Non-elastic Processes Research Articles

Using active source seismology to image the Palos Verdes Fault damage zone as a function of distance, depth, and geology

Fault damage zones provide a window into the non-elastic processes of an earthquake. Geological and seismic tomography methods have been unable to measure damage zones at depth with sufficient spatial sampling to evaluate the relative influence of depth, distance, and lithological variations. Here, we identify and analyze the damage zone of the Palos Verdes Fault offshore southern California using two 3D seismic reflection datasets. We apply a novel algorithm to identify discontinuities attributed to faults and fractures in large seismic volumes and examine the spatial distribution of fault damage in sedimentary rock surrounding the Palos Verdes Fault. Our results show that damage through fracturing is most concentrated around mapped faults and decays exponentially to a distance of ∼2 km, where fracturing reaches a clearly defined and relatively undamaged background for all examined depths and lithologies (450 m to 2.2 km). This decrease in fracturing with distance from the central fault strand exhibits similar functional form to outcrop studies. However, here we extend analysis to distances seldom accessible (∼10 km lateral distance). Separating the data by geologic units we find that the damage decay and background level differs for each unit, with the older and deeper units having higher levels of background fracturing and shallower exponential decays of fracturing with distance from the fault. Surprisingly, these differences in damage decay and background level trade-off result in a consistent damage zone width regardless of lithology or depth. We find that the damage zone has similar decay trends on both sides of the fault. When examining the damage zone at shorter (4 km vs 17 km) along strike distances, the damage zone has a more complex decay trend and at least two strands are resolvable.

Electromagnetic dipole moments and time reversal violating interactions for high energy charged baryons in bent crystals at LHC

Spin precession of channelled particles in bent crystals at the LHC gives unique possibility for measurements of constants determining T-odd, P-odd (CP) violating interactions and P-odd, T-even interactions of charm, beauty and strange charged baryons with electrons and nucleus (nucleons), similarly to the possibility of measuring their electric and magnetic moments. For a particle moving in a bent crystal new effects caused by non-elastic processes arise. In addition to the spin rotation around the effective magnetic field {varvec{B}} direction (the bending axis direction), due to electromagnetic interactions and leading to changes in spin direction in the plane orthogonal to {varvec{B}} , the spin acquires projection along the {varvec{B}} direction. Moreover, when spin rotates around the direction of the electric field {varvec{E}} or the particle momentum {varvec{k}}, a spin component along {varvec{E}} or {varvec{k}}, respectively, is induced.

Field-data analysis and hydromechanical modeling of CO2 storage at In Salah, Algeria

The permeability of a reservoir is a key parameter to determine the pressure response due to production and injection and its concomitant geomechanical response. A fractured reservoir affects the fluid flow by increased permeability, which can be further enhanced by elevated pore pressure. The CO2 storage project at Krechba, In Salah, Algeria, was concluded in 2011, but it provided unique and valuable geomechanical data and still remains an important site to study geomechanical processes. It has previously been shown that fracture injection, i.e. injection of CO2 above fracture pressure, is an important transport mechanism. Here we analyze the pressure response from the many temporary shut-ins during injection to justify a proposed correlation between pressure and permeability (power-law expressions) in the reservoir. The correlation is validated using field-data: pressure response in the reservoir and surface heave from InSAR data. Although the shut-in curves from pressure data at In Salah cannot provide the permeability directly, due to its complex injection history (rate and duration), they can show how the permeability varies with pore pressure and provide evidence of the fracture pressure. A recently developed efficient up-scaled numerical model of fully coupled poroelasticity and two-phase flow that effectively captures the main processes in the high-aspect ratio reservoir of In Salah, allows for the current analysis. This model illustrates that a static geomodel cannot explain the observed pressure response and surface heave, and is subsequently used to fit the parameters in the proposed correlation for the pressure-dependent reservoir permeability. Although there are three injection wells at In Salah, KB501, KB502 and KB503, this study is supported primarily by the data from KB501 and KB503. The correlation for the reservoir permeability provides a good match with both the pressure response in the reservoir and the surface heave above the injection wells, thus illustrating that irreversible and non-elastic processes can be approximated with non-linear material properties. For KB502 the geological setting is much more complicated and the response and behavior around the injection well is strongly depending on the behavior of a large and intersecting fracture zone and it still remains crucial to characterize properties of fault/fracture zones, such as thickness, transmissivity, stiffness and porosity.

