Subsidence Rates Research Articles

Temporally varied coastal uplift rates north of the Littoral Fault Zone since the late Quaternary in the northern South China Sea: Insights from the wave-cut platform and cosmogenic exposure dating

While understanding the long-term slip rate of active normal faults is essential for the comprehensive assessment of seismic activity, it is difficult due to the absence of age control in the erosional bedrock region. The preserved sequence of wave-cut platforms in granite allows exploration of the long-term slip rate in the footwall of some normal faults. We investigated wave-cut platforms in the southern Pearl River Delta (PRD), a coastal delta transected by the seismically active Littoral Fault Zone (LFZ) in the northern South China Sea, to derive slip rates and their impacts on the seismic hazard potential. We mapped a flight of four wave-cut platforms (T1–T4), dated the T2 and T4 platforms by 10Be cosmogenic nuclide dating, and used the absolute age to correlate the un-dated platform to global sea-level highstands. Our results allocate the ages of 128 ka, 197 ka, and 239 ka to the upper three wave-cut platforms and yield temporally various uplift rates ranging from 0.30 to 0.38 mm/a during 239–128 ka to 0.09 mm/a since 128 ka. A decrease in the uplift rate, which coincided with a decreased subsidence rate within the PRD in previous work, implied a weakened differential uplift onshore of the LFZ system. Our findings infer that the transgression event occurred as early as marine isotope stage (MIS) 7 in the PRD, consistent with the view that Pleistocene sedimentation began in MIS 5 or earlier in the PRD.

Sverdrup Basin Composite Tectono-Sedimentary Element, Canadian Arctic Islands

Abstract The Sverdrup Basin Composite Tectono-Sedimentary Element (CTSE) covers 210 000 km 2 in the Canadian Arctic Archipelago. The CTSE was initiated in the Early Carboniferous by rifting of highly deformed Early Paleozoic strata and contains a maximum of 15 km of Carboniferous–Eocene strata. Eight phases of basin development have been recognized, with each being characterized by a specific combination of tectonic and depositional regimes. The phases are separated by intervals of uplift and tectonic reorganization, and each resultant first-order sequence is regarded as a separate TSE. Carbonate sedimentation was dominant in the Late Carboniferous and Early Permian, with clastic sedimentation becoming more common in the Middle Permian. Source areas lay to the east, south and north. In the Triassic, clastic sedimentation rates increased; and by the end of the Triassic, the central basin was filled. A shallow seaway was present throughout the Jurassic. In the Early Cretaceous, subsidence rates and clastic supply increased significantly, and basic volcanism occurred over most of the CTSE. Subsidence rate, sediment supply and volcanism decreased in the Late Cretaceous. The basin was progressively deformed in the Paleogene (Eurekan Orogeny), with local foreland deposits reaching 3 km. Seventeen oil and gas fields have been discovered on salt-cored, Eurekan anticlines. A combination of stratigraphic and structural traps, involving Triassic–Jurassic strata, has the greatest potential for future hydrocarbon discoveries.

Lateral decubitus single position anterior posterior surgery improves operative efficiency, improves perioperative outcomes, and maintains radiological outcomes comparable with traditional anterior posterior fusion at minimum 2-year follow-up

