Slow Deformation Research Articles

The Corinth Rift Laboratory or an in situ Investigation on Interactions between Fluids and Active Faults

Earthquakes result from the sudden acceleration of a preliminary long-term slow deformation process. The objective of the Corinth Rift Laboratory (CRL) is to investigate in situ this quasistatic deformation process and mechanisms leading to a sudden catastrophic acceleration. Of particular interest is the characterization of the structure of the deforming zones and of the progressive localization of deformation. Special attention is given to the role of fluids but also on the influence of faults on regional fluid flow doi:10.2204/iodp.sd.s01.20.2007

Borehole Seismic and Strain Observatories in Seafloor Settings-Experiences after ODP Legs 186, 191, 195 and Future Plans

In the period of Ocean Drilling Program Legs 186, 191, and 195, we successfully deployed a set of seismo-geodetic195, we successfully deployed a set of seismo-geodetic sensors in deep seafloor boreholes in four locations (JT1, JT2, WP1, and WP2). The JT1 and JT2 borehole observa-tories are located in the landward slope of the Japan Trench,the Japan Trench,Japan Trench, where we expect seismic activity beneath the observatories. These borehole observatories gave us good platforms to look to look at the dynamic process on the plate boundary in thethe dynamic process on the plate boundary in thedynamic process on the plate boundary in the seafloor.The WP1 and WP2 are considered a part of a globala globalglobal seismic network of observatories currently distributed mostly on land and ocean islands. For permanent seismic observation in the seafloor setting, installation of broadband seismic sensors in the seafloor borehole was recommended, and candidate locations were chosen (Suyehiro et al., 2006).., 2006)., 2006). The WP1 and WP2 sites are one of the first borehole obser-vatories to implement such a permanent seafloor obser-permanent seafloor obser-seafloor obser-vatory.We called these seafloor borehole observatories �NEREID� (�Neath Seafloor Equipment for Recording Earth�s Internal Deformation). The NEREID observatories are characterized by several key features that are thought tothat are thought to to acquire optimum performance from the borehole sensors. optimum performance from the borehole sensors.Firstly, sensors are cemented at the bottom of the borehole. This is very important because long-period seismic and tilt/strain sensors are sensitive to fluid flow around them, so it isthem, so it is necessarytocouplethemtothegroundverywell.Cementing to couplethemtothegroundverywell.Cementing themtothegroundverywell.Cementing to thegroundverywell.Cementingthe groundverywell.Cementingground very well. Cementing sensors at the bottom of the borehole was able to fix sensors rigidly in place, and eliminated fluid around the sensors.in place, and eliminated fluid around the sensors. place, and eliminated fluid around the sensors.place, and eliminated fluid around the sensors., and eliminated fluid around the sensors.eliminated fluid around the sensors. fluid around the sensors.the sensors.sensors. Cementing is necessary especially for strainmeters, becauses, because, because the strain of the ground should be transmitted to the sensing cylinder of the strainmeter by some means. On land, it hasmeans. On land, it has. On land, it has been widely practiced for that purpose.at purpose. purpose.Secondly, separate cables connect borehole sensors uphole for power feeding and seafloor data recording. This is to deal with possible failure of the sensors, cables, and and connectors in the borehole during and after the installation in the borehole. It worked very well, and we were able to and we were able to replace failed sensors after the installation without affecting failed sensors after the installation without affecting operation of other sensors.Sensors deployed in these observatories were configured to target specifications needs in each location of the observa-tories. For JT1 and JT2 observatories, a tiltmeter (AG510), a a strainmeter (dilatometer and three component types), and and broadband seismometers (CMG1T, PMD) are chosen to mainly target the earthquakes and slow deformation processes below the observatory. The WP1 and WP2 obser-The WP1 and WP2 obser- WP1 and WP2 obser-vatories are important for monitoring global seismic activity,for monitoring global seismic activity, monitoring global seismic activity,ing global seismic activity, global seismic activity, so two identical broadband seismometers (Guralp CMG1T) were installed for redundancy.Data from borehole sensors are recorded in the seafloor. Electric power necessary for these sensors is provided by ais provided by a provided by a stack of seawater batteries or lithium batteries stored in aithium batteries stored in a titanium sphere. Data areitanium sphere. Data are recovered by ROV by retrievingtrievinging the data recorder because the amount of the recorded seismic data was as large as 10GB per year.We conducted visits to each observatory for data recovery and maintenance once a year or more. From most of the observatories,

