Subsidence Patterns Research Articles

Dueling dynamics of low-angle normal fault rupture with splay faulting and off-fault damage

Despite a lack of modern large earthquakes on shallowly dipping normal faults, Holocene Mw > 7 low-angle normal fault (LANF; dip<30°) ruptures are preserved paleoseismically and inferred from historical earthquake and tsunami accounts. Even in well-recorded megathrust earthquakes, the effects of non-linear off-fault plasticity and dynamically reactivated splay faults on shallow deformation and surface displacements, and thus hazard, remain elusive. We develop data-constrained 3D dynamic rupture models of the active Mai’iu LANF that highlight how multiple dynamic shallow deformation mechanisms compete during large LANF earthquakes. We show that shallowly-dipping synthetic splays host more coseismic slip and limit shallow LANF rupture more than steeper antithetic splays. Inelastic hanging-wall yielding localizes into subplanar shear bands indicative of newly initiated splay faults, most prominently above LANFs with thick sedimentary basins. Dynamic splay faulting and sediment failure limit shallow LANF rupture, modulating coseismic subsidence patterns, near-shore slip velocities, and the seismic and tsunami hazards posed by LANF earthquakes.

Active tectonics of the Circum-Pannonian region in the light of updated GNSS network data

The Pannonian basin is an extensional back-arc basin that has undergone neotectonic inversion and is currently shortening. The understanding and quantification of present-day deformation processes during this inversion are still incomplete. To this end, we investigate the active deformation of the Circum-Pannonian region via the interpolation of GNSS-derived velocity field and the derivation of the strain rate fields. For the interpolation of the velocity field, we use ordinary kriging, a strochastic interpolation method. Our results show that estimating a strain rate field that is virtually free of short-wavelength noise requires the scaling of the velocity uncertainties, i.e. assuming a minimum standard deviation of 1 mm/yr in our case. The deformation of the Circum-Pannonian region is defined by the 2–3 mm/yr, NNE-directed motion of the Dinarides, and by the 0.5–1.5 mm/yr, WSW to SSW directed motion of the eastern areas (European foreland, East Carpathians, South Carpathians, Transylvanian basin). These opposite-sense motions define a large-scale, on average NE-SW shortening and transpression-type deformation in the Dinarides as well as in the Pannonian basin, while the East and South Carpathians undergo regional N–S extension. Neotectonic structures generally show good agreement with the strain rate field, for example in the Dinarides, Eastern Alps, or in the western Pannonian basin. However, the presence of fault-parallel shortening or biaxial shortening along sinistral neotectonic structures in the central and eastern Pannonian basin show some discrepancy between current geodetic and observed neotectonic deformation. The vertical velocity field shows dominantly 100 and 1000 km wavelength signals, the former is probably related to the response of the Pannonian lithosphere-asthenosphere system to neotectonic basin inversion, while latter can possibly be explained by far-field subsidence patterns induced by the mantle response to melting of the Fennoscandian ice sheet during the current interglacial period.

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.

Sediment dispersal and basin evolution during contrasting tectonic regimes along the western Gondwanan margin in the central Andes

