scholarly journals Integration of InSAR and ground-based geophysical measurements to study an area prone to quick-clay landslide in Sweden

2021 ◽  
Author(s):  
Alireza Malehmir ◽  
Mehdi Darvishi ◽  
Faramarz Nilfouroushan
Keyword(s):  
Surface Deformation ◽  
Sar Interferometry ◽  
Coarse Grained ◽  
River Bank ◽  
Crystalline Bedrock ◽  
Geophysical Surveys ◽  
Quick Clay ◽  
Marine Clays ◽  
Geophysical Measurements

<p>Landslides and floods are the two most important geohazards in Sweden. Due to the climate change effects, it is believed that the risk of occurring these geohazards will increase in Sweden causing for example the land to become more prone to landslides. Additionally, due to the isostatic uplift caused by the retreating of the ice sheet, approximately 10,000 years ago, marine sediments involving marine clays have become exposed above sea level in Scandinavia. Infiltration of fresh water has (and is) leached the salt from the pores within the marine clays leading to the formation a special kind of clay known as the quick clay in the northern countries. These glacial clays and postglacial silts cause more ground surface instability and become slops more prone to trigger landslides, which is the case for concentration of the most landslides in the southwest of Sweden. Hence, quick-clay landslides are common geohazards in Nordic countries, which potentially could cause a considerable economical and live cost. The most recent Gjerdurm landslide in Norway was of this kind quick-clay related.</p><p>In recent years, an area close to the Göta River of southeast of Sweden has been the subject of numerous surface and airborne geophysical surveys for detailed subsurface mapping and delineation of the quick-clay and sediments hosting them including the very undulating the crystalline bedrock. These existing studies including access to borehole observations and geotechnical studies motivated us to study also long-term surface deformation in order to study climate effects, erosion, precipitation and underlying quick-clay presence in this area and neighboring regions. We employed radar data with Syntenic Aperture Radar (SAR) interferometry techniques. To this end, Sentinel-1 data from 2015 to 2019 were processed with the Small BAsline Subset (SBAS) technique to estimate time-series displacements and to generate deformation map for that region. The initial results show that the heterogenous deformation observed in the study area with maximum subsidence rate of -22 mm/yr. The deforming areas appear to be located on regions with the thickest column of the clay near the river where we anticipate also thicker quick-clay layers present. The quick-clays in this region overlie a thick (ca. 20 m) coarse-grained layer interpreted from the surface geophysical measurements to be associated with the formation and triggering of quick-clays in the area. With such a large surface deformation and the underling geology, we observe two phenomena in the study. A possible sudden risk of quick-clay landslide but also a long-term creeping of clays and destabilizing effect that may accelerate erosion at the river bank causing more landslides in the future. The cause of the large deformation is still unclear and will be investigated together with hydrogeological and geophysical data available in the study. This study however provides compelling evidence of major surface deformation that should be considered for long-term risk mitigation and planning.  </p>

Integrated 2D modeling and interpretation of geophysical and geotechnical data to delineate quick clays at a landslide site in southwest Sweden

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. EN61-EN75 ◽  
Author(s):  
Chunling Shan ◽  
Mehrdad Bastani ◽  
Alireza Malehmir ◽  
Lena Persson ◽  
Mats Engdahl
Keyword(s):  
Electrical Resistivity ◽  
Seismic Data ◽  
Coarse Grained ◽  
Data Set ◽  
Resistivity Tomography ◽  
Geotechnical Data ◽  
Reflection Seismic ◽  
Quick Clay ◽  
2D Resistivity ◽  
Marine Clays