On volume-source representations based on the representation theorem

We discuss different ways to characterize a moment tensor associated with an actual volume change of ΔV C , which has been represented in terms of either the stress glut or the corresponding stress-free volume change ΔV T . Eshelby’s virtual operation provides a conceptual model relating ΔV C to ΔV T and the stress glut, where non-elastic processes such as phase transitions allow ΔV T to be introduced and subsequent elastic deformation of −ΔV T is assumed to produce the stress glut. While it is true that ΔV T correctly represents the moment tensor of an actual volume source with volume change ΔV C , an explanation as to why such an operation relating ΔV C to ΔV T exists has not previously been given. This study presents a comprehensive explanation of the relationship between ΔV C and ΔV T based on the representation theorem. The displacement field is represented using Green’s function, which consists of two integrals over the source surface: one for displacement and the other for traction. Both integrals are necessary for representing volumetric sources, whereas the representation of seismic faults includes only the first term, as the second integral over the two adjacent fault surfaces, across which the traction balances, always vanishes. Therefore, in a seismological framework, the contribution from the second term should be included as an additional surface displacement. We show that the seismic moment tensor of a volume source is directly obtained from the actual state of the displacement and stress at the source without considering any virtual non-elastic operations. A purely mathematical procedure based on the representation theorem enables us to specify the additional imaginary displacement necessary for representing a volume source only by the displacement term, which links ΔV C to ΔV T . It also specifies the additional imaginary stress necessary for representing a moment tensor solely by the traction term, which gives the “stress glut.” The imaginary displacement-stress approach clarifies the mathematical background to the classical theory.

Non-Elastic Processes in Atom Rydberg-Atom Collisions: Review of State of Art and Problems

In our previous research, it has been demonstrated that such inelastic processes in atom Rydberg-atom collisions, as chemi-ionization and (n-n') mixing, should be considered together. Here we will review the present state of the art and the actual problems will be discussed. In this context, we will consider the influence of the (n-n')-mixing during a symmetric atom Rydberg-atom collision processes on the intensity of chemi-ionization process. It will be taken into account H(1s) + H*(n) collisional systems, where the principal quantum number n $>>$ 1. It will be demonstrated that the inclusion of (n-n') mixing in the calculation, influences significantly on the values of chemi-ionization rate coefficients, particularly in the lower part of the block of the Rydberg states. Different possible channels of the (n-n')-mixing influence on chemi-ionization rate coefficients will be demonstrated. The possibility of interpretation of the (n-n')-mixing influence will be considered on the basis of two existing methods for describing of the inelastic processes in symmetrical atom Rydberg-atom collisions.

Rate coefficients for electron impact excitation of N2

Rate coefficients for electron impact excitation of the nitrogen molecule have been determined. Calculations have been performed for all relevant non-elastic processes: rotational excitation, vibrational excitation, electronic excitation into singlet and triplet states and particularly for dissociation and ionization. The rate coefficients have been determined for both equilibrium and non-equilibrium conditions in the presence of electric and magnetic fields. For the equilibrium conditions the Maxwellian electron energy distribution function has been used for determining rate coefficients in the energy region from 0 to 17eV. In the case of the non-equilibrium conditions, where the homogenous electric and magnetic fields are present, we have calculated electron energy distribution functions needed for determining rate coefficients by use of a Monte Carlo simulation developed in our laboratory. The results for both equilibrium and non-equilibrium rate coefficients are presented in the paper and similarities and differences between them have been discussed.

Non-linear growth kinematics of opening-mode fractures

Fracture aperture is commonly assumed to be a linear function of fracture length, stress, and elastic material properties. Under constant stress, fracture opening displacement may change without concurrent length or height growth if the material effectively weakens after initial linear elastic fracture growth by changes in elastic properties or by non-elastic deformation processes. To investigate the kinematics of fracture opening and its dependence on length and height growth, we reconstructed the opening history of three opening-mode fractures that are bridged by crack-seal quartz cement. Similar crack-seal cement bridges had been interpreted to form by repeated incremental fracture opening and subsequent precipitation of quartz cement. Using scanning electron microscope cathodoluminescence imaging, we determined the thickness and number of crack-seal cement layers as a function of position along fracture length and height. Observed trends in crack-seal cement layer thickness and number of fracture opening increments are consistent with non-linear fracture growth kinematics, consisting of an initial stage of fast fracture propagation relative to aperture growth, followed by a stage of slow propagation and pronounced aperture growth. Consistent with earlier fluid inclusion observations indicating fracture opening and propagation occurring over 40–50 m.y., we interpret the second stage of pronounced aperture growth and slow propagation to result from fracture opening strain accommodated by solution-precipitation creep and concurrent slow, possibly subcritical, fracture propagation.

