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Processing and interpretation of huge array of mine seismicity data obtained in mines of Norilsk Nickel Mining and Metallurgical Company has revealed the “pulsating” mode of seismic energy release on the background of an increase in the strata pressure and, based on the information on monthly migration of reduced centers of seismic energy release within the mine fields, enabled development of a rockburst hazard criterion for individual rock mass areas. The prognostic criterion of the limiting state of a rock mass area is developed based on the ratio of kinematic characteristics of seismic events, which are the velocity of a reduced center of seismic energy release and the apparent velocity of “migration” of individual seismic events closely timed within the ranges of stress concentration zones inside the mine fields. Verification of this criterion using an ample seismic data base accumulated for a number of years in a mine of Norilsk Nickel has displayed high sensitivity of the criterion towards the change in the stress state of rock mass areas under monitoring.

In this paper we propose a processing method with several linear subarrays for the joint estimation of the apparent velocity and the direction of propagation of a seismic wave. This method estimates the parallel velocities along the directions of the considered linear subarrays, followed by a geometrical based procedure to compute the apparent velocity and the direction of propagation of the wave. Examples, using synthetic as well as field data, are presented to verify the suggested method. The proposed method can be used to determine the properties and sources of the microseism and microtremor signals acquired by seismic array data.

We present a non-linear study of the energy loss of heavy ions in solids, which is based on the transport cross section (TCS) and the extension of the Friedel sum rule (EFSR) for moving ions. We apply this approach to study the velocity dependence of the energy loss of heavy ions in the energy region below the stopping power maximum. With this formulation we are able to explain some striking effects in the energy loss of heavy ions which have been experimentally observed long time ago (Brown and Moak (1972) [14]), but have not been explained so far by the existing theoretical models: the deviations from the proportionality with ion velocity (predicted by alternative models in the low energy range), and the “apparent velocity threshold”.

Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration (DPDM) is based on accurate elevations of sources and receivers, by which static correction is completely abandoned before migration and surely the imaging quality is remarkably improved. To obtain some artificial shot gathers, high-order staggered-grid finite-difference (FD) method is adapted to model acoustic wave propagation. Since the shot gathers are always disturbed by regular interferences, the statics still must be applied to supporting the interference elimination by apparent velocity filtering method. Then all the shot gathers should be removed back to their original positions by reverse statics. Finally, they are migrated by pre-stack reverse-time depth migration and imaged. The numerical experiments show that the DPDM can ideally avoid the mistakes caused by statics and increase imaging precision.

We present a method of separation of P- and S-wave components from three-component (3C) crosswell seismic data. Based on differences between P and S waves in polarization and apparent velocity, this method separates P and S waves in a common source gather without estimating emergence angles and by means of data processing techniques including band-pass filter for preprocessing, high-resolution τ–p transform for removing tube waves and separating up-going and down-going waves, and covariance polarization analysis for correcting the direction of geophone and separating polarization. To separate P- and S-wave data, this method requires only the input of original 3C crosswell data and the first arrivals of P waves. We verify and demonstrate effectiveness and practicability of this method using 2C modeling tests as well as real 3C crosswell data.

Acoustic emission (AE) technique, as an effective method to monitor the crack characterization in concrete materials is investigated in this paper. An improved approach, based on the Akaike Information Criterion (AIC), is proposed to provide more reliable onset time determination of AE signals. The introduced parameters, quantification of the certainty degree and the apparent velocity in the improved method can help to eliminate the false or doubtful picked onset results automatically. The improved AIC method is successfully applied to the AE detection during a three-point bending test of a fiber reinforced concrete beam to analyze the crack pattern. It is shown that the proposed method is a reliable tool for automatic onset time determination and useful for the crack source location in concrete structures.