Fragility and mechanosensing in a thermalized cytoskeleton model with forced protein unfolding

We describe a model of cytoskeletal mechanics based on the force-induced conformational change of protein cross-links in a stressed polymer network. Slow deformation of simulated networks containing cross-links that undergo repeated, serial domain unfolding leads to an unusual state-with many cross-links accumulating near the critical force for further unfolding. This state is robust to thermalization and does not occur in similar protein unbinding based simulations. Moreover, we note that the unusual configuration of near-critical protein cross-links in the fragile state provides a physical mechanism for the chemical transduction of cell-level mechanical strain and extra-cellular matrix stiffness.

The Corinth Rift Laboratory or an <i>in situ</i> Investigation on Interactions between Fluids and Active Faults

Earthquakes result from the sudden acceleration of a preliminary long-term slow deformation process. The objective of the Corinth Rift Laboratory (CRL) is to investigate <i>in situ</i> this quasistatic deformation process and mechanisms leading to a sudden catastrophic acceleration. Of particular interest is the characterization of the structure of the deforming zones and of the progressive localization of deformation. Special attention is given to the role of fluids but also on the influence of faults on regional fluid flow <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.s01.20.2007" target="_blank">10.2204/iodp.sd.s01.20.2007</a>

Structural Analysis on Anisotropic Deformation Properties of Highly Porous Aluminum Material

The cell-structure of highly porous aluminum material prepared by foaming of aluminum alloy melt with titanium hydride was investigated nondestructively with fine-focus X-ray 3D-CT at several interrupt steps during slow compressive deformation. The foamed highly porous aluminum has anisotropic shape of each cell inevitably because of gravity force during solidification of foamed material and mechanical properties especially the dependence on the deformation direction of highly porous aluminum is analyzed well from the size and shape of each void composing the porous material. The statistic anisotropic distribution of these form factors such as three axial lengths and directions at the time of ellipsoidal approximation of each cell was found to be less important to improve the mechanical properties of this type of material.

Using GB-SAR technique to monitor slow moving landslide

A Ground-Based SAR (GB-SAR) interferometer was employed to measure the surface displacements of a landslide occurring in the Carnian Alps, north-eastern Italy, which has affected a national road and seriously damaged a road tunnel still under construction. Moreover, since the landslide is located on the left bank of the Tagliamento River Valley, it is feared that this mass movement might dam the river, creating a basin that would increase natural hazard for the valley inhabitants. The data collected from December 2002 to July 2005 by a conventional monitoring system, consisting of a GPS network and boreholes equipped with inclinometric tubes, showed that the landslide was moving at a quasi-constant rate of about 3 cm per year. Due to the slow deformation rate of the landslide, a recently developed GB-SAR technique based on the analysis of a restricted ensemble of coherent points was used. Two surveys, each lasting two days, were planned in December 2004 and July 2005, in order to map and measure the surface displacements that occurred over time. The results from the radar were compared with the ones derived from the GPS monitoring network. An agreement was achieved among the data collected, showing the capability of the GB-SAR technique to measure displacements even within a time span of several months between the surveys.

