Subsidence Rates Research Articles

Insights on the regional thermal evolution from semianthracite petrology of the Fengfeng coalfield, China

Igneous intrusions induce alterations in coal and minerals. Alteration degree depends upon the in-situ coal rank and maceral composition, the intrusion temperature, heat source proximity, and intrusion size. In the Permo-Carboniferous Fengfeng coalfield, coal rank increases over some 50 km distance south to north from high volatile bituminous coal to anthracite. The coal seams were commonly intruded, and the regional elevation of rank was augmented by Jurassic-Cretaceous igneous intrusions, not just burial coalification. The petrographic examination of a semianthracite from the Dashucun mine in the north of the Fengfeng coalfield shows development of coke microstructure and increased reflectance approaching the dike in the No. 2 Seam. Based on 11 samples at 50-cm horizontal intervals, random vitrinite reflectance value (Rr) declines from 5.41% at the contact to the background value of 2.05% at 5-m distance from the contact. Towards the dike, vitrinite anisotropy increases and the microtexture shows development of circular, coarse mosaic, and ribbon anisotropic coke textures and devolatilization vacuoles. Natural coke textures respond to an estimated temperature > 570 °C at the intrusion/coal contact. However, the occurrence of coke structures within a semianthracite reveals a local and regional thermal evolution. Coke textures suggest that coal rank was high volatile A bituminous coal at the time of intrusion. This has implications for burial history, heating, and subsidence rates. Assuming a paleogeothermal gradient of 40 °C/km, high volatile A bituminous coal (1% Rr) would have been buried to 3 km at the time of the Jurassic intrusion. The intrusion metamorphosed high volatile bituminous coal to natural coke and subsequent larger-scale regional metamorphism then metamorphosed the coal to semianthracite.

Radiographic fusion and subsidence rates for stand-alone cage versus anterior cage-plate construct in ACDF

Study DesignRetrospective cohort BackgroundThe addition of an anterior cervical plate to a structural allograft during ACDF is thought to provide extra stability and enhance fusion, but it may increase the risk of complications like dysphagia. Stand-alone cages were designed to provide this extra stability without the need for the plate, but these may increase a patient's risk of subsidence, cervical dislocation, and cervical kyphosis. The purpose of this study was to assess reoperation rates and radiographic outcomes during follow-up longer than 6 months for patients who underwent ACDF with a cage and plate compared to stand-alone cage. MethodsACDF cases were retrospectively identified for four fellowship trained spine surgeons from 2016 – 2020 from two academic hospitals. A total of 57 stand-alone structural allograft constructs were matched via propensity scoring with a cohort of 65 patients with plate-secured structural allograft constructs. The primary outcome was reoperation rate within the follow-up period and secondary outcomes included complications, operative characteristics, readmission within 30 days, reoperation within 30 days and within follow-up, and radiographic outcomes. Immediate post-operative radiographs were compared to final follow-up radiographs at least 6 months post-operation to assess for evidence of subsidence, fusion, and change in cervical kyphosis using the Cobb angle technique. ResultsThere were 5 patients (5.26 %) in the stand-alone cohort and 4 patients (3.15 %) in the plate cohort that had cervical reoperation at any time in follow-up (P = 0.83). At final follow-up, 58 patients (92.1 %) in the plate group and 37 patients (75.5 %) in the stand-alone group had radiographic evidence of fusion (P = 0.015). There were 38 patients (77.6 %) in the stand-alone group and 29 patients (46 %) in the plate group with evidence of subsidence (P = 0.0007). Patients with subsidence had a greater change in kyphosis angle at final follow-up and this change was significantly decreased in the plate group compared to the stand-alone group. ConclusionThe use of anterior cage-plate constructs in ACDF produces higher rates of fusion and lower rates of subsidence than stand-alone cage constructs. Subsidence significantly increases the change in kyphosis angle between post-op and final follow-up, and the presence of a spanning plate significantly reduces this angle change compared to stand-alone cages. There were no statistically significant differences in reoperation rates, regardless of radiographic evidence of subsidence.

