Short-term Deformation Research Articles

Instantaneous and short-term deformation of early-age concrete under quasi-instantaneous loading

In order to assess accurately the stresses in early-age concrete, a realistic compliance function is required. The existing compliance functions, however, have been deduced from the data of hardened concrete and thus the rapid change during the hardening process in early-age concrete cannot be considered rationally. The purpose of this study is to propose a compliance function that can describe the highly viscoelastic behaviour in very early-age concrete. A test method to estimate the instantaneous compliance without creep effect was investigated first and tests were performed to determine the instantaneous and creep compliance. While both material parameters relating to instantaneous and ageing viscoelastic compliance were constants in the existing model based on the solidification theory, the test results showed that they had a strong age dependency at very early ages. A modified compliance function was proposed to provide more realistic prediction of the behaviour of early-age concrete.

Evaluating fracture patterns within a resurgent caldera: Campi Flegrei, Italy

Understanding deformation of active calderas allows their dynamics to be defined and their hazard mitigated. The Campi Flegrei resurgent caldera (Italy) is one of the most active and hazardous volcanoes in the world, characterized by post-collapse resurgence, eruptions, ground deformation, and seismicity. An original structural analysis provides an overview of the main fracture zones. NW-SE and NE-SW fractures (normal or transtensive faults and extensional fractures) predominate along the rim and within the caldera, suggesting a regional control, both during and after the collapses. While the NE-SW fractures are ubiquitous in the deposits of the last ∼37 ka, NW-SE fractures predominate in the last 4.5 ka, during resurgence. The most recently (<4.5 ka) strained area lies in the caldera center (Solfatara area), where the faults, with an overall ∼ENE-WSW extension direction, appear to be associated with the bending due to resurgence. Solfatara lies immediately to the east of the most uplifted part of the caldera (Pozzuoli area), where domes form and culminate both on the long-term (resurgence, accompanied by volcanic activity) and short-term deformation (1982–1984 bradyseism, accompanied by seismic and hydrothermal activity). Similar volcano-tectonic behavior characterizes the short- and long-term uplifts, and only the intensity of the tectonic and volcanic activity varies, being related to varying amounts of uplift. Seismicity and hydrothermal manifestations occur during the bradyseisms, with moderate uplift, while surface faulting and eruptions occur during resurgence, with higher uplift. The features observed at Campi Flegrei are found at other major calderas, suggesting consistent behavior of large magmatic systems.

The short-term effects of running on the deformation of knee articular cartilage and its relationship to biomechanical loads at the knee

To investigate the short-term effects of recreational running on the deformation of knee articular cartilage and to examine the relationship between changes in knee cartilage volume and biomechanical modulators of knee joint load. Twenty healthy volunteers participated in a two phase cross-sectional study. Session 1 involved Magnetic Resonance Imaging (MRI) of femoral and tibial cartilage volumes prior to and following a 30 min period of relaxed sitting, which was directly followed by a recreational run of 5000 steps. Subsequently, all participants undertook a laboratory study of their running gait to compare biomechanical derived measures of knee joint loading with changes in cartilage volume. Estimates of knee joint load were determined using a rigid-link segment, dynamic biomechanical model of the lower limbs and a simplified muscle model. Running resulted in significant deformation of the medial (5.3%, P<0.01) and lateral femoral cartilage (4.0%, P<0.05) and lateral aspect of the tibial cartilage (5.7%, P<0.01), with no significant differences between genders. Maximum compression stress was significantly correlated with percentage changes in lateral femoral cartilage volume (r(2)=0.456, P<0.05). No other biomechanical variables correlated with volume changes. Limited evidence was found linking biomechanical measures of knee joint loading and observed short-term deformation of knee articular cartilage volume following running. Further enhancement of knee muscle modelling and analysis of stress distribution across cartilage are needed if we are to fully understand the contribution of biomechanical factors to knee joint loading and the pathogenesis of knee osteoarthritis (OA).