BACKGROUND CONTEXTThe advantages of lateral single position surgery (LSPS) in the perioperative period has previously been demonstrated, however 2-year postoperative outcomes of this novel technique have not yet been compared to circumferential anterior-posterior fusion (FLIP) at 2-years postoperatively. PURPOSEEvaluate the safety and efficacy of LSPS versus gold-standard FLIP STUDY DESIGN/SETTINGMulticenter retrospective cohort review. PATIENT SAMPLEFour hundred forty-two patients undergoing lumbar fusion via LSPS or FLIP OUTCOME MEASURESLevels fused, operative time, estimated blood loss, perioperative complications, and reasons for reoperation at 30-days, 90-days, 1-year, and 2-years. Radiographic outcomes included lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), PI-LL mismatch, and segmental lumbar lordosis. METHODSPatients were grouped as LSPS if anterior and posterior portions of the procedure were performed in the lateral decubitus position, and FLIP if patients were repositioned from supine or lateral to prone position for the posterior portion of the procedure under the same anesthetic. Groups were compared in terms of demographics, intraoperative, perioperative and radiological outcomes, complications and reoperations up to 2-years follow-up. Measures were compared using independent samples or paired t-tests and chi-squared analyses with significance set at p<.05. RESULTSFour hundred forty-two patients met inclusion, including 352 LSPS and 90 FLIP patients. Significant differences were noted in age (62.4 vs 56.9; p≤.001) and smoking status (7% vs 16%; p=.023) between the LSPS and FLIP groups. LSPS demonstrated significantly lower Op time (97.7min vs 297.0 min; p<.001), fluoro dose (36.5mGy vs 78.8mGy; p<.001), EBL (88.8mL vs 270.0mL; p<.001), and LOS (1.91 days vs 3.61 days; p<.001) compared to FLIP. LSPS also demonstrated significantly fewer post-op complications than FLIP (21.9% vs 34.4%; p=.013), specifically regarding rates of ileus (0.0% vs 5.6%; p<.001). No differences in reoperation were noted at 30-day (1.7%LSPS vs 4.4%FLIP, p=.125), 90-day (5.1%LSPS vs 5.6%FLIP, p=.795) or 2-year follow-up (9.7%LSPS vs 12.2% FLIP; p=.441). LSPS group had a significantly lower preoperative PI-LL (4.1° LSPS vs 8.6°FLIP, p=.018), and a significantly greater postoperative LL (56.6° vs 51.8°, p = .006). No significant differences were noted in rates of fusion (94.3% LSPS vs 97.8% FLIP; p=.266) or subsidence (6.9% LSPS vs 12.2% FLIP; p=.260). CONCLUSIONSLSPS and circumferential fusions have similar outcomes at 2-years post-operatively, while reducing perioperative complications, improving perioperative efficiency and safety.

Interaction of permafrost degradation and thermokarst lakes in the Qinghai–Tibet Plateau

The degradation of ice-rich permafrost can form thermokarst landforms such as thermokarst lakes. There are a large number of thermokarst lakes distributed in the ice-rich permafrost region of the Qinghai–Tibet Plateau. However, the effect of the spatial distribution of thermokarst lakes on permafrost degradation at a regional-scale in the Qinghai–Tibet Plateau is not fully understood. Time-series interferometric synthetic aperture radar is an established remotely-sensing tool to measure surface deformation in permafrost regions, and has been widely used in permafrost degradation investigation. In this study, we characterized spatial-temporal variations of surface deformation in the Beiluhe Basin in the Qinghai–Tibet Plateau with time series InSAR analysis, and extracted thermokarst lakes from Landset-8 images. Additionally, MODIS land surface temperature data and Stefan model were used to estimate the active layer thickness of permafrost in the basin. Results showed that the linear subsidence rate in the permafrost region within the basin generally exceeded 5 mm/yr, with a seasonal deformation amplitude of >10 mm, and the active layer thickness ranged from 2.1 m to 3.5 m. We found that permafrost degradation was concentrated in the areas with a high density of thermokarst lakes. Specifically, the density of thermokarst lakes was positively correlated with the linear subsidence rate and the seasonal deformation amplitude, and the larger active layer thickness clustered significantly in the area of thermokarst lakes. We also found that accelerated thermokarst collapse of the lake shore intensified the development of thermokarst lakes, and the lake expansion further aggravated the permafrost deformation. In addition, there is a strongly negative correlation (r = −0.78) between active layer thickness and Normalized Difference Vegetative Index in the basin, inferring that the degradation of permafrost may lead to the transformation from alpine meadow to alpine grassland and alpine desert.

