Subsidence Rates Research Articles

Hidden vulnerability of US Atlantic coast to sea-level rise due to vertical land motion

The vulnerability of coastal environments to sea-level rise varies spatially, particularly due to local land subsidence. However, high-resolution observations and models of coastal subsidence are scarce, hindering an accurate vulnerability assessment. We use satellite data from 2007 to 2020 to create high-resolution map of subsidence rate at mm-level accuracy for different land covers along the ~3,500 km long US Atlantic coast. Here, we show that subsidence rate exceeding 3 mm per year affects most coastal areas, including wetlands, forests, agricultural areas, and developed regions. Coastal marshes represent the dominant land cover type along the US Atlantic coast and are particularly vulnerable to subsidence. We estimate that 58 to 100% of coastal marshes are losing elevation relative to sea level and show that previous studies substantially underestimate marsh vulnerability by not fully accounting for subsidence.

Clinical and imaging outcomes of self-locking stand-alone cages and anterior cage-with-plate in three-level anterior cervical discectomy and fusion: a retrospective comparative study

BackgroundAnterior cervical discectomy and fusion has been considered standard management for cervical myelopathy and radiculopathy. However, the option of using self-locking stand-alone cages or cage-with-plate in three-level anterior cervical discectomy and fusion still remains controversial. The aim of this study was to evaluate the clinical and imaging outcomes of the two procedures in multilevel anterior cervical discectomy and fusion.MethodsSixty-seven patients who underwent three-level anterior cervical discectomy and fusion were enrolled in this study, of which 31 patients underwent surgery using self-locking stand-alone cages (group cage) and 36 patients using cage-with-plate (group plate). For the evaluation of clinical outcomes, modified Japanese Orthopedic Association scores, visual analogue scale for neck pain, neck disability index, Odom’s criteria and dysphagia status were measured. Imaging outcomes were evaluated by cervical sagittal angle, fusion segmental Cobb’s angle, fusion segmental height, range of motion, cage subsidence rate, fusion rate and adjacent segment degeneration. Statistical analyses were performed using the SPSS software (version 19.0).ResultsBoth groups showed improvement in modified Japanese Orthopedic Association scores, visual analogue scale for neck pain and neck disability index, after surgery, and there was no significant difference between the groups. The occurrence rate of dysphagia is significantly lower in the group cage compared with the group plate (p < 0.05). The postoperative cervical sagittal angle, fusion segmental Cobb’s angle, fusion segmental height and cage subsidence rate in the group plate were significantly superior to that in the group cage (p < 0.05). However, the rate of adjacent segment degeneration was significantly lower in the group cage compared with the group plate (p < 0.05). Both groups showed no significant difference in terms of fusion rate (p > 0.05).ConclusionsThe self-locking stand-alone cages are effective, reliable and safe in anterior cervical discectomy and fusion for the treatment of cervical myelopathy and radiculopathy. Self-locking stand-alone cages showed a significantly lower rate of dysphagia and adjacent segment degeneration, while anterior cervical cage-with-plate could provide stronger postoperative stability and maintain better cervical spine alignment.

Outcomes of fixation of Vancouver B periprosthetic fractures around cemented versus uncemented stems

BackgroundThe incidence of periprosthetic femur fracture (PPFF) in the setting of total hip arthroplasty (THA) is steadily increasing. We seek to address whether there is a difference in outcomes between Vancouver B fracture types managed with ORIF when the original stem was a press-fit stem versus a cemented stem.MethodsIn this retrospective cohort study at a level 1 trauma center, we identified 136 patients over 65 years-of-age with Vancouver B-type fractures sustained between 2005 and 2019. Patients were treated by ORIF and had either cemented or press-fit stems prior to their injury. Outcomes were subsidence of the femoral implant, time to full weight bearing, rate of the hip implant revision, estimated blood loss (EBL), postoperative complications, and the one-year mortality rate.ResultsA total of 103 (75.7%) press-fit and 33 (24.3%) cemented patients were reviewed. Patient baseline characteristics, Vancouver fracture sub-types, and implant characteristics were not found to be significantly different between groups. The difference in subsidence rates, postoperative complications, and time to weight bearing were not significantly different between groups. EBL and one-year mortality rate were significantly higher in the cemented group.ConclusionsIn geriatric patients with Vancouver B type periprosthetic fractures managed with ORIF, patients with an originally press fit stem may have lower mortality, lower estimated blood loss, and similar subsidence and hospital length of stays when compared to those with a cemented stem.