Time-Series Analysis of Mining-Induced Subsidence in the Arid Region of Mongolia Based on SBAS-InSAR

Mongolia’s substantial mineral resources have played a pivotal role in its economic progress, with mining activities significantly contributing to this development. However, these continuous mining operations, particularly at the Oyu Tolgoi copper and gold mine, have induced land subsidence that threatens both production activities and poses risks of geological and other natural disasters. This study employs the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technique to monitor and analyze time-series surface subsidence using 120 Sentinel-1A datasets from 2018 to 2022. The findings reveal that the SBAS-InSAR method successfully captures the subsidence and its spatial distribution at Oyu Tolgoi, with the maximum cumulative subsidence reaching −742.01 mm and the highest annual average subsidence rate at −158.11 mm/year. Key drivers identified for the subsidence include variations in groundwater levels, active mining operations, and changes in surface stress. This research underscores the ongoing subsidence issue at the Oyu Tolgoi mining area, providing crucial insights that could aid in enhancing mining safety and environmental conservation in the region.

Contribution of campaign GNSS toward parsing subsidence rates by time and depth in coastal Bangladesh

Contribution of campaign GNSS toward parsing subsidence rates by time and depth in coastal Bangladesh

Can zoledronic acid reduce the risk of cage subsidence after oblique lumbar interbody fusion combined with bilateral pedicle screw fixation in the elderly population? A retrospective study

BackgroundThe objective of this study was to evaluate the potential of zoledronic acid for reducing the incidence of cage subsidence and enhancing interbody fusion rates following oblique lumbar interbody fusion (OLIF) surgery, particularly as the first reported evidence of the role of zoledronic acid combined with OLIF.MethodsA retrospective analysis was conducted on data from 108 elderly patients treated for degenerative lumbar diseases using OLIF combined with bilateral pedicle screw fixation from January 2018 to December 2021. Patients were divided into the zoledronic acid (ZOL) group (43 patients, 67 surgical segments) and the control group (65 patients, 86 surgical segments). A comparative analysis of the radiographic and clinical outcomes between the groups was performed, employing univariate and multivariate regression analyses to explore the relationships between cage subsidence and the independent variables.ResultsRadiographic outcomes, including anterior height, posterior height, disc height, coronal disc angle, foraminal height, and lumbar lordosis, were not significantly different between the two groups. Similarly, no statistically significant differences were noted in the back visual analog scale (VAS) scores and Oswestry Disability Index (ODI) scores between the groups. However, at the 1-year follow-up, the leg VAS score was lower in the ZOL group than in the control group (P = 0.028). The ZOL group demonstrated a notably lower cage subsidence rate (20.9%) than did the control group (43.0%) (P < 0.001). There was no significant difference in the interbody fusion rate between the ZOL group (93.0%) and the control group (90.8%). Non-use of zoledronic acid emerged as an independent risk factor for cage subsidence (OR = 6.047, P = 0.003), along with lower bone mineral density, lower postoperative anterior height, and concave endplate morphology. The model exhibited robust discriminative performance, with an area under the curve (AUC) of 0.872.ConclusionThe administration of zoledronic acid mitigates the risk of cage subsidence following OLIF combined with bilateral pedicle screw fixation in elderly patients; however, it does not improve the interbody fusion rate.