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).

Taiwan mountain building: insights from 2-D thermomechanical modelling of a rheologically stratified lithosphere

SUMMARY The Taiwan orogen has long been regarded as a case example for studying mountain building in association with subduction processes. In this paper, we present a fully coupled thermomechanical modelling of the Taiwan collision based on a realistic viscous-elastic–plastic rheology. It satisfactorily reproduces available thermochronometric data, long-/short-term deformation patterns, heat flux and erosion/sedimentation distribution across the Taiwan orogeny. We found that a deep seated flux of Asian crustal material into the orogenic wedge should be invoked to counter-balance observed exhumation and erosion in the Central Range. However, in contrast with recent thermokinematic models of exhumation and deformation suggesting that underplating plays a significant role, we show that most constraints on exhumation and deformation can be more straightforwardly interpreted by the frontal accretion of the rheologically layered Asian crust. We finally infer that such a model is in better agreement with the basic expectation that the hot/young and buoyant Chinese continental margin should hardly be subducted beneath the cold/old and dense oceanic plate of the Philippines Sea.

Crustal rheology and depth distribution of earthquakes: Insights from the central and southern East African Rift System

The seismicity depth distribution in the central and southern East African Rift System (EARS) is investigated using available catalogs from local, regional and global networks. We select well-determined events and make a re-assessment of these catalogs, including a relocation of 40 events and, where necessary, a declustering. About 560 events are finally used for determining foci depth distribution within 6 areas of the EARS. Assuming that short-term deformation expressed by seismicity reflects the long-term mechanical properties of the lithosphere, we build yield strength envelopes from seismicity depth distribution. Using brittle and ductile laws, we predict the strength percentage spaced every 5 km (or sometimes 2 km) in the crust, for a given composition and a specific geotherm, and constrain it with the relative abundance of seismicity. Results of this modeling indicate significant local and regional variations of the thermo-mechanical properties of the lithosphere which are broadly consistent with previous studies based on independent modelings. In order to explain relatively deep earthquakes, a highly resistant, mafic lower crust is generally required. We also find evidence for changes in the strength magnitude and in the depth of the brittle–ductile transitions which are clearly correlated to tectonic provinces, characterized by contrasted thermal gradients and basement types. A clear N–S increase and deepening of the peak strength level is evidenced along the eastern branch of the EARS, following a consistent southward migration of rifting since ~ 8 Ma. We also detect the presence of a decoupling layer in the Kenya rift, which suggests persisting influences of the deep crustal structures (Archaean and Proterozoic) on the behavior of the extending crust. More generally, our results suggest that seismicity peaks and cut-off depths may provide good proxies for bracketing the brittle–ductile transitions within the continental crust.

Active deformation of Tainan tableland of southwestern Taiwan based on geodetic measurements and SAR interferometry

The D-InSAR technique is applied to detect the active fault-related folding structure of the Tainan tableland near the deformation front in SW Taiwan by using ERS SAR images during 1996–2000. The Tainan tableland is located in-between a blind fault in the west and the Houchiali fault in the east, thus the Tainan tableland is interpreted as a pop-up structure in a fold-thrust belt at active tectonic margin. Interferometric processing of six SAR images reveals the average slant range deformation (SRD) as ~ 12.5 mm/yr. The uplift rate is higher in eastern Tainan tableland than that in western Tainan tableland, and it increases from west edge of Tainan tableland and decreases across the Houchiali fault. The campaign-mode GPS data set from 1999 to 2003 indicate an average horizontal movement of 12 ± 4 mm/yr in the direction of N44°W for the Tainan tableland with respect to western coastline. Furthermore 5 precise leveling surveys across Tainan tableland over a period of 2 years show an uplift rate of ~ 14 mm/yr for the benchmarks on the tableland. Based on the 2-D analytical solution with the constraint of he inferred fault geometry, the slip rate along the inferred Tainan fault is ~ 16 mm/yr, ~ 10 mm/yr along the Houchiali fault, and ~ 25 mm/yr along the inferred Chungchou fault. Consequently we propose that active deformation of the Tainan tableland is likely resulted from the freely slipping of the Tainan fault and the Houchiali fault. The locking depth should be located on the deeper part of décollement, eastern of the Chungchou fault. In addition, the combination of D-InSAR, GPS data and the precise leveling data reveals that the short-term deformation rate is larger than long-term deformation rate, which implies that a destructive seismic event could occur in the eastern Tainan area.