Tracking surface and subsurface deformation associated with groundwater dynamics following the 2019 Mirpur earthquake

The Mirpur Mw 5.8 earthquake on September 24, 2019, produced extensive liquefaction-induced surface deformation (LISD) in the surrounding villages. Due to the complexity of seismic hazards and the occurrence of their effects on a large spatial scale, the resulting surface, and subsurface deformation are often poorly resolved. To cover spatially extended LISD, the PSInSAR technique provided subsidence and uplift rate values ranging from −110 to +145 mm/yr consistent with the spatial distribution of the mapped liquefaction features. The most prominent surface change occurred in Abdupur and Sang villages. GPR measurements were conducted to map the near-surface cracks produced by transported liquified sand into the shallow subsurface layers and other liquefaction features (elevated groundwater table, conductive clay pockets, fractures, sand dikes, and water-enriched zones). Thus, the GPR survey assisted in the reconstruction of these structural and hydrogeological features on the near surface. In addition, the highly vulnerable zones were identified and mapped using space- and ground-based remote sensing measurements supported by the field observations. The results highlight the effectiveness of the proposed novel approach for detailed assessment of the coseismic liquefaction-induced deformation on- and near-ground surfaces by identifying areas prone to failure during earthquakes and thereby can help with hazard mitigation.

Cage subsidence-Amultifactorial matter!

Retrospective cohort study OBJECTIVE: Wider cages are associated with improved decompression and reduced subsidence, but variation in cage physical properties limits consistent outcome analysis after thoracolumbar interbody fusion. This study investigated cage subsidence and its relationship to lateral and posterior approaches with afocus on the hypothesis that the larger surface area of lateral cages results in lower subsidence rates. This study retrospectively reviewed 194patients who underwent interbody fusion between 2016 and 2019 with aprimary outcome of cage subsidence. Secondary outcomes were cage distribution (patients, approaches, expandability), cage dimensions, t‑scores, length of hospital stay, blood loss, surgical time, and pelvic incidence-lumbar lordosis (PI-LL) mismatch. Medical records were reviewed for 194patients receiving 387 cages at 379 disc levels. Subsidence was identified in 35.1% of lateral cages, 40.9% of posterior cages, and 36.3% of all cages. Lower surface area (p = 0.008) and cage expandability were associated with subsidence risk. Lower anteroposterior cage length proved to be asignificant factor in the subsidence of posteriorly placed cages (p = 0.007). Osteopenic and osteoporotic patients experienced cage subsidence 36.8% of the time compared to 3.5% of patients with normal t‑scores (p = 0.001). Cage subsidence correlated with postoperative deterioration of the PI-LL mismatch (p = 0.03). Patients receiving fusion augmentation with bone morphogenic protein experienced higher fusion rates (p < 0.01). Cage subsidence is acommon complication that can significantly impact operative outcomes following thoracolumbar interbody fusion. Low t‑scores, smaller surface area, cage expandability, and lower cage length in posterior approaches contribute significantly to cage subsidence.

Water-level changes and subsidence rates along the Saigon-Dong Nai River Estuary and the East Sea coastline of the Mekong Delta

