Short-term Uplift Research Articles

Vegetation strategies for nitrogen and potassium acquisition along a climate and vegetation gradient: From semi-desert to temperate rainforest

Nutrient acquisition strategies of plants regulate water flow and mass transport within ecosystems, shaping earth surface processes. Understanding plant strategies under current conditions is important to assess and predict responses of natural ecosystems to future climate and environmental changes. Nitrogen (N) and potassium (K) (re-)utilization from topsoil and their acquisition from subsoil and saprolite were evaluated in a continental transect, encompassing three study sites – an arid shrubland, a mediterranean woodland, and a temperate rainforest – on similar granitoid parent material in the Chilean Coastal Cordillera. The short-term (<1 year) plant N and K acquisition was traced with 15N and the K analogs rubidium and cesium. To do so, the tracers were either injected into topsoil, subsoil, or saprolite, in the immediate vicinity of eight individual plants per study site and injection depth. The long-term (>decades) K uplift by plants was investigated by the vertical distribution of exchangeable K+ and Na+. Recoveries of 15N and K analogs by arid shrubland plants were similar from topsoil, subsoil, and saprolite. Mediterranean woodland shrubs recovered the tracers primarily from topsoil (i.e., 89 % of recovered 15N and 84 % of recovered K analogs). Forest plants recovered the tracers from topsoil (15N = 49 %, K analogs = 57 %) and partially from greater depth: 38 % of recovered 15N and 43 % of recovered K analogs were acquired from subsoil and saprolite, respectively. Low nutrient accessibility in the topsoil (e.g., because of frequent droughts) drives shrubland plants to expand their N and K uptake to deeper and moister soil and saprolite. Woodland and forest plants dominantly recycled nutrients from topsoil. In the forest, this strategy was complemented by short-term uplift of N and K from depth. The vertical distribution of exchangeable K indicated long-term uplift of K by roots in all three sites. This highlighted that long-term K uplift from depth complements the nutrient budget across the continental transect.

Quantitative reconstruction of Holocene ground displacements in the offshore part of the Campi Flegrei caldera (southern Italy): Perspectives from seismo-stratigraphic and archaeological data

Analysis of high-resolution seismic profiles integrated with archaeological data along the coast has allowed quantifying the last ∼10 ka BP displacements in the offshore part of the Campi Flegrei resurgent caldera, one of the world's highest-risk volcanic areas. Previous onland studies revealed that, following the Neapolitan Yellow Tuff (NYT) eruption at 15 ka, post-caldera evolution was associated with rapid ground uplift and subsidence cycles. In this paper, we use the stacking pattern of Prograding Wedges (PWs) and Aggrading Fills (AF) to reconstruct relative sea-level changes and estimate the amount of vertical deformation in the Pozzuoli Bay, the submerged part of the caldera. We document five generations of prograding wedges (PW1 to PW5), associated with as many periods of relative ground stability between uplift and subsidence. Instead, deposition of aggrading fills above prograding wedges underpins the subsidence that typically follows volcanic unrest and uplift. The older wedges PW1 and PW2 are larger and likely indicate whole-caldera uplift events. In particular, the development of PW2 starting from ∼5.2 ka is related to the rapid growth of a resurgent dome in the central part of the caldera. After ∼3.7 ka, subsidence prevailed in the caldera leading to deposition of an aggrading fill (AF2). However, subsidence was interrupted by short-term uplift episodes in historical times at (100 BCE-100 CE, 600–700 CE, 1430–1538 CE) that led to the growth of comparatively minor-sized wedges PW1 to PW3, respectively. Displacement of coastal infrastructures of the Roman age (∼2 ka BP) is consistent with the vertical motion retrieved by the seismostratigraphic analysis, and further indicates the existence of two deformation signals. A short-wavelength signal confined to the Pozzuoli Bay reflects the contribution of an intra-caldera source. This signal is superposed to a long-wavelength regional subsidence increasing between Naples and Procida Island from 1.5 to 2 mm/a, respectively. The east-to-west enhancing subsidence likely reflects the transition between the uplifting Apennines and the foundered Tyrrhenian back-arc basin.

