Coseismic deformation from the 2002 Denali Fault earthquake: contributions from synthetic aperture radar speckle tracking

Thesis (M.S.) University of Alaska Fairbanks, 2005The technique of speckle tracking can provide coseismic surface offsets for an earthquake in regions where other geodetic data are not available. These offsets can be used to map the surface deformation and create slip distribution models. This thesis uses speckle tracking to study the 2002 Mw7.9 Denali Fault earthquake, with emphasis on the central section of the rupture. The Denali Fault earthquake began with a thrust event on the Susitna Glacier fault before rupturing unilaterally west to east on the Denali and Totschunda faults with overwhelmingly right-lateral strike-slip motion. A slip distribution estimated from a combination of speckle tracking data from the central section of the rupture, GPS data, and geologic data displays highly variable slip, with four major patches of high slip along the Denali fault. Compared to the primarily GPS-derived model of Hreinsdóttir [2005], the combined model is better constrained along the central rupture and predicts slip values much closer to the geologic offset measurements. A significant releasing bend in the fault just west of the pipeline can be correlated to a patch of high slip and the second-largest pulse of moment release along the rupture, suggesting that fault geometry plays an important role in earthquake mechanics.Introduction -- Tectonic background -- Overview of SAR and speckle tracking -- Speckle tracking data -- Data processing -- Coseismic displacements determined from offsets -- 3-D fault model -- Discussion -- Conclusions -- References

Patch-Like Reduction (PLR): A SAR offset tracking amplitude filter for deformation monitoring

As complementary to Synthetic Aperture Radar (SAR) Differential Interferometry (DInSAR), SAR Offset Tracking (OT) is an efficient tool for large ground deformation monitoring in situations when DInSAR cannot work. However, SAR images are affected by speckle noise and some strong point-like scatters which can cause what is known as Patch Like (PL), a kind of errors that can be seen as homogeneous patches of almost constant deformation in the results. These errors are clearly visible in the results as non-consistent deformations along time, but they are difficult to detect with the traditional metrics that evaluate the cross-correlation results, like the Signal to Noise Ratio (SNR). This paper addresses this problem and proposes a simple amplitude filter to reduce PL named as Patch Like Reduction (PLR). The main idea is to find a sensor and scene independent threshold to remove the high amplitude pixels prone to cause PL. Five different SAR data sets and in-field GPS measurements are used to determine the optimal threshold and evaluate the performance of the proposed method. The results show that PL effects can be reduced with the proposed amplitude filter. The processing parameters of the improved OT processing chain are optimized as well to preserve the results resolution as much as possible.This work has been financially supported by China Scholarship Council (Grant No. 201806420035), the Spanish Ministry of Science and Innovation (MCINN) and the State Research Agency (AEI) project PID2020-117303GB-C21 MCIN/AEI/10.13039/501100011033. This work has also been financially supported by the Natural Science Foundation of China (Grant No. 42004011), China Postdoctoral Science Foundation (Grant No. 2020M671646), Centro para el Desarrollo Tecnológico Industrial and Ministry of Science and Technology of the People’s Republic of China (Spanish-Chinese CHINEKA project No. 2022YFE0102600), and the Ministry of Education of the People’s Republic of China (Construction Program of Space-Air-Ground-Well Cooperative Awareness Spatial Information Project B20046)Peer ReviewedPostprint (published version

Gazing at the Solar System: Capturing the Evolution of Dunes, Faults, Volcanoes, and Ice from Space