Risk assessment of snow avalanches is mostly related to weather conditions and snow cover. However, a robust risk validation requires avalanche activity data, in order to compare predictions to actual events. For this purpose in December 2009 we installed a temporary 4-element, small aperture (150 m), infrasound array in the northwestern Italian Alps. The array was installed south of Mt. Rosa, at an elevation of 2000 m a.s.l. in the valley of Gressoney, Italy, where natural avalanches are expected and avalanche control by explosives is regularly performed. A multi-channel correlation analysis is carried out on the continuous infrasound data set recorded by the array as a function of apparent velocity, back-azimuth and frequency of recorded infrasound. This allowed detectionof infrasonic signals propagating across the array from the background noise. During the 5-month-long experiment, 343 infrasonic events have been detected and characterized. These include sharp infrasonic transients (99 events) produced by explosions during avalanche control as well as longer lasting signals (244 events) possibly caused by avalanches. Although only few of these events were validated by direct avalanche observation, obtained results are promising and encouraging application of infrasound for long-term avalanche observation on wide areas, as the peak in avalanche activity in winter 2009–2010 was observed shortly after the infrasound events peaked as well.

Previous psychophysical experiments have demonstrated that various factors can exert a considerable influence on the apparent velocity of visual stimuli. Here, we investigated the effects of superimposing static luminance texture on the apparent speed of a drifting grating. In Experiment 1, we demonstrate that superimposing static luminance texture on a drifting luminance modulated grating can produce an increase in perceived speed. This supports the hypothesis that texture changes perceived speed by providing landmarks to assess relative motion. In Experiment 2, we showed that contrary to static luminance texture, dynamic luminance texture did not increase perceived speed. This demonstrates that texture must provide reliable spatial landmarks in order to generate an increase in perceived speed. The results of Experiment 3 demonstrate that perceived speed depends on the size of the area covered by texture. This suggests that luminance texture and the motion stimulus interacted with each other over a limited spatial scale and that these local responses are then pooled to determine the speed of the motion stimulus. In Experiment 4, we showed that static texture contrast could produce a greater effect than motion stimulus contrast on perceived speed and that these effects could still be observed at brief presentation times. We discuss these findings in the context of models proposed to account for phenomena in the perception of speed.

In this paper we have derived reflection and transmission coefficients of qP-waves at a corrugated interface between two different elastic half-spaces of monoclinic type. Using Rayleigh’s method, the expressions for reflection and transmission coefficients are derived in closed form for a specific interface and for the first order approximation of the corrugation. Numerical computations are performed for a specific model and the results obtained have been shown graphically. The variation of the modulus of reflection and transmission coefficients with the angle of incidence, frequency and corrugation of the interface are shown separately. These coefficients are found to be strongly influenced by the angle of incidence, frequency, elastic parameters and amplitude of the corrugation of the interface. It is found that (i) the modulus of reflection and transmission coefficients at the plane interface are independent of corrugation of the interface and that of frequency of the incident wave, (ii) the reflection and transmission coefficients of regularly reflected and transmitted waves are found to be greater than that of irregularly reflected and transmitted waves, (iii) the coefficients of irregularly reflected and transmitted waves are found to increase and decrease with increase of corrugation and frequency parameters respectively. The results of Singh and Khurana [Singh, S.J., Khurana, S., 2001. Reflection and transmission of P- and SV-waves at the interface two between monoclinic elastic half-spaces. Proc. Natl. Acad. Sci. India 71(A) (IV), 305–319] have been reduced from the present problem.

We present here two epochs of Space VLBI Observations at 18 cm of the BL-Lac type object Mkn 501. Thanks to the high resolution of these new data we have found that the inner jet is centrally brightened at its beginning but becomes extended and limb brightened at ∼ 8 mas from the core. Moreover a comparison between the two epochs shows the presence of a proper motion with apparent velocity = 6.7c. Observational data have been used to constrain the jet velocity and orientation.

We study the early evolution of active regions in the corona by analyzing 56 emerging flux regions (EFRs). We find that the initial apparent velocity of the expansion of the EFRs is 0.4–4.6 km/s, which is much lower than that inferred from Ha observations of arch filament systems or from theory.