CLINICAL AND RADIOLOGICAL OUTCOMES OF REVISION TOTAL ANKLE ARTHROPLASTY USING THE INBONE II PROSTHESIS

BackgroundThe literature on the outcome of revision total ankle arthroplasty (TAA) remains limited. We aim to report the clinical and radiological outcomes of revision TAA at a high-volume centre in the UK.MethodsRetrospective review of 28 patients that underwent 29 revision TAA procedures using INBONE II prosthesis. Demographic, radiological, and patient reported outcome measures data were analysed.ResultsThe mean (range) duration from primary TAA to revision was 87.5 (16–223) months. The main indication for the revision was aseptic loosening of the primary TAA (82.8%). Additional procedures were required in 75.9% of patients. At mean (range) follow-up of 40 (24- 60) months, the infection, re-operation, and implant survival rates were 6.9%, 6.9% and 96.5% respectively. A significant postoperative improvement in the component alignment radiographic measures was observed. Osteolysis, subsidence, loosening and heterotopic ossification rates were comparable to other reports and did not influence the clinical outcome. A significant improvement was observed in the MOXFQ (all domains) and the EQ-5D (three domains) at 24 months postoperatively.ConclusionsRevision TAA using INBONE II was associated with good short-term survival and improvement in the postoperative scores at 2 years. Maintenance of the postoperatively improved alignment was documented at follow up. The relatively high survival rate in this series supports the notion that revision TAA is a satisfactory option for failed primary TAA.

Comparison of the efficacy of ROI-C cage with Zero-P device in anterior cervical discectomy and fusion of cervical degenerative disc disease: a two-year follow-up study.

This study aimed to compare the clinical outcomes of Zero-P and ROI-C devices applied to anterior cervical discectomy and fusion (ACDF) surgery of cervical degenerative disc disease (CDDD). From January 2020 and December 2020, 56 patients with CDDD who underwent ACDF using Zero-P or ROI-C were included in this retrospective study. The outcomes included visual analogue scale (VAS) score, Japanese Orthopedic Association (JOA) score, neck disability index (NDI) score, Cobb angle, dysphagia, and bone fusion rate. Dysphagia was assessed using the Bazaz grading system. The comparison of outcomes between the two groups was based on the 2-year follow-up time point, which was defined as the last follow-up visit. The Zero-P group included 16 males and 14 females, with a mean age of 56.2 (range, 35-65) years. The ROI-C group included 11 males and 15 females, with a mean age of 57.4 (range, 36-67) years. There was no significant difference in gender and mean age between the two groups. There were no significant differences in VAS score, JOA score, NDI score, Cobb angle, dysphagia, and bone fusion rate between two groups at the last follow up visit. In the Zero-P group, the duration of surgeries involving C3-4 or C6-7 segments was significantly longer than those including C4-5 or C5-6 segments (135.0 ± 19.0 vs. 105.6 ± 17.5 min, P < 0.05). In surgeries involving C3-4 or C6-7 segments, the operation time of ROI-C was significantly shorter than that of Zero-P (106.5 ± 19.5 vs.112.2 ± 20.5 min, P < 0.05). There were no significant differences in the dysphagia or cage subsidence rates between the Zero-P and ROI-C groups (P > 0.05). The Cobb angle in the last follow-up visit in the Zero-P group (24.4 ± 4.5°) was significantly higher than that in the ROI-C group (18.1 ± 2.3°) (P < 0.05). ACDF using ROI-C device showed an efficacy similar to the Zero-P device, as well as a shorter operation time for surgeries involving C3-4 or C6-7 segments. However, ROI-C could cause more loss of Cobb angle over time, which could lead to uncomfortable symptoms.

Analysis Of Land Subsidance Rates In DKI JAKARTA In 2018, 2020 And 2022 With The DINSAR Method

Abstract DKI Jakarta, the capital city of Indonesia, as the center of growth and development has a high population. The high population has an impact on land use change in an effort to fulfill housing which directly impacts the increase in building density or Normalized Diffrence Built-up Index (NDBI). The purpose of this research is to analyze the rate of land subsidence in DKI Jakarta and analyze the effect of building density on land subsidence. The impact of high growth rates creates the potential for natural and anthropogenic disasters. This research uses the Differential Inferometry Synthetic Aperarure Radar (DinSAR) method, in observing land subsidence with accuracy reaching cm units. The data used in this research is Sentinel 1A image with observation time in 2018, 2020, and 2023. The results showed that land subsidence in DKI Jakarta was dominated in the North Jakarta area, the highest land subsidence value reached -26.08 cm/year. The fastest land subsidence occurs in densely populated areas prone to flooding. The correlation results show that there is no relationship between the high level of building density and land subsidence.