A >15-20 km-thick succession in southern Bolivia forms the most-complete stratigraphic record in western Gondwana. Upper Neoproterozoic–Carboniferous clastic rocks record ∼300 Myr of marine, nonmarine, and glacially influenced sedimentation in diverse basin systems generated by variable tectonic regimes along the western edge of Gondwana during active and passive-margin conditions. New provenance results help resolve key uncertainties regarding source regions and sediment dispersal patterns. The findings are integrated with spatial variations in stratigraphic thicknesses to evaluate regional patterns of basin subsidence, magmatism, and deformation during long-term evolution of the western Gondwanan margin in the central Andes.Detrital zircon U–Pb geochronological data for 17 sandstone samples reveal sedimentary input from Precambrian cratonic basement provinces and pre-Andean basement, magmatic arc, and fold-thrust belt source regions. The basement age signatures indicate derivation from the flanking Brasiliano (900-560 Ma) and Pampean (650-500 Ma) provinces to the south and east, and the distal Rio de la Plata craton (2400-2000 Ma) along the eastern South American margin ∼1000–1500 km to the southeast. Although the greater Amazonian craton was not a major contributor, subordinate Amazonian signatures from the Sunsás (1300-950 Ma) province to the east and northeast selectively fed the northern basin regions of the central Andes. Despite the lack of Paleozoic igneous rocks in Bolivia, detrital zircons of Ordovician age attest to the pre-Andean influence of the subduction-related Famatinian magmatic arc. Limited Devonian-Carboniferous igneous material was contributed locally from western pre-Andean highlands or regionally by axial northward transport from selected igneous sources in Argentina and Chile. Episodic recycling of Neoproterozoic–Paleozoic basin fill, including a sharp reappearance of Famatinian-age detritus, can be linked to periods of Paleozoic crustal shortening and foreland sedimentation ascribed to Famatinian, Ocloyic, Chañic, or Gondwanide phases of deformation.The spatial distribution of sediment sources along with temporal shifts in sediment routing highlight several stages in the paleogeographic evolution of the western Gondwanan margin preserved in the central Andes. Initial regional subsidence spanned a multiphase Neoproterozoic to early Paleozoic history of Rodinia breakup, Brasiliano-Pampean orogenesis, and post-orogenic back-arc extension prior to final late Paleozoic amalgamation of Gondwana. The early Paleozoic onset of subduction and Famatinian arc magmatism led to high-magnitude subsidence (>10–15 km) likely driven by Ordovician slab rollback in an extensional back-arc basin. Thereafter, intermittent Paleozoic contraction in a poorly understood pre-Andean system (best expressed in the Eastern Cordillera of Bolivia and neighboring segments of northern Argentina and southern Peru) generated transient topographic loads that produced superimposed flexural foreland and successor basin systems.

Risk Factors for Allograft Subsidence Following Anterior Cervical Discectomy and Fusion

The purpose this study was to precisely characterize patterns of allograft subsidence following anterior cervical discectomy and fusion (ACDF) utilizing computed tomography scans, determine risk factors for cervical allograft subsidence, and investigate the impact of subsidence on pseudarthrosis rates. We performed a retrospective review of patients undergoing 1-to 3-level ACDF utilizing allograft interbodies with anterior plating between 2011 and 2019. Subsidence measurements were performed by 2 independent reviewers on computed tomography scans obtained 6months postoperatively. Subsidence was then classified as mild if subsidence into the inferior and superior endplates were both ≤2mm, moderate if the worst subsidence into the inferior- or superior endplate was between 2 and 4mm, or severe if the worst subsidence into the inferior- or superior endplate was ≥4mm. Multivariate analysis was performed to identify risk factors for the development of subsidence. We identified 98 patients (152 levels) for inclusion. A total of 73 levels demonstrated mild subsidence (≤2mm), 61 demonstrated moderate subsidence (2-4mm), and 18 demonstrated severe subsidence (≥4mm). On multivariate analysis, risk factors for severe subsidence included excessive vertebral endplate resection and lower screw tip to vertebral body height ratio. Severe subsidence was associated with an increased rate of pseudarthrosis (94.1% vs. 13.6%) without an associated increase in reoperation rate. Following ACDF with allograft interbodies, 50% of interbodies will subside >2mm and 10% of interbodies will subside >4mm. Risk factors for severe subsidence should be mitigated to decrease the risk of pseudarthrosis.

Characterizing Spatiotemporal Patterns of Land Subsidence after the South-to-North Water Diversion Project Based on Sentinel-1 InSAR Observations in the Eastern Beijing Plain

