InSAR Models Research Articles

Investigation of a Small Landslide in the Qinghai-Tibet Plateau by InSAR and Absolute Deformation Model

Landslides are one of the major geohazards in the Qinghai-Tibet Plateau, and have recently increased in both frequency and size. SAR interferometry (InSAR) has been widely applied in landslide research, but studies on monitoring small-scale landslides are rare. In this study, we investigated the performance of Small Baseline Subsets method (SBAS) in monitoring small-scale landslide and further developed a new deformation model to obtain the absolute deformation time series. The results showed that SBAS could well capture the small-scale landslide characteristics including spatiotemporal abnormal displacement and progressive failure processes. The newly developed absolute deformation model further detected the process of landslide details, such as instances of noticeable creeps induced by rainfall and snowmelt. Finally, a conceptual model of the kinematics-based failure mechanism for small-scale landslide was proposed. This study extended the monitoring capability of InSAR and improved our knowledge on the deformation in the frozen ground regions.

Mining Deformation Life Cycle in the Light of InSAR and Deformation Models

The Sentinel-1 constellation provides an effective new radar instrument with a short revisit time of six days for the monitoring of intensive mining surface deformations. Our goal is to investigate in detail and to bring new comprehension of the mine life cycle. The dynamics of mining, especially in the case of horizontally evolving longwall technology, exhibit rapid surface changes. We use the classical approach of differential radar interferometry (DInSAR) with short temporal baselines (six days), which results in deformation maps with a low decorrelation between the satellite images. For the same time intervals, we compare the radar results with prediction models based on the Knothe–Budryk theory for mining subsidence. The validation of the results with ground levelling measurements reveals a high level of resemblance of the DInSAR subsidence maps (−0.04 m bias with respect to the levelling). On the other hand, aside from the explicable exaggeration, the location of the subsidence trough needs improvement in the forecasted deformations (0.2 km shift in location, a deformation velocity four times higher than in DInSAR). In addition, a time lag between DInSAR (compatible with extraction) and prediction is revealed. The model improvement can be achieved by including the DInSAR results in the elaboration of the model parameters.

Coseismic and Postseismic Deformation of the 2016 Mw 6.6 Aketao Earthquake from InSAR Observations and Modelling

On November 25, 2016, the Mw 6.6 Aketao earthquake occurred in Xinjiang, western China. We used the combination of ascending Sentinel-1A, descending Sentinel-1B and ascending ALOS-2 PALSAR data to measure the coseismic deformation. The line-of-sight (LOS) coseismic deformation implies that the earthquake was dominated by right-lateral strike-slip. Ignoring the fault-perpendicular deformation, the fault-parallel and up–down deformation was extracted based on the combination of Sentinel-1A and 1B observations. Results show that the maximum fault-parallel deformation is ~ 13.7 cm at the north wall and the minimum is ~ −16.5 cm at the south wall of the Muji fault. Then, coseismic slip distribution was derived using the steepest descent method (SDM) based on a single-segment fault model using the three InSAR LOS observations as constraints. The slip distribution reveals two slip centers. The maximum slip of the eastern center is 0.5 m at a depth of 8.8 km, where the rake angle is ~ 181.2°. The maximum slip of the western center is 0.6 m at a depth of 10.8 km, where the rake angle is ~ 181.1°. The derived seismic moment obtained equals the Mw 6.6 earthquake. In this study, postseismic deformation time series in 1.5 years after the earthquake were retrieved from 26 multi-temporal Sentinel-1 descending scenes. The postseismic LOS deformation at the north and south walls of Muji fault both increases with time but in opposite directions. The cumulative deformation is 60–80 mm at the north wall, and –30 to −20 mm at the south wall. The postseismic deformation shows similar patterns with the coseismic deformation, and has the same mechanism. There is no obvious lock at the unbroken gap.

