure increase and fault slip contribute to the surface deformation.

This work addresses the topic of the generation of large scale maps of ground deformation originated by dynamic processes of the Earth using spaceborne Synthetic Aperture Radar (SAR) systems. The main focus is put on the development of new interferometric processing techniques for SAR data and on the proposal, design and experimental implementation of an acquisition mode with wide-swath capabilities, able to improve the accuracy of the measurements., Diese Arbeit befasst sich mit dem Thema der Erstellung von Karten der Bodenverformung im großen Maßstab, die durch dynamische Prozesse der Erde verursacht werden. Die Erstellung dieser Karten erfolgt anhand von akquirierten Daten von satellitengestützen Radar Systemen mit synthetischer Apertur (SAR). Der Schwerpunkt liegt auf der Entwicklung neuer interferometrischer Verarbeitungstechniken für gegenwärtige SAR Aufnahmemoden. Außerdem wurde ein innovativer Aufnahmemodus für große Streifenbreiten entwickelt, der die Genauigkeit der Messungen beträchtlich verbessert.

Measurements of present‐day surface deformation are essential for the assessment of long‐term seismic hazard. The European Space Agency's Sentinel‐1 satellites enable global, high‐resolution observation of crustal motion from Interferometric Synthetic Aperture Radar (InSAR). We have developed automated InSAR processing systems that exploit the first ~5 years of Sentinel‐1 data to measure surface motions for the ~800,000‐km2 Anatolian region. Our new 3‐D velocity and strain rate fields illuminate deformation patterns dominated by westward motion of Anatolia relative to Eurasia, localized strain accumulation along the North and East Anatolian Faults, and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western Anatolia. We show that automatically processed Sentinel‐1 InSAR data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions. These results are important for assessing the relationship between strain accumulation and release in earthquakes. Plain Language Summary Satellite‐based measurements of small rates of motion of the Earth's surface made at high spatial resolutions and over large areas are important for many geophysical applications including improving earthquake hazard models. We take advantage of recent advances in geodetic techniques in order to measure surface velocities and tectonic strain accumulation across the Anatolia region, including the highly seismogenic and often deadly North Anatolian Fault. We show that by combining Sentinel‐1 Interferometric Synthetic Aperture Radar (InSAR) data with Global Navigation Satellite System (GNSS) measurements we can enhance our view of surface deformation associated with active tectonics, the earthquake cycle, and anthropogenic processes.

This work addresses the topic of the generation of large scale maps of ground deformation originated by dynamic processes of the Earth using spaceborne Synthetic Aperture Radar (SAR) systems. The main focus is put on the development of new interferometric processing techniques for SAR data and on the proposal, design and experimental implementation of an acquisition mode with wide-swath capabilities, able to improve the accuracy of the measurements., Diese Arbeit befasst sich mit dem Thema der Erstellung von Karten der Bodenverformung im großen Maßstab, die durch dynamische Prozesse der Erde verursacht werden. Die Erstellung dieser Karten erfolgt anhand von akquirierten Daten von satellitengestützen Radar Systemen mit synthetischer Apertur (SAR). Der Schwerpunkt liegt auf der Entwicklung neuer interferometrischer Verarbeitungstechniken für gegenwärtige SAR Aufnahmemoden. Außerdem wurde ein innovativer Aufnahmemodus für große Streifenbreiten entwickelt, der die Genauigkeit der Messungen beträchtlich verbessert.

We consider the viscoelastic rheology of the solid Earth under the Antarctic Peninsula due to ice mass loss that commenced after the breakup of the Larsen-B ice shelf. We extend the previous analysis of nearby continuous GPS time series to include 5 additional years and the additional consideration of the horizontal components of deformation. They show strong uplift from ∼2002 to 2011 followed by reduced uplift rates to 2018. Modeling the GPS derived uplift as a viscoelastic response to ongoing regional ice unloading from a new ice model confirms earlier estimates of low upper-mantle viscosities of ∼0.3–3 × 1018 Pa s in this region but allows a wide range of elastic lithosphere thickness. The observed and modeled north coordinate component shows little non-linear variation due to the location of ice mass change to the east of the GPS sites. However, comparison of the observed and modeled east coordinate component constrains the upper mantle viscosity to be less than ∼9 × 1018 Pa s, consistent with the viscosity range suggested by the uplift rates alone and providing important, largely independent, confirmation of that result. Our horizontal analysis showed only marginal sensitivity to modeled lithospheric thickness. The results for the horizontal components are sensitive to the adopted plate rotation model, with the estimate based on ITRF2014 suggesting that the sum of residual plate motion and pre-2002 GIA is likely less than ∼±0.5 mm/year in the east component.