Radio magnetotellurics (RMT), electrical resistivity tomography (ERT), and high-resolution reflection seismic data were collected along four lines to characterize the geometry and physical properties of geologic structures at a quick-clay landslide site in southwest Sweden. The site is situated in the Göta River valley where the normally consolidated materials mainly consist of glacial and postglacial sediments. Geotechnical data suggest the presence of quick clays above coarse-grained layers. These layers play a key role in the formation of quick clays and landslide triggering. The RMT and ERT data were individually and jointly inverted in 2D to study the resolution of resulting models for each data set. The resistivity models from the joint inversions demonstrate superior resolution and accuracy compared with individual ones. The geometry and location of shallower structures resolved in the 2D resistivity models from joint RMT&ERT inversions correlated well with those imaged in the reflection seismic data and observed in the existing geotechnical boreholes. The models were poor in resolving deeper resistive bedrock at locations where the thickness of the conductive overburden exceeds a certain limit. However, information from the reflection seismic data could be used to estimate the depth to the top of the bedrock along all the four lines. Comparison between the geotechnical data and the resistivity models suggested that quick clays overlying the coarse-grained layer have higher electrical resistivity than the marine clays. We further validated and refined the obtained results by performing synthetic tests. We showed that integration of ERT and RMT data with reflection seismic data is ideal for quick-clay landslide studies especially when the clay materials are thick.

scholarly journals Subsurface characterization of a quick-clay vulnerable area using near-surface geophysics and hydrological modelling

Solid Earth ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 1685-1705
Author(s):  
Silvia Salas-Romero ◽  
Alireza Malehmir ◽  
Ian Snowball ◽  
Benoît Dessirier
Keyword(s):  
Large Scale ◽  
Geophysical Methods ◽  
Hydrological Modelling ◽  
P Wave ◽  
Coarse Grained ◽  
Near Surface ◽  
Reflection Seismic ◽  
Geotechnical Investigations ◽  
Quick Clay ◽  
Near Surface Geophysics

Abstract. Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identify coarse-grained materials associated with the development of quick clays. We present the results of reflection seismic investigations on land and in part of the Göta River in Sweden, along which many quick-clay landslide scars exist. This is the first time that such a large-scale reflection seismic investigation has been carried out to study the subsurface structures associated with quick-clay landslides. The results also show a reasonable correlation with radio magnetotelluric and travel-time tomography models of the subsurface. Other ground geophysical data, such as high magnetic values, suggest a positive correlation with an increased thickness of the coarse-grained layer and shallower depths to the top of the bedrock and the top of the coarse-grained layer. The morphology of the river bottom and riverbanks, e.g. subaquatic landslide deposits, is shown by side-scan sonar and bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary glacial and postglacial deposits, is clearly revealed. An extensive coarse-grained layer (P-wave velocity mostly between 1500 and 2500 m s−1 and resistivity from approximately 80 to 100 Ωm) exists within the sediments and is interpreted and modelled in a regional context. Several fracture zones are identified within the bedrock. Hydrological modelling of the coarse-grained layer confirms its potential for transporting fresh water infiltrated in fractures and nearby outcrops located in the central part of the study area. The modelled groundwater flow in this layer promotes the leaching of marine salts from the overlying clays by seasonal inflow–outflow cycles and/or diffusion, which contributes to the formation of potential quick clays.

scholarly journals Detecting Long-Term Deformation of a Loess Landslide from the Phase and Amplitude of Satellite SAR Images: A Retrospective Analysis for the Closure of a Tunnel Event

2021 ◽  
Vol 13 (23) ◽  
pp. 4841
Author(s):  
Yaru Zhu ◽  
Haijun Qiu ◽  
Zijing Liu ◽  
Jiading Wang ◽  
Dongdong Yang ◽  
...  
Keyword(s):  
Local Governments ◽  
Surface Deformation ◽  
Failure Surface ◽  
Deformation Characteristics ◽  
Spatiotemporal Evolution ◽  
Loess Landslide ◽  
Landslide Deformation ◽  
Term Creep ◽  
Offset Tracking