Sentinel-1 observations of the 2016 Menyuan earthquake: A buried reverse event linked to the left-lateral Haiyuan fault

Knowledge on the interaction of active structures is essential to understand mechanics of continental deformation and estimate the earthquake potential in complex tectonic settings. Here we use Sentinel-1A radar imagery to investigate coseismic deformation associated with the 2016 Menyuan (Qinghai) earthquake, which occurred in the vicinity of the left-lateral Haiyuan fault. The ascending and descending interferograms indicate thrust-dominated slip, with the maximum line-of-sight displacements of 58 and 68mm, respectively. The InSAR observations fit well with the uniform-slip dislocation models except for a larger slip-to-width ratio than that predicted by the empirical scaling law. We suggest that geometric complexities near the Leng Long Ling restraining bend confine rupture propagation, resulting in high slip occurred within a small area and much higher stress drop than global estimates. Although InSAR observations cannot distinguish the primary plane, we prefer the west-dipping solution considering aftershocks distribution and the general tectonic context. Both InSAR modelling and aftershock locations indicate that the rupture plane linked to the Haiyuan fault at 10km depth, a typical seismogenic depth in Tibet. We suggest that the earthquake more likely occurred on a secondary branch at a restraining bend of the Haiyuan fault, even though we cannot completely rule out the possibility of it being on a splay of the North Qilian Shan thrusts.

Application of InSAR Modeling for Monitoring of Territories Under Landslides Risk in Armenia

In this article we describe works (that were carried out in the frames of NATO Project: NATO CLG: ESP.EAP.CLG. 983876) that have done for creating DEM for selected areas of Armenia with high level of risk where natural disasters such as grounds sedimentation, landslides, mudflows, earthquakes periodically happen. In the future the obtained DEM will be used to create regional system for the monitoring of natural disasters (to control topographic changes on the territories with high level of risk) in the territory of Armenia using tools such as InSAR modeling, systems of mathematical interpretation of digital models, GIS technologies and mathematical models for processing satellite images. The results of monitoring will be periodically presented to local authorities to take measures in order to prevent probable natural disasters impact on population and communications.

Use of a GPS-Derived Troposphere Model to Improve InSAR Deformation Estimates in the San Gabriel Valley, California

We evaluate the potential of troposphere models derived from ground meteorological data (pressure, temperature, and relative humidity) and Global Positioning System (GPS) data to improve InSAR measurements and models derived from them. We test this approach on an ERS-2/Envisat data set collected during a transient surface deformation episode that occurred from January to July 2005 in the San Gabriel Valley, southern California, USA. We find that the interferometric phase change observed over the corresponding period cannot be solely attributed to hydrological uplift associated with rising groundwater levels but also includes a significant contribution from differential tropospheric delay due to differing quantities of water vapor in the troposphere on the two SAR observation dates. We show that, if the tropospheric phase contribution is mistakenly interpreted as the range change associated with changes in groundwater storage, both the surface displacement and the groundwater storage coefficient may be overestimated by up to 30%. This method could be applied in real time where meteorological measurements are available near one or more GPS permanent site(s).

Three Dimensional Deformation of Mining Area Detection by InSAR and Probability Integral Model

Abstract. A new solution algorithm that combined D-InSAR and probability integral method was proposed to generate the three dimensional deformation in mining area. The details are as follows: according to the geological and mining data, the control points set should be established, which contains correct phase unwrapping points in subsidence basin edge generated by D-InSAR and several GPS points; Using the modulus method to calculate the optimum parameters of probability integral prediction; Finally, generate the three dimensional deformation of mining work face by the parameters. Using this method, the land subsidence with big deformation gradients in mining area were correctly generated by example TerraSAR-X images. The results of the example show that this method can generate the correct mining subsidence basin with a few surface observations, and it is much better than the results of D-InSAR.

Using InSAR to detect active deformation associated with faults in Suban field, South Sumatra Basin, Indonesia

Suban field in southern Sumatra, Indonesia, is a fractured carbonate/crystalline wet-gas reservoir in a tectonically active island-arc setting. Reservoir-scale right-oblique reverse faults and folds that have trapped the hydrocarbons have been related previously to deformation in the back-arc setting of Sumatra associated with oblique subduction of the Indo-Australian Plate at the Sunda trench. Increased well productivity in some parts of the field was inferred to correlate with completing wells in the damage zones of critically stressed faults. Satellite interferometry acquired in 2008 through 2011 involving specially stacked and filtered interferograms, following prior applications to heavy-oil fields and Arctic sea ice, reveals active deformation in Suban field. Several areas of localized subsidence potentially exceeding ∼5 mm/yr have been identified in the field. Horizontal movements of comparable magnitude were resolved above the major right-oblique, critically stressed fault zone in the southwestern part of the field, corroborating wellbore-based inferences from the reservoir. Block-tectonic models constrained by GPS measurements across the entire Sumatra contractional orogen predict comparable magnitudes and directions for horizontal motions observed locally at Suban. The combination of InSAR and GPS-based plate-tectonic models provides a robust tool for monitoring the deformation of oil and gas fields in tectonically active areas.