Temporal differences in the influence of ischemic factors and deformation on the metabolism of engineered skeletal muscle

Prolonged periods of tissue compression may lead to the development of pressure ulcers, some of which may originate in, for example, skeletal muscle tissue and progress underneath intact skin, representing deep tissue injury. Their etiology is multifactorial and the interaction between individual causal factors and their relative importance remain unknown. The present study addressed the relative contributions of deformation and ischemic factors to altered metabolism and viability. Engineered muscle tissue was prepared as previously detailed (14) and subjected to a combination of factors including 0% oxygen, lactic acid concentrations resulting in pH from 5.3 to 7.4, 34% compression, and low glucose levels. Deformation had an immediate effect on tissue viability {[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay}, which increased with time. By contrast, hypoxia evoked metabolic responses (glucose and lactate levels) within 24 h, but viability was only reduced after 48 h. In addition, lactic acidification downregulated tissue metabolism up to an acid concentration ( approximately 23 mM) where metabolism was arrested and cell death enhanced. A similar tissue response was observed during glucose deprivation, which, at negligible concentration, resulted in both a cessation of metabolic activity and a reduction in cell viability. The combination of results suggests that in a short-term (<24 h) deformation, extreme acidification and glucose deprivation increased the level of cell death. By contrast, nonextreme acidification and hypoxia influenced tissue metabolism, but not the development of cell death. These data provide more insight into how compression-induced factors can lead to the onset of deep tissue injury.

Shear Induced Crystallization, a Relaxation Phenomenon in Polymer Melts: A Re‐Collection

Thread‐like nuclei for the crystallization of polymers which are formed at high deformation rates in a temperature range close to the equilibrium melting point appear to be practically stable at temperatures where spherulites are melting. However, the fact that the great majority of experiments on flow induced crystallization have been carried out at temperatures below the melting temperature of the spherulites leads to the conclusion that the precursors for elongated structures, as formed under those conditions, are practically stable from the moment of their creation. In other words: their relaxation times are much longer than any deformation time applied. As a consequence, deformation times as independent parameters lose their importance in these experiments. Long lasting deformations under low stresses can yield the same precursors as short term deformations under high loads. Apparently the only condition is that the applied specific work is the same.

Modelling a mine-by test at the Mont Terri rock laboratory, Switzerland

An instrumented mine-by test was conducted at the Mont Terri rock laboratory, Switzerland in 1997–1998 to assess issues associated with tunnel excavation in a middle Jurassic claystone known as the Opalinus Clay. Excavation-induced stresses resulted in unusually large deformations and the development of an excavation disturbed zone (EDZ) around the tunnel where the observed dominant mode of yielding consisted of extensional fracturing. From field and laboratory observations, it has been observed that Opalinus Clay exhibits responses that often are not represented adequately by linear-elastic or elasto-plastic models. In particular, strong non-linear elastic behaviour at low stresses was observed in laboratory tests. This behaviour has been captured by a phenomenological-based model, known as the stress-dependent modulus (SDM) model. The concepts of the SDM model have been extended to a piece-wise pore pressure formulation that captures the hydromechanical rockmass response. These models were implemented into a finite difference method numerical code and used to simulate the short-term deformations and pore pressure response of the ED-B mine-by test. These simply calibrated models provided a reasonable fit to the field data, particularly in regions of unloading where rockmass deformations were not dominated by dilation.