Of some peculiarities of generalized rheological body. 2

Peculiarities of high-rank rheological bodies (RB) formation through unification of two RBs with lesser number of elements were analyzed. The necessary and sufficient conditions for the nonsingularity of complex RB are formulated, which lie in the equality of difference between the quantity of parallel and consecutive connections in the formed RB to one, and the RB relaxation times that are composed in case of parallel connections and aftereffect times in case of consecutive connection were different. The function of relaxation creeping were built, with the help of which the cores are built, as well as resolutions of integral equations of the 2 nd kind, which describe nonelastic processes in media with aftereffects.

Plasticity and ultra-low stress induced twin boundary migration in nanotwinned Cu by in situ nanoindentation studies

Nanotwinned metals have rare combinations of mechanical strength and ductility. Previous studies have shown that detwinning occurs in plastically deformed nanotwinned metals. Although molecular dynamics simulations have predicted that fine nanotwins can migrate at low stress, there is little in situ evidence to validate such predictions. Also it is unclear if detwinning occurs prior to or succeeding plastic yielding. Here, by using in situ nanoindentation in a transmission electron microscope, we show that a non-elastic detwinning process in nanotwinned Cu occurred at ultra-low indentation stress (0.1 GPa), well before the stress necessary for plastic yielding. Furthermore, the in situ nanoindentation technique allows us to differentiate dislocation-nucleation dominated microscopic yielding preceding macroscopic yielding manifested by dislocation-transmission through twin boundaries. This study thus provides further insights for understanding plasticity in nanotwinned metals at microscopic levels.

Rate coefficients for electron impact excitation of CO

Rate coefficients for electron impact excitation of the CO molecule have been calculated both for equilibrium and non-equilibrium conditions in the presence of electric and magnetic fields. The rate coefficients have been determined for all relevant non-elastic processes: rotational excitation, vibrational excitation, electronic excitation into singlet and triplet states and particularly for ionization. In the case of non-equilibrium conditions, we had to determine electron energy distribution functions needed for rate coefficients calculations. The distribution functions were obtained by employing a Monte Carlo simulation developed in our laboratory. The simulations were performed for moderate values of electric field over gas number density ratios, E/N, from 0 to 1000Td. Also, the rate coefficients have been determined in presence of magnetic field for typical values of magnetic field over gas number density ratios, B/N, from 500 to 3000 Hx. The results of equilibrium rate coefficients along with non-equilibrium ones have been shown.

Tracing causes for the stress sensitivity of elastic wave velocities in dry Castlegate sandstone

SUMMARY The stress sensitivity of elastic wave velocities in dry rock is a resultant of two types of processes—elastic and non-elastic processes. Both processes are activated under stress and both are associated with stress-induced changes in the rock structure. Although they are of the same origin, their stress-dependency may differ. Inthisstudy,asetofteststhatseparatetheelasticandnon-elasticprocessesisusedtoevaluate the impact of each process on the stress sensitivity of the elastic wave velocities. The tests rely on comparing the stress sensitivity of wave velocities during uniform loading/unloading over a long stress interval (involving both elastic and non-elastic processes) with the stress sensitivity seen in low-amplitude stress oscillations (assumed to be affected mainly by elastic processes). Our study on dry, weak sandstone shows that the impact of elastic and non-elastic processes on the stress sensitivity of the elastic wave velocities is significantly different. This implies that the processes ought to be described separately in order to provide a better foundation for predictive rock physics models. Observationsonartificiallyfracturedsamplesindicatethatlarge,horizontalfracturesreduce the axial wave velocities, whereas they have no notable impact on the stress sensitivity of the velocities. This suggests that the closed macro-fractures contain damaged areas with reduced stiffness which are apparently insensitive to stress changes. A few basic processes—elastic opening and closure of cracks, friction-controlled shear sliding of closed cracks associated with opening or closure of wing cracks, and crushing of asperities in fractures or grain contacts—may be used to intuitively explain the observations.