The partial contribution of CO2-emission losses from subsidence in small-holder oil palm plantation on a tropical peatland in West Kalimantan, Indonesia

Abstract. Astiani D, Widiastuti T, Ekamawanti HA, Ekyastuti W, Roslinda E, Mujiman. 2022. The partial contribution of CO2-emission losses from subsidence in small-holder oil palm plantation on a tropical peatland in West Kalimantan, Indonesia. Biodiversitas 23: 6539-6545. Carbon storage in tropical peat ecosystems over thousands of years, especially within peat soil, is in huge quantity. Degradation of peat ecosystems is generally caused by human factors, whether intentional or not, damaging the carbon storage function of tropical peatlands, where forest clearing, drainage development, and burning of land converted to agriculture and plantations result in significant greenhouse gas emissions. Tropical peat in the Kubu Raya District of West Kalimantan, which has a relatively large area of peat, has been degraded as a cause of uncontrolled drainage and land fires caused by a lack of management after its forest cover was lost. The main impact is an increase in peat CO2 emissions due to changes in land use, especially lowering groundwater levels. Subsequently, the subsidence process also occurs after land clearing. This study aims to obtain the proportion of carbon biomass loss due to the CO2 emission process from reducing the peat layer due to subsidence. Data collection was executed for two years, where CO2 emission was monitored bi-weekly, and the subsidence was measured bi-monthly. The results demonstrate groundwater levels dictate the peat CO2 emission and subsidence. Lowering GWL 30 to -85 cm increases CO2 by more than three times, approximately. The rate of peat subsidence shows similar trends to the emission. The proportion of peat biomass loss on CO2 emission was between 58.9 to 73.5%, except for GWL ~5 cm, where the proportion was the highest at 82%. The results of this study are beneficial in explaining the part of the subsidence that impacts the sources of CO2 emissions from the small-holder oil palm and GWL management on peatlands.

Earthquake affects subsidence in Jakarta using Sentinel-1A time series images and 2D-MSBAS method

Excessive groundwater extraction has been well known as the main factor causing land subsidence in several cities in Jakarta Basin, Indonesia. This area is surrounded by active geological structures and has thick sediments. This study emphasizes the impacts of earthquakes on subsidence over Jakarta and its surroundings by using the Sentinel-1A images and 2D-MSBAS (Multidimensional Small Baseline Subset) method. Sixty-one ascending and 66 descending Sentinel-1A images were utilized to derive 121 deformation maps from 26 March 2017 to 2 July 2019 by using the 2D-MSBAS method. Linear and nonlinear displacement variations were analyzed to understand earthquake impacts on the subsidence and their seasonal characteristics. On 23 January 2018, the Mw 5.9 earthquake shaking off the coast of Java significantly affected ground surface subsidence in Jakarta. A cumulative magnitude and linear rate increase of the subsidence reached approximately -196 mm and -44 mm/yr, respectively, during the period of this study. Besides the subsidence rate changes, the earthquake also affected the expansion of the localized subsiding areas at several sites. The earthquake-activated fault affected the ground surface of the surrounding area, moving east and subsiding in the western part of the study area. Meanwhile, variations of the nonlinear subsidence to the seasonal precipitation depended on the aquifer system behavior to retain an elastic expansion and land cover types in the investigated regions.

Coastal Melaleuca wetlands under future climate and sea-level rise scenarios in the Mekong Delta, Vietnam: vulnerability and conservation

Melaleuca wetland ecosystems play crucial roles in ecology and human livelihood, yet the ecosystems are vulnerable to climate change and relative sea-level rise (SLR) impacts. Documents and research on climate change and SLR impacts on coastal Melaleuca wetlands in the Mekong Delta, Vietnam, are currently limited. Therefore, the present study aimed to identify changes in habitat suitability for a coastal Melaleuca wetland species in response to different future climate change and SLR scenarios, in the West Sea of the Mekong Delta, with the aid of an ensemble species distribution model (SDM) and the Sea Level Affecting Marshes Model (SLAMM). Melaleuca species occurrence records, bioclimatic and eco-physiological variables were utilized to predict potential distribution of the species in response to current and future climate scenarios (i.e. RCP4.5 and 8.5) for the year 2070. Wetland maps for 2020, a digital elevation model (DEM) and localized site-specific parameters (i.e. historic trend of SLR, erosion, subsidence and overwash) were utilized as input data for SLAMM to simulate spatial distribution of Melaleuca/forested wetlands under the two SLR scenarios. The final habitat suitability for the Melaleuca wetland species was identified based on these two resultant datasets, climatic suitability and spatial distribution of the wetlands. Simulated results suggested mean losses in suitable habitat of 29.8% and 58.7% for stable and subsidence scenarios, respectively, for the year 2070 in comparison to the baseline scenario. SLR combined with considerable subsidence rate was suggested as one of the main drivers responsible for the habitat suitability loss. The findings obtained from the current work are useful sources for planning conservation areas for the Melaleuca wetlands, to protect and preserve the ecosystems and their important services under future climate and SLR scenarios.