Measurements of present‐day surface deformation are essential for the assessment of long‐term seismic hazard. The European Space Agency's Sentinel‐1 satellites enable global, high‐resolution observation of crustal motion from Interferometric Synthetic Aperture Radar (InSAR). We have developed automated InSAR processing systems that exploit the first ~5 years of Sentinel‐1 data to measure surface motions for the ~800,000 km2 Anatolian region. Our new 3D velocity and strain rate fields illuminate deformation patterns dominated by westward motion of Anatolia relative to Eurasia, localized strain accumulation along the North and East Anatolian Faults, and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western Anatolia. We show that automatically processed Sentinel‐1 InSAR data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions. These results are important for assessing the relationship between strain accumulation and release in earthquakes.

Space-borne Synthetic Aperture Radar (SAR) Interferometry (InSAR) is now a key geophysical tool for surface deformation studies. The European Commission’s Sentinel-1 Constellation began acquiring data systematically in late 2014. The data, which are free and open access, have global coverage at moderate resolution with a 6 or 12-day revisit, enabling researchers to investigate large- scale surface deformation systematically through time. However, full exploitation of the potential of Sentinel-1 requires specific processing approaches as well as the efficient use of modern computing and data storage facilities. Here we present LiCSAR, an operational system built for large-scale interferometric processing of Sentinel-1 data. LiCSAR is designed to automatically produce geocoded wrapped and unwrapped interferograms and coherence estimates, for large regions, at 0.001° resolution (WGS-84 system). The products are continuously updated in a frequency depending on prioritised regions (monthly, weekly or live update strategy). The products are open and freely accessible and downloadable through an online portal. We describe the algorithms, processing, and storage solutions implemented in LiCSAR, and show several case studies that use LiCSAR products to measure tectonic and volcanic deformation. We aim to accelerate the uptake of InSAR data by researchers as well as non-expert users by mass producing interferograms and derived products.

Objectives: Goal-setting is one of the most common strategies used to increase physical activity. Current practice is often based on specific, measurable, achievable, realistic, and time-bound (SMART) goals. However, theory and research suggests that this approach may be problematic. Open goals (e.g., "see how well you can do") have emerged as a possible alternative, but are yet to be tested experimentally in physically active tasks. In a walking-based session, this study aimed to experimentally compare the effects of open, SMART and do-your-best goals with a control condition on distance walked and psychological variables related to engagement. Design: Repeated measures design (mixed model). Method: Participants (N = 78; Mage = 55.88) were randomly assigned to one of four goal conditions: an open, SMART, or do-your-best goal, or a control condition ("walk at your normal pace"), before completing a baseline and two manipulated attempts of a 6-min walking test. Results: Open, SMART, and do-your-best goals achieved greater distance walked, and higher ratings of perceived exertion, than the control across both experimental attempts. Open and SMART goals led to greater enjoyment of the session. However, SMART goals led to higher pressure/tension, while open goals led to higher perceptions of performance and higher interest in repeating the session. Conclusions: These findings provide preliminary evidence for the efficacy of setting open goals in physical activity, and suggest that they may be more psychologically adaptive to pursue than SMART or do-your-best goals. Implications are discussed, and recommendations are made for future goal-setting research in physical activity.

For the first time it has been shown that the GOCE mission can resolve temporal variations in Earth’s gravity field, based on gradiometric measurements. The geophysical interpretation of the combined distributed fault-slip solution shows improved modeling capabilities compared to a solution merely derived from GNSS data. The fine-scale gravity field information can map here structural details which have been introduced as additional constraint in the distributed-slip modeling., In dieser Arbeit wird zum ersten Mal gezeigt, dass die GOCE-Mission zeitlich veränderliche Signale des Erdschwerefeldes, basierend auf Gradiometer-Messungen, auflösen kann. Die geophysikalische Interpretation der gemeinsamen Inversion von GNSS, GRACE und GOCE-Daten zeigt eine Verbesserung der Modellbildung im Gegensatz zu einer rein geometrischen Lösung, da räumliche Strukturen aus hochauflösender Schwerefeldinformation abgeleitet werden können.