The eastern Beijing plain has been suffering severe subsidence for the last decades, mainly associated with the long-term excessive extraction of groundwater resource. Since the end of 2014, the annual water supply in Beijing plain has reached several hundred million cubic meters because of the South-to-North Water Diversion (SNWD) Project, which has reduced the groundwater exploitation and changed the status of land subsidence. In this work, we first obtain the current spatiotemporal variations of land subsidence in the eastern Beijing plain by using progressive small baseline subsets (SBAS) InSAR time series analysis method with Sentinel-1 SAR data acquired from July 2015 to December 2021. Then, we analyze the correlations between InSAR-derived subsidence and groundwater level change by applying the cross wavelet method. The results show that two major subsidence zones are successfully detected with the maximum deformation rate of −150 mm/yr and maximum cumulative deformation of −950 mm. Besides, the ground deformation at different stages from 2016 to 2021 reveal that the area and magnitude of major deformation significantly slow down, even in the regions with severe subsidence, especially in the year of 2017, which is about two years later than the start time of SNWD Project in Beijing. Further, we find the InSAR-derived subsidence lags groundwater level change with about 1–2-month lagging time, indicating that the dynamic variation of groundwater level fluctuation may be the main factor affecting the uneven subsidence in the severe subsiding zones. Last, differential subsidence rates are identified at both sides of geological faults, such as Nankou-Sunhe fault and Nanyuan-Tongxian fault, from the observed deformation map, which could be explained that the groundwater flow is blocked when a fault is encountered. These findings can provide significant information to reveal the deformation mechanisms of land subsidence, establish the hydrogeological models and assist decision-making, early warning and hazard relief in Beijing, China.

Mapping and characterizing land deformation during 2007–2011 over the Gulf Coast by L-band InSAR

Land subsidence, known to have occurred in many parts of Gulf Coast of the United States (GC) as a consequence of complex geological conditions, high-intensity resource exploitation and land use. This subsidence has caused extensive damage to buildings and other infrastructures. By exploiting 1650 images from 33 ALOS-1 paths during 2007–2011 using multi-temporal interferometric synthetic aperture (InSAR) techniques, we have constructed, for the first time, a deformation map over 500,000 km2 of the 1900-km-long GC, with an RMSE of <10 mm/yr. The GC is generally stable, but numerous land deformation zones have been discovered, including at least 30 subsidence patterns and 14 uplift features. The maximum rate of subsidence measured is about 56 mm/yr at Stratton Ridge Oil Field, Texas. Most of the identified ground instabilities are newly discovered as a result of this study. The land deformation along GC is caused by both regional geological conditions and human activities that have influenced natural surroundings and consequentially exacerbated ground instability. Depressurization of petroleum reservoirs and aquifer compaction related to groundwater withdrawal are the principal impactors on observed subsidence. Other processes, including wastewater injection, sulfur/salt mining, dewatering, oxidation, and construction work, also contributed to the InSAR-mapped ground instability. Our large-scale deformation mapping will help the scientific community and relevant agencies better understand land deformation rates and extents, identify the processes responsible for the coastal deformation, and provide a critical dataset for hazard prediction and mitigation in the GC.

Integrated coastal subsidence analysis using InSAR, LiDAR, and land cover data

Land subsidence is an important cause of relative sea-level rise along the Gulf Coast. There is a lack of effective monitoring of coastal subsidence with high accuracy and high spatial resolution for improving coastal risk assessment and mitigation. This study is the first attempt to integrate satellite interferometric synthetic aperture radar (InSAR) and airborne light detection and ranging (LiDAR) methods to investigate the spatiotemporal pattern of coastal subsidence. The study area is around Eagle Point, Texas, a region known for its fast rate of relative sea-level rise in recent decades. From 2006 to 2011, the line-of-sight velocities were up to −33 mm/year based on ascending ALOS-1 PALSAR-1 images. From 2016 to 2021, the vertical velocities were up to −34 mm/year based on ascending and descending Sentinel-1 images. Additional details of the subsidence pattern were revealed by incorporating the surface difference derived from 1-m airborne LiDAR results. Comparisons of the InSAR-derived velocities from image time series and the LiDAR-derived surface changes from time-lapsed observations were conducted at different spatial levels with linkages to land cover patterns and topography. The results showed that local subsidence rates could vary significantly below the spatial resolution of InSAR results, indicating a valuable role of airborne LiDAR results in extending InSAR results to parcel and building levels and explaining subpixel uncertainties. Also, subsidence appeared to be stronger in vegetated areas than in developed areas and negatively correlated with surface imperviousness. The magnitude of subsidence was not correlated with elevation along selected transect lines. Overall, this study demonstrated the benefits of combining InSAR results with other geospatial datasets to characterize coastal subsidence. In particular, the high vertical accuracy of InSAR results and the high spatial resolution of airborne LiDAR results could be complementary, highlighting the necessity of multi-resolution data fusion to support studies on coastal flood vulnerability, infrastructure reliability, and erosion control.