Current motion and short-term deformations in the Suez–Sinai area from GPS observations

We analyze data from four GPS campaigns carried out between 1997 and 2002 on a network of 11 sites in the Suez-Sinai, the area of collision between the African and the Arabian plates. This is the key area to understand how and in which way Sinai behaves like a sub-plate of the African plate and the role played between seismic and geodetic (long term) deformation release. Our analysis shows that, on average, the Suez-Sinai area motion (in terms of ITRF00 velocities) matches African plate motion (NNR-NUVEL-1A model). However, the baseline length variations show transient deformations in Sinai and across the Gulf of Suez, reaching up a maximum value of about 1.5 cm in five years. Since current geodynamical models do not predict significant tectonic deformation in this area, we worked under the hypothesis that a contribute may be due to post-seismic relaxation. Under this hypothesis, we compared the baselines length variations with the post-seismic relaxation field associated with five major local earthquakes occurred in the area, testing two different viscoelastic models. Our results show that the transient deformations are better modelled for viscosity values of 1018 Pa s in the lower crust and 1020 Pa s in the asthenosphere. However, since the modelled post-seismic effect results modest and a certain amount of the detected deformation is not accounted for, we think that an improved modelling should take into account the lateral heterogeneities of crust and upper mantle structures.

Present-day deformation across the southwest Japan arc: Oblique subduction of the Philippine Sea plate and lateral slip of the Nankai forearc

We estimate long-term/permanent crustal deformation in the Nankai forearc, southwest Japan, that accumulated over one earthquake deformation cycle in the Nankai subduction zone. A short-term deformation due to an oblique subduction of the Philippine Sea plate is modeled based on coseismic fault slips associated with interplate thrust earthquakes at the Nankai Trough, and subtracted from the interseismic crustal velocity field observed by GPS. The long-term/permanent deformation left in the data shows arc-parallel movement of the forearc at a rate of 5— 10 mm/yr. We interpret that the forearc movement, driven by the oblique plate convergence, is accommodated by steady aseismic slip on the deep portion of the fault plane of the Median Tectonic Line (MTL) on the rear boundary of the Nankai forearc. The rate of the forearc movement is consistent with the geological slip rate of the MTL in the late Quaternary, and also with that expected from deflection of the slip vector of the 1946 Nankai earthquake from the current plate convergence vector.

Short-term flexural creep deformation in synroc-C

The flexural creep behaviour of synroc-C in an inert atmosphere was studied at temperatures of 860°C, 900°C and 940°C under constant-load conditions in four-point bending. Applied stresses ranged from 100 to 160 MPa. Individual creep curves show primary and secondary creep but little or no tertiary creep stage. The log of the creep rate was found to increase linearly with log of the applied stress at each temperature over the entire stress range. Analysis of the creep data using the Norton power-law function revealed that the stress exponent decreased from 3.3 ± 0.6 for the 860°C and 900°C data to 2.0 ± 0.2 for the 940°C data, and an activation energy of 440 ± 40 kJ/mol was obtained over the entire temperature and stress range. Comparative analysis with the theta-projection equation was found to adequately represent the data yielding an activation energy of 464 kJ/mol while also showing a trend for the stress exponent to decrease with increasing temperature. Microstructural examination revealed extensive cavitation on the tensile surface of the creep specimens subjected to higher stresses at 900°C and 940°C. Dynamic high temperature X-ray diffraction analysis indicated little change in the phase assemblage apart from a slight reduction in the amount of the hollandite phase at higher temperatures which was attributed to a minor amount of oxidation. The possible creep damage mechanism was explored with reference to creep test results and microstructural modifications and the implications of the observations are discussed.