Kinematic and geometric analysis of fault-related folds in a rift setting: The Dannemarie basin, Upper Rhine Graben, France

The Upper Rhine Graben (URG) developed in the Alpine foreland from mid-Eocene to Pliocene as part of the West European rift system. The Dannemarie basin occupies the SW termination of the URG and is bordered by the Vosges fault zone (west) and the Illfurth fault zone (east). We constructed a 3D model of faults and principal pre- and syn-rift stratigraphic surfaces, using all available subsurface and surface geological and geophysical data. The model shows: (1) syn-rift strata thinning across kilometre-scale, fault-parallel, monoclinal flexures associated with basin margin faults; and (2) major basin-margin faults terminating laterally into major flexures. Sequential cross-section restorations show that these flexures accommodated deposition of over 1300 m of syn-rift strata (Salt Series which is 42–63% of the basin fill). These folds are interpreted as syn-rift fault-propagation folds that developed above normal faults. Their geometry is replicated in a trishear numerical model using reasonable parameter values. Fold development was controlled principally by: (1) reactivation of favourably oriented basement faults; (2) the presence of a thick viscous layer (principally Triassic evaporites) allowing decoupling between crystalline basement and competent Jurassic cover; and (3) a relatively slow deformation rate.

Real-time enveloping with rotational regression

Enveloping, or the mapping of skeletal controls to the deformations of a surface, is key to driving realistic animated characters. Despite its widespread use, enveloping still relies on slow or inaccurate deformation methods. We propose a method that is both fast, accurate and example-based. Our technique introduces a rotational regression model that captures common skinning deformations such as muscle bulging, twisting, and challenging areas such as the shoulders. Our improved treatment of rotational quantities is made practical by model reduction that ensures real-time solution of least-squares problems, independent of the mesh size. Our method is significantly more accurate than linear blend skinning and almost as fast, suggesting its use as a replacement for linear blend skinning when examples are available.

Real-time enveloping with rotational regression

Enveloping, or the mapping of skeletal controls to the deformations of a surface, is key to driving realistic animated characters. Despite its widespread use, enveloping still relies on slow or inaccurate deformation methods. We propose a method that is both fast, accurate and example-based. Our technique introduces a rotational regression model that captures common skinning deformations such as muscle bulging, twisting, and challenging areas such as the shoulders. Our improved treatment of rotational quantities is made practical by model reduction that ensures real-time solution of least-squares problems, independent of the mesh size. Our method is significantly more accurate than linear blend skinning and almost as fast, suggesting its use as a replacement for linear blend skinning when examples are available.

Tectonically controlled, time-predictable basaltic volcanism from a lithospheric mantle source (central Basin and Range Province, USA)

Understanding the evolution of basaltic volcanic fields is critical to our concepts of basaltic magmatism and to volcanic risk assessment. We summarize physical volcanological, geochemical, and time–volume characteristics of the Plio-Pleistocene part of the Southwestern Nevada Volcanic Field (SNVF) as an example of an extremely low volume-flux end member of basaltic fields. The SNVF has produced 17 volcanoes of dominantly trachybasaltic composition over the past 5 Myr with a total volume of slightly less than 6 km 3. Eruptive fissure lengths, volumes, and inferred lava effusion rates decreased between Pliocene- and Pleistocene-age volcanoes. Major element data suggest that most of the magmas underwent similar degrees of fractionation during ascent, and trace element compositions indicate a decrease in the degree of partial melting of the lithospheric mantle source since ∼ 3 Ma. Isotopic data support an interpretation wherein magmas ascended relatively quickly from their source regions with little if any interaction with crustal rocks. Relationships between age and cumulative erupted volume indicate that the repose interval between eruptive episodes is determined by the volumes of prior episodes and, since ∼ 3 Ma, an average eruption rate of ∼ 0.5 km 3/Myr, i.e., the field is time-predictable. All of these features support a model wherein magmatism is a passive result of regional tectonic strain. Partial melt resides in pockets of lithospheric mantle that are relatively enriched in hydrous minerals; slow deformation focuses melt, occasionally resulting in sufficiently high melt pressure to drive dikes upward and feed eruptive episodes. Larger source volumes result in larger eruptive volumes and wider dikes that relieve relatively more strain in the crust than smaller volume events, and therefore are followed by longer repose intervals required for recovery of crustal stresses. We suggest that time-predictability may be a fundamental property of tectonically controlled basaltic fields, where melt accumulation and ascent are controlled by tectonic strain rate. This behavior contrasts with magmatically controlled fields where magma flux is sufficiently high to overwhelm local tectonic strain, eruptions are primarily caused by magmatic processes that build pressure in reservoirs, and the systems are more likely to be volume-predictable.