Southeast Asian deltas are highly threatened areas for flooding as a response to the combined effects of natural compaction and subsidence exacerbated by human impacts, e.g. oil, gas and water extraction, retention of sediment discharge due to river damming and sand mining, land use changes, sea-level rise and storm-induced water-level setup. Tide-induced water-level fluctuations on different time- and spatial scales, seasonal variations of freshwater runoff and sea-level setup can amplify the impact of sea-level rise and of storm surges on the coastal environment and its inhabitants. Moreover, increasing populations accompanied by growing societal demands can lead to further pressure on delta areas. For the Vietnamese Mekong Delta (VMD) and the Saigon-Dong Nai River (SGDNR), rates of subsidence of several cm/yr have already been determined, but for the coastal area, which is most vulnerable to sea-level rise and storm surges, a lack of detailed spatial and temporal information of this parameter exists. To assess the influence of tide- and water-level fluctuations, records from 11 stations, from the tectonically stable position Vung Tau north of the SGDNR entry to Ganh Hao in the southern VMD, were analyzed. The results reveal a relative sea-level rise at Vung Tau reaching 2.2 ± 0.3 mm/yr for the period from 1987-2015, while along the VMD those rates show a spatially variation from 5.6 ± 0.3 mm/yr at Ben Trai to 13.5 ± 0.7 mm/yr at My Thanh. Considering Vung Tau as tectonically stable, these numbers indicate subsidence rates of the coastal sections along the VMD ranging from 3.4 ± 0.3 mm/yr to 11.3 ± 0.7 mm/yr. It is likely that the rates of subsidence along the coast of VMD have accelerated since 2005. They are not only up to 4 times higher than the mean sea-level rise but are variable along the whole SGDNR estuary and the VMD East Sea coastline. Additionally, the importance of daily, fortnightly and seasonal water level fluctuations due to tides and atmospheric influence, which are acting on top of the long-term relative sea-level rise, is shown. Especially the identified regional variations make these data valuable for setting regional priorities for protection strategies to mitigate riverine and marine flooding, especially when both coincide.

494 Comparison of Disc Height Restoration and Subsidence Rates Between Static Versus Expandable Titanium Cages for Lateral Lumbar Interbody Fusion

INTRODUCTION: It has been shown that expandable cages for transforaminal lumbar interbody fusion (TLIF) are associated with increased rates of subsidence. However, as lateral lumbar interbody fusion (LLIF) cages offer substantially larger footprints, this may offset the risks. METHODS: A retrospective review was performed of a consecutive adult patients undergoing LLIF with either static or expandable cages from 2013-2021. Demographics and surgical details were collected. Posterior disc height (PDH), subsidence, and fusions status were compared between patients with static and expandable cages. Follow-up were reported at minimum 6-months and 1-year. RESULTS: A total of 120 patients had 173 cages implanted: 96 patients with 143 static cages vs. 24 patients with 30 expandable cages. Mean age was 63.4 and 62.4% were male. There were no significant differences in age, gender, BMI, smoking, or osteoporosis. Overall, PDH was significantly increased following LLIF (4.1 v 7.4 mm, p &lt; 0.001). Static and expandable cage types had similar magnitude (3.7 v 3.3 mm, p = 0.311) and percentage (89.0% v 121.5%, p = 0.127) change in PDH, respectively. Overall incidence of cage subsidence at 6-months and 1-year was 6.9% and 10.4% respectively. There was no significant difference in subsidence rates between cage types at 6 months (7.0% v 6.7%, p = 0.949) and 1-year (11.2 v 6.7%, p = 0.461). Radiographic evidence of fusion was present in 92.7% of cases at 1-year, and both cage types achieved similar fusion rates as well (92.2% v 95.6%, p = 0.555). CONCLUSIONS: LLIF static and expandable cages offer similar PDH restoration depending on surgical goals. Expandable cages seem to be less prone to subsidence than smaller TLIF cage counterparts and offer similar fusion rates to static cages. Larger cohort studies are warranted to further validate these findings which are ongoing.

Midline Lumbar Fusion Versus Posterior Lumbar Interbody Fusion Involving L5-S1 For Degenerative Lumbar Diseases: A Comparative Study.

A retrospective cohort study to evaluate the efficacy and safety of midline lumbar fusion (MIDLF) for lumbosacral fusion compared to posterior lumbar interbody fusion (PLIF). Patients who had undergone posterior lumbosacral fusion surgery were divided into a MIDLF group (n=37) and a PLIF group (n=42). The follow-up time was at least 12months. The operation data, recovery condition, complications, clinical outcomes, and status of implants and fusion were compared between the 2 groups. The MIDLF group experienced significantly less blood loss, lower postoperative creatine kinase levels and total drainage volume, earlier time to ambulation, and less hospital stay times after surgery compared to the PLIF group (P<0.05). The mean postoperative back pain visual analog scale scores in the MIDLF group were significantly lower than the PLIF group (P<0.05). The improvement in Oswestry Disability Index scores during 3-month follow-up displayed a significant difference between the 2 groups (P < 0.05). The fusion rate tended to be higher in the MIDLF group; however, the difference was not significant (P > 0.05). There was no significant difference in respect to screw loosening and cage subsidence rate. There were 2 cases of complications both occurring in the PLIF group. MIDLF is safe and effective for lumbosacral fusion and in line with the concept of enhanced recovery after surgery.