Chronostratigraphy and tectono‐sedimentary history of the Eastern South Pyrenean foreland basin (Ripoll Syncline, North‐East Spain)

AbstractThis paper contributes to an understanding of the tectono‐sedimentary evolution of the South Pyrenean foreland system by reviewing the chronostratigraphic framework of the basin infill in its eastern sector. Six sections are analysed and cross‐correlated to build a 6.5 km thick composite magnetostratigraphy that represents the complete record of the Cadí Nappe in the Ripoll Syncline. New and previous magnetostratigraphic sections are integrated with available biostratigraphy to provide a new age calibration of the sedimentary succession of the Cadí Nappe, encompassing from Palaeocene to Middle Lutetian age. The proposed correlation with the Geomagnetic Polarity Time Scale aims at best reconcile magnetostratigraphic data with the regional biochronology built on the marine Shallow Benthic Zonation (SBZ biozones), the continental mammalian biochronology (MP levels) and the newly collected charophyte data. A subsidence analysis was performed on the calibrated composite succession, resulting in two well‐defined intervals bounded by a hiatus. A Palaeocene to Early Eocene interval with low (11–21 cm/kyr) total subsidence rates, and an Early to Middle Eocene interval, characterised by high (70–75 cm/kyr) total subsidence rates. The detailed trends in both subsidence and sedimentation mark the development and evolution of the foreland depozones, from distal foreland depozones to foredeep and wedge‐top depozones, relative to the emplacement of the Pedraforca Nappe and Cadí Thrust Nappe. The most pronounced sedimentary shift in the Cadí Nappe occurred at 49 Ma, with the rapid drowning of the carbonate platforms and its transition into talus and deep basinal environments. Carbonate platforms collapsed and resedimented on the talus of the elongated trough, newly formed parallel to the orogenic front. This marked the onset of tectonic subsidence triggered by the submarine emplacement of the Lower Pedraforca Nappe. The emersion of the orogenic wedge drove the entry of siliciclastics, lagged by 1 Myr, into the Ripoll Trough. The foredeep filled rapidly (5.5 km thickness in less than 7 Myr) compared to other South Pyrenean regions, favoured by its semi‐enclosed palaeogeography. The emplacement of the Vallfogona Thrust as early as the Middle Lutetian (43 Ma) brought the Cadi Nappe into a wedge‐top setting. However, the Ripoll growth syncline continued acting as a temporary sink for alluvial sedimentation while a foredeep developed further south in the autochthonous Ebro Basin. The flexural response of the Iberian plate to the tectonic thickening of the Axial Zone counterbalanced for a period the local uplift of the Cadi Nappe, providing accommodation space for the top sediments filling the Ripoll Syncline.

Systematic Review and Meta-Analysis of the Effect of Osteoporosis on Reoperation Rates and Complications after Surgical Management of Lumbar Degenerative Disease.

There is considerable heterogeneity in findings and a lack of consensus regarding the interplay between osteoporosis and outcomes in patients with lumbar degenerative spine disease. Therefore, the purpose of this systematic review and meta-analysis was to gather and analyze existing data on the effect of osteoporosis on radiographic, surgical, and clinical outcomes following surgery for lumbar degenerative spinal disease. A systematic review was performed to determine the effect of osteoporosis on the incidence of adverse outcomes after surgical intervention for lumbar degenerative spinal diseases. The approach focused on the radiographic outcomes, reoperation rates, and other medical and surgical complications. Subsequently, a meta-analysis was performed on the eligible studies. The results of the meta-analysis suggested that osteoporotic patients experienced increased rates of adjacent segment disease (ASD; p=0.015) and cage subsidence (p=0.001) while demonstrating lower reoperation rates than non-osteoporotic patients (7.4% vs. 13.1%; p=0.038). The systematic review also indicated that the length of stay, overall costs, rates of screw loosening, and rates of wound and other medical complications may increase in patients with a lower bone mineral density. Fusion rates, as well as patient-reported and clinical outcomes, did not differ significantly between osteoporotic and non-osteoporotic patients. Osteoporosis was associated with an increased risk of ASD, cage migration, and possibly postoperative screw loosening, as well as longer hospital stays, incurring higher costs and an increased likelihood of postoperative complications. However, a link was not established between osteoporosis and poor clinical outcomes.