Behavior near critical for a conducting drop in an electric field

The time scales for the behavior of a conducting drop undergoing slow deformation in a uniform electric field are examined. Below the critical electric field strength, equilibrium shapes are possible and approached exponentially. At the critical value, the convergence behaves as t−1. Above (but still near) critical, there is a period of slow elongation near the critical equilibrium shape. The time scale, τ, for this period of slow growth behaves like τ∼(β−βc)−1∕2, where β is the electric field strength and βc is the critical electric field strength. In addition, the dependence of the time scales on the viscosities of the drop and of the surrounding fluid is examined. The theoretical results compare favorably with boundary integral numerical computations. Asymptotically, the time scales depend linearly on the viscosity ratio for both large and small values. These linear relations remain accurate well outside the expected regions of validity, and the entire range of viscosity ratios can be reasonably approximated by a piecewise linear combination of the two. Thus, an equation is obtained that determines the duration of the period of slow deformation and predicts the time to breakup.

Breakup behavior of a conducting drop suspended in a viscous fluid subject to an electric field

The slow axisymmetric deformation of a conducting drop surrounded by a viscous insulating fluid subject to a uniform electric field is considered. Numerical computations, based on a boundary integral formulation, are used to follow the behavior of relatively inviscid and viscous drops right up to breakup. The type of breakup seen depends on the ratio of the viscosity of the drop to that of the surrounding fluid, and on the electric field strength. The different types of breakup possible are small droplets being emitted from the ends of the drop with a charge greater than the Rayleigh limit, the formation of what appear to be pointed ends with the subsequent ejection of thin jet-like structures, or the formation of thin jet-like structures without the pointed ends. The different types of breakup are examined and the different regions of the parameter space where each occurs is determined. Also, by considering different stress balances, local equilibrium solutions that allow for a conical drop end are derived. Several sets of solutions, corresponding to different stress balances, are found. However, none of the conical end solutions appear to be compatible with the pointed ends seen in the numerical results.

Ar‐Ar dating of late Cenozoic basaltic volcanism in northern Syria: Implications for the history of incision by the River Euphrates and uplift of the northern Arabian Platform

Ar‐Ar dating of basalt flows capping terrace deposits of the River Euphrates in northern Syria has provided a new quantitative chronology for the late Cenozoic evolution of this important river system and for the associated history of surface uplift of the northern Arabian Platform through which it flows, a region of relatively strong crust that has experienced only slow deformation. Notably, fluvial deposits ∼65 m above the Euphrates are overlain by basalt dated to 2717 ± 20 ka, those ∼45 m above the river are overlain by basalt dated to 2116 ± 39 ka, and those 8–9 m above the river are overlain by basalt dated to 402 ± 11 ka. These new dates require the previous dating scheme, based on Paleolithic archaeology, to be revised; the Euphrates terrace deposits and the associated incised valley are much older than was previously thought. Rates of incision by the Euphrates, providing a proxy for regional surface uplift that is inferred to be the isostatic response to regional erosion, have varied significantly over the past ∼3 Ma, with indications that between ∼1.2 and ∼0.9 Ma, there was regional subsidence, which gave rise to fluvial aggradation. This unusual pattern, involving reversals in the sense of vertical crustal motions, is interpreted to be a consequence of a relatively cold and thin mobile lower crustal layer, no more than ∼5 km thick, evidently due to the presence of a much thicker underlying layer of mafic underplating at the base of the crust. This study thus indicates previously unsuspected complexity in the isostatic response to regional erosion in an area of high crustal stability.

