Ground Cracks Research Articles

A Hybrid Coupled Model for Groundwater-Level Simulation and Prediction: A Case Study of Yancheng City in Eastern China

The over-exploitation of groundwater has led to a significant drop in groundwater levels, which may lead to a series of geological disasters and ecological environmental problems such as ground subsidence and ground cracks. Therefore, through studying the dynamic change characteristics of groundwater, we can grasp the dynamic changes in groundwater level over time and invert the hydrogeological parameters, which provides an important basis for the management of groundwater resources. In this study, the confined aquifer III groundwater between 2005 and 2014 in Yancheng City was selected as the research object, and the Back Propagation (BP) neural network, Spatial-temporal Auto Regressive and Moving Average (STARMA) model, and BP-STARMA model were used to predict the spatial and temporal evolution trends of groundwater. In order to compare the prediction effectiveness of the BP-STARMA model, the fitting and prediction accuracies of the three models were measured from the perspectives of time and space. The results of the Relative Squared Error (RSE), Normal Mean Squared Error (NMSE), Root-Mean-Squared Error (RMSE), and Mean Absolute Error (MAE) were used to assess the robustness of the BP-STARMA model. The results showed that the fitting of the RMSE of BP-STARMA model was reduced by 39.92%, 38.35%, 30.25%, 31.55%, and 13.57% compared with the STARMA model, and by 22.2%, 8.7%, 15.9%, 28.5%, and 4.42% compared with the BP neural network model, respectively. Collectively, this shows that the BP-STARMA model has a better spatiotemporal prediction of groundwater level than the STARMA and BP neural network models, is more applicable to spatially continuous time-discrete spatiotemporal sequences, and is more applicable to spatiotemporal sequences that respond to natural geographic phenomena.

28th September 2018 Mw 7.5 Sulawesi Supershear Earthquake, Indonesia: Ground effects and macroseismic intensity estimation using ESI-2007 scale

The 28th September 2018 Sulawesi Supershear earthquake (MW 7.5) was one of the deadliest earthquakes in the recent history of Indonesia causing ∼4000 causalities. The earthquake caused a ∼ 177 km long surface rupture along the Palu-Karo fault. Apart from surface rupture, the earthquake caused extensive earthquake environmental effects (EEEs) around the Palu-Donggala area of Central Sulawesi, Indonesia, which includes tsunami, coastal landslide, liquefaction, ground cracks and more than 7300 landslides in hilly areas. Initial post-event analysis and reports assigned a Modified Mercalli Intensity (MMI) of VII to VIII in Palu City and the surrounding area. Building damage and ground effects caused by the earthquake suggested that seismic intensity was understated. Here we applied the EEEs information from field survey data, published reports, and remote sensing tools to determine macroseismic intensity using the Environmental Seismic Intensity (ESI-07) Scale. The ESI-07 intensity derived from the ground effects suggests the maximum intensity of X-XI, which is 3–4° higher than the traditional intensity estimated by the United States Geological Survey (USGS) and the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG). ShakeMaps were generated considering the ESI-07 values. The ShakeMap was compared with the instrumentally derived ShakeMap for the Palu earthquake, which proves that the ShakeMap prepared from the instrumental data or structural damage data is underrated. We argue that proper documentation of the EEEs is necessary for such damaging earthquakes for future earthquake hazard mapping and planning in the study area and other earthquakes in Indonesia. In addition, this will help in defining the on-fault and off-fault damage zone towards reducing the seismic risk of the Palu Donggala area.

Numerical analysis on the seismic performance of subway station in ground crack area

The site soil with ground cracks would cause strong motion and large deformation under major earthquakes, which brings a serious threat to underground structures. However, the ground crack effect on the seismic response of underground structures was unclear. This study developed a series of numerical analyses to study the seismic performance and damage mechanism of a rectangular-section subway station located in a ground crack area. After verification of the developed model, the structural responses of the subway stations in different sites subject to different earthquakes were evaluated in terms of acceleration response, inter-story drift, and damage pattern. Furthermore, a parameter analysis was performed to address the effects of structural position in the site, structural overburden depth and dynamic shear modulus of soils on the seismic performance of the subway station in the ground crack area. The results showed that the presence of ground crack exacerbated the shear deformation of the site soil and increased the internal forces of the lateral members, resulting in substantial damage to the subway station. The subway station in the ground crack area had poorer seismic performance than the station in the uncracked area, especially for station crossing the ground crack. Particularly, the ground crack effect on the seismic performance of subway stations should be carefully considered in the design of shallow-buried underground structures in soft soils.