Information about the long-term spatiotemporal evolution of landslides can improve the understanding of landslides. However, since landslide deformation characteristics differ it is difficult to monitor the entire movement of a landslide using a single method. The Interferometric Synthetic Aperture Radar (InSAR) and pixel offset tracking (POT) method can complement each other when monitoring deformation at different landslide stages. Therefore, the InSAR and improved POT method were adapted to study the pre- and post-failure surface deformation characteristics of the Gaojiawan landslide to deepen understanding of the long-term spatiotemporal evolution characteristics of landslides. The results show that the deformation displacement gradient of the Gaojiawan landslide exhibited rapid movement that exceeded the measurable limit of InSAR during the first disaster. Moreover, the Gaojiawan landslide has experienced long-term creep, and while studying the post-second landslide’s failure stability, the acceleration trend was identified via time series analysis, which can be used as a precursor signal for landslide disaster warning. Our study aims to provide scientific reference for local governments to help prevent and mitigate geological disasters in this region.

scholarly journals Mathematical Framework for Breathing Chimera States

2022 ◽  
Vol 32 (2) ◽  
Author(s):  
O. E. Omel’chenko
Keyword(s):  
Coupled Oscillators ◽  
Analytic Solution ◽  
Coarse Grained ◽  
Mathematical Framework ◽  
Intensive Study ◽  
Phase Oscillators ◽  
Chimera States ◽  
The Subject ◽  
Self Consistency

AbstractAbout two decades ago it was discovered that systems of nonlocally coupled oscillators can exhibit unusual symmetry-breaking patterns composed of coherent and incoherent regions. Since then such patterns, called chimera states, have been the subject of intensive study but mostly in the stationary case when the coarse-grained system dynamics remains unchanged over time. Nonstationary coherence–incoherence patterns, in particular periodically breathing chimera states, were also reported, however not investigated systematically because of their complexity. In this paper we suggest a semi-analytic solution to the above problem providing a mathematical framework for the analysis of breathing chimera states in a ring of nonlocally coupled phase oscillators. Our approach relies on the consideration of an integro-differential equation describing the long-term coarse-grained dynamics of the oscillator system. For this equation we specify a class of solutions relevant to breathing chimera states. We derive a self-consistency equation for these solutions and carry out their stability analysis. We show that our approach correctly predicts macroscopic features of breathing chimera states. Moreover, we point out its potential application to other models which can be studied using the Ott–Antonsen reduction technique.

scholarly journals Long-Term Behavior of Coarse-Grained Rockfill Material and Their Constitutive Modeling

2021 ◽  
Author(s):  
Erich Bauer
Keyword(s):  
Mechanical Response ◽  
Coarse Grained ◽  
Geological Condition ◽  
Dam Foundation ◽  
Solid Hardness ◽  
Rockfill Materials ◽  
Materials Used ◽  
Creep And Stress Relaxation ◽  
Long Term Behavior

For the long-term behavior and safety assessment of rockfill dams, not only the shape of the dam body, the loading history, the geological condition of the dam foundation and abutments, the assessment of possible seismic hazards and seepage events caused by defects of the sealing are important, but also the time dependent mechanical behavior of the dam materials used can be of significant influence. In this paper a novel hypoplastic constitutive model for moisture sensitive, coarse-grained rockfill materials is presented. In the constitutive equations, the so-called solid hardness is a key parameter to reflect the influence of the state of weathering on the mechanical response. With respect to the evolution equation for the solid hardness, creep and stress relaxation can be modeled for dry and wet states of the material in a unified manner. The performance of the model is demonstrated by comparing the numerical simulation with experimental data.

Role of surface water in the formation of underground water in Aghstafachai-Ganjachai interfluve and its usage prospects

2020 ◽  
pp. 58-62
Author(s):  
A.R. Ibrahimova ◽  
Keyword(s):  
Underground Water ◽  
Point Of View ◽  
Tectonic Structure ◽  
Climate Type ◽  
Geophysical Surveys ◽  
Mineralization Degree ◽  
Well Data