Development of Pag-asa Reefs, West Philippine Sea: Role of Relative Sea Level Change and Wave Exposure

Atoll reefs are associated with subsiding regions. In the West Philippine Sea, the Kalayaan Island Group is an emergent feature of the region’s atoll reefs. In this study, we established the long-term rate of subsidence in the Pag-asa Atoll Reefs by indicators of sea level positions on the seafloor and in Pag-asa Island. For submerged indicators of paleo-sea levels, a multibeam bathymetry with a 5-m resolution was used as the primary data source. Four pairs of submerged terraces and scarps, interpreted as former coral reef flats and reef fronts, respectively, were mapped. The terraces, PARa-d, from shallowest to deepest, occur at depth ranges of 7–10, 36–45, 82–90, and 115–120 m. The step-like morphology of the slopes off Pag-asa is likely due to the backstepping of reefs during the overall rise of sea level from the Last Glacial Maximum (LGM). Terraces PARa-d are interpreted as records of reef re-establishments during the stillstand periods following meltwater pulse event (MWP)-1C, MWP-1B, MWP-1A, and MWP-2B/2A. There is no clear morphological indicator of coral terraces that can be attributed to the LGM period. Variation in the widths and depths of the terraces between the leeward and windward sides of the island is also observed. Greater wave exposure appears favorable for coral reef terrace growth in Pag-asa, except for deeper terraces. The possible absence of the deepest terrace on the north side and an LGM terrace is attributed to possible thinner coral reef accretion due to the combination of cooler waters and possible swifter winds prior to 14 kyr. Correlation of the terrace depths and beach rock elevations as Pag-asa with the paleo-sea level of correlative stillstand events indicate long-term subsidence of 1.2 mm/yr between 15–12 kyr that declined to 0.3 mm/yr between 12 kyr to present. With sea level rise due to global warming and continuing subsidence, Pag-asa Island is threatened by coastal erosion, more frequent inundation, and groundwater salinization that needs to be addressed through proper adaptation practices.

Retrospective Case Series of Porous Titanium Cages in Oblique Lumbar Interbody Fusion Surgery Assessing Subsidence, Fusion and Functional Outcomes

Purpose: Implant subsidence is a possible complication of spinal interbody fusion. We aim to evaluate porous titanium cages subsidence, fusion and functional outcomes in patients subjected to oblique lumbar interbody fusion (OLIF) with these novel devices. Methods: Our institutional review board approved a single-center experience which included 60 patients who underwent OLIF from June 2018 to June 2020 utilizing the porous titanium implants. Data was collected in accordance with the Declaration of Helsinki, and written informed consent was obtained. Imaging studies including radiographs 1, 3, 6 and 12 months and computed tomography (CT) scan at 6 months obtained during routine postoperative follow-up visits, were studied for signs of implant subsidence, fusion and clinical parameters to determine the effectiveness of surgery such as Oswestry disability index (ODI). Results: Radiographic subsidence occurred in 1 out of 89 porous titanium interbody cages (1.1%). No subsidence was observed in the posterior screws and rods fixation group (N = 57). However, one case of subsidence occurred in the lateral plate fixation group (N = 3). The subsidence occurred in an osteoporotic elderly patient operated for adjacent segment disease, and she was later revised with posterior instrumentation using cemented screws and rods. She had an uneventful recovery. Fusion rates were evaluated under CT scan at 6 months with a rate of 88%. In terms of clinical outcomes, ODI decreased significantly from 20.3 preop to 10.7 postop with a P-value < 0.05. Conclusions: In our study, the subsidence rate was lower than previously reported in the literature. Also, we had good fusion rates at 6 months likely due to the porous titanium cages use. We had no subsidence in the posterior instrumented group and one case in the lateral fixation group with improved clinical outcomes.