New understanding and exploration direction of hydrocarbon accumulation in Termit Basin, Niger

Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration direction of Termit superimposed marine—continental rift basin are discussed. The Termit basin is superimposed with two-phase rifts (Early Cretaceous and Paleogene). The subsidence curves from two wells on the Trakes slope in the east of the basin show high subsidence rate in the Late Cretaceous, which is believed to be high deposition rate influenced by transgression. However, a weak rift may also be developed. The depositional sequences in the Termit basin were controlled by the Late Cretaceous marine transgression cycle and the Paleogene lacustrine transgression cycle, giving rise to two types of superimposed marine—continental “source-sink” deposits. The marine and continental mixed source rocks developed universally in the whole basinduring the marine transgression period, and are overlaid by the Paleogene Sokor 1 reservoir rocks and Sokor 2 caprocks developed during the lacustrine transgression period, forming the unique superimposed marine—continental basin in WCARS. The early low geothermal gradient in the Termit basin resulted in the late hydrocarbon generated by the source rock of Upper Cretaceous Yogou in Paleogene. Mature source rock of Upper Cretaceous Donga developed in the Trakes slope, so that the double-source-supply hydrocarbon and accumulation models are proposed for the Trakes slope in which formed the oil fields. Due to virtue of the newly proposed hydrocarbon accumulation model and the exploration activities in recent years in the Termit superimposed marine—continental rift basin, an additional effective exploration area of about 2500 km2 has been confirmed in the east of the basin. It is believed that potential domains such as Sokor 1, Donga and Upper Cretaceous lithologic traps in the southeast of the basin are key expected targets for exploration and frontier evaluation in future.

Estimating Aquifer System Storage Loss With Water Levels, Pumping and InSAR Data in the Parowan Valley, Utah

AbstractIn the Parowan Valley of Utah, groundwater levels have declined by as much as 30 m over the past 50 years with accompanying subsidence rates of up to 5 cm/year. Traditional methods to estimate groundwater storage change use a combination of groundwater level and storativity estimates, but there is often considerable uncertainty in these. In this study, we demonstrate a new method that relies on a combination of geodetic data from InSAR, as well as groundwater level and pumping data, to estimate both the total groundwater storage loss and the percentages of storage loss in fine‐ and coarse‐grained layers within an aquifer system. We find that when aggregated over all of Parowan Valley, fine‐ and coarse‐grained layers account for roughly equal portions of the total groundwater storage loss. However, in confined aquifers, fine‐grained layers account for most of the storage loss. This has important implications on the source of groundwater in depleting aquifer systems, as many models do not account for fine‐grained layers as a source of water. We find that in the Parowan Valley, the aquifer depletion is roughly 12.5% of the volume of pumped groundwater, meaning that the remainder of pumped groundwater is sourced from net inflow. This study presents the first method that combines geodetic and in situ groundwater data to provide estimates of groundwater storage change that account for both coarse‐ and fine‐grained intervals, which are typically present in significant amounts in the major unconsolidated aquifer systems of the world.

Neogene subsidence rates of the southern Peri Pannonian realm (1D basin modeling): Constraints on the extensional geodynamic drivers of the asymmetric Toplica basin (central-southern Serbia)