InSAR observations and models of crustal deformation due to a glacial surge in Iceland

Surges are common at all the major ice caps in Iceland. Ice masses of gigatons may shift from the upper part of the outlet glacier towards the terminus in a few months, advancing the glacier front by up to several kilometres. The advancing ice front may be up to 100 m thick, increasing the load on crustal rocks correspondingly. We use the observed change in crustal loading during a surge of the western part of the Vatnajokull ice cap, Iceland, during 1993–1995 and the corresponding elastic crustal deformation, surveyed with interferometric synthetic aperture radar, to investigate the material properties of the solid Earth in this region. Crustal subsidence due to the surge reaches ∼75mm at the edge of the Siðujokull outlet glacier. This signal is mixed with a broad uplift signal of ∼12 mm/yr, relative to our reference area, caused by the ongoing retreat of Vatnajokull in response to climate change. We disentangle the two signals by linear inversion. Finite element modelling is used to investigate the elastic Earth response of the surge, as well as to confirm that no significant viscoelastic deformation occurred as a consequence of the surge. The modelling leads to estimates of the Young’s modulus and Poisson’s ratio of the underlying Earth. Comparison between the observed and modelled deformation fields is made using a Bayesian approach that yields the estimate of a probability distribution for each of the free parameters. Residuals indicate a good agreement between models and observations. One-layer elastic models result in a Young’s modulus of 43.2–49.7 GPa (95 per cent confidence) and Poisson’s ratio of 0–0.27, after removal of outliers. Our preferred model, with two elastic layers, provides a better fit to the whole surge signal. This model consists of a 1-km-thick upper layer with an average Young’s modulus of 12.9–15.3 GPa and Poisson’s ratio of 0.17, overlying a layer with an average Young’s modulus of 67.3–81.9 GPa and Poisson’s ratio of 0.25.

Joint earthquake source inversions using seismo-geodesy and 3-D earth models

A joint earthquake source inversion technique is presented that uses InSAR and long-period teleseismic data, and, for the first time, takes 3-D Earth structure into account when modelling seismic surface and body waves. Ten average source parameters (Moment, latitude, longitude, depth, strike, dip, rake, length, width and slip) are estimated; hence, the technique is potentially useful for rapid source inversions of moderate magnitude earthquakes using multiple data sets. Unwrapped interferograms and long-period seismic data are jointly inverted for the location, fault geometry and seismic moment, using a hybrid downhill Powell-Monte Carlo algorithm. While the InSAR data are modelled assuming a rectangular dislocation in a homogeneous halfspace, seismic data are modelled using the spectral element method for a 3-D earth model. The effect of noise and lateral heterogeneity on the inversions is investigated by carrying out realistic synthetic tests for various earthquakes with different faulting mechanisms and magnitude (Mw 6.0-6.6). Synthetic tests highlight the improvement in the constraint of fault geometry (strike, dip and rake) and moment when InSAR and seismic data are combined. Tests comparing the effect of using a 1-D or 3-D earth model show that long-period surface waves are more sensitive than long-period body waves to the change in earth model. Incorrect source parameters, particularly incorrect fault dip angles, can compensate for systematic errors in the assumed Earth structure, leading to an acceptable data fit despite large discrepancies in source parameters. Three real earthquakes are also investigated: Eureka Valley, California (1993 May 17, Mw 6.0), Aiquile, Bolivia (1998 February 22, Mw 6.6) and Zarand, Iran (2005 May 22, Mw 6.5). These events are located in different tectonic environments and show large discrepancies between InSAR and seismically determined source models. Despite the 40-50 km discrepancies in location between previous geodetic and seismic estimates for the Eureka Valley and Aiquile earthquakes, the seismic data are found to be compatible with the InSAR location. A 30° difference in strike between InSAR and seismic-derived source models is also resolved when taking 3-D Earth structure into account in the analysis of the Eureka Valley earthquake. The combination of both InSAR and seismic data further constrains the dip for the Zarand earthquake, and in all cases the seismic moment is more robustly constrained in the joint inversions than in the individual data set inversions. Unmodelled lateral heterogeneities in Earth and the models could partly explain some of the observed source parameter discrepancies related to the seismic data. © The Authors 2014. Published by Oxford University Press on behalf of The Royal Astronomical Society.