The geological condition may vary largely from one support to another for a long span bridge. The effect of geological variability and spatial variation produced by propagation and coherence loss of seismic ground motion on the response of long span suspension bridges is investigated in this article. The case of Jiangyin Yangtse River Bridge, a suspension bridge with a main span of 1385 m, is studied in detail. Numerical results show that the geological difference at the supports has a significant effect on the seismic response of long span suspension bridges and, that it is unacceptable to neglect the difference. The effect of the propagation of seismic ground motion on the response of long span suspension bridges is far more important than that of the coherence loss. The response of bridges varies greatly with the horizontal apparent velocity in a very complex way, and there is a critical horizontal velocity for a given response quantity.

When the mobility of a recrystallization front is varying periodically along the front and a uniform pressure P is acting on it and the specific front energy, γ , is constant, the front will, after a transient move forward with a stationary shape and a constant apparent velocity in a direction perpendicular to the direction in which the mobility is varying. The corresponding apparent mobility M app was determined in a semi-analytic way. When the width of the variation in mobility is small compared to the length λ = γ / P , M app is given by the simple expression 1/ M app =〈1/ M 〉. With increasing values of λ the front becomes increasingly wavy, provided the variation in mobility is not too small, and M app approaches a constant value independent of the variation in mobility.

Apparent velocity of ultrasound (AVU) (Signet™, OsteoTechnology Cambridge, MA) at the patella was measured on 568 children and adolescents, aged 8 to 18 years. Trend analysis revealed a significant trend ( p p p p p

In the Tohoku District, the northeastern part of Honshu, Japan, a conspicuous phase is frequently observed between P and S phases in seismograms for events in the lower seismic plane of the double-planed deep seismic zone. This phase is dominant in the vertical component and has an apparent velocity almost equal to or slightly smaller than the P phase. We have never found this phase in seismograms for events in the upper seismic plane. From these characteristics, the phase is interpreted as SP, converted from S to P at the upper boundary of the descending oceanic plate (UBP). Using the travel times of the SP waves, we estimated the location of the UBP beneath the Tohoku District to be just above the upper seismic plane of the double-planed deep seismic zone. This position is consistent with those determined from the analyses of the travel times of the ScSp and PS waves, which are respectively the seismic wave converted from ScS to P and that from P to S at the UBP.

The purpose of this work was to investigate the capability of a model, which explicitly accounts for multiple sources of nonequilibrium, to predict the transport of nonequilibrium sorption-constrained solute in a stratified porous medium. Microaquifer experiments reported in the literature served as the source of the data that were analyzed. The best available information was used to identify values for all model input parameters, allowing the multiprocess nonequilibrium (MPNE) model to be used in a predictive mode. The prediction produced by the MPNE model provided a good description of the breakthrough curve obtained at a given velocity. A breakthrough curve obtained at a slower velocity could be simulated when the apparent velocity dependence of the physical nonequilibrium parameters was taken into account. Based on the reported results, the MPNE model would seem to provide a valid representation of sorption dynamics and solute transport for stratified systems influenced by sorption capacity heterogeneity and multiple sources of nonequilibrium. The relative and combined impact of interlayer mass transfer, chemical nonequilibrium, and sorption capacity heterogeneity on the transport of a sorbing solute was elucidated.

A direct measurement of apparent velocities for oceanic paths was made with an array of sensitive ocean bottom seismographs. The measurement was performed by recording waves from shallow earthquakes which occurred in the area close to trench axes and which were accurately located by the land seismological network in Japan. The range of epicentral distances is from 500 to 1,800 km. The observed P travel times are less than those in the Jeffreys-Bullen tables by 6–10 s for the range of distances. Since the dimension of the OBS array is about 400 km, the apparent velocities are determined quite precisely and show little dependence on the epicentral distances. The average value of the apparent velocities for the range 500–1,700 km is 8.64 ± 0.13 km/s. An offset of travel times, which is thought to be associated with a low-velocity layer underneath the oceanic lithosphere, has been observed. These results indicate that a high-velocity layer with a velocity of 8.6 km/s exists in the lower part of the oceanic lithosphere. Beneath the 8.6-km/s layer there is a thin low-velocity layer under which the velocity of the P wave is again 8.6 km/s.