Study on the Development Law of Mining-Induced Ground Cracks under Gully Terrain

Coal seam mining in the gully area easily causes ground cracks and even induces landslides, which endanger the safety of mining areas. In this paper, combined with the mining conditions of a mining area in southern Shanxi Province, China, ground crack mapping, crack width dynamic monitoring, and the numerical simulation method are used to study the static and dynamic evolution law and the formation mechanism of ground cracks in the gully area. The research shows that ground cracks mainly include dynamic in-plane cracks and boundary cracks. The dynamic in-plane cracks show the characteristics of “opening first and closing later”. The boundary cracks show the characteristics of “only opening and not closing”. It is found that the closure of the dynamic in-plane cracks will decrease (compared with plain areas). The development of ground cracks experiences three stages: the initial formation stage, the dynamic development stage, and the gradually stable stage. The “goaf–surface” structure model and force chain arch structure model are established to more intuitively analyze the formation mechanism of ground cracks. The research results have a specific reference value for preventing ground disasters caused by underground coal mining and land ecological restoration.

The earthquake environmental effects (EEEs) of the 6th February 2018, Hualien earthquake (Mw=6.4): A contribution to the seismic hazard estimation in the epicentral area

The macroseismic intensity of the February 6, 2018, Mw 6.4, Hualien earthquake, which caused extensive damage around the Hualien area of eastern Taiwan is reassessed using the Environmental Seismic Intensity (ESI-07) scale. We compiled data on earthquake environmental effects (EEEs) caused by the 2018 Hualien earthquake, which includes surface ruptures, ground cracks, liquefaction, and occasional landslides, and estimated the epicentral intensity (I0) as well as site-specific intensities. We found that the ESI-07 epicentral intensity of the Hualien quake in 2018 is IX. We note that the epicentral area of the 2018 Hualien earthquake was the mesoseismal area of the October 22, 1951, (Mw 6.6) Hualien earthquake, as reported in primary contemporary sources and historical earthquake catalogs. The 1951 Hualien earthquakes also caused prominent surface ruptures, liquefaction, and ground cracks. Consequently, we reassess the macroseismic intensities of this historical seismic event and compare it to the Hualien earthquake in 2018. The comparison suggests similar epicentral intensities for the two earthquakes (IX and X ESI-07). Moreover, we conducted a systematic comparison between intensity obtained using different scales which revealed the differences of two to three degrees between the ESI-07 and traditional intensity scales. This result reconfirms the significance of documentation and recording of earthquake environmental effects to make intensity assessments for modern seismic events consistent with the historical earthquake records. Moreover, a re-evaluation of historical earthquake intensity in eastern Taiwan could be performed in order to update the seismic hazard map. Application of the ESI-07 intensity scale of recent and historical earthquakes will be helpful in post-earthquake recovery efforts for a future earthquake. The prepared ShakeMaps from the ESI-07 values suggests completely different shapes to the previously generated ShakeMaps considering the peak ground acceleration or peak ground velocity. It suggests that the ShakeMaps prepared from the earthquake environmental effects can be complemented with the instrumental based intensity map to have a better seismic hazard prediction and future land use planning for the region.