Monitoring Land Subsidence and its Effect on Surabaya Coastal Inundation by Utilizing GPS Campaigns Data

Land subsidence is a process of land movement based on a certain datum (geodetic reference frame) in which there are various variables causing it. This phenomenon occurs in many big cities in Indonesia, which is the city of Surabaya. The Surabaya city has a type of soil in the form of alluvial soil which is prone to movement. The accumulation of land subsidence that occurs will certainly cause its own losses. As a result, it can damage urban infrastructure so that in the future it can cause disruption to the environment, economic activities, and social life in the region. In addition, the Surabaya area is also a coastal area. Coastal areas have characteristics where this area will be strongly influenced by natural events. One of the natural events that affect the oceans and coastal areas is global temperature changes. The phenomenon of global temperature changes can affect sea level rise. If sea level rise occurs accompanied by an increase in the rate of land subsidence, this can result in flooding or inundation in coastal areas. Considering that the city of Surabaya is a metropolitan city that has a high population density and a continuous level of development, mitigation efforts are important in following up on land subsidence in this area. One of the efforts that can be applied is by conducting GPS observations. The outcomes of the GPS observations were then processed using scientific software in the form of GAMIT/GLOBK. According to the study’s findings indicated that Surabaya is experiencing land subsidence in the northern and eastern coastal areas with a range of 0.2 – 83.3 mm/year. The point that experienced a significant decline was in the border area of Tandes and Asemrowo, namely station BM35. Furthermore, land subsidence conditions influence the extent of tidal inundation, where in 2032 tidal inundation will inundate 105.411 km2.

A Preliminary Result of Land subsidence Monitoring by Using Low-Cost GNSS in Bandung Basin

Land Subsidence is one of the issues faced by major cities in Indonesia. The need for a land subsidence monitoring station that operates continuously is one of the most important aspects today. The current use of low-cost GNSS (Global Navigation Satellite System) is expected to help in dealing with this problem. This study aims to evaluate Low-Cost GNSS for monitoring land subsidence in Bandung Basin. The Measurement of Low-Cost GNSS using Chip-GNSS U-Blox (single frequency) and the microstrip antenna was assembled itself. The monitoring of land subsidence was carried out at one point(TK01) with an observation period from March 2021 to December 2021. The result of data processing shows the value of the coordinate standard deviation of the TK01 point during the measurement period ranges from ± 1.5 cm. The results of vertical component processing show the standard deviation in the vertical direction is ± 3.5 cm. The rate of land subsidence resulting from linear regression at the point of TK01 from March 2021 to December 2021 in this study was -13.9 cm/year with a standard deviation value of ±0.32 cm/year.

Radiographic comparison of L5-S1 lateral anterior lumbar interbody fusion cage subsidence and displacement by fixation strategy: anterior plate versus integrated screws.

The aim of this study was to radiographically compare cage subsidence and displacement between L5-S1 lateral anterior lumbar interbody fusion (ALIF) cages secured with an anterior buttress plate and cages secured with integrated screws. Consecutive patients who underwent L5-S1 lateral ALIF with supplemental posterior fixation by a single surgeon from June 2016 to January 2021 were reviewed. Radiographs were analyzed and compared between the two groups based on the type of fixation used to secure the L5-S1 lateral ALIF cage: 1) anterior buttress plate or 2) integrated screws. The following measurements at L5-S1 were analyzed on radiographs obtained preoperatively, before discharge, and at latest follow-up: 1) anterior disc height, 2) posterior disc height, and 3) segmental lordosis. Cage subsidence and anterior cage displacement were determined radiographically. One hundred thirty-nine patients (mean age 60.0 ± 14.3 years) were included for analysis. Sixty-eight patients were treated with an anterior buttress plate (mean follow-up 12 ± 5 months), and 71 were treated with integrated screws (mean follow-up 9 ± 3 months). Mean age, sex distribution, preoperative L5-S1 lordosis, preoperative L5-S1 anterior disc height, and preoperative L5-S1 posterior disc height were statistically similar between the two groups. After surgery, the segmental L5-S1 lordosis and L5-S1 anterior disc heights significantly improved for both groups, and each respective measurement was similar between the groups at final follow-up. Posterior disc heights significantly increased after surgery with integrated screws but not with the anterior buttress plate. As such, posterior disc heights were significantly greater at final follow-up for integrated screws. Compared with patients who received integrated screws, significantly more patients who received the anterior buttress plate had cage subsidence cranially through the L5 endplate (20.6% vs 2.8%, p < 0.01), cage subsidence caudally through the S1 endplate (27.9% vs 0%, p < 0.01), and anterior cage displacement (22.1% vs 0%, p < 0.01). In this radiographic analysis of 139 patients who underwent lateral L5-S1 ALIF supplemented by posterior fixation, L5-S1 cages secured with an anterior buttress plate demonstrated significantly higher rates of cage subsidence and anterior cage displacement compared with cages secured with integrated screws. While the more durable stability afforded by cages secured with integrated screws suggests that they may be a more viable fixation strategy for L5-S1 lateral ALIFs, there are multiple factors that can contribute to cage subsidence, and, thus, definitive presumption cannot be made that the findings of this study are directly related to the buttress plate.