Late Cenozoic transpressional ductile deformation north of the Nazca–South America–Antarctica triple junction

The southern Andes plate boundary zone records a protracted history of bulk transpressional deformation during the Cenozoic, which has been causally related to either oblique subduction or ridge collision. However, few structural and chronological studies of regional deformation are available to support one hypothesis or the other. We address along- and across-strike variations in the nature and timing of plate boundary deformation to better understand the Cenozoic tectonics of the southern Andes. Two east–west structural transects were mapped at Puyuhuapi and Aysén, immediately north of the Nazca–South America–Antarctica triple junction. At Puyuhuapi (44°S), north–south striking, high-angle contractional and strike-slip ductile shear zones developed from plutons coexist with moderately dipping dextral-oblique shear zones in the wallrocks. In Aysén (45–46°), top to the southwest, oblique thrusting predominates to the west of the Cenozoic magmatic arc, whereas dextral strike-slip shear zones develop within it. New 40Ar– 39Ar data from mylonites and undeformed rocks from the two transects suggest that dextral strike-slip, oblique-slip and contractional deformation occurred at nearly the same time but within different structural domains along and across the orogen. Similar ages were obtained on both high strain pelitic schists with dextral strike-slip kinematics (4.4±0.3 Ma, laser on muscovite–biotite aggregates, Aysén transect, 45°S) and on mylonitic plutonic rocks with contractional deformation (3.8±0.2 to 4.2±0.2 Ma, fine-grained, recrystallized biotite, Puyuhuapi transect). Oblique-slip, dextral reverse kinematics of uncertain age is documented at the Canal Costa shear zone (45°S) and at the Queulat shear zone at 44°S. Published dates for the undeformed protholiths suggest both shear zones are likely Late Miocene or Pliocene, coeval with contractional and strike-slip shear zones farther north. Coeval strike-slip, oblique-slip and contractional deformation on ductile shear zones of the southern Andes suggest different degrees of along- and across-strike deformation partitioning of bulk transpressional deformation. The long-term dextral transpressional regime appears to be driven by oblique subduction. The short-term deformation is in turn controlled by ridge collision from 6 Ma to present day. This is indicated by most deformation ages and by a southward increase in the contractional component of deformation. Oblique-slip to contractional shear zones at both western and eastern margins of the Miocene belt of the Patagonian batholith define a large-scale pop-up structure by which deeper levels of the crust have been differentially exhumed since the Pliocene at a rate in excess of 1.7 mm/year.

A mechanical fluid-dynamical model for ground movements at Campi Flegrei caldera

We present here a consistent model, which explains the mechanisms of unrest phenomena at Campi Flegrei (Italy), both at short-term (years) and at secular scales. The model consists basically of two effects: the first one is related to the elastic response of the shallow crust to increasing pressure within a shallow magma chamber; the second involves the fluid-dynamics of shallow aquifers in response to increasing pressure and/or temperature at depth. The most important roles in the proposed model are played by the effect of lateral stress–strain discontinuities marking the inner caldera borders and by the response of the geothermal system to the increase of pressure and/or temperature coming from the magma chamber. The model takes into account most results of recent research, and it is able to explain in a unitary way most of geophysical observations recently collected at Campi Flegrei. Some new results, presented in this paper, explain the mechanism of generation of seismicity in terms of Coulomb stress changes, and the difference between secular and short-term deformations, in terms of the non linear effect of the bordering discontinuities. The coupled effects of magma chamber stresses with the dynamics of shallow fluids provide results for a semi-quantitative interpretation of observed ground deformation, seismicity and of their time evolution. The model has very important implications for the hazard assessment during unrest phenomena. It represents, for the part involving the fluid-dynamical response, the ideal continuation of the basic, fundamental models and intuitions of Oliveri del Castillo and coworkers (Oliveri del Castillo, A., Quagliariello, M.T., 1969. Sulla genesi del bradisimo flegro. Atti Associazione Geofisica Italiana, 18th Congress, Napoli, pp. 557–594; Casterano, L., Oliveri del Castillo, A., Quagliariello, M.T., 1976. Hydromdynamics and geodynamics in the Phlegraean Fields area of Italy. Nature, 264, 161–154).