Identification of active deformation zone associated with the 28th April 2021 Assam earthquake (Mw 6.4) using the PSInSAR time series

The co-seismic deformation of the 28th April 2021 Assam earthquake with a magnitude of 6.4 has been investigated using the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR). The results obtained from the PSInSAR are validated with the results of the Global Positioning System (GPS). It is observed that the co-seismic deformation of the earthquake is not visible because of the atmospheric noise. Therefore, we used the Sentinel-1 time-series data of the area to minimize the atmospheric noise effect the data using the Atmospheric Phase Screening (APS) processing of Sentinel-1 time series data. The time-series analysis shows minor changes that occurred during the earthquake. Firstly, the detection of coherence-based changes was carried out to identify the most affected areas, caused by the earthquake. The results of time series analysis suggest that the region located to the north of the Brahmaputra River is subsiding at a much faster rate (−25 to -75 mm/y) than its southern counterpart, where the southern part is subsiding with an average velocity of −0.1 to −15 mm/y. The subsided locations identified using the PSInSAR are further confirmed by the presence of liquefaction features, ground cracks, and tilted buildings related to post-liquefaction ground settlement. To see the deformation along the Bomdila Fault (BF), re-analysis of the available GPS results has been carried out and the derived results reveal a significant amount of deformation (∼4 mm/y) associated with BF and Jorhat Fault (JF); whereas the deformation associated with Kopili Fault (KF) is 3.14 mm/y. Further, our results suggest the presence of compressional strain in the BF zone, while extensional strain in the KF zone. The earthquake focal mechanism analysis suggests that the event of the April 2021 was primarily associated with the BF rather than the KF.

Research on the Applicability of DInSAR, Stacking-InSAR and SBAS-InSAR for Mining Region Subsidence Detection in the Datong Coalfield

Intensive and large-scale underground coal mining has caused geological disasters such as local ground subsidence, cracks and collapse in the Datong coalfield, China, inducing serious threats to local residents. Interferometric synthetic aperture radar (InSAR) has the capability of surface deformation detection with high precision in vast mountainous areas. DInSAR, stacking-InSAR and SBAS-InSAR are commonly used InSAR-related deformation analysis methods. They can provide effective support for mine ecological security monitoring and prevent disasters. We use the three methods to conduct the deformation observation experiments in the Datong coalfield. Sentinel-1A data from November 2020 to October 2021 are used. As a result, a total of 256 deformations in the Datong coalfield were successfully detected by the three methods, of which 218 are mining deformations, accounting for 85% of the total deformations. By comparing the results of the three methods, we found that DInSAR, stacking-InSAR, and SBAS-InSAR detected 130, 256, and 226 deformations in the Datong coalfield, respectively, while the deformations caused by coal mining were 128, 218, and 190. DInSAR results with long spatiotemporal baselines are seriously incoherent. SBAS-InSAR results of displacement rate are more precise than stacking-InSAR, and the mean standard deviation is 1.0 mm/a. However, for areas with lush vegetation or low coherence, SBAS-InSAR has poor performance. The detection deformation area results of DInSAR and SBAS-InSAR are subsets of stacking-InSAR. The displacement rates obtained by stacking-InSAR and SBAS-InSAR are consistent; the mean difference in the displacement rate between the two methods is 2.7 mm/a, and the standard deviation is 5.1 mm/a. The mining deformation locations and their shapes in the study area can be identified with high efficiency and power by stacking-InSAR. Therefore, with a comprehensive understanding of the advantages and limitations of the three methods, stacking-InSAR can be an effective and fast method to identify the level, location and range of mining deformation in lush mountainous areas.

Experimental Analysis on Mechanical Characteristics of Foundation Soil in Rift Valley Area of Kenya Nairobi-Malaba Railway

The Rift Valley section of Kenya Nairobi-Malaba Railway locates in the Great Rift Valley of East Africa, with complex engineering geological conditions and well-developed geological structures. During the rainy season from March to May 2018, four large-scale ground fissures were formed in the first-stage project of the Nairobi-Malaba Railway of the valley floor section, accompanied by uneven surface settlement and trenches, seriously endangering the safety of the railway and its nearby projects. Through field investigation, it is preliminarily considered that the main reason induced ground fissures and surface settlement is the underlying soil layer being eroded by groundwater. The gully is further formed by surface water erosion on a base of uneven surface subsidence. The geological exploration trench at DK77 ground fissure revealed that the overlying soil layer is respectively grayish-yellow silty clay, cyan-gray volcanic ash, and brownish-yellow silty clay from top to bottom, and the underlying bedrock is volcanic tuff with wide cracks. The fluid flows out or into the bedrock through the cracks developing channels for groundwater up-down flowage. Under the erosion of groundwater to the underlying soil, this study proved the possibility of the occurrence of uneven settlement. When exposed to the groundwater, the underlying soil will exhibit special physical and mechanical properties which are conducive to the occurrence of ground cracks and subsidence. The conventional geotechnical tests are conducted for the three types of overlying soil, and the results reveal the causes of ground fissures and surface settlement from the physical and mechanical properties of the overlying soil and provide a basis for the further qualitative analysis of the mechanism of ground fissures and surface settlement.

