Surface Displacement Rates Research Articles

Building a General Algorithm for Seismic Hazard Analysis in the Sunda Arc through Geodynamic Simulations

Abstract Because of its well-documented subduction zone and outer island arc, Sumatra provides a unique setting for studying and forecasting earthquakes within the seismically active Sunda Arc. This study builds on previous research that utilized Global Positioning System data and the Akaike information criterion to analyze probabilistic seismic hazard functions. However, this study replaces surface displacement rate data with a forward model derived from previous fault modeling results to create a more broadly applicable earthquake forecasting algorithm. Although the best-fit model patterns generated by this new algorithm are consistent with past studies, the forward model demonstrates a lower degree of fit compared to models utilizing natural surface displacement data. This discrepancy highlights the need to refine the fault parameter models to estimate surface displacement rates. Despite this limitation, the study makes a valuable contribution by developing a general algorithm applicable to other subduction zones within the Sunda Arc region. With further refinement and incorporation of more accurate fault modeling and data, this algorithm has the potential to formulate the best-fit earthquake spatial forecast models. This approach could be applied to other seismically active areas, particularly those near subduction zones.

Rock glaciers across the United States predominantly accelerate coincident with rise in air temperatures

Despite their extensive global presence and the importance of variations in their speed as an essential climate variable, only about a dozen global time series document long-term changes in the velocity of rock glaciers – large tongue-shaped flows of frozen mountain debris. By analysing historical aerial photographs, we reconstruct here 16 new time series, a type of data that has not previously existed for the North American continent. We observe substantial accelerations, as much as 2–3 fold, in the surface displacement rates of rock glaciers across the mountains of the western contiguous United States over the past six to seven decades, most consistent with strongly increasing air temperatures in that region. Variations between individual time series suggest that different local and internal conditions of the frozen debris bodies modulate this overall climate response. Our observations indicate fundamental long-term environmental changes associated with frozen ground in the study region.

Study on the dry shrinkage characteristics and size effect of swell-shrink characteristic soil.

Swell-shrink characteristic soils exhibit a high susceptibility to cracking during the drying process, which poses a significant risk of various geological disasters. Among these, the occurrence of drying shrinkage acts as a prerequisite for the cracking phenomenon. Therefore, it is of utmost importance to comprehend the specific characteristics associated with the drying shrinkage mechanism. To investigate the drying shrinkage behavior of swell-shrink characteristic soils, a series of drying shrinkage experiments were conducted on long strip samples of red clay and expansive soil. Utilizing three-dimensional digital image correlation (DIC) technology, the surface displacement, strain, and anisotropic shrinkage rates of the soil samples during the drying process were obtained, and the size effect on the drying shrinkage of swell-shrink characteristic soil were analyzed. The research findings are as follows: The displacement development of the soil samples in the X and Y directions can be divided into two stages: a linear growth stage and a stable displacement stage. In the Z direction, the soil surface deformation can be divided into three stages: soil surface arching, vertical shrinkage, and shrinkage stabilization. The drying shrinkage of swell-shrink characteristic soil exhibits anisotropy, with the vertical shrinkage rate being the largest, followed by the longitudinal and then the transverse directions. Additionally, the soil sample shrinkage exhibits a size effect, whereby the shrinkage rates in all directions increase with increasing sample width and thickness. During the drying shrinkage process, the stress state on the soil surface evolves from initial tensile strain to subsequent compressive strain. The strain at different positions and times within the soil sample is not uniform, resulting in the non-uniformity and anisotropy of the sample shrinkage. This study provides important insights into the cracking mechanism of swell-shrink characteristic soils and serves as a valuable reference for related laboratory experiments, which will contribute to better prediction and control the geological hazards caused by the drying shrinkage of swell-shrink characteristic soils.