Short and long term deformation patterns in the Aegean‐Anatolian Systems: Insights from space geodetic data (GPS)

Geodetic measurements (GPS) in the eastern Mediterranean suggest higher rates of motion, of about 10 mm/yr, in the Aegean ‐ Western Anatolian zone with respect to those in the central‐eastern Anatolia. In this work we explore the plausibility of the hypothesis that the observed kinematics may be significantly influenced by post ‐ seismic relaxation processes induced by the seismic activation of the North Anatolian Fault since 1939. The major implications of this hypothesis are tentatively quantified by a simplified model, constituted by an elastic lithosphere (100 km thick) coupled with a viscous asthenosphere (250 km thick with a viscosity of 1019 Pa s). The predicted perturbation of the displacement and stress fields is consistent with geodetic velocities and could also account for the major features of seismic activity in the period considered.

Protein folds: laws of form revisited.

efore Darwin, most biologists adheredto a platonic model of nature. Thisimplied that the biological realm con-sisted of a finite set of essentially immutablenatural forms that, like inorganic formssuch as atoms or crystals, are an intrinsicpart of the eternal order of the world. Justas, today, we account for the form of atomsand crystals by a set of physical laws or‘constructional rules’, so pre-darwinianbiologists sought to account for the originof biological forms in terms of a set ofgenerative physical laws often referred to asthe ‘laws of form’.For many biologists today, platonicbiology is an anachronism irretrievably laidto rest, and the idea that biological formsmight be intrinsic features of nature generat-ed by physical laws is treated with increduli-ty. However, recent advances in proteinchemistry suggest that at least one set ofbiological forms — the basic protein folds —is determined by physical laws similar tothose giving rise to crystals and atoms. Theygive every appearance of being invariantplatonic forms of precisely the type that thepre-darwinian biologists were seeking. Protein folds, the basic constructionalunits of proteins, each consist of a foldedchain of between 80 and 200 amino acids.Some proteins consist of a single fold, butmost are a combination of two or more.During the 1970s, as the three-dimensionalstructure of an increasing number of foldswas determined, it became apparent thatthe folds could be classified into a finitenumber of distinct structural families con-taining a number of closely related forms.The fact that protein folds could be classifiedin this manner provided the first line ofevidence that the folds might be naturalforms.Further evidence that the folds doindeed represent a finite set of naturalforms is provided by detailed structuralstudies carried out over the past two decadeswhich have revealed that the structure ofthe folds can be accounted for by whatamounts to a set of ‘constructional rules’governing the way that the various sec-ondary structural motifs, such as a-helicesand b-sheets, can be combined and packedinto compact three-dimensional structures.One is inevitably reminded of the atom-building rules governing the assembly ofsubatomic particles into the 92 atoms of theperiodic table. Consideration of these ‘constructionallaws’ suggests that the total number ofpermissible folds is bound to be restrictedto a very small number — about 4,000,according to one estimate. Confirmationthat this is probably so is provided by a differ-ent type of estimate, based on the discoveryrate of new folds. Using this method,Cyrus Chothia of Britain’s Medical ResearchCouncil estimated that the total number offolds utilized by living organisms may not bemore than 1,000. Subsequent estimates havegiven figures of between 500 and 1,000.Whatever the final figure, the fact thatthe total number of folds represents a tinystable fraction of all possible polypeptideconformations, determined by the laws ofphysics, reinforces the notion that the folds,like atoms, represent a finite set of built-innatural forms.The robustness of the folds offers anoth-er clue. The fact that the folds can retaintheir native conformations in the face ofmultiple different sorts of short-term defor-mations caused by the molecular turbulenceof the cell, and in the face of extensive, long-term evolutionary changes in their amino-acid sequences, is precisely what would beexpected if they are natural forms, specifiedby physical law. Again, the fact that thesame fold can be specified by many differ-ent, apparently unrelated amino-acidsequences, suggesting multiple separate dis-coveries during the course of evolution, isfurther evidence that the folds are intrinsicfeatures of the order of nature. Finally, thefact that in many cases the same fold isadapted to very different biochemical func-tions is precisely what would be expected ifprotein functions are secondary adaptationsof a set of primary, immutable, naturalforms. If forms as complex as the protein foldsare intrinsic features of nature, might someof the higher architecture of life also be deter-mined by physical law? The robustness ofcertain cytoplasmic forms, for example thespindle apparatus and the cell form of ciliateprotozoans such as