Stability Control of Slopes in Open-Pit Mines and Resilience Methods for Disaster Prevention in Urban Areas: A Case Study of Fushun West Open Pit Mine

During the century-long mining process of the Fushun west open pit, slope slippage and deformation caused varying degrees of horizontal deformation, uneven settlement, and ground cracks on the surface of the urban areas, which caused a certain degree of damage to buildings and infrastructure and affected the livings of residents in the surrounding communities. In this study, a set of building reinforcement and community resilience enhancement methods that can resist slope deformation was proposed to improve the ability of urban areas to cope with slope geological hazards and emergency response. The main research contents included: Firstly, this paper systematically analyzed the deformation mechanism of the dip sloping and the inverse dip sloping section of the open pit mine, which was based on the field measured data and simulation calculation results. In other words, the horizontal deformation of the stratum in the dip sloping section was dominant, while the stratum in the inverse dip sloping section was prone to ground cracks and uneven settlement. In view of this, three surface deformation characteristic subdivisions of the surrounding urban area were proposed. In addition, a study on the damage characteristics of buildings with different types of foundations and structures under the influence of side slope deformation were carried out, and the anti-deformation reinforcement measures for load-bearing members mainly based on steel fiber concrete, carbon fiber materials and profile steel were proposed. Finally, a three-level disaster emergency setting system for urban areas around open pit mine was established, and the disaster prevention and resilience enhancement strategy for build and unbuilt the communities around the side slopes was constructed. The study aims to provide technical support to the overall resilience and response of the urban communities adjacent to open-pit mine slopes against consequent geological hazards and emergencies, thereby promoting sustainable urban development.

Earthquake-induced landslide monitoring and survey by means of InSAR

Abstract. This study uses interferometric synthetic aperture radar (SAR) techniques to identify and track earthquake-induced landslides as well as lands prone to landslides, by detecting deformations in areas struck by earthquakes. The pilot study area investigates the Mila region in Algeria, which suffered significant landslides and structural damage (earthquake: Mw 5, 7 August 2020). DInSAR analysis shows normal interferograms with small fringes. The coherence change detection (CCD) and DInSAR analysis were able to identify many landslides and ground deformations also confirmed by Sentinel-2 optical images and field inspection. The most important displacement (2.5 m), located in the Kherba neighborhood, caused severe damage to dwellings. It is worth notice that CCD and DInSAR are very useful since they were also able to identify ground cracks surrounding a large zone (3.94 km2 area) in Grarem City, whereas the Sentinel-2 optical images could not detect them. Although displacement time-series analysis of 224 interferograms (April 2015 to September 2020) performed using LiCSBAS did not detect any pre-event geotechnical precursors, the post-event analysis shows a 110 mm yr−1 subsidence velocity in the back hillside of Kherba.

Characteristics of ground cracks caused by the MS 6.4 Yangbi earthquake and the corresponding tectonic significance

An MS 6.4 earthquake occurred near Yangbi County, Dali Bai Autonomous Prefecture, Yunnan Province, at 21:48 on May 21, 2021. The earthquake location is characterized by complex geological structures, with multiple active faults distributed around the epicenter that is located at the west edge of the Sichuan-Yunnan rhombic block (25.67°N, 99.87°E). A total of 42 ground cracks are found by earthquake field investigations. The cracks are mainly concentrated in the Ⅷ degree area on the west side of the Yangbi River. Among these, 9 coseismic tectonic ground cracks generated by shear fractures are found in three villages (i.e., Akechang, Meijia-Lijia, and Huajiazhuang), which are distributed along the strike of the northwest-trending linear folds, showing the tectonic characteristics of right-lateral tension or left-stepping cracks. The structural attribute of ground cracks sustains the kinematic properties of the Weixi-Qiaohou fault, namely right-lateral strike-slip.