Early Cretaceous stratigraphic and basinal evolution of the Danish Central Graben: a review

An integrated seismic–stratigraphic study of the Lower Cretaceous Cromer Knoll Group was undertaken as part of a recent comprehensive analysis of the Upper Jurassic – lowermost Cretaceous petroleum system in the Danish Central Graben. This study of the basal group of the post-rift package yielded an updated regional assessment of the distribution of the Valhall, Tuxen, Sola and Rødby Formations. This is documented by four high resolution isochore maps (presented here) that record temporal shifts in subsidence patterns from the latest Ryazanian to the earliest Cenomanian. The distribution and thickness variation of the mud-dominated Valhall Formation (latest Ryazanian – early Hauterivian) at the base of the group attests to the progressive fill of inherited syn-rift morphology. The dominant depositional theme is thus ponding in, and onlap from, the main inherited depocentres, although growth faults and incipient inversion locally controlled stratigraphic architecture, and new depocentres were initiated in the east of the graben (Ål and Outer Rough Basins). The isochores for the succeeding, increasingly chalk-rich Tuxen, Sola and Rødby Formations (Hauterivian – earliest Cenomanian) document the regional weakening of syn-rift patterns but emphasize the shift in sedimentation patterns controlled by accelerating inversion activity in the east (Adda–Tyra area, Søgne Basin) and increased local subsidence. The latter sometimes coincided with syn-rift depocentres, such as the Roar Basin and the Arne-Elin Graben, but was also significant in the new Early Cretaceous depocentres in the west of the graben, particularly the Outer Rough Basin. The evolution of the Early Cretaceous basin recorded by this dataset reveals significant shifts in the subsidence pattern in the late Valanginian – early Hauterivian, in large part due to early inversion in the east, and during the late Aptian – early Albian when subsidence was focussed in central and western sub-basins, probably locally due to salt withdrawal. These events, in combination with sea-level change, had implications for the accumulation and preservation of Barremian and early Aptian reservoir chalks.

Monitoring ground movement at Volcán de Colima, Mexico, using Sentinel-1 data and SqueeSAR ®

Volcán de Colima is a highly active stratovolcano in western Mexico, which presents a significant hazard to over 300 000 people who live within c. 40 km of the volcano. Because of its persistent activity, the volcano is actively monitored and researched, and understanding the patterns of behaviour is vital to accurate hazard assessment. Sentinel-1 synthetic aperture radar (SAR) images from ascending and descending orbits allow 1D and 2D ground motions to be retrieved using multi-interferogram techniques. SqueeSAR ® 's unique processing allows a better characterization of subtle ground movements in remote, rural mountainous areas compared with many other multi-interferogram techniques. A dataset of 147 SAR scenes (2017–19) has been processed to show patterns of lava subsidence (&lt;150 mm of downward vertical deformation over 2 years), as well as volcano deflation and apparent westward lateral movement. These data indicate that viscous andesitic lava flows may remain mobile for years following eruption and emplacement, and that the entire volcanic edifice is subsiding. Despite the apparent quiescence, volcanic edifices can remain highly dynamic after the termination of explosive or effusive activity. We interpret that the western flank of Volcán de Colima may become steeper with time and may be of long-term concern for hazard assessment activities. Thematic collection: This article is part of the Remote sensing for site investigations on Earth and other planets collection available at: https://www.lyellcollection.org/topic/collections/remote-sensing-for-site-investigations-on-earth-and-other-planets

Aquifer depressurization and water table lowering induces landscape scale subsidence and hydrophysical change in peatlands of the Hudson Bay Lowlands

