Space-time Changes Research Articles

3-D Simulation of Earthquake Generation Cycles and Evolution of Fault Constitutitve Properties

The earthquake generation cycle consists of tectonic loading, quasi-static rupture nucleation, dynamic rupture propagation and stop, and subsequent stress redistribution and fault restrengthening. From a macroscopic point of view, the entire process of earthquake generation cycles should be consistently described by a coupled nonlinear system of a slip-response function, a fault constitutive law and a driving force. On the basis of such a general idea, we constructed a realistic 3-D simulation model for earthquake generation cycles at a transcurrent plate boundary by combining the viscoelastic slip-response function derived for a two-layered elastic-viscoelastic structure model, the slip-and time-dependent fault constitutive law that has an inherent mechanism of fault restrengthening, and the steady relative plate motion as a driving force into a single closed system. With this model we numerically simulated the earthquake generation cycles repeated in a seismogenic region on a plate interface, and examined space-time changes in shear stress, slip deficits and fault constitutive properties during one complete cycle in detail. The occurrence of unstable dynamic slip brings about decrease both in fault strength and shear stress to a constant residual level. After the arrest of dynamic slip, the breakdown strength drop △σp, of fault is restored rapidly and the process of stress accumulation resumes in the seismogenic region. On the other hand, the restoration of the critical weakening displacement D c proceeds gradually with time through the interseismic period. The restoration of D c can be regarded as the macroscopic manifestation of the microscopic recovery process of fractal fault surface structure. Through numerical simulation with a multi-segmented fault model, we examined the effects of viscoelastic faultto-fault interaction. The effect of transient viscoelastic stress transfer through the asthenosphere is significant as well as the direct effect of elastic stress transfer, and it possibly explains the time lag of the sequential occurrence of large events along a plate boundary.

Quantum criticality for few-body systems: path-integral approach.

We present the path-integral approach to treat quantum phase transitions and critical phenomena for few-body quantum systems. Allowing the space and time variables to have discrete values, we turn the quantum problem into an effective classical lattice problem. Imposing the constraint that any change in space time must preserve the scaling invariance of Brownian paths, we show that the mapped classical lattice system has a known scaling behavior when the particle is free, which breaks down when the strength of the interaction potential reaches a certain value. In principle, any quantity with known scaling behavior may be used to determine the transition point. We illustrate the method by numerically evaluating the correlation length and the radial mean distance for a system composed of a single particle in the presence of an attractive Pöschl-Teller potential in one and three dimensions. The method is general and has potential applicability for large systems.

Ionospheric plasma bubble zonal drift: a methodology using OI 630 nm all-sky imaging systems

With the recent advances in all-sky imaging technology for nightglow emission studies, the F-region OI 630 nm emission has become an important tool for ionospheric/thermospheric coupling studies. At equatorial and low latitude regions, the all-sky imaging observations of the OI 630 nm emission show quasi north-south aligned intensity depletion bands, which are the optical signatures of large scale F-region plasma irregularities. By observing the motion of the intensity depleted bands it is possible to infer the ionospheric plasma zonal velocity of the depletion. The north-south aligned structures seen in the field of view of the all-sky imaging system corotate with the ionospheric plasma, so that by calculating the spatial displacements occurring during successive OI 630 nm emission images we can infer the ionospheric plasma drift velocity. However, the plasma bubbles have their own internal space-time dynamics leading to changes in their shape and dimensions and this may induce some errors in the calculated drift velocities. In this paper we take into account the space-time changes in the plasma bubbles in order to calculate the ionospheric plasma zonal drift velocities using the OI 630 nm nightglow emission.

Time-space structure and variability of surface temperature frontal zones in the ocean (based on AVHRR satellite data)

Satellite monitoring of large-scale ocean fields allows collection and analyse of information on dynamics processes in various areas of the ocean. Investigation of the World Ocean processes involves the determination of space-time changes of sea surface temperature (SST). Water temperature of the ocean is one of major characteristics of surface water masses. Distribution of water temperature depends not only on regional climate peculiarities but also on formation of high gradient temperature zones. These zones emerge due to interaction of different current structure, circulation and eddies. Some more important characteristics of such zones are space dimensions and time of existence (lifetime). Space-time scales of the above structure have not been investigated in detail. The aim of the paper is to study space-time changes of the surface temperature frontal zones and frontal partitions in the ocean by AVHRR satellite information.