INSAR AND FINITE ELEMENT ANALYSIS OF GROUND DEFORMATION AT LAKE URMIA CAUSEWAY (LUC), NORTHWEST IRAN

Abstract. Precise long-term deformation monitoring of causeways and bridges is of vital task for maintenance and management work related to transportation safety. In this study, we analyse the settlement of Lake Urmia Causeway (LUC), northwest Iran, using observations from InSAR and Finite Element Model (FEM) simulation. For InSAR processing, we analyse 58 SAR images of ENVISAT, ALOS and TerraSAR-X (TSX) using the SBAS technique to assess the settlement of embankments in the years 2003–2013. The InSAR results show deflation on both embankments with a peak velocity of > 5 cm/year in the satellite Line Of Sight (LOS) direction. The InSAR observations are then used to construct a settlement compaction model for the cross section at the distance of 4 km from the most western edge of the causeway, using a 2D Finite Element Model. Our FEM results suggest that settlement of the embankments will continue in the future due to consolidation phenomenon.

InSAR analysis of the 2008 Reno‐Mogul earthquake swarm: Evidence for westward migration of Walker Lane style dextral faulting

Analysis and modeling of InSAR data covering the 2008 Reno‐Mogul M 4.7 earthquake swarm indicate that the main event was produced by slip on a previously unrecognized strike‐slip fault in the Reno basin. Deformation of 0.5–2.5 cm in radar line‐of‐sight was produced by the main event and post‐seismic slip over an area of more than ∼150 km2. This earthquake is one of the smallest magnitude events modeled with InSAR to date in the seismically active western Basin and Range, and it provides new insights into regional neotectonic relations. Inverse modeling of the InSAR data suggests that the earthquake swarm was generated by 25–75 cm of dextral displacement on a N44W‐striking fault with a ∼3 km rupture length and a rupture depth of ∼2 km. The InSAR‐detected strike‐slip ground deformation is unique for the Reno basin which is in the purely extensional domain of the Sierra Nevada‐Basin and Range Transition Zone, an area dominated by north‐striking normal faults. The InSAR modeling of the 2008 earthquake swarm supports the concept of westward migration of Walker Lane transcurrent faulting and overprinting of extensional Basin and Range structures, in this case the westward migration of dextral shear associated with the northern Walker Lane into the extension‐dominated Reno basin.

The 2010–2011 Canterbury, New Zealand, seismic sequence: Multiple source analysis from InSAR data and modeling

The 2010–2011 Canterbury sequence is a complex system of seismic events that started with a Mw7.1 earthquake and continued with large aftershocks with dramatic consequences, particularly for the city of Christchurch. We model the main earthquakes using InSAR data, providing displacement maps and the respective modeling for the September 4th, 2010, February 22nd, 2011 and June 13th, 2011 events. Relocated aftershocks, field and GPS surveys are used to constrain models obtained by inversion of InSAR data; the fault slip distribution is retrieved with a variable patch size approach aimed at maximizing the spatial resolution on the fault plane. For the September 2010 earthquake we estimated significant slip values below 10 km depth; the calamitous February 2011 event in Christchurch is modeled with a double fault source with slip values less than 2 m down to 7 km depth; for the second June 13th event in Christchurch we identified a NW‐SE striking fault as responsible for the earthquake. Last, we introduce the use of InSAR coherence maps to quickly detect the areas subject to soil liquefaction in Christchurch, as shown for the two main events.