The depositional history of the Hudson Bay Lowlands (HBL) in Ontario, Canada has created a low relief, poorly drained landscape, favouring the formation of one of the largest peatland complexes in the world. High volume dewatering associated with resource extraction in this area, such as the De Beers Victor Diamond Mine, tests the ability of the underlying confining layer to limit water losses in the peatlands above. This research quantifies the deepening of water tables and increase in effective stress related to mine dewatering and the resulting changes to bog and fen peatland hydrophysical structure and function. Long-term implications of these impacts are discussed. One impacted and two unimpacted transects were instrumented for meteorological (precipitation and evapotranspiration) and hydrophysical (hydraulic head, hydraulic conductivity (Ksat), and surface elevation) monitoring over a 12-year period in the vicinity of the Victor Mine. Over this study period, the unimpacted peatlands operated within relative hydrological equilibrium, demonstrated through shallow water tables, negligible subsidence, and stable Ksat. Contrastingly, all impacted peatlands experienced deeper watertables, larger downwards gradients, and measurable long-term subsidence (4–15 cm). Hydrological impacts were highest in bogs with a thin underlying confining layer even if they were farther from the point of dewatering, highlighting the need for environmental monitoring programs which incorporate an assessment of aquitard thickness. Where subsidence occurred, associated decreases in Ksat deflected bog-fen-tributary flow-paths deeper, reducing the upwards transport of solute rich water to downgradient fens. The long-term effects of these landscape scale changes should be studied further, particularly since climate change in this region will potentially increase water deficits and further alter peatland connectivity. Peatland studies should be conducted in different landscapes experiencing water table lowering due to drought or depressurization in order to better understand the associated subsidence patterns and hydrophysical changes in varying geological and morphological regimes.

Characterization of the Land Deformation Induced by Groundwater Withdrawal and Aquifer Parameters Using InSAR Observations in the Xingtai Plain, China

Long-term overexploitation of groundwater has led to significant land subsidence and ground fissures in the Xingtai plain. These geo-hazards have threatened the safety of buildings and infrastructures. It is extremely important to investigate the coupling relationship between land deformation and hydraulic head change for controlling land subsidence and mitigating ground fissures. In this study, we obtained the spatial and temporal evolution of land deformation in the Xingtai plain by using Envisat/ASAR data during 2009~2010 and Sentinel-1A data during 2015~2021. Combining InSAR results, head observations and geological data, we investigated the response of land deformation to head change and estimate the aquifer parameters. First, joint analysis of displacement time series and head changes infers that land subsidence was mainly caused by the inelastic compaction in aquitards. Compared with the subsidence patterns during 2009~2010, both the rate and spatial extent of land subsidence increased obviously during 2015~2021. Second, seasonal fluctuations in hydraulic head resulted in significant seasonal deformation with an amplitude of 10~30 mm and peak time of January~March, of which the spatial–temporal distribution was consistent with that of the rapid subsidence. Third, obvious differences in the deformation rate and seasonal amplitude were observed across the Longyao ground fissures and other three potential fissures during 2015~2021, suggesting that the activity of ground fissures increased compared with that during 2009~2010. Finally, using InSAR results and head observations, we estimated the elastic and inelastic skeletal storativity, with values ranging from 0.9 × 10−3 to 12.4 × 10−3 and 6.2 × 10−3 to 88.0 × 10−3, respectively. The comparison between elastic and inelastic skeletal storativity suggests that ~84.5% of total subsidence was irreversible and permanent.

Monitoring Subsidence over the Planned Jakarta–Bandung (Indonesia) High-Speed Railway Using Sentinel-1 Multi-Temporal InSAR Data

Investigation of subsidence situations is important for the design of railway lines. Traditional geological investigations are expensive. Multi-temporal InSAR (MT-InSAR) analysis has shown great potential for detecting subsidence areas along large-scale manmade linear features (LMLFs). The disadvantage of applying high-resolution SAR data such as that from TerraSAR-X and COSMO-SkyMed data is the high cost. By contrast, the free and open data from Sentinel-1 A/B offer an unprecedented opportunity for InSAR applications. Despite these advantages, research investigating the potential for monitoring subsidence along LMSFs using multi-temporal Sentinel-1 InSAR data at the design stage of LMSFs is limited. This paper explores the monitoring ability of MT-InSAR analysis with Sentinel-1 A/B multi-temporal data in an experiment along the planned Jakarta-Bandung high-speed railway in Bandung, Indonesia. Subsidence patterns along the route of the planned high-speed railway were analyzed in detail. By means of validation using 12 leveling points, the root mean square error (RMSE) of the average displacement velocity that was obtained from the MT-InSAR results was found to be 10.31 mm/yr. This paper demonstrates the potential of Sentinel-1 multi-temporal INSAR data to detect potential subsidence areas along planned LMLFs (e.g., the planned high-speed railway that is the focus of this study), serving as a reference for further planning of monitoring subsidence over planned LMLFs.