With the objective to quantify the Neogene extensional geodynamic drivers of the Peri Pannonian Realm s.l., a series of 1D basin models were carried out by integrating the available geological and geochemical data extracted from the landlocked Toplica Basin (central-southern Serbia; Serbo-Macedonian Unit). The modeling was conducted on four wells located immediately south of Jastrebac Mt., in the area of the Toplica Basin. The investigated southernmost point of the Peri Pannonian Ream s.l. (areas surrounding the basin, to the south of rivers Danube and Sava) underwent intense tectonically-driven subsidence episodes, which lasted from the Lower Miocene up to the Pliocene. The restored Neogene burial history (subsidence rates), paleotemperature, and calibrated paleo-heat fluxes (or changes in the ancient crustal or basal heat flow) indicated a two-staged crustal stretching of the wider Toplica area. The combined tectonic, i.e., thermal subsidence, resulted in a very high sedimentation rate, having an average ca. 300–400 m/Ma (Čučale unit). The intense tectonically-driven subsidence is consistent with the involvement of extensional processes, affecting the crustal and lithospheric layers of the retreating Adria/Dinarides, amplified by a distant Carpathian rollback stage. The regional extension led to the asymmetric opening and the formation of the Toplica Lower Miocene mesosaline to the freshwater lacustrine system. Higher participation of mixed microbiologically reworked/terrestrial organic matter incorporated in oil-prone Type II kerogen mainly characterized the investigated lacustrine sedimentary sequence. The latest Oligocene–earliest Neogene subsidence onset was characterized by elevated temperatures, affecting the early development of the oil window (ca. at 16 Ma). The 1D models also showed that the Lower Čučale unit achieved ca. 50% transformation ratio for the Type II organic matter. The two intra-Neogene extensional episodes suggested the existence of the Early Neogene “syn-rift” stage, followed by a thermal sagging. The Neogene continuous thinning of the overriding Serbo-Macedonian continental crust contributed to the “negative inversion” of the former pre-Neogene nappes. Therefore, Neogene tectonic reactivation induced contemporaneous subsidence, further allowing the extensional rise of the Jastrebac core complex.

No Difference in Subsidence Between Modern Monoblock and Modular Titanium Fluted Tapered Femoral Stems

BackgroundSubsidence remains a concern when utilizing tapered fluted titanium (TFT) femoral stems and may lead to leg length discrepancy, impingement, instability, and failure to obtain osseointegration. This study aims to compare stem subsidence across 3 modern TFT stems. Our secondary aim was to investigate the influence of bicortical contact or “scratch fit” on subsidence, as well as the role of intraoperative imaging in maximizing bicortical contact and preventing stem subsidence. MethodsA retrospective review of 271 hip arthroplasties utilizing modern TFT stems at a single institution was performed. Three stem designs were included in the analysis: 1 monoblock TFT stem (n = 91) and 2 modular TFT stems (n = 90; n = 90). Patient demographics, Paprosky femoral bone loss classification, bicortical contact, utilization of intraoperative imaging, and stem subsidence (comparison of initial postoperative radiograph to the latest follow-up radiograph—minimum 3 months) were recorded. ResultsThere was no statistically significant difference in overall subsidence (P = .191) or the incidence of subsidence >5 millimeters between stems (P = .126). Subgroup analysis based on femoral bone loss grading showed no difference in subsidence between stems. Increased bicortical contact was associated with reduced subsidence (P = .004). Intraoperative imaging was used in 46.5% (126 of 271) of cases; this was not correlated with bicortical contact (P = .673) or subsidence (P = .521). ConclusionAll 3 modern TFT stems were highly successful and associated with low rates of subsidence, regardless of modular or monoblock design. Surgeons should select the stem that they feel is most clinically appropriate.

Cenozoic Subsidence History of the Northern South China Sea: Examples from the Qiongdongnan and Yinggehai Basins

The Qiongdongnan and Yinggehai Basins are important petroliferous basins. To study the Cenozoic subsidence characteristics of these two basins, their controlling factors, and their implications, we studied the basins’ subsidence characteristics via one-dimensional, two-dimensional, and holistic subsidence. Then, we compared the basins’ subsidence characteristics based on the evolution of several particular geological processes that occurred in the South China Sea (SCS) and adjacent areas. The results indicated that the change in the holistic subsidence of both basins occurred episodically. In addition, the subsidence in these two basins differed, including their subsidence rates, the migration of the depocenters, and the changes in the holistic subsidence. The dynamic differences between the two basins were the main factors controlling the differences in the subsidence in the two basins. In the Qiongdongnan Basin, the subsidence characteristics were primarily controlled by the mantle material flowing under the South China Block in the Eocene and the spreading of the SCS from the Oligocene to the Miocene. In the Yinggehai Basin, the subsidence characteristics were primarily controlled by the coupling between the uplift of the Tibetan Plateau and the strike-slip motion of the Red River Fault before the Early Miocene and by only the effect of the strike-slip motion of the Red River Fault from the Middle Miocene to the Late Miocene. Since the Pliocene, the subsidence characteristics of both basins have been principally controlled by the dextral strike-slip motion of the Red River Fault. The major faults contributed to the spaciotemporal variations in the subsidence within each basin.