Detection of slow‐moving landslides through automated monitoring of surface deformation using Sentinel‐2 satellite imagery

AbstractLandslides are one of the most damaging natural hazards and have killed tens of thousands of people around the world over the past decade. Slow‐moving landslides, with surface velocities on the order of 10−2–102 m a−1, can damage buildings and infrastructure and be precursors to catastrophic collapses. However, due to their slow rates of deformation and at times subtle geomorphic signatures, they are often overlooked in local and large‐scale hazard inventories. Here, we present a remote‐sensing workflow to automatically map slow‐moving landslides using feature tracking of freely and globally available optical satellite imagery. We evaluate this proof‐of‐concept workflow through three case studies from different environments: the extensively instrumented Slumgullion landslide in the United States, an unstable lateral moraine in Chilean Patagonia and a high‐relief landscape in central Nepal. This workflow is able to delineate known landslides and identify previously unknown areas of hillslope deformation, which we consider as candidate slow‐moving landslides. Improved mapping of the spatial distribution, character and surface displacement rates of slow‐moving landslides will improve our understanding of their role in the multi‐hazard chain and their sensitivity to climatic changes and can direct future detailed localised investigations into their dynamics.

Dynamic deformation monitoring and scenario simulation of the Xiaomojiu landslide in the Jinsha River Basin, China

The Xiaomojiu landslide is a typical high-elevation, long-runout landslide located in the Jinsha River Corridor. In this study, sequential InSAR time-series estimation was used to calculate the line of sight (LOS) surface displacements with descending and ascending Sentinel-1 images, and it turned out that the cumulative LOS surface displacement of the landslide was up to −78.4 mm during the period from October 2017 to April 2021 with the maximum LOS surface displacement rate of −38.5 mm/year. The landslide body could be divided into five zones (A, B1, B2, B3, and C) according to its topographical characteristics together with the LOS surface displacement time series. Combining engineering geological characteristics, LOS cumulative surface displacements with site investigation suggest that the Xiaomojiu landslide is likely to be a precipitation-triggered ancient traction rock landslide at the accelerated deformation stage. A dynamic simulation of the Xiaomojiu landslide with the PFC3D software shows that it could take approximately 65 s for the Xiaomojiu landslide from start-up to acceleration to deceleration to build-up of a barrier lake, followed by a simulation from the barrier lake to outburst floods with the HEC-RAS software indicating that the maximum depth of the outburst floods could be 13.5 m (15%), 24.6 m (25%), 42.1 m (50%), and 50.3 m (75%) along Qinghai-Tibet Plateau Transportation Corridor (QTPTC). It is believed that the results of this study provide a reference for landslide prevention along the QTPTC and the Jinsha River.

Study on Land Subsidence Simulation Based on a Back-Propagation Neural Network Combined with the Sparrow Search Algorithm

Rapid simulation of land subsidence can provide an effective means of facilitating its management and control. This paper innovatively introduced a back-propagation (BP) neural network subsidence simulation model which was optimized by the sparrow search algorithm (SSA), hereinafter referred to as the SSA-BP model, to simulate land subsidence in Tongzhou District, Beijing. First, based on the time series interferometric synthetic aperture radar (InSAR) monitoring, different technologies such as spatial analysis, Google Earth Engine (GEE), and machine learning were utilized together with a variety of multi-source spatial data, including groundwater level, compressible layer thickness, Visible Infrared Imager Radiometer Suite (VIIRS) nighttime light images, and the OpenStreetMap (OSM) road distribution. Furthermore, we determined the optimal grid scale for land subsidence research and worked out a multifactor-driven SSA-BP land subsidence simulation model for which sensitivity analysis was performed with great care. Main conclusions: (1) From November 2010 to January 2020, the average annual surface displacement rate in Beijing’s subcentre, Tongzhou, ranged from −133.9 to +3.9 mm/year. (2) Our SSA-BP land subsidence simulation model allows for a relatively high overall accuracy. The average root mean square error (RMSE) is 5.00 mm/year, the average mean absolute error (MAE) is 3.80 mm/year, and the average coefficient of determination (R2) is 0.83. (3) Sensitivity analysis shows that the SSA-BP model driven by multiple factors has a far better simulation performance than the model driven by any single weighting factor, and displays the highest sensitivity to the groundwater level factor among all the weighting factors. In terms of subdividing the study area, our SSA-BP land subsidence model runs with multifunctional zones displayed a higher accuracy than that without. This paper made use of a machine learning model to simulate land subsidence in Beijing’s Tongzhou District and explored the sensitivity of different factors to land subsidence, which is helpful for its scientific prevention.