Petroleum Systems Along the Foldbelt Associated to the Maranon-Oriente-Putomayo Foreland Basins: ABSTRACT

Along strike variations in structural style of the foldbelt associated to the Maranon-Oriente-Putumayo (MOP) Basins and timing of deformation accounts for the major variations in their petroleum systems. Space-time changes in structural style controlled the timing of maturation and generation as well as reservoir and seal quality. Source rock distribution and richness could vary along the foldbelt, however, they are difficult to document. The Foldbelt associated to the Oriente and Putumayo Basins is characterized by thick-skinned style of deformation and contains the only commercial accumulations. A thick sedimentary wedge of the Tena Formation in front of the Napo and Cutucu Uplifts documents Late Cretaceous/Paleocene deformation (Peruvian Phase). AFT data in the Putumayo, Napo and Cutucu Uplifts documents a Middle Eocene Uplift (Incaic Phase) followed by a Late Miocene Pliocene renewal of uplift. The main phase for hydrocarbon generation and migration was from Late Cretaceous to Middle Eocene, therefore, the productive structures must have an older component. Biodegradation and water washing accounts for the destruction of the largest accumulation of heavy oil in the southern plunge of the Napo Uplift. The Peruvian segment includes the salt-related Santiago and Huallaga Foldbelts which are still poorly explored. Although there are strong indications formore » salt movement and basin inversion since Mesozoic times, the main episode of folding and thrusting was Late Miocene to Pliocene. This is supported by AFT and modern seismic data. Although there are several structures showing Mesozoic thinning against the salt, the major episodes of salt withdrawal took place during the Tertiary. This accounts for significant burial of the reservoir rocks with concomitant reduction of the primary porosity.« less

EXTRA DIMENSIONS AND POSSIBLE SPACE-TIME SIGNATURE CHANGES

Exact static, spherically symmetric solutions to the Einstein-Maxwell-scalar equations, with a dilatonic-type scalar-vector coupling, in D-dimensional gravity with a chain of n Ricci-flat internal spaces are considered, with the Maxwell field potential having two nonzero components: the temporal, Coulomb-like one and the one pointing to one of the extra dimensions. The properties and special cases of the solutions are discussed, in particular, those when there are horizons in the space-time. Two types of horizons are distinguished: the conventional black-hole (BH) ones and those at which the physical section of the space-time changes its signature (the latter are called T-horizons). Two theorems are proved, one fixing the BH- and T-horizon existence conditions, the other claiming that the system under study cannot have a regular center. The stability of a selected family of solutions under spherically symmetric perturbations is studied. It is shown that only black-hole solutions are stable, while all others, in particular, those with T-horizons are unstable.

Topology and topology change in general relativity

If one assumes the existence of an everywhere nonsingular Lorentzian metric and an SL(2, C) spinor structure one may derive selection rules governing topology change in a compact spacetime with boundary. If the boundary of spacetime is everywhere spacelike then its Kervaire semi-characteristic must vanish modulo two. Roughly speaking this says that Wheeler wormholes are conserved modulo two. If one allows boundaries which are partly timelike then one must add to this conservation law the kink number of the metric on the boundary. Contrary to one's naive expectation the kink number, which is a measure of how often the light cone tips over on the boundary, does not appear to be a diagnostic for causality violation.

Transition Amplitudes in 2+1 Dimensional Quantum Gravity

Transition amplitudes for space-time evolution without topology change are studied in 2+1 dimensional pure gravity. The space is assumed to be a compact Riemann surface. Our analysis will be a first step for the analysis of topology change and third quantization in space-time. The torus case is detailed. It is shown that, in this case, the dynamical structure of 2+1 dimensional gravity is essentially identical to that of a massless relativistic point particle and a transition is admitted to occur from the initial state to the final states if and only if they are connected by the classical solution. This property of the transition amplitude is consistent with that obtained in the vierbein formalism and coincide with that of a massless relativistic point particle, though our theory involves some adhoc assumptions.