Monitoring of ground subsidence using PS-InSAR technique in the Southeast Texas (SETX) Region

The southeast Texas (SETX) coastal area, owing to its unique geographical location and geological attributes, is facing a spectrum of geological challenges, such as ground subsidence, flooding, and coastal erosion. This study endeavors to evaluate the recent instances of ground subsidence and their associated rates, focusing on comprehending their implications for flooding within SETX. Employing the Persistence Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique, this study employs Sentinel-1 SAR satellite data with descending orbit observations spanning from January 2020 to March 2023. Our findings indicate that both the northwestern and eastern regions of Houston have been settled with rates up to 2 cm/year. This settlement trend is consistent with data derived from GPS and groundwater level measurements. This investigation explicitly shows the substantial temporal and spatial variations in subsidence rates, predominantly influenced by localized groundwater extraction due to urbanization (e.g., population growth, land development, etc.). By advocating for the integration of InSAR, GPS, and groundwater measurements, this research aspires to make valuable contributions toward the mitigation of subsidence and flood-related hazards in the SETX area.

Exploring mining-induced subsidence effects on Alnus glutinosa (L.) Gaertn. through dendrogeomorphic analysis and mining data

Mining operations can have a significant impact on the environment, which may result in surface lowering due to overburden disturbance, commonly referred to as mining subsidence. This issue has been extensively studied in many engineering studies. However, the dendrogeomorphic approach can provide additional insights into this issue. This study examined the tree-ring response of black alder (Alnus glutinosa (L.) Gaertn.) to subsidence. The analysis of subsidence activity was exclusively conducted through tree-ring eccentricity (EC). Using the Knothe method, the theoretical radius of main subsidence influence range was determined to differentiate between periods of mining influence and non-mining influence. Significantly higher event-response (It) index (p = 0.0001) was calculated during years with mining influence. Nevertheless, the use of the It index alone is insufficient for reconstructing the subsidence events as the process is continuous. When comparing the recorded reactions of the onset of EC across different subsidence rates from 2012 to 2015, no distinctive differences were found in tree growth response. The use of dendrogeomorphology and tree-ring eccentricity has proven valuable in studying the subsidence process. Nonetheless, new challenges persist, particularly regarding secondary processes like landslide activity or residual subsidence.

Reduced Subsidence With PEEK-Titanium Composite Versus 3D Titanium Cages in a Retrospective, Self-Controlled Study in Transforaminal Lumbar Interbody Fusion.