While polarimetric persistent scatterer InSAR (PSI) is an effective technique for increasing the number and quality of selected PS pixels, existing methods are suboptimal; a polarimetric channel combination is selected for each pixel based either on amplitude, which works well only for high-amplitude scatterers such as man-made structures, or on the assumption that pixels in a surrounding window all have the same scattering mechanism. In this paper, we present a new polarimetric PSI method in which we use a phase-based criterion to select the optimal channel for each pixel, which can work well even in nonurban environments. This algorithm is based on polarimetric optimization of temporal coherence, as defined in the Stanford Method for PS (StaMPS), to identify the scatterers with stable phase characteristics. We form all possible copolar and cross-polar interferograms from the available polarimetric channels and find the optimum coefficients for each pixel using defined search spaces to optimize the temporal coherence. We apply our algorithm, PolStaMPS, to an area in the Tehran basin that is covered primarily by vegetation. Our results confirm that the algorithm substantially improves on StaMPS performance, increasing the number of PS pixels by 48%, 80%, and 82% with respect to HH+VV, VV, and HH channels, respectively, and increasing the signal-to-noise ratio of selected pixels.

The interferometric coherence is a measure of the correlation between two SAR images and constitutes a commonly used estimator of the phase quality. Its estimation requires a spatial average within a 2-D window, usually named as multilook. The multilook processing allows reducing noise at the expenses of a resolution loss. In this letter, we analyze the influence of the multilook size while applying a polarimetric optimization of the coherence. The same optimization algorithm has been carried out with different multilook sizes and also with the nonlocal SAR filter filter, which has the advantage of preserving the original resolution of the interferogram. Our experiments have been carried out with a single pair of quad-polarimetric RADARSAT-2 images mapping the Mount Etna's volcanic eruption of May 2008. Results obtained with this particular data set show that the coherence is increased notably with respect to conventional channels when small multilook sizes are employed, especially over low-vegetated areas. Conversely, very decorrelated areas benefit from larger multilook sizes but do not exhibit an additional improvement with the polarimetric optimization.

For the first time it has been shown that the GOCE mission can resolve temporal variations in Earth’s gravity field, based on gradiometric measurements. The geophysical interpretation of the combined distributed fault-slip solution shows improved modeling capabilities compared to a solution merely derived from GNSS data. The fine-scale gravity field information can map here structural details which have been introduced as additional constraint in the distributed-slip modeling., In dieser Arbeit wird zum ersten Mal gezeigt, dass die GOCE-Mission zeitlich veränderliche Signale des Erdschwerefeldes, basierend auf Gradiometer-Messungen, auflösen kann. Die geophysikalische Interpretation der gemeinsamen Inversion von GNSS, GRACE und GOCE-Daten zeigt eine Verbesserung der Modellbildung im Gegensatz zu einer rein geometrischen Lösung, da räumliche Strukturen aus hochauflösender Schwerefeldinformation abgeleitet werden können.

The interferometric coherence is a measure of the correlation between two SAR images and constitutes a commonly used estimator of the phase quality. Its estimation requires a spatial average within a 2-D window, usually named as multilook. The multilook processing allows reducing noise at the expenses of a resolution loss. In this letter, we analyze the influence of the multilook size while applying a polarimetric optimization of the coherence. The same optimization algorithm has been carried out with different multilook sizes and also with the nonlocal SAR filter filter, which has the advantage of preserving the original resolution of the interferogram. Our experiments have been carried out with a single pair of quad-polarimetric RADARSAT-2 images mapping the Mount Etna's volcanic eruption of May 2008. Results obtained with this particular data set show that the coherence is increased notably with respect to conventional channels when small multilook sizes are employed, especially over low-vegetated areas. Conversely, very decorrelated areas benefit from larger multilook sizes but do not exhibit an additional improvement with the polarimetric optimization.