Can spacetime be probed below the string size?

Strings may be explored, through a scattering process at planckian energies, down to distances of the order of the string size. We show that this is possible if the energy is not so extreme to cause a gravitational instability and when the scattering angle approaches some critical value from below. Above this angle, the distance starts increasing, thus departing from the usual position-momentum uncertainty relation, and in no instance is the resolution smaller than the string length. This suggests that below the Planck scale the very concept of space-time changes meaning.

Start-up procedures for continuous flow emulsion polymerization reactors

Experiments have been carried out using a continuous flow back-mixed emulsion polymerization reactor. Styrene was used as monomer. Particular attention was given to the effects of start-up procedure on reactor behaviour. Steady feed rates were not always accompanied by steady conversions of monomer. In some cases, especially at high initiator concentrations, oscillations occurred in the conversion. For a given feed composition and space time changes i start-up procedure could affect both transient and long term reactor behaviour. In some cases eventual conversions could be tripled by changing the sta procedure. When conversions reached a high and near-constant value, significant increases in the average size of polymer particles could still occur. T was accompanied by an increase in the average number of radicals per particle. The results cannot be described by simple reactor models and it is sugge that more than one process for particle formation might be operative.

Kinks and cobordism

This paper is concerned with the situation in which the topology of space (or space-time) changes to produce a new manifold that is cobordant with, but not necessarily of the same homotopy type as, the original manifold. The relevance to kink field theories is discussed. It is shown that whenever the concept of degree of mapping is applicable then the degree is conserved under the bordism relation. This has the consequence that certain (topological) fermions arising in general relativity are always conserved in number, even when changes in topology are permitted.

Tarbela reservoir, Pakistan: A region of compressional tectonics with reduced seismicity upon initial reservoir filling

The Tarbela reservoir is located on the Indus River in the lesser Himalayas of northern Pakistan, a region of considerable natural seismicity. A microseismic survey conducted prior to impounding has indicated that crustal shortening under horizontal north-south compression dominates present-day tectonics, resulting in thrusting and strike-slip motion along numerous faults. The reservoir was first partially filled for a few weeks in 1974 and then completely filled in 1975. In both cases, the microseismic activity decreased slightly during the impounding period and recovered quickly upon commencement of drainage or establishment of a constant reservoir level. In tectonic environments where the maximum principal stress is horizontal and the tectonic system is compressive, a vertical surface load can move the crustal stresses away from a Navier-Coulomb failure criterion, and hence can temporarily decrease seismicity. The observed rapid recovery of seismicity may alternately be explained by: (1) high rates of tectonic strain accumulation which, in turn, increase horizontal stresses at crustal depths; they may quickly overcome the stabilizing effects of the small vertical stress changes and increased friction across faults from reservoir loading and, hence, may return the crustal stress system to one of failure; or (2) high diffusivity of the basement rock results in a pore pressue increase after a few weeks of raised reservoir head; the raised pore pressure equally reduces the effective horizontal and vertical stresses and brings the crustal system back to failure. Since direct monitoring of pore pressure at crustal depths is not available at Trabela, it is presently not possible to distinguish between the two alternatives. Indirect observations, such as long-term monitoring of space-time changes in seismicity, may aid in the resolution of this ambiguity. A few reservoirs, located in regions with preferentially extensional or pure strike-slip tectonics, have triggered or induced seismic activity, whereas Tarbela reservoir, in a region of convergent tectonics, has (to present) only slightly modified the natural seismicity. Here, in a region of active Himalayan tectonics, it is likely that any severe earthquake to occur in the near future would occur sooner or later, regardless of the presence of the reservoir. Within hundreds of years a major earthquake near Tarbela appears tectonically inevitable. Yet the presence of the reservoir may strongly affect, say, the time of occurrence, exact location, and the details of rupture of an earthquake. The time most likely for inducing a tectonic stress release (if any) would be during or shortly after a rapid draw-down of the reservoir, when the decrease in pore pressure from its high level at crustal depths lags behind the instantaneous stress decrease from reservoir unloading.