Slip distribution of the 2011 Tohoku earthquake derived from joint inversion of GPS, InSAR and seafloor GPS/acoustic measurements

We invert the fault slips of 2011 Mw 9.0 Tohoku earthquake with constraints from GPS, InSAR and seafloor GPS/acoustic measurements. The seismogenic fault geometry is constructed according to slab contours of Japan Trench. Steepest Descent method and Laplacian smoothing are used to solve slip distribution and regularize the solution. We firstly take GPS displacement in two postseismic periods, the first 8h right after mainshock from 5:55 to 14:00 UTC and the 13days from 12 March 2011 to 25 March 2011, to solve for the postseismic slips. The solved postseismic slips are adopted to remove postseismic signal in InSAR and seafloor observation. In order to estimate the effect of postseismic correction and contribution from different geodetic datasets, we invert several coseismic slips with constraints from GPS (Model 1), corrected InSAR (Model 2), combination of GPS and corrected seafloor measurements (Model 3), combination of GPS and corrected InSAR and seafloor measurements (Model 4), and combination of GPS and initial InSAR and seafloor measurements (Model 5). From the comparison of these slip models, we find combined datasets could give more slip details, which is closer to a joint inversion result constrained from both seismic and geodetic datasets (Koketsu et al., 2011). RMSE of seafloor measurements has dropped about 4cm after applying postseismic correction. We consider the Model 4, which combines three datasets and takes postseismic correction, to be the preferred solution among all the estimated models. It suggests a maximum slip of 49.87m, located at a depth of 5km around the epicenter, and has a geodetic moment of 3.14×1022Nm (Mw 8.96) by assuming a shear modulus of 4×1010Pa.

The polarimetric InSAR model and a novel method for parameter inversion of the three-layer vegetation

When the real vegetation is composed of three layers,the accuracy of the traditional three-stage vegetation parameter inversion method becomes lower.To solve this problem,a new polarimetric SAR interferometric coherence model was established.Based on this new model,the reason why the accuracy of the tranditional three-stage vegetation parameter inversion method becomes lower was analyzed and a new vegetation parameter inversion method based on dual-baseline polarimetric SAR interferometry was proposed.Compared to the tranditional inversion method,this new method is more suitable to the three-layer vegetation constructions and has higher accuracy.Experimental results validated the correctness and the superiority of the new method.

S02 InSARを用いた火山変動検出と数値モデリングによるマグマ移動メカニズムの研究(日本火山学会研究奨励賞・学会賞記念講演,口頭発表)

S02 InSARを用いた火山変動検出と数値モデリングによるマグマ移動メカニズムの研究(日本火山学会研究奨励賞・学会賞記念講演,口頭発表)

Co-eruptive subsidence at Galeras identified during an InSAR survey of Colombian volcanoes (2006–2009)

Establishing a time series of deformation is one of the keys to understanding and predicting the magmatic behaviour of active volcanoes. Satellite techniques represent an increasingly useful tool for measuring volcanic deformation over timescales spanning days to decades. Colombia contains numerous young or active volcanoes, many of which are inaccessible. We use L-band (23.6 cm wavelength) radar data acquired between 2006 and 2009, to survey 15 active volcanoes along the Colombian segment of the Northern Volcanic Zone. Analysis of 100 interferograms showed that the majority of volcanoes were not deforming. However, independent interferograms display an average subsidence of 3 cm on the northeast flank of Galeras, coinciding with the January 2008 eruption. We combine InSAR, field measurements and source modelling to determine the origin, size and location of the source of subsidence at Galeras. Our results suggest that this signal was caused by deflation of the magma chamber associated with the January 2008 event. Modelling provides insight into the depth to source (~ 2 km) and a volume change (− 6.5 × 10 5 m 3) which is consistent with that derived from modelling contemporaneous tilts and the volume of material erupted. Previous studies based on various datasets support the existence of a resident/recurring chamber at this location, over a decadal timescale. Our InSAR results corroborate the hypothesis of shallow magma storage beneath Galeras and provide the first piece of evidence that can be linked to a particular eruption.

Extension on the Tibetan plateau: recent normal faulting measured by InSAR and body wave seismology