P45. Titanium cervical cage subsidence: postoperative CT analysis defining incidence and associated risk factors

<h3>BACKGROUND CONTEXT</h3> Substantial variability in both the measurement and classification of subsidence limits the strength of conclusions that can be drawn from previous studies. <h3>PURPOSE</h3> The purpose of this study was to precisely characterize patterns of cervical cage subsidence utilizing computed tomography scans, determine risk factors for cervical cage subsidence and investigate the impact of subsidence on pseudarthrosis rates. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>METHODS</h3> We performed a retrospective review of a patients who underwent one- to three-levels of ACDF utilizing titanium interbodies with anterior plating between the years 2018 to 2020. Subsidence measurements were performed by two independent reviewers on CT scans obtained 6 months postoperatively. Subsidence was then classified as mild if subsidence into the inferior and superior endplate were both ≤2mm, moderate if the worst subsidence into the inferior or superior endplate was between 2 to 4mm, or severe if the worst subsidence into the inferior or superior endplate was ≥4mm. <h3>RESULTS</h3> A total of 51 patients (100 levels) were included in this study. A total of 48 levels demonstrated mild subsidence (<2mm), 38 demonstrated moderate subsidence (2–4mm), and 14 demonstrated severe subsidence (>4mm). Risk factors for severe subsidence included male gender, multilevel constructs, greater mean vertebral height loss, increased cage height, lower Taillard Index, and lower screw tip to vertebral body height ratio. Severe subsidence was not associated with an increased rate of pseudarthrosis. <h3>CONCLUSIONS</h3> Following ACDF with titanium cervical cages, subsidence is an anticipated postoperative occurrence and is not associated with an increased risk of pseudarthrosis. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Development of the Whitehorse trough as a strike-slip basin during Early to Middle Jurassic arc-continent collision in the Canadian Cordillera

Abstract The Whitehorse trough is a synorogenic basin in the northern Cordillera that resulted from arc-collision processes along the northwestern margin of North America, but its filling history and tectonic significance remain uncertain. New detrital zircon U-Pb-Hf isotope analyses of 12 rock samples, including six basal sandstones that sit unconformably on Triassic rocks of Stikinia, were combined with published detrital zircon and fossil data to establish the depositional ages of synorogenic Laberge Group strata in Yukon and test proposed links between Intermontane terrane exhumation and basin-filling events. Laberge Group strata yielded 205–170 Ma and 390–252 Ma detrital zircon populations that indicate derivation from local Late Triassic to Middle Jurassic arc and syncollisional plutons and metamorphosed Paleozoic basement rocks of the Stikinia and Yukon-Tanana terranes. Basal sandstone units have Early Jurassic depositional ages that show the Whitehorse trough filled during early Sinemurian, late Sinemurian to Pliensbachian, and Toarcian subsidence events. Late Triassic to Early Jurassic detrital zircon grains confirm that syncollisional plutons near the northern trough were exhumed at 0.5–7.5 mm/yr and replicate their excursion to subchondritic Hf isotope compositions as a result of increasing crustal contributions from Rhaetian to Sinemurian time. The new detrital zircon data, combined with recent constraints for Triassic–Jurassic metamorphism and magmatism in Yukon, require modification of published forearc to syncollisional basin models for the Whitehorse trough. We reinterpret Jurassic subsidence patterns and architecture of the Whitehorse trough to reflect sinistral transtension within a transform fault system that resulted from the reorganization of subduction after end-on arc collision.