Wide Area Detection and Distribution Characteristics of Landslides along Sichuan Expressways

Wide area landslide detection is a major international research hotspot in the field of geological hazards, and the integration of multi-temporal optical satellite images and spaceborne interferometric synthetic aperture radar (InSAR) appears to be an effective way to realize this. In this paper, a technical framework is presented for wide area landslide detection: (i) multi-temporal satellite optical images are used to detect landslides with distinguishable geomorphological features; (ii) Generic Atmospheric Correction Online Service (GACOS) assisted InSAR stacking is employed to generate annual surface displacement rate maps in radar line of sight using satellite SAR images from both ascending and descending tracks, which are in turn utilized to automatically detect active landslides from ground motion using hotspot analysis, and (iii) the distribution characteristics of the detected landslides are investigated by examining their relationships with topographic and hydrological factors. Three expressways in Sichuan Province, China—namely the Yakang (Ya’an-Kangding), Yaxi (Ya’an-Xichang), and Lushi (Luding-Shimian) expressways—and their surrounding regions (a total area of approximately 20,000 square kilometers) were chosen as the study area. A total of 413 landslides were detected, among which 320 were detected using multi-temporal satellite optical images, and 109 were detected using GACOS-assisted InSAR stacking. It should be noted that only 16 landslides were detected by both approaches; these landslides all exhibited not only obvious geomorphological features but also ground motion. A statistical analysis of the topographic and hydrological factors shows that of the detected landslides: 81% are distributed at elevations of 1000–2500 m, over 60% lie within the elevation range of 100~400 m, and 90% present with medium and steep slopes (20°~45°), and 80% are located within areas seeing an annual rainfall of 950~1050 mm. Nine landslides were found to pose potential safety hazards to the expressways. The research findings in this paper have directly benefitted the Sichuan expressways; equally important, it is believed that the technical framework presented in this paper will provide guidance for hazard mitigation and the prevention of transportation hazards in the future.

InSAR Study of Landslides: Early Detection, Three-Dimensional, and Long-Term Surface Displacement Estimation—A Case of Xiaojiang River Basin, China

Landslides, a major natural geohazard, obstruct municipal constructions and may destroy villages and towns, at worst causing significant casualties and economic losses. Interferometric Synthetic Aperture Radar (InSAR) technique offers distinct advantages on landslide detection and monitoring. In this paper, a more systematic workflow is designed for InSAR study of landslides, in terms of three levels: (i) early detection on regional scale, (ii) three-dimensional (3D) surface displacement rates estimation on detailed scale, and (iii) time series analysis on long-term temporal scale. The proposed workflow is applied for landslide research on the Xiaojiang River Basin, China, using ascending and descending Sentinel-1 images acquired from March 2017 to May 2019. First, the landslide inventory has been mapped and updated using InSAR stacking method, supporting geohazard prevention on a regional scale. A total of 22 active landslides are identified, ranging from medium to super large scale. Compared with the existing inventory, three unrecorded landslides are newly detected by our approach, and five recorded landslides are detected significant expansion of their boundaries. Then, specific to a detected landslide, Baobao landslide, a Total Least Squares–Kalman Filter-based approach is presented. Two outcomes are provided for further spatial-temporal pattern analysis: 3D displacement rates, providing an intuitive insight on the spatial characteristics and sliding direction of landslide, which are analyzed to deep the understanding of its kinematic mechanism, and long-term time series, which contribute to deduce the dynamic evolution of landslide, presenting benefits in landslide forecasting.