Model of individual collisions for description of electron transport in matter

Distributions of electron characteristics are constructed with the use of data of elastic and nonelastic processes of interaction between electrons and matter. The data are taken from the National Nuclear Data Center, http://www.nndc.bnl.gov/. These characteristics are used for developing the technique of modeling the electron transport in matter. The developed model does not use the well-known slowdown approximation and multiple scattering theories. The comparison of some moments of the distributions with the NIST data is carried out. The satisfactory fit of some results computed by using the developed model and MCNP results is obtained.

Attenuation of Seismic Body Waves in the Mantle

Summary The attenuation of seismic body waves is a direct measure of the absorption due to nonelastic processes within the Earth. Accurate amplitude decrement data for seismic body waves require the measurement of the spatial decay rate along a given ray, but measurements are restricted to the surface of the Earth. Recent studies have shown that the average Q for shear, throughout the mantle is about 600 and that the average Q for the upper 600 km of the mantle is an order of magnitude less than the rest of the mantle. Spectral amplitude comparison of the seismic phases SKS and SKP with common paths in the mantle and core allows the Q, for compression, in the mantle to be estimated. Preliminary results indicate that the Q for compression is at least 2.5 times that for shear.

R-matrix calculations of theAg2elastic electron scattering off theLi2molecule

Elastic electron scattering off the lithium dimer in the $^{2}A_{g}$ symmetry is studied. $R$-matrix calculations in the fixed-nuclei approximation are presented for a set of internuclear separations as well as energies of the stable negative ion. The aim of this work is to study effects of the polarization taken into account in the outer region on the elastic scattering cross sections. This work is the first part of a larger project dealing with ${\mathrm{Li}}_{2}$ leading to calculations of nonelastic processes like vibrational excitation and dissociative electron attachment.

The rate coefficients of the chemi-ionization processes in slow Li*(n) + Na collisions

The semi-classical method for determining the rate coefficients of the chemi-ionization processes in slow non-symmetric atom–Rydberg atom collisions is applied to the Li*(n) + Na case. Calculated rate coefficients are compared with the existing experimental data from the literature. Obtained results have confirmed that resonant mechanism of non-elastic processes in atom–Rydberg atom collisions are fully applicable to non-symmetric chemi-ionization processes. The rate coefficients of such processes in Li*(n) + Na collisions are determined in the regions of principal quantum number and temperature 4 ⩽ n ⩽ 20 and 700 K ⩽ T ⩽ 1100 K which can be of interest for possible further experiments. Also, the potential curves of several lowest Σ states of the molecular ion LiNa+, as well as the values of the square of dipole matrix element for the transition between X2Σ+- and A2Σ+-states, are presented in this paper.

Subsidence, Compaction, and Gravity Sliding: Implications for 3D Geometry, Dynamic Rupture, and Seismic Hazard of Active Basin- Bounding Faults in Southern California

In southern California, high rates of measured geodetic shortening occur where active basin-bounding faults thrust early-Cenozoic rocks over young uncon- solidated sediments. This implies that compaction, subsidence, and other nonelastic processes of footwall deformation may play an important role in contributing to the high rates of observed crustal strain. Even in the absence of active tectonic short- ening, sediment compaction alone can produce surficial motions that mimic deep fault slip or elastic strain accumulation. Differential compaction and subsidence of footwall sediments relative to hanging-wall rocks can lead to increased vertical sep- aration, basinward collapse, and fault rotation about horizontal axes. Such effects contribute to net horizontal and vertical motions in both geologic and geodetic data, and—if not properly accounted for—result in incorrect estimates of the inferred seismic hazard. Subsidence and compaction also increase the potential for gravity sliding toward the basin and the development of significant nonplanar 3D fault geometry. A prime example occurs along the San Cayetano fault that bounds the eastern Ventura basin. At shallow levels, a large thrust sheet (the Modelo Lobe) with low dip extends out in front of the more steeply dipping, planar fault segment by over 4 km, is nearly 2 km thick, and occupies over 60 cubic km. This geometry is strongly indicative of gravity-driven failure resulting from hanging-wall uplift, basinward tilt, and collapse, enhanced by footwall subsidence and compaction. Failure of this mega-slide off the hanging-wall block most likely occurred within the Rincon Formation, a thick ductile shale sequence that often accommodates detachment slip. This 3D geometry has significant implications for how the fault may behave during dynamic rupture and implies that additional care should be taken in extrapolating near-surface measure- ments or estimates of fault slip and dip to seismogenic depths.