Gazing imaging holds promise for improved understanding of surface characteristics and processes of Earth and solar system bodies. Evolution of earthquake fault zones, migration of sand dunes, and retreat of ice masses can be understood by observing changing features over time. To gaze or stare means to look steadily, intently, and with fixed attention, offering the ability to probe the characteristics of a target deeply, allowing retrieval of 3D structure and changes on fine and coarse scales. Observing surface reflectance and 3D structure from multiple perspectives allows for a more complete view of a surface than conventional remote imaging. A gaze from low Earth orbit (LEO) could last several minutes allowing for video capture of dynamic processes. Repeat passes enable monitoring time scales of days to years. Numerous vantage points are available during a gaze (Figure 1). Features in the scene are projected into each image frame enabling the recovery of dense 3D structure. The recovery is robust to errors in the spacecraft position and attitude knowledge, because features are from different perspectives. The combination of a varying look angle and the solar illumination allows recovering texture and reflectance properties and permits the separation of atmospheric effects. Applications are numerous and diverse, including, for example, glacier and ice sheet flux, sand dune migration, geohazards from earthquakes, volcanoes, landslides, rivers and floods, animal migrations, ecosystem changes, geysers on Enceladus, or ice structure on Europa. The Keck Institute for Space Studies (KISS) hosted a workshop in June of 2014 to explore opportunities and challenges of gazing imaging. The goals of the workshop were to develop and discuss the broad scientific questions that can be addressed using spaceborne gazing, specific types of targets and applications, the resolution and spectral bands needed to achieve the science objectives, and possible instrument configurations for future missions. The workshop participants found that gazing imaging offers the ability to measure morphology, composition, and reflectance simultaneously and to measure their variability over time. Gazing imaging can be applied to better understand the consequences of climate change and natural hazards processes, through the study of continuous and episodic processes in both domains

Fusion of remotely sensed displacement measurements: current status and challenges

International audienc

Surface deformation analysis in Northeast Italy by using PS-InSAR and GNSS data

In the present study, we exploited the potential of satellite-based geodetic data for detecting and measuring surface displacement in Northeast Italy. In this contest, we focused mainly on 1) the estimation of the interseismic deformation during the satellites’ observation period, 2) the detection and analysis of the main deformation patterns, and 3) the correlation of the signals to the active tectonic structures. Despite the low convergence rates (~ 1.5-3 mm/yr), Northeast Italy is an active tectonic area, as testified by the instrumental and historical seismicity. The Adria-Eurasia convergence is mainly accommodated by the thrusts and strike-slip faults of the Southeastern Alps and the External Dinarides, located in the northern and northeastern sectors of the study area. The Venetian-Friulian plain and the Adriatic coasts, affected by active subsidence, dominate the southern region. We used the Stanford Method for Persistent Scatterers (StaMPS) applied to Sentinel-1 SAR images acquired along the ascending and descending orbit tracks between 2015 and 2019. Based on a stack of single-master differential interferograms, we detected coherent and temporally stable pixels based on amplitude and phase noise analysis. After applying spatial-temporal filters and additional post-processing operations to refine the measurements, we used Adria-fixed GNSS velocities derived by permanent stations in the study area to calibrate the InSAR velocities. The outcome consists of Line-OF-Sight (LOS) mean ground velocity maps derived by displacement time series along the radar directions for each satellite track. The combination of the