Co-Seismic Surface Ruptures of the CE 1738 M 7.6 Dangjiang Earthquake Along the NW Continuation of the Xianshuihe Fault Zone and Tectonic Implications for the Central Tibetan Plateau

The role of large-scale strike-slip faults in high-elevation areas in absorbing the strain resulting from plate convergence has yet to be scientifically understood. The Dang Jiang Fault (DJF), as the NW continuation of the Xianshuihe Fault Zone (XFZ) in the central Qinghai-Tibetan Plateau, may provide an excellent testing ground for this question, given its high slip rate, sparse vegetative cover, minimal modification, and possible relationship with the CE 1738 Dangjiang destructive earthquake. However, co-seismic surface ruptures and seismotectonics remain in dispute because of inconvenient transportation and lack of oxygen at high altitudes. Thus, field investigations are conducted here to determine co-seismic surface ruptures. The newly synthesized data from geologic observations, historical record reviews, geomorphic mapping, trench logging, and sample dating indicate that the CE 1738 Dangjiang earthquake produced an ∼100 km-long surface rupture that includes offsets of gullies, linear scarps and troughs, sag ponds,en echelonfractures, and pressure ridges. The magnitude is re-estimated asM7.6, with average and maximum strike-slip displacements of ∼2.1 ± 0.1 m and ∼3.5 ± 0.1 m, respectively. The DJF has undergone multiple seismic faulting events, and the linear fitting surface displacement rate in the Holocene is ∼6.3 ± 1.9 mm/yr with a 95% confidence interval. This study implies that the seismic hazard of the DJF cannot be underestimated given that its elapsed time is close to or beyond the recurrence interval of major earthquakes and that the oblique convergence of the Qiangtang Block might be accommodated by the clockwise rotation of the block through repeated left-lateral strike-slip movements along the southern boundary of the Bayan Har Block.

Variable inflation rate of a magmatic deformation source beneath Aira caldera after the 1914 eruption of Sakurajima volcano: Inferences from a linear Maxwell viscoelastic model constrained by geodetic data

Temporal variation of ground surface displacement rates at volcanoes may represent changes to the volumetric magma supply rate over time. If crustal rock responds elastically to a magmatic deformation source, the volume change of the source has a simple one-to-one relation to the surface deformation. For viscoelastic crustal rock, however, the correlation is not always straightforward, particularly at volcanoes where crustal viscosity is lowered by a high geothermal gradient. For a continuous inflation of the deformation source, the viscoelastic surface displacement depends on the balance between the uplift due to magma supply and subsidence due to viscoelastic relaxation. In this study, using a 3D finite element model composed of an elastic layer underlain by a linear Maxwell viscoelastic layer with a spatially uniform viscosity, we estimate the temporal variation of volumetric magma supply rate into the upper crust beneath Aira caldera in southern Kyushu, Japan, after the 1914 eruption of Sakurajima volcano. It is found that the geodetic data, including levelling and GNSS displacement fields, require a sill-like magmatic deformation source at a depth of 11 km to inflate at the following rates for six different periods: (I) ~6.9–9.4 × 106 m3/yr in 1914–1934, (II) ~9.1–16.7 × 106 m3/yr in 1934–1960, (III) ~1.6–3.8 × 106 m3/yr in 1960–1968, (IV) ~8.1–11.0 × 106 m3/yr in 1968–1976, (V) ~ −1.0–2.2 × 106 m3/yr in 1976–1997, and (VI) ~5.8–9.4 × 106 m3/yr in 1997–2007. The constrained viscosity (ηc) of the viscoelastic crust ranges from ~5 × 1018 Pa s to ~1020 Pa s or more. The lowest and highest values produce the best fit to the data in the earliest period and in period V showing surface subsidence, respectively, but for the other periods any viscosity is acceptable unless it is lower than ~1018 Pa s. The lowest viscosity providing the best fit in the earliest period indicates that viscoelastic displacement in response to the 1914 eruption plays an important role in the surface deformation field. The observed surface subsidence in period V can be explained either by inflation or deflation of the deformation source, depending on whether ηc is lower or higher than ~1019 Pa s, respectively. The subsequent surface recovery in period VI requires an increase in the inflation rate for any case of ηc. The volume of magma accumulated since the 1914 eruption (ΔV) is predicted to be ~0.6–0.8 km3 in 2020. The estimated inflation/deflation rate of the deformation source, in comparison with the observed volumetric eruption rate, reveals that a significant eruption occurs only when ΔV is ~0.4 km3 or more. However, even if ΔV is beyond the critical value, the eruptive activity does not depend on ΔV. The temporal inflation rate inferred in this study gives an opportunity to discuss eruptive dynamics in relation to the observed eruptive activity, such as a quantitative relationship between magma supply rate into, and discharge rate from, a deformation source.