Geological and geotechnical investigation on the origin of ground cracks across road section between Butajira and Worabe towns and at Ureb Kebele in the western part of Central Main Ethiopian Rift

Geological and geotechnical investigation on the origin of ground cracks across road section between Butajira and Worabe towns and at Ureb Kebele in the western part of Central Main Ethiopian Rift

An Appraisal of Ground Failure and Hydrogeological Changes Associated with the 28 April 2021 Mw 6 Sonitpur Earthquake, Assam, India, Using Field Evidences and InSAR Measurements

Abstract Widespread damage and coseismic ground disturbances are generally associated with large magnitude and/or shallow focus earthquakes. Surprisingly, a deep focus (34 km), moderate magnitude earthquake (Mw 6) occurred near the Kopili fault zone in Sonitpur district, Assam, India, on 28 April 2021 and created intense ground shaking and extensive damage along the Brahmaputra Valley. We undertook a field survey within a day after the earthquake and carried out Interferometric Synthetic Aperture Radar (InSAR) analysis to map any coseismic ground deformation features. Our field survey revealed extensive liquefaction features and several coseismic secondary ground cracks along the alluvial tracts of the Brahmaputra River system. InSAR analysis revealed a sinistral slip up to ∼60 mm along a north-northwest–south-southeast-oriented previously unmapped lineament or fault. Field investigations revealed coseismic hydrological changes including a sudden rise and fall in the water level by 0.3–0.5 m followed by the injection of sand materials up to a thickness of 1.25 m in dug wells and the appearance of water in seasonally dried river channels and ponds. Interferometric coherence analysis during pre-, co-, and postseismic periods further confirmed the coseismic surge in water at five major tributary rivers of the Brahmaputra River. We speculate that the pressure difference at the shallow unconfined aquifer system of the mountain-front alluvial fan induced by coseismic stresses must have caused channeling of groundwater to the rivers and the contemporaneous water level fluctuations in wells. Amplification of seismic waves at the thick, unconsolidated sedimentary strata of the Brahmaputra Valley could have enhanced the extensive damage due to the 2021 Sonitpur earthquake. The present study has implications in estimating damage potential along the Brahmaputra Valley for future earthquakes.

CALCULATION OF THE BEARING CAPACITY OF A TWO-SLOT STRIP FOUNDATION

The results of computer modeling of the process of formation and development of areas of plastic deformations in the connected base of a double-slit ribbon foundation are presented. All calculations are performed using computer programs developed with the participation of the author. These programs allow you to take into account all the variety of physical and mechanical properties of the foundation soil (volume weight, internal friction angle, specific adhesion, lateral pressure coefficient and deformation modulus) and the foundation material (elastic modulus and Poisson's ratio). In the calculations, it is assumed that the value of the lateral pressure coefficient of the soil is 0.75, as is typical for cohesive clay soils, and the same value for the foundation material is assumed to be 0.43 (converted through the Poisson's ratio). Based on the results of calculations, it was possible to determine the features of the stress state of the base of the double-slit foundation and the process of development of plastic areas in the core of the foundation. First of all, the part of the bearing capacity of the base of the double-slit foundation that contacts its side surface is realized, and the inclusion of the side surface of the slit foundation in the work occurs from the bottom up. Then the part of the base that is located directly under the soles of the walls in the ground (cracks) is included in the work. It is established that the smaller the distance between the slits, the greater the bearing capacity of the base and the greater its part falls on the side surface. The bearing capacity of the base of a double-slit foundation is directly proportional to the depth of its foundation (the height of the cracks). The part of the load-bearing capacity realized on the side surface of the foundation can reach 60 % or more of its full value. An engineering method for calculating the load-bearing capacity of the base of a double-slit foundation, including simple formulas and graphs, is proposed. The method is formalized in a calculator program. The verification calculations showed a high degree of accuracy in approximating the results of the numerical experiment.