Tectonic subsidence patterns in the multi-stage extension systems: Insights from quantitative backstripping analysis and modelling of the margins of Dahra and Beda Platforms, Sirt Basin, Libya

Quantitative analysis of tectonic subsidence patterns of 13 wells from the margins of Dahra and Beda Platforms provides new insights into the development of two major fault blocks in a tectonically active region of the western Sirt Basin. Backstripped subsidence curves and tectonic subsidence rates reveal four different tectonic stages (I–IV) from the Late Cretaceous to Middle Eocene. Continental rifting was initiated during the Cenomanian-Turonian period. Model curves predict maximum crustal stretching factor is 1.11 for this stage. From Campanian to Maastrichtian an exponentially decaying subsidence behaviour is described in the backstripped curves, indicating a stage of thermal sagging associated with the widespread distribution of Maastrichtian shallow-marine sediments according to a regional transect that crosses the margins of both platforms. Rapid short-term subsidence alterations from thermally driven long-term sagging, were recognised during the Palaeocene. The stretching factors for this third stage are about 1.3 for the southeastern margin of the Dahra Platform and >1.21 for the Amin High. The termination of subsidence during the Eocene is defined as a thermal subsidence stage. The stretching factor possibly decreased to an average 1.18 on both platforms. However, well data indicate that the Middle Eocene sediments exposed along the margins of Dahra and Beda Platforms, indicating that the sedimentary rocks of the post-Eocene succession, were whether not deposited or were mostly removed by erosion in the study area, due to a subsequent regional phase of differential uplift during the Oligocene-Miocene. This uplift phase is clearly distinguished on the tectonic subsidence curve from the Middle Maradah Trough.

Lateral Lumbar Interbody Fusion Using Expandable vs Static Titanium Interbody Cages: A Prospective Cohort Study of Clinical and Radiographic Outcomes.

Expandable cages are a recent development employed to reduce subsidence and improve fusion compared with static cages as they alleviate the need for repeated trialing or overdistraction of the disc space. This study aimed to compare the radiographic and clinical outcomes in patients undergoing lateral lumbar interbody fusion (LLIF) with either an expandable or static titanium cage. This was a prospective study of 98 consecutive patients undergoing LLIF performed over a 2-year period, with the first 50 patients receiving static cages and the following 48 receiving expandable cages. Radiographic evaluation included interbody fusion status, cage subsidence, and change in segmental lordosis and disc height. Clinical evaluation assessed patient-reported outcome measures (PROMs), including the Oswestry Disability Index, visual analog scale (VAS) for back and leg pain, and short form-12 physical and mental health survey scores collected at 3, 6, and 12 months postoperatively. The 98 patients had 169 cages impacted (84 expandable vs 85 static). Mean age was 69.2 years, and 53.1% were women. There was no significant difference between the 2 groups in terms of age, gender, body mass index, or smoking status. The expandable cage group had higher rates of interbody fusion (94.0% vs 82.9%, P = 0.039) at 12 months as well as significantly reduced implant subsidence rates at all follow-up timepoints (4% vs 18% at 3 months; 4% vs 20% at 6 and 12 months). Patients from the expandable cage group showed a mean 1.9 more points of reduction in VAS back pain (P = 0.006) and 2.49 points greater reduction in VAS leg pain (P = 0.023) at 12-month follow-up. Expandable lateral interbody spacers resulted in significantly improved fusion rates with reduced subsidence risks and statistically significant improvement in PROMs up to 12 months postoperatively compared with impacted lateral static cages. The data provide clinical relevance in favoring expandable cages over static cages for enhanced fusion outcomes in lumbar fusions.