Retrospective Study. To compare subsidence and radiographic fusion rates of titanium-surface polyetheretherketone (PEEK-Ti) and 3D-Titanium (3D-Ti) cages, implanted within the same patient concurrently, during multi-level transforaminal lumbar interbody fusions (TLIF). Forty-eight patients were treated with both PEEK-Ti and 3D-Ti cages during 2- or 3-level TLIF and instrumented posterolateral fusion (108 spinal levels in all). Equivalent bone graft material was implanted within each patient. Radiographic analysis of CT and/or X-ray imaging was performed retrospectively for each spinal level throughout 12-month follow-up period. Fusion was defined as bridging trabecular bone and subsidence was incursion into one/both vertebral bodies >20% cage height. Outcomes were analyzed with Fisher's exact test. At 6-months post-operative follow-up, incidence of subsidence was significantly lower for PEEK-Ti cages, with 4.8% subsidence, compared to a 27.9% subsidence rate for 3D-Ti cages (P = .007). Fusion rates were comparable at 100% for PEEK-Ti and 95.5% for 3D-Ti. Results at 12-months showed similar but not statistically significant trends of less subsidence with PEEK-Ti than 3D-Ti cages (14.3% PEEK-Ti, 37.5% 3D-Ti), and similar fusion rates of 100% for PEEK-Ti and 91.7% for 3D-Ti. Thirty-nine out of 48 total patients were available for follow-up at 6 months and 20 patients at 12 months. CT availability at 6 and 12-months was 100% and 90%, respectively. A significantly lower subsidence rate was associated with a PEEK-Ti cage, compared to 3D-Ti, 6 months after TLIF. Results may not be generalized across technologies due to differences in cage designs; additional research studies are warranted.

Treatment of cervical ossification of posterior longitudinal ligament with titanium alloy trabecular bone three-dimensional printed artificial vertebral body

To evaluate the effectiveness of using titanium alloy trabecular bone three-dimensional (3D) printed artificial vertebral body in treating cervical ossification of the posterior longitudinal ligament (OPLL). A retrospective analysis was conducted on clinical data from 45 patients with cervical OPLL admitted between September 2019 and August 2021 and meeting the selection criteria. All patients underwent anterior cervical corpectomy and decompression, interbody bone graft fusion, and titanium plate internal fixation. During operation, 21 patients in the study group received titanium alloy trabecular bone 3D printed artificial vertebral bodies, while 24 patients in the control group received titanium cages. There was no significant difference in baseline data such as gender, age, disease duration, affected segments, or preoperative pain visual analogue scale (VAS) score, Japanese Orthopaedic Association (JOA) score, Neck Disability Index (NDI), vertebral height, and C 2-7Cobb angle ( P>0.05). Operation time, intraoperative blood loss, and occurrence of complications were recorded for both groups. Preoperatively and at 3 and 12 months postoperatively, the functionality and symptom relief were assessed using JOA scores, VAS scores, and NDI evaluations. The vertebral height and C 2-7 Cobb angle were detected by imaging examinations and the implant subsidence and intervertebral fusion were observed. The operation time and incidence of complications were significantly lower in the study group than in the control group ( P<0.05), while the difference in intraoperative blood loss between the two groups was not significant ( P>0.05). All patients were followed up 12-18 months, with the follow-up time of (14.28±4.34) months in the study group and (15.23±3.54) months in the control group, showing no significant difference ( t=0.809, P=0.423). The JOA score, VAS score, and NDI of the two groups improved after operation, and further improved at 12 months compared to 3 months, with significant differences ( P<0.05). At each time point, the study group exhibited significantly higher JOA scores and improvement rate compared to the control group ( P<0.05); but there was no significantly difference in VAS score and NDI between the two groups ( P>0.05). Imaging re-examination showed that the vertebral height and C 2-7Cobb angle of the two groups significantly increased at 3 and 12 months after operation ( P<0.05), and there was no significant difference between 3 and 12 months after operation ( P>0.05). At each time point, the vertebral height and C 2-7Cobb angle of the study group were significantly higher than those of the control group ( P<0.05), and the implant subsidence rate was significantly lower than that of the control group ( P<0.05). However, there was no significant difference in intervertebral fusion rate between the two groups ( P>0.05). Compared to traditional titanium cages, the use of titanium alloy trabecular bone 3D-printed artificial vertebral bodies for treating cervical OPLL results in shorter operative time, fewer postoperative complications, and lower implant subsidence rates, making it superior in vertebral reconstruction.