Ground Fracture Development and Surface Fracture Evolution in N00 Method Shallowly Buried Thick Coal Seam Mining in an Arid Windy and Sandy Area: A Case Study of the Ningtiaota Mine (China)

An observatory was established at the Ningtiaota Mine (China) in order to investigate the surface deformation pattern of N00 method workings mining in shallow buried thick coal seams in a windy-sand area. The observatory allows one to measure the coupling between the periodic changes of parameters related to ground subsidence and ground cracks with workings advancement. The data monitored in the field indicate that when the adjacent mining workings are mined below the ground, a sinkhole basin with a larger impact area will be formed. New ground fractures are formed above the mining area to connect with the fractures above the mining face. As a consequence a new pattern of “O” circle distribution beyond the working face is formed, which develops rapidly during the working face recovery. In addition, the dynamic fractures in coal mining are characterized by the phenomenon of self-healing. Our findings will help to protect the surface environment of the mine area during shallow buried high-intensity mining activities in the Lime Tower coal mine, and are also an important guideline in other windy beach mining areas.

The AD 1755 Lisbon Earthquake-Tsunami: Seismic source modelling from the analysis of ESI-07 environmental data

This work presents a macroseismic analysis of the AD 1755 Lisbon Earthquake-Tsunami event by means of the combination of intensity data derived from the EMS-98 scale and the ESI-07 scale (Environmental damage). About 600 records of secondary earthquake environmental effects (EEEs) for the whole Spain have been used to define intensities, focused on the SW portion of the Iberian Peninsula. The Spanish data have been complemented with 308 EEEs records from Portugal. The analyses indicate maximum intensities of X EMS-ESI along the Atlantic margin of the Iberian Peninsula with 76 records of Tsunami environmental effects (TEEs). An important amplification (VIII – VII) occurred all along the Guadalquivir basin and the adjacent Betic front at epicentral distances of 300–700 km. In these zones 55 records of ground effects (ground cracks, Liquefactions and slope movements) are catalogued. In the rest of the territory of the Peninsula the most widespread effects were hydrogeological changes with 505 records in Spain and 196 in Portugal (total 701 records) covering all the intensity levels. Increase of flow discharges in springs and elevation of water level in wells was the common groundwater response to seismic shacking, especially in SW Iberia. In this zone water elevation in wells was between 5 and 3 m and persistent increases of discharges long-lasting (several days to two months). Persistent discharges on springs were linked in 143 cases to important SW-NE crustal faults (e.g., Alentejo-Plasencia Fault). From the Intensity distribution the historic seismic scenarios are explored by means of the development of empirical ShakeMaps. These consider the three classical seismic sources proposed for this earthquake: Gorringe Bank (G); Marques de Pombal Fault (M) and Atlantic delamination beneath the Gulf of Cadiz (C). However, individually these seismic sources are too small and unable to generate the resulting seismic scenario depicted by the intensity map developed in this work, with onshore seismic accelerations (PGA) up to 0.82 g. These acceleration values and the great amplification experienced throughout the Guadalquivir basin (0.34–0.52 g) are only possible considering a combination of the three seismic sources (GMC Source) probably related to shallow subduction or lithospheric delamination beneath SW Iberia and the Gulf of Cadiz. This will suggest an NNE-SSW offshore rupture length of 350–360 km with an overall rupture area of c. 84,500 km2 resulting in an event magnitude 8.6 Mw calculated from empirical relationships. The results demonstrate the efficacy of these kind of approaches for better identifying and modelling seismic sources for historical events.

Revisiting the Most Destructive Earthquake Sequence in the Recent History of Greece: Environmental Effects Induced by the 9, 11 and 12 August 1953 Ionian Sea Earthquakes