Movement characteristics of a creeping slope influenced by river erosion and aggradation: Study of Xinwulü River in southeastern Taiwan

The average surface displacement rate of 0.1 m/year of the studied slope adjacent to the Xinwulü River has been measured over the past three decades. Damage to the retaining structures of a highway and tunnel through the slope has frequently been reported. Maintenance and reconstruction have been required at intervals of several to ten years. In this study, multi-temporal remote sensing images, site investigations, and ground and tunnel monitoring are interpreted to clarify the movement characteristics of the slope and the factors that affect them. The results of this study reveal that riverbed erosion and aggradation of the adjacent river dominate the movement characteristics of the slope. When the riverbed is low, the direction of slope movement ranges between that of the maximum slope gradient and the dip direction of foliation. Gravitational deformation, which is associated with a deep slip surface, is the main cause of movement; it is facilitated by gullies that develop upward from the sides of the Xinwulü River and the surrounding sliding masses. When the riverbed is high as a result of the aggradation of debris from upstream, the slope moves in the direction of the maximum gradient. Water washes out the slope toe, which has a relatively low strength because it has previously been displaced. Slope collapses occur frequently along the river bank, and gullies actively grow upward, stimulating the movement of the sliding masses with a shallow slip surface. Furthermore, the cyclic erosion and aggradation of the river account for the formation of shallow and deep slip surfaces of 33 m and 90 m, respectively. The results of this study demonstrate the effects of riverbed erosion and aggradation on the creeping deformation and stability of the adjacent slope in the Xinwulü River region; this is valuable for formulating countermeasures to protect the study site and maintain the existing tunnel.

SOME FEATURES OF CURRENT TECHNOGENIC MOVEMENTS OF THE EARTH’S CRUST

We describe the history of studying the current crustal movements by various methods and discuss technogenic effects recorded at large water-reservoir zones and mineral deposits in Siberia. Initially, classical surveying techniques aimed to obtain high-accuracy ground-based measurements of height, tilt and direction. Modern geodesy techniques and methods for measuring absolute gravity are now available to investigate displacement, deformation, tilt and other phenomena taking place on the Earth’s surface. These methods are used to estimate kinematic parameters of the crust areas (e.g. rates of subsidence and horizontal movements) and to monitor fluid motions in mineral deposits. Such data are critical for ensuring a proper management of the mineral deposits. In this article, we analyse technogenic processes observed in the Ust Balyk oil-gas field, the Zapolyarny gas deposit, the water-reservoir zone at the Sayano-Shushenskaya hydroelectric power station (SSHPS) on the Yenisei river, and large open-pit mines in the Kuzbass basin. Our analysis is based on surface displacement rates estimated from the data collected in different periods of observations at large man-made facilities. In the study of the hydro technical objects, we estimated the displacement rates at 5.0 mm per year. In the northern areas of the West Siberian petroleum basin, subsidence rates amounted to 20–25 mm per year in the early 2000s. These estimates were supported by the high-accuracy gravity measurements showing an increase up to 6–7 microGal per year in the oil-gas field development areas. We assess a possibility of triggering effects related to weak seismicity due to a high stress accumulation rate (1 KPa per hour) in the SSHPS area. A connection between earth tides and catastrophic events, such as gas emissions in high amounts on mining sites, is discussed. Having analysed the surface monitoring records taken in South Primorye in September 2017, we conclude that underground nuclear explosions in North Korea in this period did not cause any significant displacement of the surface in this most southerly region of the Russian Far East territories.