MT-InSAR Unveils Dynamic Permafrost Disturbances in Hoh Xil (Kekexili) on the Tibetan Plateau Hinterland

Hoh Xil is an uninhabited extremity secluded on the Tibetan Plateau hinterland. A complete mapping of ground motion variation in Hoh Xil is essential for in-depth understanding of terrain’s responses to climate change on the Tibetan Plateau. However, the inaccessibility and extremely harsh environment impeded extensive field investigations on landform alteration and its formative process. Such difficulty can be resolved by Interferometric Synthetic Aperture Radar (InSAR), which enables a broad detection of subtle permafrost motions at millimeter precision. This study, for the first time, accomplished a Multi-temporal InSAR (MT-InSAR) deformation mapping from 2015 to 2020 in Hoh Xil, with a wide coverage of about 200,000 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . 1,592 Sentinel-1 images were processed based on the small baseline subset (SBAS) technique. The results show that Hoh Xil was experiencing dynamic permafrost disturbances. Thawing permafrost with both the linear subsidence rate higher than 2 mm/yr and the periodic amplitude over 2 mm was primarily detected in areas of flat or gentle slopes. The InSAR cumulative deformation is highly correlated with permafrost thawing depth. Significant lag times were identified between seasonal oscillation of InSAR deformation and land surface temperature (LST). Thermokarst landforms of retrogressive thaw slumps and thermokarst lakes broadly formed and dynamically evolved as a consequence of permafrost degradation. Particularly, widespread thawing permafrost characterized by the spatial clustering of thermokarst lakes appeared to occur in areas adjacent to large lakes. The discovered dynamic permafrost disturbances in Hoh Xil manifested even the secluded Tibetan Plateau hinterland was facing the threat of climate change.

Измерение современных движений на станции «Талая» (юго-западная часть Байкальского рифта)

The rates of modern displacements are an important factor in the modern geodynamics of the Baikal rift system. Reflection of strong earthquakes in the experimental values of displacements is still to be discussed, as well as the question of modern vertical movements. According to the measurements of 1992–2022, performed by the methods of absolute gravimetry and space geodesy, the velocities of vertical and horizontal movements at the Talaya seismic station (Baikal Rift). The displacement rates were determined as 1.7 mm/year – 1.9 mm/year at the SEE relative to the Irkutsk point (Siberian platform). A set of methods was used to obtain the vertical velocity val-ues for different epochs, pre-, co- and post-period of Kultuk earthquake (2008, M = 6.3, 25 km to the epicenter). Subsidence rates vary from 1.1 mm/yr to 3.3 mm/yr. Possible signs of the preparation of Baikal earthquakes have been identified.