We use InSAR and body wave modelling to determine the faulting parameters for a series of five Mw 5.9–7.1 normal faulting earthquakes that occurred during 2008, including the March 20 Yutian earthquake (Mw 7.1), one of the largest normal faulting events to have occurred recently on the continents. We also study three earlier normal faulting earthquakes that occurred in southern Tibet between 1992 and 2005. Coseismic deformation for each of these eight events is measured with ascending and descending interferograms from ENVISAT, ERS and ALOS SAR data. Elastic dislocation modelling of the line-of-sight InSAR displacements and body wave seismological modelling of P and SH waves are used to estimate fault parameters and are found to be in good agreement for all the events studied. The use of InSAR to measure deformation allows a relatively precise determination of the fault location in addition to resolving the focal plane ambiguity. Only five of the eight events are associated with a clear surface topographic feature, suggesting that an underestimation of the amount of extension would result from using the surface expressions of normal faulting alone. The observations, in all cases, are consistent with slip on planar surfaces, with dips in the range 40–50°, that penetrates the uppermost crust to a depth of 10–15 km. We find no evidence for active low-angle (dip less than 30°) normal faulting. The contribution of the normal faulting to overall extension estimated by summing seismic moments over earthquakes for the past 43 yr is 3–4 mm yr−1, or 15–20 per cent of the rates of extension measured across the plateau using GPS. 85 per cent of the moment release in normal faulting over the past 43 yr has occurred in regions whose surface height exceeds 5 km. This observation adds weight to the suggestions that the widespread normal faulting on the plateau is the result of variations in the gravitational potential energy of the lithosphere.

The 1995 November 22,Mw7.2 Gulf of Elat earthquake cycle revisited

SUMMARY The 1995 November 22, Mw= 7.2 Nuweiba earthquake occurred along one of the left-stepping segments of the Dead Sea Transform (DST) in the Gulf of Elat (Aqaba). It was the largest earthquake along the DST in at least 160 yr. The main shock was preceded by earthquake swarms north and south of its NE-striking rupture since the early 1980s, and was followed by about 6 months of intense aftershock activity, concentrated mainly northwest and southeast of the main rupture. In this study we re-analyse ERS-1 and ERS-2 InSAR data for the period spanning the main shock and 5 post-seismic years. Because the entire rupture was under the Gulf water, surface observations related to the earthquake are limited to distances greater than 5 km away from the rupture zone. Coseismic interferograms were produced for the earthquake +1 week, +4 months and +6 months. Non-linear inversions were carried out for fault geometry and linear inversions were made for slip distribution using an ascending–descending 2-frame data set. The moment calculated from our best-fitting model is in agreement with the seismological moment, but trade-offs exist among several fault parameters. The present model upgrades previous InSAR models of the Nuweiba earthquake, and differs from recent teleseismic waveform inversion results mainly in terms of slip magnitude and distribution. The moment released by post-seismic deformation in the period of 6 months to 2 yr after the Nuweiba earthquake is about 15 per cent of the coseismic moment release. Our models suggest that this deformation can be represented by slip along the lower part of the coseismic rupture. Localised deformation along the Gulf shores NW of the main rupture in the first 6 months after the earthquake is correlated with surface displacements along active Gulf-parallel normal faults and possibly with shallow M > 3.9, D < 6 km aftershocks. The geodetic moment calculated by modelling this deformation is more than an order of magnitude larger than expected for a single M∼ 4 aftershock, but could be a result of a sequence of aftershocks and/or aseismic slip. The major aftershocks and the slip along Gulf-parallel normal faulting NW of the main rupture are associated with positive Coulomb stress changes induced by the main event.

Coseismic slip model of the 2007 August Pisco earthquake (Peru) as constrained by Wide Swath radar observations

SUMMARY The Pisco earthquake (M w 8.0; 2007 August 15) occurred offshore of Peru’s southern coast at the subduction interface between the Nazca and South American plates. It ruptured a previously identified seismic gap along the Peruvian margin. We use Wide Swath InSAR observations acquired by the Envisat satellite in descending and ascending orbits to constrain coseismic slip distribution of this subduction earthquake. The data show movement of the coastal regions by as much as 85 cm in the line-of-sight of the satellite. Distributed-slip model indicates that the coseismic slip reaches values of about 5.5 m at a depth of ∼18–20 km. The slip is confined to less than 40 km depth, with most of the moment release located on the shallow parts of the interface above 30 km depth. The region with maximum coseismic slip in the InSAR model is located offshore, close to the seismic moment centroid location. The geodetic estimate of seismic moment is 1.23 × 10 21 Nm (M w 8.06), consistent with seismic estimates. The slip model inferred from the InSAR observations suggests that the Pisco earthquake ruptured only a portion of the seismic gap zone in Peru between 13.5 ◦ S and 14.5 ◦ S, hence there is still a significant seismic gap to the south of the 2007 event that has not experienced a large earthquake since at least 1687.