Application of LuTan-1 SAR Data in Railway Subsidence Monitoring

Abstract. InSAR technology is currently a crucial tool for large-scale surface deformation monitoring, particularly excelling in regional subsidence monitoring. In this study, focusing on the Jinan section of the Shandong railway, newly launched LUTAN-1 satellite SAR data was employed. DInSAR and Stacking techniques were applied to analyze the subsidence in response to the long-term operation load of high-speed trains and surrounding human activities. Through the analysis of data from June 2023 to December 2023, regional subsidence was identified in this section, with a subsidence rate reaching 8 cm/year. Comparative analysis between DInSAR technology monitoring results and precise leveling monitoring results showed consistency in the subsidence deformation trend in the region, achieving centimeter-level deformation monitoring in the study area.The LuTan-1 satellite provided robust SAR data support for railway subsidence monitoring, offering substantial reliability and accuracy to deepen the understanding of railway subsidence issues. These research findings hold significant practical implications for adopting timely maintenance and repair measures, ensuring the safety and reliable operation of the railway system.

Liquefaction ground deformations and cascading coastal flood hazard in the 2023 Kahramanmaraş earthquake sequence

The 2023 Kahramanmaraş earthquake sequence produced extensive liquefaction-induced ground deformations and ongoing flooding along the shoreline of the Mediterranean port city of İskenderun, Türkiye. This study compiles field observations and analyses from cross-disciplinary perspectives to investigate whether earthquake-induced liquefaction was a significant factor for increasing the flood hazard in İskenderun. Geotechnical reconnaissance observations following the earthquakes included seaward lateral spreading, settlement beneath buildings, and failures of coastal infrastructure. Three presented lateral spreading case histories indicate consistent ground deformation patterns with areas of reclaimed land. Persistent scatterer interferometry (PSI) measurements from synthetic aperture radar (SAR) imagery identify a noticeably greater rate of pre- and post-earthquake subsidence within the İskenderun coastal and urban areas relative to the surrounding regions. The PSI measurements also indicate subsidence rates accelerated following the earthquakes and were typically highest near the observed liquefaction manifestations. These evaluations suggest that while the liquefaction of coastal reclaimed fill caused significant ground deformations in the shoreline area, ongoing subsidence of İskenderun and other factors likely also exacerbated the flood hazard. Insights from this work suggest the importance of evaluating multi-hazard liquefaction and flood consequences for enhancing the resilience of coastal cities.

Benefits of tropical peatland rewetting for subsidence reduction and forest regrowth: results from a large-scale restoration trial

Drainage and deforestation of tropical peat swamp forests (PSF) in Southeast Asia cause carbon emissions and biodiversity loss of global concern. Restoration efforts to mitigate these impacts usually involve peatland rewetting by blocking canals. However, there have been no studies to date of the optimal rewetting approach that will reduce carbon emission whilst also promoting PSF regeneration. Here we present results of a large-scale restoration trial in Sumatra (Indonesia), monitored for 7.5 years. Water levels in a former plantation were raised over an area of 4800 ha by constructing 257 compacted peat dams in canals. We find peat surface subsidence rates in the rewetted restoration area and adjoining PSF to be halved where water tables were raised from ~ − 0.6 m to ~ − 0.3 m, demonstrating the success of rewetting in reducing carbon emission. A total of 57 native PSF tree species were found to spontaneously grow in the most rewetted conditions and in high densities, indicating that forest regrowth is underway. Based on our findings we propose that an effective PSF restoration strategy should follow stepwise rewetting to achieve substantial carbon emission reduction alongside unassisted regrowth of PSF, thereby enabling the peat, forest and canal vegetation to establish a new nature-based ecosystem balance.