LOS datasets yields vertical and east-west velocity maps, which are mostly in agreement with GNSS data and previous geodetic studies. Based on our measurements, we observe a significant positive velocity gradient of 1 mm/yr across the westernmost sector of the Alpine system, suggesting an aseismic motion of the root of the Bassano-Valdobbiadene thrust. The positive vertical gradients (~1 and up to 2 mm/yr) across the Alpine-Dinaric systems in the central and eastern sectors and the eastward motion that increases northeastward (1-2 mm/yr) may be related to the active Alpine-Dinaric thrusts and strike-slip faults. We also suggest that the detected westward motion of the Friulian plain (around Udine) might be attributed to the presence of tectonic structures characterized by transcurrent-transpressive kinematics. Finally, we detect other signals, such as the significant subsidence (2-4 mm/yr) along the coasts and on the southern Venetian-Friulian plain, confirming the correlation between subsidence and the geological setting of the study area. In conclusion, our study confirms the potential of MT-InSAR and GNSS data for the estimation of the surface deformations in response to active tectonics, even in areas characterized by low deformation rates, such as Northeast Italy.In the present study, we exploited the potential of satellite-based geodetic data for detecting and measuring surface displacement in Northeast Italy. In this contest, we focused mainly on 1) the estimation of the interseismic deformation during the satellites’ observation period, 2) the detection and analysis of the main deformation patterns, and 3) the correlation of the signals to the active tectonic structures. Despite the low convergence rates (~ 1.5-3 mm/yr), Northeast Italy is an active tectonic area, as testified by the instrumental and historical seismicity. The Adria-Eurasia convergence is mainly accommodated by the thrusts and strike-slip faults of the Southeastern Alps and the External Dinarides, located in the northern and northeastern sectors of the study area. The Venetian-Friulian plain and the Adriatic coasts, affected by active subsidence, dominate the southern region. We used the Stanford Method for Persistent Scatterers (StaMPS) applied to Sentinel-1 SAR images acquired along the ascending and descending orbit tracks between 2015 and 2019. Based on a stack of single-master differential interferograms, we detected coherent and temporally stable pixels based on amplitude and phase noise analysis. After applying spatial-temporal filters and additional post-processing operations to refine the measurements, we used Adria-fixed GNSS velocities derived by permanent stations in the study area to calibrate the InSAR velocities. The outcome consists of Line-OF-Sight (LOS) mean ground velocity maps derived by displacement time series along the radar directions for each satellite track. The combination of the LOS datasets yields vertical and east-west velocity maps, which are mostly in agreement with GNSS data and previous geodetic studies. Based on our measurements, we observe a significant positive velocity gradient of 1 mm/yr across the westernmost sector of the Alpine system, suggesting an aseismic motion of the root of the Bassano-Valdobbiadene thrust. The positive vertical gradients (~1 and up to 2 mm/yr) across the Alpine-Dinaric systems in the central and eastern sectors and the eastward motion that increases northeastward (1-2 mm/yr) may be related to the active Alpine-Dinaric thrusts and strike-slip faults. We also suggest that the detected westward motion of the Friulian plain (around Udine) might be attributed to the presence of tectonic structures characterized by transcurrent-transpressive kinematics. Finally, we detect other signals, such as the significant subsidence (2-4 mm/yr) along the coasts and on the southern Venetian-Friulian plain, confirming the correlation between subsidence and the geological setting of the study area. In conclusion, our study confirms the potential of MT-InSAR and GNSS data for the estimation of the surface deformations in response to active tectonics, even in areas characterized by low deformation rates, such as Northeast Italy