Post‐Earthquake Fold Growth Imaged in the Qaidam Basin, China, With Interferometric Synthetic Aperture Radar

AbstractQuestions regarding the development of folds and their interactions with the seismic faults within thrust systems remain unanswered. However, estimating fault slip and earthquake hazards using surface observations and kinematic models of folding requires an understanding of how the shortening is accommodated during the different phases of the earthquake cycle. Here, we construct 16‐years of interferometric synthetic aperture radar time series across the North Qaidam thrust system (NE Tibet), where three Mw 6.3 earthquakes occurred along basement faults underlying shortened folded sediments. The analysis reveals spatio‐temporal changes of post‐earthquake surface displacement rates and patterns, which continue more than 10 years after the seismic events. The decomposition of the Sentinel‐1 ascending and descending line of sight velocities into vertical and shortening post‐earthquake components indicates that long‐term transient uplift and shortening is in agreement with the deformation that might be expected from kinematic models of folding. Long‐term uplift coincides spatially with young anticlines observed in the geomorphology, with steep gradients in the forelimbs, gentle gradients in the back‐limbs, an absence of subsidence in the footwalls, and higher gradients along interpreted bedding planes. Long‐term shortening is also different from the surface displacements expected for typical time‐varying creep on a narrow dislocation interface and shows rates higher than the average convergence across the whole region. These findings provide evidence for anelastic fold buckling during the post‐earthquake phase and highlight the contribution of distributed aseismic deformation to the growth of topography.

A Bayesian inference framework for fault slip distributions based on ensemble modelling of the uncertainty of underground structure: with a focus on uncertain fault dip

SUMMARYThe model prediction errors that originate from the uncertainty of underground structure are often a major contributor of the errors between the data and the model predictions in fault slip estimation using geodetic or seismic waveform data. However, most studies on slip inversions either neglect the model prediction errors or do not distinguish them from observation errors. Several methods that explicitly incorporated the model prediction errors in slip estimation, which has been proposed in the past decade, commonly assumed a Gaussian distribution for the stochastic property of the model prediction errors to simplify the formulation. Moreover, the information on both the slip distribution and the underground structure is expected to be successfully extracted from the data by incorporating the stochastic property of the model prediction errors. In this study, we propose a novel flexible Bayesian inference framework for estimating fault slips that can accurately incorporate non-Gaussian model prediction errors. This method considers the uncertainty of the underground structure, including fault geometry, based on the ensemble modelling of the uncertainty of Green’s functions. Furthermore, the framework allows the estimation of the posterior probability density function (PDF) of the parameters of the underground structure by calculating the likelihood of each sample in the ensemble. We performed numerical experiments for estimating the slip deficit rate (SDR) distribution on a 2-D thrust fault using synthetic data of surface displacement rates, which is the simplest problem setting that can essentially demonstrate the fundamental idea and validate the advantage of the proposed method. In the experiments, the dip angle of the fault plane was the parameter used to characterize the underground structure. The proposed method succeeded in estimating a posterior PDF of SDR that is consistent with the true one, despite the uncertain and inaccurate information of the dip angle. In addition, the method could estimate a posterior PDF of the dip angle that has a strong peak near the true angle. In contrast, the estimation results obtained using a conventional approach, which introduces regularization based on smoothing constraints and does not explicitly distinguish the prediction and observation errors, included a significant amount of bias, which was not noted in the results obtained using the proposed method. The estimation results obtained using different settings of the parameters suggested that inaccurate prior information of the underground structure with a small variance possibly results in significant bias in the estimated PDFs, particularly the posterior PDFs for SDR, those for the underground structure, and the posterior predicted PDF of the displacement rates. The distribution shapes of the model prediction errors for the representative model parameters in certain observation points are significantly asymmetric with large absolute values of the sample skewness, suggesting that they would not be well-modelled by Gaussian approximations.