SHORT- AND LONG-TERM BEHAVIOUR OF AXIALLY LOADED COMPOSITE PROFILED WALLS.

Keywords NEW SOUTH WALES UNIVERSITY, STRATHCLYDE UNIVERSITY, WOLLONGONG UNIVERSITY WALLS, COMPOSITE, PROFILED, AXIALLY, LOADED, AXIAL, LOADS, BEHAVIOUR, SHORT TERM, LONG TERM, WALLING, FORMWORK, SHEETING, STEEL, INFILLED, CONCRETE, CORES, SUSTAINED, TESTS, DEFORMATION, EFFECTIVE, MODULUS, METHODS, DESIGN, INFILL, RESPONSES, TIME DEPENDENT, COLUMNS, REINFORCED, SLENDERNESS, EFFECT, ECCENTRICITY, STRUCTURES... Show All

Relation of ongoing deformation rates to the subduction zone process in southern Alaska

The rate and orientation of ongoing strain associated with subduction of the Pacific plate and the accretion of the Yakutat terrane to southern Alaska has been estimated at 13 sites from Global Positioning System measurements made in June 1993 and 1995. Along the Gulf of Alaska coast near Cape Yakataga, the average rate of deformation, relative to Fairbanks, was ≈38 mm/yr at N32°W. Further inland, above the region where the dip of the downgoing Pacific plate changes from about 10° to &gt;30°, the deformation rate was ≈12mm/yr at N26°W. In the Sourdough/Paxson area, the deformation rate drops to 2–5 mm/yr and suggests a low short‐term deformation rate across the Denali fault. Elastic straining of the overriding plate due to back‐slip on a main thrust zone with an average dip of about 10° can account for the overall rate and distribution of short‐term compressional strain across south central Alaska. Above the transitional region between unstable and stable sliding we suggest that strain associated with ≈15 mm/yr of right‐lateral strike‐slip occurs also. If the strain accumulated since the two 1899 earthquakes (both MW=8.1) from the offshore Pamplona fault zone to south of the Border Ranges fault (down‐dip width ≈100 km) was seismically released on a single fault it would correspond to a M=8.1 earthquake.

The restless, resurgent Campi Flegrei nested caldera (Italy): constraints on its evolution and configuration

We have collected new stratigraphic data in the Campi Flegrei caldera through surface geological mapping and study of cores drilled to various depths. We integrate these data with geological, geochronological and geophysical constraints available in the literature to reconstruct the volcanic and deformational history of the caldera. The caldera is a resurgent, nested structure resulting from two main collapses related to the Campanian Ignimbrite (37 ka) and the Neapolitan Yellow Tuff (12 ka) eruptions. While the structure is affected by a broad subsidence, ongoing local resurgence and unrest occur inside the younger, nested caldera structure. Although most of the caldera floor consists of multiple structural blocks due to long-term deformations, magmas were able to erupt only in one sector of the resurgent part. The caldera has shown signs of unrest during the past 25 years, with short-term deformations that have generated a net uplift of 3.5 m. The short-term deformations are related to the Neapolitan Yellow Tuff caldera resurgence and interpreted as the net result of brittle and ductile components. The long-term deformations likely represent the sum of the permanent, brittle component of each short-term deformational event.