Applications of SAR Interferometry in Earth and Environmental Science Research

This paper provides a review of the progress in regard to the InSAR remote sensing technique and its applications in earth and environmental sciences, especially in the past decade. Basic principles, factors, limits, InSAR sensors, available software packages for the generation of InSAR interferograms were summarized to support future applications. Emphasis was placed on the applications of InSAR in seismology, volcanology, land subsidence/uplift, landslide, glaciology, hydrology, and forestry sciences. It ends with a discussion of future research directions

Measuring and modelling the earthquake deformation cycle at continental dip-slip faults

In order for an earthquake to become a natural disaster, it needs to be significantly large, close to vulnerable populations or both. The largest earthquakes in the world occur in subduction zones, where cool, shallowly dipping fault planes enable brittle failure over a large area. However, these earthquakes often occur far away from major cities, reducing their impact. Similar, low angle fault planes can be found in continental fold and thrust belts, where sub-horizontal decollements offer large potential rupture areas. These seismic sources are often much closer to major urban centres than off-shore subduction zone sources. It is therefore essential to understand the processes that control how strain is accommodated and released in such settings. Much of our current understanding of the earthquake cycle comes from studying strike-slip faults. Can our knowledge of strike-slip faults be transferred over to dip-slip faults, and in particular, fold and thrust belts? Previous work has suggested that there may be significant differences between strike-slip and dip-slip settings, and therefore further study of the earthquake cycle in dip-slip environments is required. The recent launch of Sentinel-1, and the extensive Synthetic Aperture Radar (SAR) archive of the European Space Agency (ESA), offer an opportunity to obtain measurements of strain in dip-slip environments that can contribute to our understanding. In this thesis, I use geodetic measurements to contribute to our understanding of the earthquake cycle. Enhanced surface deformation rates following earthquakes (so called postseismic deformation) show temporal and spatial variation. Such variation can be used to investigate the material properties of faults and the surrounding medium. I collate measurements of postseismic velocity following contintental earthquakes to examine the temporal evolution of strain following an earthquake over multiple timescales. The compilation show a simple relationship, with velocity inversely proportional to time since the earthquake. This relationship holds for all fault types, with no significant difference between dip-slip and strike-slip environments. Such lack of difference implies that, at least in terms of the temporal evolution of near field postseismic deformation, both environments behave similarly. I compare these measurements with the predictions of various models that are routinely used to explain postseismic deformation. I find that the results are best explained using either rate-strengthening afterslip or power-law creep in a shear zone with high stress exponent. Such a relationship indicates that fault zone processes dominate the near-field surface deformation field from hours after an earthquake to decades later. This implies that using such measurements to determine the strength of the bulk lithosphere should only be done with caution. I then collate geodetic measurements from throughout the earthquake cycle in the Nepal Himalaya to constrain the geometry and frictional properties of the fault system. I use InSAR to measure postseismic deformation following the 2015 Mw~7.8 Gorkha earthquake and combine this with Global Navigation Satellite System (GNSS) displacements to infer the predominance of down-dip afterslip. I then combine these measurements with coseismic and interseismic geodetic data to determine fault geometries which are capable of simultaneously explaining all three data sets. Unfortunately, the geodetic data alone cannot determine the most appropriate geometry. It is therefore necessary to combine such measurements with other relevant data, along with the expertise to understand the uncertainties in each data set. Such combined measurements ought to be understood using physically consistent models. I developed a mechanically coupled coseismic-postseismic inversion, based on rate and state friction. The model simultaneously inverts the coseismic and postseismic surface deformation field to determine the range of frictional properties and coseismic slip which can explain the data within uncertainties. I applied this model to the geodetic data compilation in Nepal and obtained a range of values for the rate-and-state 'a' parameter between 0.8 - 1.6 x 10^-3, depending on the geometry used. Whilst the Nepal Himalaya is well instrumented, many continental collision zones suffer from a severe lack of data. The Sulaiman fold and thrust belt is one such region, with very sparse GNSS data, but significant seismicity. I apply InSAR to part of the Sulaiman fold and thrust belt near Sibi to examine the evolution of strain throughout the seismic cycle. I tie together observations from ERS, Envisat and Sentinel-1 to produce a time series of displacements over 25 years long which covers an earthquake which occurred in 1997. Using this time series, I investigate the contributions of different parts of the earthquake cycle to the development of topography. I find that postseismic deformation plays a clear role in the construction of short wavelength folds, and that the combination of coseismic and postseismic deformation can reproduce the topography over a variety of lengthscales. The shape of the frontal section of the fold and thrust belt, including the gradient of the topography, is roughly reproduced in a single earthquake cycle. This suggests that fold and thrust belts can maintain their taper in a single earthquake cycle, rather than through earthquakes occurring at different points throughout the belt. I find that approximately 1000 earthquakes like the 1997 event, along with associated postseismic deformation, can reproduce the topography seen today to first order. Such a result may aid our use of topography as a long-term record of earthquake cycle deformation. I finish by drawing these various findings together and commenting on common themes. Afterslip plays an important role in the earthquake cycle, contributing to the surface deformation field in multiple locations, over multiple timescales, and generating topography. This afterslip can be explained using a rate-strengthening friction law with a*sigma between 0.2 and 1.54 MPa. Combining this rate dependence with the static coefficient of friction determined from other methods, such as critical taper analysis, would enable a more complete picture of fault friction to be determined. Fault geometry in fold and thrust belts may control the size of potential ruptures, with junctions and changes in dip angle potentially arresting ruptures. In order to fully determine the role of fault geometry and friction in controlling the earthquake cycle in dip-slip settings, I suggest a more thorough exploitation of the wealth of InSAR data which is now available. These data then need to be combined with measurements from other fields, and models produced which are consistent within the uncertainties of each data set. I suggest that measurements of topography and insights from structural geology may help with understanding the long term and short term processes governing earthquake patterns in an area. As both observations and models are developed, interdisciplinary teams may be able to better constrain the key controls on earthquake hazard in continental dip-slip settings