Spatial and Temporal Evolution of Ground Subsidence in the Beijing Plain Area Using Long Time Series Interferometry

Due to the overexploitation of water resources, ground subsidence is becoming increasingly problematic in Beijing, China's political, economic, and cultural capital. This article aims to investigate the relationship between ground subsidence and changes in groundwater depth, and water supply from a long-term point of view. Multisource synthetic aperture radar (SAR) data using the interferometric SAR (InSAR) technique were adopted in this research, combined with a set of leveling and ground subsidence data in the Beijing Plain area from 2003 to 2020. The InSAR results demonstrate that ground subsidence in the plain area increased steadily from 2003 to 2015, expanding from sporadic to continuous laminar dispersion and producing five major subsidence centers. The South-to-North Water Diversion Project (SNWDP) that was completed in 2008 and 2015 considerably reduced the demand for groundwater supply in the Beijing Plain area. Since then, the groundwater level depth has continued to increase. However, since 2016, the ground subsidence rate has dramatically slowed down. The obtained results showed that, thanks to the SNWDP, which resulted in a decline in groundwater exploitation and an increase in renewable water recycling, the ground subsidence in Beijing's plain area has been effectively managed.

Monitoring and Assessment of SBAS-InSAR Deformation for Sustainable Development of Closed Mining Areas—a Case of Nanzhuang Mining Area

Closed mining areas are an important potential resource, and rational use of them are critical to implementing sustainable development strategies. To guide the more reasonable development and utilization of the closed mining areas, we proposed a method of surface deformation monitoring and subsidence risk assessment of the closed mining areas with SBAS-InSAR technology. Based on the analysis of deformation, a risk assessment model integrating subsidence hazard and subsidence vulnerability was proposed. Subsidence hazard include accumulate deformation and the subsidence rate of the last year. The tunnels and the land use types are used to assess the subsidence vulnerability. This method can achieve deformation monitoring and risk assessment of the closed mining areas, and the proposed method is validated by taking the Nanzhuang mining areas as an example. The results showed that the main subsidence areas in the closed mining areas are located in the tunnel in the southwest and the gangue pile area in the northeast of the mining areas, while the deformation in the vegetation-rich forested area is low. The area of low, medium and high subsidence risk zones is 65.5%, 27.8% and 6.7% respectively.

Land subsidence hazard in Indonesia: Present research and challenges ahead

Land subsidence has become a significant silent hazard in the big cities across Indonesia that aggravates future sustainable development. Land subsidence hazards hard-hit Java as the most densely populated island. This paper reviews Indonesia’s land subsidence hazards, particularly subsidence cases across the big cities on Java Island, Jakarta, Semarang, and Bandung. Generally, land subsidence research in Indonesia can be categorized into two broad focuses: monitoring subsidence rate and investigating land subsidence mechanism. This paper aims to present a comprehensive summary of the current status of land subsidence research in Indonesia and discusses the challenging issues encountered in research and mitigation measures. A qualitative literature review was used in this study for reviewed articles in the Google Scholar database published in Indonesian and English up to 2020. Land subsidence in Jakarta, Bandung, and Semarang is still ongoing at a high rate. Its mechanism is highly influenced by excessive groundwater withdrawal, although other natural and anthropogenic factors also play a part. This review proposes recommendations to alleviate the impacts of land subsidence hazards in Indonesia and for further research

Land subsidence prediction model based on its influencing factors and machine learning methods

Land subsidence has caused huge economic losses in the Beijing plains (BP) since 1980s. Building land subsidence prediction models that can predict the development of land subsidence is of great significance for improving the safety of cities and reducing economic losses in Eastern Beijing plains. The pattern of evolution of land subsidence is affected by many factors including groundwater level in different aquifers, thicknesses of compressible layers, and static and dynamic loads caused by urban construction. First, we used the small baseline subset Interferometric Synthetic Aperture Radar (SBAS‐InSAR) technology on 47 ENVISAT ASAR images and 48 RADARSAT‐2 images and used Persistent Scatterers Interferometric Aperture Radar (PS-InSAR) technology on 27 Sentinel-1 images to obtain the land subsidence monitoring results from June 2003 to September 2018. Second, the accuracy of the InSAR monitoring results was validated by using leveling benchmark land subsidence monitoring results. Finally, we built land subsidence rate prediction models and land subsidence gradient prediction models by combining land subsidence influencing factors and four machine learning methods including support vector machine (SVM), Gradient Boosting Decision Tree (GBDT), Random forest (RF) and Extremely Randomized Trees (ERT). The findings show: (1) The InSAR monitoring results revealed that the Beijing Plain has experienced serious land subsidence during the 2003–2010, 2011–2015 and 2016–2018 periods. (2): The InSAR monitoring results agreed well with the leveling benchmark monitoring results with the Pearson correlation coefficients of two monitoring results were all greater than 0.95 during the 2003–2010, 2011–2015 and 2016–2018 periods, respectively. (3): We found that the land subsidence prediction based on ERT method is the optimal model among four land subsidence prediction models and that the prediction performance of land subsidence prediction model based on ERT method will be greatly improved when apply this prediction model in sub study areas where the land subsidence mechanism is similar owning to the similar hydrogeological parameters.