Ground Surface Deformation Analysis Integrating InSAR and GPS Data in the Karstic Terrain of Cheria Basin, Algeria

Karstic terrains are usually dominated by aquifer systems and/or underground cavities. Overexploitation of groundwater in such areas often induces land subsidence and sometimes causes sinkholes. The Cheria basin in Algeria suffers from severe land subsidence issues, and this phenomenon has been increasing in recent years due to population expansion and uncontrolled groundwater exploitation. This work uses GPS data and persistent scatterer interferometry synthetic aperture radar (PS-InSAR) techniques to monitor the land subsidence rate by employing Sentinel-1 satellite data for the period from 2016 to 2022. Our results demonstrate that the Cheria basin experiences both uplift and subsidence in places, with an overall substantial change in the land surface. The total cumulative subsidence over 6 years reached a maximum of 500 mm. Comparison of land deformation between PSI and GPS showed root mean square error (RMSE) values of about 2.83 mm/year, indicating that our analyzed results are satisfactorily reproducing the actual changes. Nonetheless, these results can be used to extract the susceptible zones for vertical ground displacement and evaluate the surface deformation inventory map of the region for reducing damages (e.g., human losses, economic impact, and environmental degradation) that may occur in the future (e.g., sinkholes) and can be further utilized in perspective for a sinkhole early warning system.

Improving the Resolution of GRACE/InSAR Groundwater Storage Estimations Using a New Subsidence Feature Weighted Combination Scheme

GRACE observations and land subsidence data derived from InSAR both assess groundwater storage changes. However, GRACE data at local scales are restricted by the coarser spatial resolution of satellite systems, and inversion of Groundwater Storage Anomalies (GWSA) by InSAR requires extensive and unavailable lithological data. Here, we propose a New Subsidence Feature Weighted Combination (NSFWC) scheme to enhance the spatial resolution of GRACE-derived GWSA from 0.5° to 0.05°. This method can not only retain the spatial distribution of groundwater changes but also reflect local details related to surface subsidence. A case study was executed to evaluate the performance of the NSFWC scheme in the Beijing Plain, which has seriously overexploited groundwater. Results showed that the simulated GWSA were consistent with in situ measurements in most regions, with a correlation coefficient of 0.85 and an RMSE of 4.41 mm/year. Additionally, there were 22 overexploited wells in the Beijing Plain, although groundwater levels generally recovered after the South to North Water Diversion Project. Simultaneously, four cones of depression were detected by the InSAR technology, where the maximum cumulative subsidence and subsidence rate achieved −198.52 mm and −53.09 mm/year, respectively. This paper provides data support and technical guarantees for small-scale groundwater resources management.

Differences in CO2 Emissions on a Bare-Drained Peat Area in Sarawak, Malaysia, Based on Different Measurement Techniques

The drainage and cultivation of peatlands will lead to subsidence and mineralisation of organic matter, increasing carbon (C) loss as more CO2 is emitted. There is little information about carbon emissions from bare peat soil. A study was undertaken to measure the CO2 emissions from a logged-over peat swamp area that was purposely vegetation-free. We aimed to report CO2 emissions from a bare, drained peatland developed for an oil palm plantation. For 12 months, we used eddy covariance (EC), closed chambers, and soil subsidence measurements to derive CO2 emissions from a logged-over peat swamp area. Significant variations in the estimated soil CO2 efflux were observed in the three tested measurement techniques. The average CO2 flux rate measured by the EC technique was 4.94 ± 0.12 µmol CO2 m−2 s−1 (or 68.55 tonnes CO2 ha−1 year−1). Meanwhile, the soil CO2 efflux rate measured by the closed chamber technique was 4.19 ± 0.22 µmol CO2 m−2 s−1 (or 58.14 tonnes CO2 ha−1 year−1). Subsidence amounted to 1.9 cm year−1, corresponding to 36.12 tonnes CO2 ha−1 year−1. The estimation of the C loss was found to be highest by the EC technique, lower by the soil chamber technique, and lowest by the peat subsidence rate technique. The higher CO2 emission rate observed in the EC technique could be attributed to soil microbial respiration and decomposing woody residues in the nearby stacking rows due to the large EC footprint. It could also be affected by CO2 advection from oil palms adjacent to the study site. Despite the large differences in the CO2 emission rates by the different techniques, this study provides valuable information on the soil heterotrophic respiration of deep peat in Sarawak. Carbon emissions from a bare peat area cover only a fraction of the soil CO2 respiration component, i.e., the soil heterotrophic respiration. Further investigations are needed to determine the CO2 emissions by soil microbial activities and plant roots from other peat areas in Sarawak.