Early identification and characteristics of potential landslides in the Bailong River Basin using InSAR technique

The Bailong River Basin is located in the southeast of Gansu Province and situated at the intersection of the Qinghai-Tibet Plateau, the Loess Plateau, and the Sichuan Basin. Geohazards, such as landslides and debris flows, have high frequency and wide distribution due to the impact of rainfall, tectonic activity, and earthquakes. These phenomena pose a serious threat to the safety of life and property of the local people. Investigating a new method to detect potential landslide and study its characteristics is important to provide key supports for local disaster prevention and mitigation.In this study, an InSAR technique called Small Baseline Subset was selected to process 60 Sentinel-1A SAR images acquired from March 2018 to March 2019. Moreover, the study area was clipped into 8 blocks to improve the efficiency of data processing and minimize the errors caused by the complex terrain of the region.On the basis of the abovementioned method, the mean surface displacement rates ranging from -158 and 100 mm/year along the line-of-sight direction were detected during March 2018 and March 2019. A total of 114 potential landslides were investigated and identified in the Bailong River Basin based on optical image interpretation and field survey. Statistical analysis of their basic information shows that most of the potential landslides tend to develop in the S, SSW, and SSE-faced slope with a gradient of 20°-40°. The elevation difference of potential landslides is less than 150 m. The slope material is mostly composed of slope deposits and heavy weathered rocks, such as phyllite. The majority of potential landslides have an area less than 5×104 m2.Yahuokou landslide, which was investigated as a potential landslide with displacement rates > 38 mm/year, broke and ran into Min River from 19 July 2019. On the basis of the analysis of landslide pre-cursory deformation and geomorphology, the landslide was divided into three sections: source, propagation, and accumulation areas. The successful identification of potential landslide demonstrates the applicability and efficiency of InSAR technique in landslide investigation and identification. This research provides foundation and scientific support for landslide mapping and disaster prevention in Bailong River Basin. © 2021, Science Press. All right reserved.

Identification of landslide-prone slopes at Paglajhora area, Darjeeling Himalaya, India

Paglajhora area, located in the southeastern part of the Kurseong town in the Darjeeling Himalaya region, India, experiences frequent slope failure especially in monsoon season. Due to the intricate disposition of major thrust zones (MCT, MBT, etc.), heavy rainfall, neotectonic and anthropogenic activities, etc., the cause of slope failure is not similar all over the area, which makes difficult to categorize the landslides based on their mode of failure. The present work is aimed to demarcate the landslide-prone areas from the surface displacement (horizontal) map derived by optical image correlation (OIC) technique applying normalized cross-correlation (NCC) algorithm of two temporal Landsat 8 OLI (level 1TP) images, supported by the ground field survey. Results indicate that the overall range of surface displacement (horizontal) rate in the study area varies from 0.4 to 8 m/year out of which the range 0.5–1.5 m/year being dominant classifying the slide type as slow-to-very slow earth flow with a velocity class varying from 3 to 2. Places showing relatively higher displacement values (3 to 8 m/year) match accurately with the already reported slide zones and the large exposed scarp surfaces noticed during the field surveys or distinguished from the satellite imagery. Areas with lower displacement rates (< 1.5 m/year) experience very slow earth flow, which are confirmed by the presence of cracks and steps on the major roads. Depths of shallow subsurface slip planes are established from dipole-dipole geo-electric surveys in few locations showing moderate surface velocity.

Tectonic Division in and around the Izu Peninsula Based on the Soft Clustering of Surface Displacement Rate Field

Tectonic Division in and around the Izu Peninsula Based on the Soft Clustering of Surface Displacement Rate Field

Urban subsidence monitoring by SBAS-InSAR technique with multi-platform SAR images: a case study of Beijing Plain, China