InSAR Time-Series Analysis for Monitoring Ground Displacement Trends in the Western Hellenic Arc: The Kythira Island, Greece

Kythira Island is situated at the western Hellenic Arc, which is a region of very high seismicity and tectonic activity. On 8 January 2006, a large seismic event of Mw = 6.7 occurred close to Kythira, in association with the Hellenic subduction zone. We present an extensive multi-temporal interferometry study of ground displacements in Kythira Island exploiting SAR data of a decade, from 2003 to 2009, and from 2015 to 2019. The line-of-sight displacement field for the 2003–2009 time period presents small-scale displacements that do not exceed −3 mm/y, identified to the East of Kythira’s airport, and 3 mm/y in the central part of the island. We exploit then Sentinel-1 data from 2015 to 2019, of both descending and ascending Sentinel-1 SAR imaging modes to decompose the line-of-sight measured deformation to vertical and east–west motion components. Higher vertical displacement rates characterize the central part of the island, with a maximum value of 5 mm/y. This short-term uplift rate exceeds by an order of magnitude the long-term geologic uplift rate of ~0.13 mm/y found in the island during the Quaternary. We discuss possible regional geophysical explanations for this discrepancy. Strike-slip components are detected in the N–E coast of the Potamos village, where horizontal displacements occur, with an east-ward trend and a maximum value of −3 mm/y. These insights are valuable input for the systematic monitoring of this high seismic risk island and the dynamic assessment of its hazard potential.

A fresh look at self-employment, stress and health: accounting for self-selection, time and gender

PurposePast research on self-employment and health yielded conflicting findings. Integrating predictions from the Stressor-Strain Outcome model, research on challenge stressors and allostatic load, we predict that physical and mental health are affected by self-employment in distinct ways which play out over different time horizons. We also test whether the health impacts of self-employment are due to enhanced stress (work-related strain) and differ for man and women.Design/methodology/approachWe apply non-parametric propensity score matching in combination with a difference-in-difference approach and longitudinal cohort data to examine self-selection and the causal relationship between self-employment and health. We focus on those that transit into self-employment from paid employment (opportunity self-employment) and analyze strain and health over four years relative to individuals in paid employment.FindingsThose with poorer mental health are more likely to self-select into self-employment. After entering self-employment, individuals experience a short-term uplift in mental health due to lower work-related strain, especially for self-employed men. In the longer-term (four years) the mental health of the self-employed drops back to pre-self-employment levels. We find no effect of self-employment on physical health.Practical implicationsOur research helps to understand the nonpecuniary benefits of self-employment and suggests that we should not advocate self-employment as a “healthy” career.Originality/valueThis article advances research on self-employment and health. Grounded in stress theories it offers new insights relating to self-selection, the temporality of effects, the mediating role of work-related strain, and gender that collectively help to explain why past research yielded conflicting findings.

The episodic rise, net growing rate and kinematics of radial faults of the Salinas de Oro diapir using paleoseismological techniques (NE Spain). Salt upwelling versus karstic subsidence