With the purpose of water resources estimation of Aghstafachai-Ganjachai interfluve, geophysical surveys have been carried out. As a result, based on the well data, the maps were developed and interface conditions of the territory specified. The tectonic structure of Aghstafachai-Ganjachai interfluve lowland is associated with the formation of a sole artesian basin on its territory. Aghstafachai, Hasansu, Tovuzchai, Zeyemchai, Shamkirchai, Goshgarchai, Ganjachai and Kurekchai, being the main source of groundwater recharge, created a combined alluvial cone on the territory. The underground water of these rivers were studied in the sloping plain and the estimation of its volume carried out as well. It was revealed that the underground water on a large part of studied territory is fresh and less mineralized. From the bacteriological point of view, it is clean water. The content of microelements and harmful chemical substances in the water does not exceed the standards set for the drinkable water. Despite the long-term usage, the quality of the underground water, the mineralization degree and chemical composition remain unchanged. The regime of underground water is characterized with the irrigated climate type. Hydrogeological indexes and the parameters of ground water horizon in the studied area justify the possibility of their research for water supply.

Multi-scale influence of topography on shallow-marine successions associated with long-term transgressions

2021 ◽  
Author(s):  
Miquel Poyatos-Moré ◽  
Ernesto Schwarz ◽  
Salvador Boya ◽  
Luz Elena Gomis-Cartesio ◽  
Ivar Midtkandal
Keyword(s):  
Regional Scale ◽  
Coarse Grained ◽  
Continuous Exposure ◽  
Entire Study ◽  
Shallow Marine ◽  
Sedimentary Characteristics ◽  
Multi Scale ◽  
Depositional Processes ◽  
Mouth Bars

<p>Thick shallow-marine successions associated with long-term transgressions are less well known than their thin, well-sorted counterparts, widely studied due to their potential to form good reservoirs. In these successions, particularly in storm-dominated examples, bioturbation can obliterate primary sedimentary characteristics, making stacking patterns and sequences difficult to define, and challenging our understanding of the main controls in their resulting depositional architecture. This study presents an example from the Jurassic of the Neuquén Basin (Argentina), with the aim to: a) refine the depositional model of a thick, shallow-marine succession associated with a long-term, early post-rift transgression, b) constrain multi-scale controls on stratigraphic architecture and lateral facies variability, and c) discuss their preservation and response to post-depositional processes. To do this, a <300 m-thick succession has been studied along a >10 km continuous exposure, with mapping, sedimentary logging and correlation of stratigraphic units, integrated with subsurface, biostratigraphic and ichnological data. The succession shows an overall retrogradational-aggradational-retrogradational stacking pattern, with several higher frequency regressive units (parasequences and parasequence sets, PSS). The lower part (PSS I) comprises laterally-discontinuous (10's of m) mouth-bars and distributary channel fills, dominated by several m-thick coarsening- and fining-up sandstone packages and m-scale erosive conglomeratic lenses. Above these, the succession (PSS II-IV) is composed by laterally-continuous (>100's of m) storm-dominated lower-shoreface to upper-offshore deposits, dominated by <1m-thick fine-grained and highly bioturbated tabular muddy sandstones and sandy mudstones, with rarely-preserved HCS and bioclastic-rich limestones; their internal characteristics and bed boundaries are diffuse due to pervasive bioturbation, suggesting overall low sedimentation rates and recurrent periods of colonization. The coarse-grained nature and lithology of the mouth bars and channel fills in the lower succession (PSS I) are consistent with a proximal sediment source, associated with erosion of intra-basinal highs. Its variable thickness, lateral distribution and onlap against underlying syn-rift deposits demonstrates partial infill of localized higher-accommodation areas. The well-sorted and finer-grained nature of the shoreface-offshore strata the middle and upper succession (PSS II-IV) indicates a more mature, distal source, with sediment redistributed by longshore currents, and then intensely bioturbated. These deposits display well-defined parasequences internally composed of laterally-continuous bedsets (<5 m-thick). They extend along the entire study area, but show a significant vertical thickness variability. The integration of outcrop and subsurface data mapping (well and seismic) reveals this variability records the stratigraphic response of transgression over a complex, regional-scale ramp-step and underfilled rift topography, which controlled the location of main thickness and facies changes, and promoted areas of favored biogenic reworking. This study offers new insights in how to interpret thick transgressive successions based on primary depositional mechanisms and postdepositional processes, and provides useful tools to understand and predict the nature and potential preservation of these deposits in limited subsurface datasets.</p>

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