Ectopic recurrence of dysplastic gangliocytoma of the cerebellum (Lhermitte–Duclos disease): a case report

Lhermitte-Duclos disease is a rare clinical entity characterized by slow deformation of the cerebellar lesion. A 53-year-old woman presented with Lherimitte-Duclos disease manifesting as ataxic gait, occipital headache, and loss of consciousness. Magnetic resonance imaging demonstrated striated and laminar pattern lesions in the right cerebellar hemisphere and vermis. She underwent subtotal removal of the vermis compressing the brainstem, but the cerebellar hemisphere appeared normal and was preserved. Histological findings were consistent with Lherimitte-Duclos disease. Two years later, magnetic resonance imaging revealed enlargement of the right hemispheric lesion. Intraoperative appearance of the hemisphere demonstrated marked enlargement of the folia. Subtotal removal was performed. Histological examination showed no malignant findings. Lhermitte-Duclos disease may recur, and should be carefully followed up as a low-grade neoplasm, not as a hamartomatous disorder.

Behaviour of a conducting drop in a highly viscous fluid subject to an electric field

We consider the slow deformation of a relatively inviscid conducting drop surrounded by a viscous insulating fluid subject to a uniform electric field. The general behaviour is to deform and elongate in the direction of the field. Detailed numerical computations, based on a boundary integral formulation, are presented. For fields below a critical value, we obtain the evolution of the drop to an equilibrium shape; above the critical value, we calculate the drop evolution up to breakup. At breakup it appears that smaller droplets are emitted from the ends of the drop with a charge greater than the Rayleigh limit. As the electric field strength is increased the ejected droplet size decreases. A further increase in field strength results in the mode of breakup changing to a thin jet-like structure being ejected from the end. The shape of all drops is very close to spheroidal up to aspect ratios of about 5. Also, for fields just above the critical value there is a period of slow deformation which increases in duration as the critical field strength is approached from above. Slender-body theory is also used to model the drop behaviour. A similarity solution for the slender drop is obtained and a finite-time singularity is observed. In addition, the general solution for the slender-body equations is presented and the solution behaviour is examined. The slender-body results agree only qualitatively with the full numerical computations. Finally, a spheroidal model is briefly presented and compared with the other models.

Two Radar Interferometric Approaches to Monitor Slow and Fast Land Deformation

Differential interferometric synthetic aperture radar (DInSAR) is a deformation measurement technique that couples two interesting characteristics. First, being based on remotely sensed data it offers operational advantages, like low cost data acquisition, wide area coverage, and temporally regular acquisitions. Second, it can be based on rigorous modeling and estimation procedures, which allows some of the most advanced techniques to derive measurements with high quality standards, comparable with those of some geodetic methods. The scope of this paper is to describe two complementary approaches to measure slow (from a few millimeters up to some centimeters per year) and fast land deformation (up to few meters per year). Emphasis is given to the description of the former approach, which requires multiple SAR images of the same phenomenon and an advanced analysis procedure. The effectiveness of both approaches is illustrated through two applications on mining areas of small spatial extent located in Spain. In one case the DInSAR capability to fully detect shape and magnitude of an unknown fast deformation phenomenon is highlighted, whereas in the second one a detailed deformation map is derived over an urban area, where deformations up to 30mm∕year occur.

Evolutionary nature of destruction of solids and media

The mechanical response of solids and media to loading is considered as their evolution under external applied forces, during which self-organization takes place in the loaded materials and media. The destruction of indiscriminately all solids and media is shown to evolve by a common evolution scenario giving rise to the formation of a hierarchy of block structures in them. The destruction process is statistically strictly ordered. It starts from the lattice scale and proceeds up to the size of tectonic plates in geomedia. The criterion of universal fractal divisibility of solids and media is found and justified experimentally and theoretically. It is demonstrated that the Ltders fronts, fracture waves and slow deformation fronts in geomedia comprise a special class of movements, so-called “slow movements”, in nonlinear media and materials. This class of movements represents the collective processes in a loaded nonlinear medium and results from self-organization in this medium.