This paper explores the use of trenching and paleoseismological techniques to determine salt flow rates into a salt diapir for the first time in the literature. The Salinas de Oro diapir, located in the northern Spanish Pyrenees, is an oval-shaped Triassic-salt stock that extends vertically for ≫7 km down to the Paleozoic basement. Salt dissolution subsidence and diapir growth are coeval active processes. Karstification is responsible for the development of large sinkholes, a thick caprock and the monocline folding and ring faulting of the Cretaceous and Early Tertiary limestone rim. The evaporite karstic aquifer discharges high-concentration water of up to 137 g/l of total dissolved solids and a conductivity over 200 mS/cm into the Salado Creek, which drains the diapir top. The salinity monitoring of this drainage provides a maximum karstic surface lowering rate of around 2.8 mm/yr. Salt upwelling has caused the 150 m uplift of the annular limestone escarpment and the development of ≫3000 m long radial grabens with up to 90 m of vertical offset that disrupt drainages, displace Quaternary deposits and overprint concentric faults. The 260 cm drag folding of lacustrine facies exposed in a 42 m long and 6.5 m deep trench due to the creep motion of the western radial fault of Azanza Graben yielded a minimum short-term uplift slip rate of 1.75 mm/yr for the last 1485 years and provides a minimum salt supply rate of over 5 mm/yr considering karstification lowering. This value that is several hundred times higher than average, evidence the discontinuous growth of Salinas de Oro diapir.

Transient uplift of a long-term quiescent coast inferred from raised fan delta sediments

We present the first example of a short-term uplift transient within the long-term stagnant forearc of the Arica Bend, northernmost Chile. We date a storm deposit embedded into fan delta sediments, which were deposited close to sea level and are now located ~40 m higher. The radiocarbon age is ca. 10 ka, yielding an average uplift rate of ~4 mm/yr. During the Holocene, the section has been dissected by the Lluta River, the long profile of which shows geomorphic response to coastal uplift. However, the coast of the Arica Bend is characterized by million- year-scale relative subsidence and current global positioning system surveyed quiescence. We therefore interpret the inferred uplift signal to represent a transient increase in uplift rates throughout the Holocene. Similar short-term transients have been globally documented in relation to various subduction zone settings, although their causes still remain a matter of debate and need further investigation. We propose that periods of increased surface uplift may also occur in long-term quiescent forearcs, possibly due to temporal variations of plate interface properties (i.e., strength and/or seismic locking) that induce thickening beneath the coast.

Short-Term Uplift Rates and Surface Deformation along the Reelfoot Fault, New Madrid Seismic Zone

Abstract This study of variability in the amount and rate of deformation along the intraplate Reelfoot fault of the New Madrid seismic zone (NMSZ) utilizes diverse research methods, including geophysics, geomorphology, and fluvial sedimentology. The transpressional Reelfoot fault deforms late Holocene Mississippi River sediment into the Tiptonville dome and adjacent Reelfoot basin. Because Reelfoot Lake submerges a portion of the basin, subbottom acoustic profiling of the lake was used to quantify the relief on the uplift. At the natural levee of the abandoned Tiptonville meander, the most appropriate landform along the scarp for measuring cumulative structural relief, a maximum relative vertical uplift of approximately 11.3 m was measured. To identify spatial and temporal variability in surface deformation using geologic methods, we relate fluvial sedimentation to three documented earthquake events during the past 2300 yr (Tuttle et al. , 2002, 2005), which is the approximate age of the oldest deformed floodplain sediment (Guccione et al. , 2002). Radiocarbon dates from organic material in fluvial and lacustrine sediment indicate that most of the uplift occurred during the last two major seismic events. A minimum of 1.6–3.9 m of uplift was associated with the seismic episode at A.D. 1450±150 and a maximum of 5.9–8.2 m of uplift was associated with the 1812 episode. We estimate a mean short-term uplift rate of 1.2 cm/yr (0.4–2.1 cm/yr with 80% probability) or a mean short-term slip rate of 1.3 cm/yr (0.5–2.3 cm/yr with 80% probability). These values are approximately 2.5 times higher than the long-term rates based on the total amount of uplift averaged over the past 2300 yr (Mueller et al. , 1999; Van Arsdale, 2000). Estimating deformation rates associated with individual earthquake recurrences provides information on fluctuating activity of the NMSZ.