Deformations in Transform Faults with Rotating Crustal Blocks

A continuum model of deformation of a transform fault is considered. The fault interior is modelled as a part of a plate fragmented into a large number of angular blocks. The blocks are not joined together by any binder, but are rather held together due to external compression such that they can, in principle, rotate independently. Significant numbers of blocks involved in the deformation process permit a continuum description of the deformation, which in view of the possibility of independent rotations, necessitates the application of the Cosserat theory. The crucial point in the described model is the interconnection between the rotations and the normal stresses associated with the angular shape of the blocks: the rotating blocks ‘elbow’ one another. Furthermore, elbowing produces compressive stresses independent of the direction of rotations. Consequently, the constitutive equations become non-linear involving absolute values of the components of the curvature tensor. The paper analyses a simple shear of a fault under constraining compression acting in the direction normal to the fault. An infinite layer subjected to opposite displacements and zero rotations at the edges is considered. It is shown that block rotations can lead to complex deformation patterns. There exists a displacement threshold proportional to the pressure: for imposed displacements below the threshold, the deformation pattern coincides with the conventional one as predicted for a classical elastic isotropic layer with uniform displacement gradient in the absence of block rotations. When the imposed displacement exceeds the threshold value, boundary zones of non-uniform rotations, displacement gradients and dilatation emerge. It is interesting to note that these features, which could be mistaken for indicators of non-elastic or localisation processes, occur in a situation where only elastic processes are acting at the scale of blocks and no friction or other energy dissipation processes take place.

Investigation of coupled hydraulic–geomechanical processes at the KTB site: pressure‐dependent characteristics of a long‐term pump test and elastic interpretation using a geomechanical facies model

AbstractThe German Continental Deep Drilling Program comprising a pilot borehole down to 4000 m and a main borehole down to 9101 m in southeast Germany (KTB) is continuing to provide a unique opportunity for the identification of important factors and processes in deep‐seated fluid and energy transfer. In situ stress conditions significantly impact flow, transport and exchange characteristics of fracture networks that dominate the permeability of crystalline reservoir rocks. In this paper, several scales of information are combined to present a fully three‐dimensional hydraulic finite element model of the principal KTB fault zones, and linked to a geomechanical model describing the alteration of the hydraulic parameters with stress changes caused by fluid extraction. The concept of geomechanical facies is introduced to define and characterize architectural elements in the subsurface system. Evaluation of a long‐term pump test in the KTB pilot hole, June 2002–July 2003, coupled with a geomechanical model gives an insight into some of the elastic and nonelastic processes controlling hydraulic transport in the basement rocks. Trends in the decline of the permeability and the degree of storage in the system could only partially be explained by elastic processes, clearly indicating the importance of nonelastic processes. A number of inelastic processes are suggested as areas for further research.

Molecular versus squared Woods–Saxon α-nucleus potentials in the 27Al(α, t)28Si reaction

The differential cross-section of the 27Al(α, t)28Si reaction for 64.5 MeV incident energy has been reanalysed in DWBA with full finite range using a squared Woods–Saxon (Michel) α-nucleus potential with the modified value of the depth parameter α = 2.0 as reported in a comment article by Michel and Reidemeister. This new value produces significant improvement in fitting the data of the reaction with its overall performance, in some cases, close to that previously observed for the molecular potential. Although the non-monotonic shallow molecular potential with a soft repulsive core and the Michel potentials produce the same quality fits to the elastic scattering and non-elastic processes, they are not phase equivalent. The two types of potential produce altogether different cross-sections, particularly at large reaction angles. The importance of the experimental cross-sections at large angles for both elastic scattering and non-elastic processes is elucidated.

Phase Problem in Nuclear Scattering Additional Constraints for the Analysis of Elastic Scattering Data

An integral equation has been derived for spin-½ particles which allows the determination of the phase of the scattering amplitude – an important prerequisite for a unique optical potential analysis. In extension of previous approaches the method takes account of the presence of non-elastic processes and of the pecularities of charged-particle scattering. In the realistic case of incomplete data with uncertainties the integral equation provides an additional constraint for the analysis of elastic scattering data.