Morphometric analysis and genetic implications of pro-deltaic sea-floor undulations in the northern Alboran Sea margin, western Mediterranean Basin

Several fields of seafloor undulations from pro-deltaic wedges in the northern margin of Alboran Sea, Western Mediterranean Basin, are described in this paper. A series of elongated, subparallel bathymetric undulations are distinguished in the foreset-to-bottomsets regions of the Holocene pro-deltaic wedges related with the Guadalfeo and Verde–Seco rivers. Multibeam data, surficial sediment samples and high-resolution seismic profiles have been used in this study, and integrated in a Geographical Information System. Quantitative measurement of key morphometric parameters (wave-length, height, asymmetry, length and wave-form index) was performed on multibeam data and seismic profiles using the ArcGis software. Wave-form index and depth data were analysed statistically, and a cluster analysis was carried out in each area. According to these results, we infer that sea-floor undulations in the study areas are best explained by the influence of strong sediment flows normal to bathymetric contours, probably coupled with the effect of subsequent slow sediment deformation processes such as sediment creeps. The influence of bottom-current activity is considered less likely, as the position of river mouths and the very high slope gradients seems to be the key factors which control the development of these sea-floor undulations. The Alboran Sea sea-floor undulations are compared with those of other fields in shallow-water environments and the different processes of formation evaluated.

3D numerical model of snow deformation without failure and its application to cold room mechanical tests

Abstract A three-dimensional model developed for the slow deformation, without macroscopic failure, of a stratified snow cover has been used to simulate laboratory mechanical tests performed on sieved snow. The model is based on a non-linear visco-elastic constitutive law for snow whose parameters depend on the snow temperature and density. Snow densification is derived from the bulk viscous strain. The model has been implemented in the Flac3D finite-difference code. The experimental device is a convergent channel in which snow is forced at a constant velocity in the range 1–100 μm s − 1 . Although snow is compressed under plane strain conditions, the channel geometry allows obtaining a multi-axial stress-state. Since the testing conditions involve ranges of variation of both the snow density and the strain-rate wider than those encountered for a natural snowpack, the constitutive relations of the model had to be modified. In this paper we present the constitutive model for snow, some details about its implementation into the Flac3D code, and its application to the numerical simulation of the mechanical tests. The comparison of the model and experimental results shows a relatively good agreement, although snow microstructure is accounted for only through its density. However, the treatment of the non-linearity of the viscosity must be improved. This 3D numerical model can be regarded as an interesting tool for assessing a constitutive law for snow on the basis of cold-room experiments, as well as for studying natural snow covers.

Contemporary kinematics of the Upper Rhine Graben: A 3D finite element approach

The Upper Rhine Graben (URG), a Cenozoic intra-plate rift situated in the Alpine foreland, is presently characterised by relative slow tectonic deformation and low to medium seismicity. Concurrently, it is a region with a significant amount of ongoing subsidence in two recent depocentres (0.1 to 0.2 mm/a geological, 1 mm/a geodetical rate). In this paper, the recent kinematic behaviour of the URG is simulated using a 3D finite element model, containing three lithospheric layers (upper mantle, lower crust and upper crust) with different rheological properties. First order fault structures (e.g. border faults) are implemented as frictional contact surfaces within the upper crustal layer. The stresses generated by applying lateral displacements over a time period of 10 ka are insufficient to obtain a match between predicted and observed stress magnitudes. Therefore, a technique of “combined pre-stressing” has been developed to avoid unrealistic deformation and unrealistic stress magnitudes within the model. The stress magnitudes and stress directions predicted are calibrated against in-situ stress measurements and stress indicator data. For benchmarking of the modelling results, the vertical surface displacements predicted are compared to surface uplift derived from geological and geomorphological data. Furthermore, predicted fault slip rates are compared to available geological and geodetical data. Parameters derived from the calculated stress tensor, such as fracture potential and the regime stress ratio are also analysed in order to describe the possible kinematic behaviour of the URG. The modelling results suggest that the URG is currently being reactivated as a sinistral strike–slip system with the central segment of the URG forming a restraining bend and the two recent depocentres situated in releasing bend settings. The modelling results suggest that both sinistral shearing and mantle uplift are active mechanisms driving the recent kinematics of the URG and that the recent subsidence within the two depocentres is re-enforced by ongoing mantle uplift additionally.