Late Pleistocene landscape evolution in south-central Chile constrained by luminescence and stable cosmogenic nuclide dating

Landscapes in tectonically active regions develop in response to a complex interplay between rapid tectonic deformation and surface processes. In order to understand the evolution of these environments and distinguish between the different factors, it is fundamental to identify and quantify geomorphic processes and rates on different time scales. The forearc of south-central Chile provides an ideal setting to elucidate the response of surface processes to climatic and tectonic forcing. However, in contrast to northern Chile, this region has attracted little attention due to difficulties in quantifying the age of geomorphic surfaces. We use luminescence and stable cosmogenic nuclides ( 3 He, 21 Ne) on conglomeratic units in the Central Depression and fluvial valley fills in the Coastal Cordillera to constrain exposure and burial ages of these units that form major landscape elements in the southern Chilean forearc. Our data indicate that disturbances in the drainage network are controlled by local uplift, which may be caused by deformation above an active blind thrust. In the Coastal Cordillera, local short-term uplift rates reach a minimum of 0.27 mm a −1 and are on the same order as late Quaternary minimum incision rates of 0.15 mm a −1 to 0.43 mm a −1 . The valley fills in the Coastal Cordillera have depositional ages of 80 ka and 255 ka, respectively. Exposure ages of the extensive alluvial surfaces in the Central Depression cluster between 135 ka and 175 ka and between 240 ka and 280 ka. Hence, the deposition of these surfaces broadly coincides with marine isotope stages (MIS) 6 and 8 and appears to be climatically driven.

Comparison of long-term and short-term uplift rates along an active blind reverse fault zone (Bajo Segura, Se Spain)

The seismic activity of the Guardamar-Torrevieja zone (Eastern Betic Cordillera, SE Spain) can be associated with the Bajo Segura fault zone, an E-W reverse blind fault with secondary NW-SE dextral faults. A high-precision levelling profile 30 kilometers long was set up and levelled in 1997 to monitor the vertical displacement of this active fault zone. This profile runs parallel to an older high-precision levelling line included in the Spanish first order levelling network measured by the Instituto Geografico Nacional (IGN) in two different campaigns (1934 and 1976). The 1997 line was relevelled in 2003 and 10 new benchmarks were set up, both to increase benchmark density and to restore some of the 1997 benchmarks that had been destroyed. We have used the 1976 IGN and the 2003 measurement to construct a recent vertical movements profile with a significant time difference (27 years). This recent vertical movements profile shows that the vertical movements are very small, nearly equal to the error bars, with a 0.2 mm/year rise in the town of Guardamar, and a 0.2 mm/year subsidence of the southern part of the profile (Punta Prima) respect to the town of Torrevieja. These movements could be related to the activity of the Bajo Segura and the San Miguel faults respectively. Using geological markers we have deduced uplift rates of 0.1 mm/year during the last 3 million years. Therefore, these preliminary results indicate that geodetically (short-term deformation) determined uplift rates are similar to those estimated from geological markers (long term deformation).

A unified interpretation of vertical movement in Himalaya and horizontal deformation in Tibet on the basis of elastic and viscoelastic dislocation theory