Land Subsidence Characteristics and Numerical Analysis of the Impact on Major Infrastructure in Ningbo, China

For the construction and safe operation of major infrastructure in coastal cities, the impact of regional land subsidence that has occurred or is slowly proceeding deserves attention. Previous studies have mainly focused on the surrounding land subsidence caused during construction or operation, as well as the superposition effect of land subsidence caused by groundwater extraction. However, research on the different impacts of damage due to land subsidence in the construction and operation of urban infrastructure needs to be carried out according to the actual geological environmental conditions, reflected in parameters such as the soil properties and common loads. Numerical simulation cannot fully reflect the details of reality; however, it can avoid the influence of other conditions to focus on different factors influencing land subsidence and thus highlight the contribution of a single factor influencing land subsidence. Therefore, in this paper, we adopt field measurement data and carry out a numerical simulation analysis of different influencing factors. First, taking the Ningbo Jiangdong subsidence center (now located in Yinzhou District) as an example, area growth, cumulative subsidence and the occurrence and development of the subsidence rate of a typical urban subsidence funnel area are analyzed. Then, taking the Ningbo Chunxiao–Meishan area as an example, based on the physical and mechanical characteristics of the main soil layers in the coastal reclamation area, a numerical analysis of the self-weight/backfill and surcharge consolidation settlement of the soil layer (considering the water permeability/impermeability of the bottom surface) and a numerical analysis of the nonuniform settlement caused by pile foundation engineering are carried out. Finally, the Ximenkou–Gulou area is taken as the analysis object. Numerical simulation of metro tunnel pipeline deformation is carried out considering uniform/nonuniform settlement. The results show that the comprehensive prohibition of groundwater exploitation is beneficial to slow the land subsidence rate, while the sedimentation of silty clay in Layer 4 (muddy clay) is the largest among all the soil layers. Compared with uniform settlement, nonuniform settlement is more likely to cause connection failure between tunnel segments. The above research results can provide references for the prevention and control of land subsidence and thus the safe operation of major infrastructure.

Diachronous basin evolution along northern South China Sea: Result of a migrating Hainan plume?

The diachronous basin evolution from west to east along the northern margin of the South China Sea (SCS) is closely related to the formation of the SCS, but in details remains ambiguous. We focused our study on the crustal structure and Cenozoic subsidence and sedimentary evolution of the Pearl River Mouth Basin (PRMB) and the Qiangdongnan Basin (QDNB) to reveal the divergences between the western and eastern segments of this margin. The back-stripping method and gravity modeling were employed based on drilling wells and geophysical data. We revealed that the crustal structure of the PRMB has a wedge shape, thinning monotonously from the coastline to the continent ocean transition (COT), while that of the QDNB has a symmetrical shape, thinning intensively in the Central Canyon. The characteristics of multi-episodic sedimentation and subsidence evolution were revealed in the PRMB, and its rapid subsidence rates were roughly synchronized with the decrease in the seafloor spreading rate of the SCS basin. However, the sedimentary and subsidence rate curves mainly featured accelerated sedimentation and subsidence in the western QDNB and an accelerated subsidence rate curve but a slow sedimentation rate curve in the eastern QDNB after 11.6 Ma. Some low-velocity conduits, which might be the crustal magmatic footprints of the Hainan mantle plume, were revealed in the middle and eastern QDNB. One possible dynamic model that can cause accelerated subsidence after 11.6 Ma in the eastern QDNB is that the Hainan mantle plume has migrated northwestward which may be derived from the contemporaneous southeastward movement of the South China Block. This conjecture coincides with magmatism and subsidence rate variations in the northwestern margin and is evidenced by the low-velocity conduits in the eastern QDNB.