Causes of Variable Shortening and Tectonic Subsidence During Changes in Subduction: Insights From Flexural Thermokinematic Modeling of the Neogene Southern Central Andes (28–30°S)

AbstractThe Andes of western Argentina record spatiotemporal variations in morphology, basin geometry, and structural style that correspond with changes in crustal inheritance and convergent margin dynamics. Above the modern Pampean flat‐slab subduction segment (27–33°S), retroarc shortening generated a fold‐thrust belt and intraforeland basement uplifts that converge north of ∼29°S, providing opportunities to explore the effects of varied deformation and subduction regimes on synorogenic sedimentation. We integrate new detrital zircon U‐Pb and apatite (U‐Th)/He analyses with sequentially restored, flexurally balanced cross sections and thermokinematic models at ∼28.5–30°S to link deformation with resulting uplift, erosion, and basin accumulation histories. Tectonic subsidence, topographic evolution, and thermochronometric cooling records point to (a) shortening and distal foreland basin accumulation at ∼18–16 Ma, (b) thrust belt migration, changes in sediment provenance, and enhanced flexural subsidence from ∼16 to 9 Ma, (c) intraforeland basement deformation, local flexure, and drainage reorganization at ∼12–7 Ma, and (d) out‐of‐sequence shortening and exhumation of foreland basin fill by ∼8–2 Ma. Thrust belt kinematics and the reactivation of basement heterogeneities strongly controlled tectonic load configurations and subsidence patterns. Geo/thermochronological data and model results resolve increased shortening and combined thrust belt and intraforeland basement loading in response to ridge collision and Neogene shallowing of the subducted oceanic slab. Finally, this study demonstrates the utility of integrated flexural thermokinematic and erosion modeling for evaluating the geometries, rates, and potential drivers of retroarc deformation and foreland basin evolution during changes in subduction.

Spatiotemporal evolution and surface response of land subsidence over a large-scale land creation area on the Chinese Loess Plateau

• The land-creation area shows exponentially decaying subsidence with fill compaction. • The long-term subsidence trend is primarily controlled by the fill thickness. • The significant ground subsidence zone varies as the land-creation area expands. • Most subsidence in YND will continue for about 7.2 years after InSAR observation. For Yan’an (China) and many other cities on the Loess Plateau, development is limited by a severe lack of available land. To support the city’s sustainable development, the Yan’an New District (YND) was constructed in 2012 through a mountain excavation and city construction (MECC) project. However, rapid land creation and urbanization have caused extensive anthropogenic land subsidence, which may impose new constraints on YND development. This study investigated the spatiotemporal development pattern and long-term temporal response of land subsidence related to land creation in the YND. First, 95 Sentinel-1 images acquired from 2016 to 2019 were analyzed with the small baseline subset (SBAS) interferometric synthetic aperture radar (InSAR) method to reveal the long-term displacement rates and spatiotemporal displacement patterns in the YND region. The interrelationship between the spatiotemporal variations in ground subsidence and the land creation history was also discussed. Then, an exponential model was employed to characterize the InSAR time series to assess the long-term displacement trends and temporal response of the land-subsidence process related to land creation. The results suggest that the observed long-term subsidence patterns in the land creation area showed an exponentially decaying trend with the fill compaction process. The newer and thicker the loess fill foundation was, the greater the subsidence rate and the smaller the decay trend over the same observation time, indicating slower stabilization relative to the compaction of the filling loess. The spatial variation in the significant land subsidence zone gradually shifted toward the newly formed fill area as the land creation area expanded. In addition, the ground displacement response estimates highlighted that most of the Qiaoergou subsidence zone in the YND will continue to sink for approximately 7.2 years following the InSAR observations used here. These findings have important implications for disaster mitigation and urban planning in similar large-scale land creation areas.