The present-day convergence rate between the Indian and the Eurasian plates has been estimated to be about 50 mm/year. At the collision boundary extending along the Himalayas, about 40% of the total convergence is consumed by the subduction of the Indian plate beneath the Eurasian plate. The rest of about 60% is consumed by the internal deformation of the Eurasian plate. The present crustal movement in this region is characterized by rapid uplift along the high Himalayas and large-scale horizontal deformation in and around Tibet. The fundamental causes of these two different types of crustal movement are the same: interaction between the Indian and the Eurasian plates. In this study we represent the plate interaction by steady increase in tangential displacement discontinuity (dislocation) across the interface that divides a surface layer overlying a viscoelastic half-space into the Indian and the Eurasian plates. First, given a steady slip of 20 mm/year at the plate interface with a ramp-shaped undulation below the high Himalayas, we computed the profile of surface uplift rates along a line perpendicular to the Himalayan arc. The result accords with observed free-air gravity anomalies and the intermediate- and short-term uplift rates estimated, respectively, from the present heights of river terraces and levelling data. This means that the rapid uplift of the high Himalayas is due to the steady slip along the ramp-shaped plate interface below it. Second, given the steady slips of 20 mm/year along the 2000-km-long collision boundary and 50 mm/year along the remaining portions of the India–Eurasia plate boundary, we computed the increase rates of horizontal deformation in and around Tibet. The result accords with the observed strikes and slip rates of major Quaternary active faults. This means that the horizontal deformation in and around Tibet is due to the slip deficits of 30 mm/year at the collision boundary. From these two results we can conclude that the present rapid uplift of the high Himalayas and large-scale horizontal deformation in and around Tibet are consistently explained by a single plate interaction model based on elastic and viscoelastic dislocation theory. This study sheds new light on the driving mechanism of the crustal deformation in the India–Eurasia collision zone as follows. The plate interaction on single plate interface consists of coexisting two different physical mechanisms: (1) slip along the ramp undulation (spatial changes in slip direction), (2) slip deficit at the collision boundary (spatial changes in slip rates). As a consequence, the two different types of crustal deformation in the India–Eurasia collision zone are driven by these two different physical mechanisms.

Variable rates of Late Quaternary surface uplift along the Banda Arc-Australian plate collision zone, eastern Indonesia

Abstract Radiometrically dated emergent coral terraces from southeastern Indonesia provide estimates of differential vertical strain in the Banda Arc-continent collision complex. At Semau island, two samples from the lowest emergent reef (5–7 m) yield 230 Th dates that correspond to the 5a ( c. 83 ka) sea-level highstand and a low surface uplift rate of 0.2–0.3 m per 1000 years. At Rote island, samples from the lowest emergent reef ( c. 1–2 m) on both north and south sides of the island yield late Holocene ages and an average short-term uplift rate of c. 1–1.5 m per 1000 years. Similarity of ages from different samples on the north coast of Rote suggests possible coseismic emergence. Survey data from nine emergent reefs and marine notches up to 170 m in altitude on the south side of Rote indicate that uplift rates may have been c. 1–1.5 m per 1000 years for c. 120 000–130 000 years. Combined with previous studies, these results indicate that late Quaternary surface uplift rates vary an order of magnitude along the strike of the Banda orogen. Vertical displacement rates are greatest in young parts of the orogen where the shelf-slope break recently has been underthrust beneath the orogenic wedge, as at Rote, and in older parts of the orogen where retroarc thrust faulting occurs, as at Alor island.

Neotectonically controlled fluvial features, Wałbrzych Upland, Middle Sudeten Mts, southwestern Poland

The landscape of the Wałbrzych Upland, Sudeten Mts, southwestern Poland, has developed over a long time involving three main stages: (I) the Oligocene-Early Pliocene, (II) the Late Pliocene-Early Pleistocene, and (III) the Middle-Late Pleistocene. Stage III is neotectonically controlled and is discussed in detail. The entire Wałbrzych Upland was covered by a continuous ice cover during the early Saalian and at least in its marginal part during the Elsterian. The pre-early Saalian fluvial landscape shows no evidence of tectonic activity in contrast with that of post-early Saalian time. The post-early Saalian valleys have been formed during the intensive and short-term uplift of the mountain upland with simultaneous re-activation of fault zones. The main geomorphological effects of this uplift are: abandonment of valleys; formation of deep river valleys cut within bedrock; varying shapes of newly incised valleys; highly irregular longitudinal profiles of channels; varying numbers of terraces and their heights along the valleys; tilting of terraces; and formation of fault scarps at some fault lines. The main geological effects are: variable thicknesses of alluvial deposits caused by rotation of bedrock blocks; synsedimentary increases of thickness of alluvial deposits at some fault lines; and breaking of the continuity of some alluvial surfaces at the major fault lines. The uplift of the Wałbrzych Upland was controlled by glacio-isostatic rebound after the early Saalian glaciation supplemented by localised extensional tectonics. Total tectonic uplift was about 40–50 m.