Characterization of Ground Deformation Associated with Shallow Groundwater Processes Using Satellite Radar Interferometry

Shallow groundwater processes maylead to ground deformation and even geohazards. With the features of day-and-night accessibility and large-scale coverage, time-series interferometric synthetic aperture radar (InSAR) has proven a useful tool for mapping the deformation over various landscapes at cm to mm level with weekly to monthly updates. However, it has limitations such as, decorrelation,atmospheric artifacts, topographic errors, andunwrapping errors, in particular for the hilly, vegetated, and complicated deformation patterns. In this dissertation, I focus on characterizing the ground deformation over landslides, aquifer systems, and mine tailings impoundment, using the designed advanced time-series InSAR strategy, as well as theinterdisciplinary knowledge of geodesy, hydrology, geophysics, and geology. Northwestern USA has been exposed to extreme landslide hazards due to steep terrain, high precipitation, and loose root support after wildfire. I characterize the rainfall-triggered movements of Crescent Lake landslide, Washington State. The seasonal deformation at the lobe, with larger magnitudes than the downslope riverbank, suggests an amplified hydrological loading effect due to a thicker unconsolidated zone. High-temporal-resolution InSAR and GPS data reveal dynamic landslide motions. Threshold rainfall intensities and durations wet seasons have been associated with observed movement upon shearing: antecedent rainfall triggered precursory slope-normal subsidence, and the consequent increase in pore pressure at the basal surface reduces friction and instigates downslope slip over the course of less than one month. In addition, a quasi-three-dimensional deformation field is created using multiple spaceborne InSAR observations constrained by the topographical slope, and is further used to invert for the complex geometry of landslide basal surface based on mass conservation. Aquifer skeletons deform in response to hydraulic head changes with various time scales of delay and sensitivity. I investigate the spatio-temporal correlation among deformation, hydrological records and earthquake records over Salt Lake Valley, Utah State. A clear long-term and seasonal correlation exists between surface uplift/subsidence and groundwater recharge/discharge, allowing me to quantify hydrogeological properties. Long-term uplift reflects the net pore pressure increase associated with prolonged water recharge, probably decades ago. The distributions of previously and newly mapped faults suggest that the faultsdisrupt the groundwater flow andpartition hydrological units. Mine tailings gradual settle as the pore pressure dissipates and the terrain subsides, andtailings embankment failures can be extremely hazardous. I investigate the dynamics of consolidation settlement over the tailings impoundment in the vicinity of Great Salt Lake, Utah State, as well as its associated impacts to the surrounding infrastructures. Largest subsidence has been observed around the low-permeable decant pond clay at the northeast corner.The geotechnical consolidation model reveals and predicts the long-term exponentially decaying settlement process. My studies have demonstrated that InSAR methods can advance our understanding about the potential anthropogenic impacts and natural hydrological modulations on various geodynamic settings in geodetic time scale

NASA geodynamics program investigations summaries: A supplement to the NASA geodynamics program overview

The development of a time series of global atmospheric motion and mass fields through April 1984 to compare with changes in length of day and polar motion was investigated. Earth rotation was studied and the following topics are discussed: (1) computation of atmospheric angular momentum through April 1984; (2) comparisons of psi sub values with variations in length of day obtained by several groups utilizing B.I.H., lunar laser ranging, VLBI, or Lageos measurements; (3) computation of atmospheric excitation of polar motion using daily fields of atmospheric winds and pressures for a short test period. Daily calculations may be extended over a longer period to examine the forcing of the annual and Chandler wobbles, in addition to higher frequency nutations