The August 1953 seismic sequence comprised the most destructive events in the recent history of Greece. The mainshock on 12 August, and its foreshocks on 9 and 11 August, devastated the southern Ionian Islands. The existing literature emphasized the destructive effects of the earthquakes on buildings, as well as to the emergency response and recovery actions. This resulted in a large gap in capturing the full picture of the earthquake’s environmental effects. The present study aims to fill this gap by reconstructing the most complete picture possible of the primary and secondary effects on the environment of the southern Ionian Islands by the August 1953 earthquakes. This reconstruction is based on all available sources, comprising not only the existing scientific literature, but especially sources that have not been considered to date, including newspapers of local and national circulation. In total, 120 cases of the earthquake’s environmental effects were identified, comprised of 33 cases of primary and 87 cases of secondary effects. In descending order of occurrence, slope failures, co-seismic uplift, hydrological anomalies, ground cracks, tsunami, liquefaction, dust clouds, hydrocarbon-related phenomena, jumping stones and vegetation effects were distributed mainly in Cephalonia Island and secondarily in the Ithaki and Zakythos Islands. The primary effects were mainly detected in eastern Cephalonia, which presented uplift of up to 70 cm, while the majority of the secondary effects were triggered in specific zones with characteristics that made them susceptible to the occurrence of earthquake-related hazards.

Geological hazard interpretation and hazard evaluation of open pit mines based on Unmanned Aerial Vehicle images

Over-exploitation of open-pit mines has caused extensive development of geological hazards, posing serious threats to people and buildings in the area. Based on the UAV tilt-tilt photography technology, this paper generates a real-world 3D model of the study area, taking the molybdenum mine of Songshumao in Yangjiajiaozi, Xingcheng City, Liaoning Province as an example, and combines orthophotography, high-precision DEM data and field geological survey research to establish a geohazard interpretation marker for the study area and interpret various types of geohazards such as landslides, landslides, dangerous rocks, ground cracks and unstable slopes in the study area. Based on the hierarchical analysis method combined with the geological environment characteristics, the geological hazard risk evaluation model and index system were established, and five indexes were selected, including geological hazard range, stratigraphic lithology, slope, elevation, vegetation coverage, etc. The study area was divided into high, medium and low risk zones, and the geological hazard risk zoning map was obtained to complete the geological hazard risk evaluation of the study area.

5G IoT-based geohazard monitoring and early warning system and its application

With the expansion of human production activities, geological disasters caused by slope instability are occurring more frequently. Hence, the research on effective monitoring and forecasting of the geotechnical stability of slopes is of great significance for the prevention and mitigation of slope geological disasters. In this study, a landslide monitoring and early warning system based on 5G Internet of Things (IoT) technology is introduced. The system monitors important indicators such as three-dimensional surface displacement, rainfall, and ground cracks using Global Navigation Satellite System equipment and various IoT sensors deployed on site. The key monitoring data are transmitted and displayed by 5G communication and advanced data visualization technologies. An early warning guideline is established by combining the surface deformation rate–time curve according to a four-level early warning method as well as embedded vector maps such as the topographic and geomorphological remote sensing map of the monitoring area, the geological section map, and the monitoring point distribution map. The system has the functions of accurate acquisition, rapid transmission, automatic search, and comprehensive analysis and is applied to the study of creep slopes of the Lianhe terraces in Youxi County, Fujian Province, with remarkable results.

Primary and Secondary Environmental Effects Triggered by the 30 October 2020, Mw = 7.0, Samos (Eastern Aegean Sea, Greece) Earthquake Based on Post-Event Field Surveys and InSAR Analysis

On 30 October 2020, an Mw = 7.0 earthquake struck the eastern Aegean Sea. It triggered earthquake environmental effects (EEEs) on Samos Island detected by field surveys, relevant questionnaires, and Interferometric Synthetic Aperture Radar (InSAR) analysis. The primary EEEs detected in the field comprise coseismic uplift imprinted on rocky coasts and port facilities around Samos and coseismic surface ruptures in northern Samos. The secondary EEEs were mainly observed in northern Samos and include slope failures, liquefaction, hydrological anomalies, and ground cracks. With the contribution of the InSAR, subsidence was detected and slope movements were also identified in inaccessible areas. Moreover, the type of the surface deformation detected by InSAR is qualitatively identical to field observations. As regards the EEE distribution, effects were generated in all fault blocks. By applying the Environmental Seismic Intensity (ESI-07) scale, the maximum intensities were observed in northern Samos. Based on the results from the applied methods, it is suggested that the northern and northwestern parts of Samos constitute an almost 30-km-long coseismic deformation zone characterized by extensive primary and secondary EEEs. The surface projection of the causative offshore northern Samos fault points to this zone, indicating a depth–surface connection and revealing a significant role in the rupture propagation.