Comparison of radiographic and clinical outcomes between ALIF, OLIF, and TLIF over 2-year follow-up: a comparative study

BackgroundRegarding the increasing adoption of oblique lateral interbody fusion (OLIF) for treating degenerative lumbar disorders, we aimed to evaluate whether OLIF, one of the options for anterolateral approach lumbar interbody fusion, demonstrate clinical superiority over anterior lumbar interbody fusion (ALIF) or posterior approach, represented by transforaminal lumbar interbody fusion (TLIF).MethodsPatients who received ALIF, OLIF, and TLIF for symptomatic degenerative lumbar disorders during the period 2017–2019 were identified. Radiographic, perioperative, and clinical outcomes were recorded and compared during 2-year follow-up.ResultsA total of 348 patients with 501 correction levels were enrolled in the study. Fundamental sagittal alignment profiles were substantially improved at 2-year follow-up, particularly in the anterolateral approach (A/OLIF) group. The Oswestry disability index (ODI) and EuroQol-5 dimension (EQ-5D) in the ALIF group were superior when compared to the OLIF and TLIF group 2-year following surgery. However, comparisons of VAS-Total, VAS-Back, and VAS-Leg revealed no statistically significance across all approaches. TLIF demonstrated highest subsidence rate of 16%, while OLIF had least blood loss and was suitable for high body mass index patients.ConclusionsRegarding treatment for degenerative lumbar disorders, ALIF of anterolateral approach demonstrated superb alignment correction and clinical outcome. Comparing to TLIF, OLIF possessed advantage in reducing blood loss, restoring sagittal profiles and the accessibility at all lumbar level while simultaneously achieving comparable clinical improvement. Patient selection in accordance with baseline conditions, and surgeon preference both remain crucial issues circumventing surgical approach strategy.

Seismic-based paleoenvironmental analysis of the Paleocene carbonate shelf in Ajdabiya Trough, north-central of Libya

Abstract The results of the seismic and well logs interpretation, together with previous literature, were used to construct a generalized model of the development of the Paleocene reefs, and a depositional model for the Paleocene carbonate shelf in Ajdabiya Trough that focuses on the initiation, growth, and demise of the reefs in this basin. The Intisar reefs began as algal-foraminiferal banks. Growth of the reefs was halted by a short-lived transgression that drowned reefs and led to shale deposition of Kheir shales. The inversion of 3-D seismic data to acoustic impedance has allowed for a better determination of the main facies in Intisar reefs. These facies reflect different depositional conditions and different ages. They are: 1) algal-foraminiferal packstone/grainstone; 2) bioclastic grainstone/packstone; 3) coralline floatstone/bindstone; 4) reefal boundstone and; 5) bio-lithoclastic talus. The Upper Sabil consists of a prograding carbonate shelf with ramp platform morphology, and its differentiated deposits indicate four main depositional facies tracts: 1) inner shelf margin; 2) barrier reefs; 3) pinnacle reefs and; 4) outer shelf margin. The proposed model for the growth of the Paleocene reefs in the Ajdabiya Trough represents consecutive stages of development: 1) the Lower Sabil Carbonate was deposited during the very early Upper Paleocene time; 2) the influx of the Sheterat Shale during the major marine transgression; 3) the sea-level began a very slow fall due to variable subsidence of the underlying strata (a deposition of micrite over the Sheterat Shale, the lower part of the Upper Sabil Carbonate); 4) the rise in sea level is evident from an increase in foraminifera and algae constituents over the high areas of the lower part of the Upper Sabil Carbonate; 5) the isolated Intisar reefs were born under the proper local circumstances. The rate of subsidence was very slow, and the coral reef had significant upward growth and; 6) a major transgression happened at the end of the Paleocene, and the consequent deepening of the water in the area drowned and killed the Intisar reefs and capped it with Kheir Shale.