Surface Deformation Monitoring and Subsidence Mechanism Analysis in Beijing based on Time-series InSAR

Abstract. This article uses 43 Sentinel-1A image datasets covering Beijing to obtain time series surface deformation information in the study area from January 2022 to October 2023. It analyzes the causes of land subsidence by integrating precipitation and urban construction. The main research results are as follows: (1) Three distinct subsidence areas are identified in the eastern part of Chaoyang District in Beijing (Subsidence Area A), the northwestern part of Tongzhou District in Beijing (Subsidence Area B), and Yanjiao Town in Hebei Province (Subsidence Area B), which is adjacent to Beijing. Subsidence Areas A and B exhibit a dispersed pattern, with maximum land subsidence rates exceeding −30 mm/year. In contrast, Subsidence Areas C displays a funnel-shaped subsidence, where the majority of areas experience land subsidence rates exceeding −25 mm/year, with a maximum rate reaching −45 mm/year. (2) Precipitation has a significant impact on surface deformation in the study area, and there is a strong correlation between precipitation and land subsidence, with correlation values of 0.77, 0.77, and 0.74, respectively. (3) Urban construction has a certain impact on land subsidence, but the degree of impact varies in different regions.

Holocene relative sea-level variation and coastal changes in the Bay of Cádiz: New insights on the influence of local subsidence and glacial hydro-isostatic adjustments

The Bay of Cádiz is located in South-western Spain (Andalusia region) and constitutes an example of a typical estuarine salt marsh environment. In this study we reconstruct its Holocene morpho-evolution and relative sea-level change history by assembling a geodatabase of geological sea-level markers derived from boreholes and bibliographic data, standardized to the most recent international guidelines for RSL studies. The identified high-precision sea-level index points were compared to a number of new site-specific glacio-hydro-isostatic adjustment (GIA) models in order to disentangle potential components which influenced the sea-level evolution and finally obtain the vertical displacement (VD) trends that affect this coastal area by using a Bayesian statistical approach including Monte Carlo simulations. In general, the whole area was affected by overall subsidence related to the local sediment compaction, which had an impact on the morpho-evolution of the different zones with a variable entity and completely outclassed the GIA-driven component. Between 6.7 and 3.0 ka BP, the northern sector of the bay was characterized by subsidence rates of about - 0.65 mm/yr while, during the last 3.0 ka, the general trend appears to be homogeneous for both the main sectors of the bay with an average subsidence rate of - 1.6 mm/yr. The Holocene RSL curve from the Gulf of Cádiz aligns with past reconstructions, revealing subtle differential trends in subsidence rates in the northern and southern sectors of the Bay of Cádiz due to varying substratum.

Deformation, evolution and controls of halokinetic megaflaps driven by vertically-stacked and laterally-shifting depocenters

Megaflaps comprise steeply dipping to overturned panels of the oldest suprasalt strata flanking steep diapirs, and represent the roofs of early inflated salt. These large-scale structures result from salt-sediment interaction at minibasin scales and entail multiple kilometres of folding and vertical relief. They are divided into two end-member types (halokinetic and contractional) and form by some combination of limb rotation and kink-band migration. They can be difficult to image and interpret adjacent to flaring diapirs and beneath allochthonous salt due to steep bedding dips and suboptimal illumination.Using physical models, we investigate halokinetic megaflaps driven by differential loading. Models with vertically-stacked vs. laterally-shifting loading above a prekinematic layer have been run to determine the main processes and mechanisms controlling the growth and kinematic evolution of megaflaps. Parameters such as the thickness of the prekinematic cover, the width of the proto-salt wall, the synkinematic sedimentation rate, and variations in the mechanical properties of the prekinematic cover have been tested to evaluate their role in megaflap generation. The experimental results demonstrate that in absence of tectonic forces, halokinetic megaflaps are generated by a combination of 1) an early increase of pressure-head gradient between two adjacent minibasins with different rates of sedimentation and subsidence, and 2) the disappearance of this gradient that occurs when welding occurs beneath the more quickly subsiding minibasin. The geometry, kinematic evolution, and degree of small-scale deformation of the megaflaps in our analogue models are consistent with both exposed (e.g., Paradox Basin) and seismically imaged halokinetic megaflaps (e.g., deepwater northern Gulf of Mexico).