Elastic and Inelastic Ground Deformation in Shanghai Lingang Area Revealed by Sentinel-1, Leveling, and Groundwater Level Data

Shanghai Lingang New City, located in the southeast corner of Shanghai, was constructed by land reclamation from 2002 to 2005, in an area where the geological structure is prone to subsidence over time. Firstly, we explore the spatio-temporal pattern of ground subsidence and its mechanism using the Persistent Scatterers Interferometric Synthetic Aperture Radar (PSInSAR) technique by processing 50 scenes of Sentinel-1A images acquired from May 2016 to May 2018. In order to assess the accuracy of PSInSAR derived deformation, we collect the first-class leveling data at two benchmarks located in the study area; the comparison between the two settlement indicates that the maximum difference is 1.93 mm and 2.9 mm, respectively, which validates the PSInSAR’s high accuracy. We then obtain the skeleton release coefficients by the joint analysis of PSInSAR measurements and groundwater level data. Finally, we find that this coastal area has undergone both elastic and inelastic deformation from 2016 to 2018. The outcome shows that the combination of different techniques is conductive to understand the deformation mechanism of the aquifer system in these coastal areas, which is expected to be a valuable reference for ground subsidence monitoring and groundwater extraction management.

Characterizing Spatiotemporal Patterns of Land Deformation in the Santa Ana Basin, Los Angeles, from InSAR Time Series and Independent Component Analysis

The excessive extraction and recharge of groundwater lead to long-time seasonal land subsidence in Los Angeles, USA, and especially in the Santa Ana basin. The rate of land subsidence in the Santa Ana basin has been rising, which could pose a danger to infrastructure and human lives. However, the most recent research on land surface deformation in the area was conducted using the traditional parameter estimation method, resulting in little understanding of the regional spatiotemporal characteristics. The parametric method consists of a least square linear inversion, using the pre-defined mathematical geometric or geophysical theoretical models to describe groundwater deformation, and it requires precise external environmental variables and accurate geophysical parameters, which are more difficult to implement. In this study, multitemporal InSAR-derived deformation time series are analyzed by using 69 descending C-band Sentinel-1A SAR scenes acquired from 2015 to 2018. A method based on independent component analysis (ICA) is applied to characterize the spatial pattern and temporal evolution of land subsidence in the Santa Ana basin. The results reveal two different spatial and temporal deformation patterns in the basin. First, a widespread seasonal deformation is identified by the first component, related to annual seasonal groundwater level changes, and the overall deformation shows a concentrated spatial pattern. The second component captures a long-term signal with a large-scale spatial pattern. For quantitative assessment, the obtained deformation time series are compared with the GNSS data, validating an accuracy of millimeters. We further calculate the cross-correlation coefficient and the elastic skeletal storage coefficient from the ICA-derived seasonal deformation and groundwater level, which reveals that the deformation responds quickly (i.e., a lag of 8 days) to the change in groundwater and the Santa Ana aquifer retains almost the same elasticity for at least 15 years. Quantifying the spatiotemporal characteristics of the deformation in the Santa Ana basin can provide a reference for the monitoring and managing of groundwater.

A regionally consistent 3D seismic-stratigraphic framework and age model for the Quaternary sediments of the northern North Sea

The thick succession of Quaternary sediments that is preserved in the northern North Sea provides a valuable record of the climate and environmental changes of the last ∼2.6 million years. However, the general lack of chronological control on these sediments, combined with gaps in high-resolution seismic data coverage, has hindered our understanding of the detailed sediment infill history of this margin. Here we use a large (35,000 km2) high-resolution 3D seismic cube, supplemented by other 2D and 3D seismic datasets, to map more than 20 horizons within the Quaternary Naust Formation. We extend these horizons across large parts of the northern North Sea to establish a robust seismic framework that is used to assess the correspondence between existing chronostratigraphic ages. Whereas there is good agreement between most existing ages, the correlation of horizons between the Troll Field and the North Sea trough-mouth fan suggests that the sediments preserved at the base of the Norwegian Channel may have been deposited significantly later than assumed previously. Geomorphological forms preserved close to the base of the Norwegian Channel provide evidence for sediment disturbance by ice-stream activity, and document a two-stage glacial build-up during a mid-Pleistocene glaciation. We suggest a new age model for the Quaternary sediments of the northern North Sea, in which the deposition of sediments within the Norwegian Channel occurred as recently as 0.35 Ma in response to prior sediment loading and subsidence within the North Sea trough-mouth fan. In addition to providing new insights into the extent and timing of glacial events, the development of a regionally consistent 3D seismic-stratigraphic framework has implications for the age of the Peon gas discovery and for reconstructing spatial and temporal patterns of Quaternary sediment subsidence and fluid overpressure in the North Sea Basin.