ABSTRACT Beijing, as the capital of China, suffers severe subsidence caused by groundwater withdrawal. In this paper, the SBAS-InSAR technique was used to detect surface deformations in the Beijing plain. 47 scenes Envisat ASAR images obtained during June 2003 to August 2010, and 24 Radarsat-2 images obtained during November 2010 to December 2013 were employed to retrieve vertical deformation characteristic over this area. The deformation magnitude, evolution process and spatial distribution of representative targets that occurred during 11 years were retrieved. The vertical surface displacement rates during two periods were validated via leveling observations, which have an RMSE =1.15mm/a, which indicates that the two types of subsidence matched very well. The interferometric results revealed that the subsidence during the two periods show similar special distributions and have an uneven spatial-temporal trend. The scope and deformation rates of funnels continuously increased with from 2003 to 2013. Meanwhile, multiple expressways and urban ring roads spanned the subsidence funnel with sharp deformation rate, and showed different subsidence properties along their paths. Additionally, the spatial and temporal correlation analyses between the deformation measurements and the dynamic variation of groundwater pumping was also performed to explore the response relationship.

Surface Deformation over Permafrost Environment of the Tanggula Section in the Qinghai-Tibet Plateau Using Active Microwave Spectral Imagines

Changes of permafrost and the active layer affect geophysical process, water circulation, biological diversity and carbon storage. The monitoring of ground surface deformations is crucial and necessary to estimate the degradation of permafrost environment. In this study, the ground motions of the Tanggula section in the Qinghai- Tibet Plateau (QTP), a region with limited in situ measurements at spatial scale, have been investigated by the small baseline SAR interferometry (SBAS-InSAR). In total, 17 C-band ENVISAT ASAR images (acquired from January 1, 2009 to August 19, 2010) were employed. The results show that the ground surface motion was primarily in the range of – 7.6 mm per year to 6.7 mm per year, and the correlation coefficients and the P-values between deformations and Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperatures (LSTs) were ranged from -0.24 to -0.47 and from 0.09 to 0.41, respectively. And the precision file of the surface displacement rates map is showed that the estimated displacement velocity is reliable. Our study has observed that the majority of ground surface (approximately 70%) was relatively stable in the study period with displacements in the range of -2 mm per year to 2 mm per year and the ground subsidence is larger than the ground heave, implying the necessity of time series deformations surveillance derived from satellites in the permafrost environment.

Estimation of frictional properties and slip evolution on a long-term slow slip event fault with the ensemble Kalman filter: numerical experiments

SummaryA variety of slow slip events at subduction zones have been observed. They can be stress meters for monitoring the stress state of megathrust faults during their earthquake cycles. In this study, we focus on long-term slow slip events (LSSEs) recurring at downdip portions of megathrust faults among such slow earthquakes. Data analyses and simulation studies of LSSEs have so far been executed independently. In atmosphere and ocean sciences, data assimilations that optimally combine data analyses and simulation studies have been developed. We develop a method for estimating frictional properties and monitoring slip evolution on an LSSE fault, with a sequential data assimilation method, the ensemble Kalman filter (EnKF). We executed numerical twin experiments for the Bungo Channel LSSE fault in southwest Japan to validate the method. First, based on a rate- and state-dependent friction law, we set a rate-weakening circular LSSE patch on the rate-strengthening flat plate interface, whose critical nucleation size is larger than that of the patch, and reproduced the observed Bungo Channel LSSEs with recurrence times of approximately 7 yr and slip durations of 1 yr. Then, we synthesized the observed data of surface displacement rates at uniformly distributed stations with noises from the simulated slip model. Using our EnKF method, we successfully estimated the frictional parameters and the slip rate evolution after a few cycles. Secondly, we considered the effect of the megathrust fault existing in the updip portion of the LSSE fault, as revealed by kinematic inversion studies of Global Navigation Satellite System (GNSS) data and added this locked region with a slip deficit rate in the model. We estimated the slip rate on the locked region only kinematically, but the quasi-dynamic equation of motion in each LSSE fault cell includes the stress term arising from the locked region. Based on this model, we synthesized the observed surface displacement rate data for the actual distribution of GNSS stations and executed EnKF estimations including the slip rate on the locked region. The slip rate on the locked region could be quickly retrieved. Even for the actual distribution of GNSS stations, we could successfully estimate frictional parameters and slip evolution on the LSSE fault. Thus, our twin numerical experiments showed the validity of our EnKF method, although we need further studies for actual GNSS data analyses.