Over 200 earthquakes in the distance range 30°–90° and azimuthal range 0°–360°, recorded at Indian WWSSN stations, have been used in the present study. We have treated the four WWSSN recording stations i.e. New Delhi, Poona, Shillong and Kodai-Kanal, as Super Large Aperture Seismic Array (SLASA) Network with New Delhi being its cross-over point. Short period P-wave data as obtained from these stations have been analysed using a least square technique. Slowness and azimuthal anomalies have been computed for all these events. Relative time residuals have also been calculated. A velocity model has been derived on the basis of the slowness and travel-time data. The results do not indicate presence of any triplication in the travel-time curve. Variations in the relative residuals refer to the tectonic features beneath the recording stations. The P-wave velocity increases continuously in the lower mantle region and there is no indication for the presence of any appreciable velocity gradient.

Poisson's ratios of the upper and lower crust and the sub-Moho mantle beneath central Honshu, Japan, are investigated using three independent methods that are based on S to P ratios of apparent velocities, the Wadati diagrams and an inversion of P and S arrivals. Shallow earthquakes at distances of 200—500 km from the Nagoya University Telemeter Network are used for the apparent velocity ratio method. Crustal and subcrustal earth-quakes under the network are used for the other two methods. The network consists of wide-band seismometers with three components which are particularly suitable for detecting S waves. The three different methods give a consistent result for Poisson's ratio σ, that is, (1) σ = 0.23 ± 0.01 in the upper crust, (2) σ = 0.26−0.28 in both the lower crust and in the sub-Moho mantle. The result indicates a sharp contrast in σ between the upper and the lower crust rather than at the Moho. The low σ in the upper crust can only be explained by the presence of a substantial amount of free quartz, indicating granitic rocks. A higher σ in the lower crust suggests that this portion is presumably less saturated in silica and may be even undersaturated, pointing to intermediate to mafic rocks. The sub-Moho σ is almost equal to the σ averaged over the entire upper mantle that has been estimated from the Wadati diagrams of deep shocks beneath Japan but is higher than those calculated from Pn and Sn velocities in oceanic and stable continental regions.

In this Note, some geometric and kinematic features of a plasmon which is both ejected and expanding relativistically are discussed. It is shown that the apparent shape of the plasmon is given by Eq.(17), and that the apparent velocity of its outermost edge away from the core can be superluminal even when the ejection is at a considerable angle to the line of sight.

We present here results of three refraction profiles obtained during the “Minos” cruise (March–April, 1986) in the northern Red Sea (above 25°N) with our new marine seismic observation system, the Ocean Bottom Vertical Seismic Array (OBVSA). In the first part of the paper, we briefly describe the instrument and give some of its main characteristics. In the second part, we present a velocity-depth model for each one of the three non-reversed profiles. The model is first inferred from interpretation of the hodochron, using the slope intercept method and assuming plane interfaces, and iteratively modified by application of a ray tracing program. Our results support other data collected durng the cruise with Expanding Spread Profiles and reported elsewhere in this issue by Gaulier et al. (1988). The two northern profiles are about 50 km long and are oriented N15 °E. The recording instrument was located at the southern extremity of the profiles at 26°35′N, 34°46′E and 27°00′N, 34° 26′E respectively. The basement velocity was found to be in the 5.2–5.8 km s −1 range. The Moho is located at about 14 km below the sea level. The upper mantle apparent velocity is about 7.3 km s −1 . The southern profile is 40 km long, oriented S45° W with the OBVSA located at its eastern extremity, at 26°06'N, 35°23′E. The Moho depth is about 11.5 km. The crustal structure under the eastern part of the profile is interpreted as being of the oceanic type.

Alterations in acetylcholinesterase (AChE) activity were investigated in middle endplate (MEP), distal endplate (DEP) and non-endplate (NEP) regions of rat diaphragm muscle after phrenic nerve transection either intrathoracically (low, 3–5 mm nerve stump) or in the neck (high, 50–55 mm nerve stump). When the phrenic nerve was severed low, the time of initial loss of AChE activity in MEP and DEP regions was 20 h. In contrast, when the nerve was transected in the neck, the onset time of AChE activity loss was delayed in both MEP and DEP regions to 24 h. Therefore, the onset time of loss of AChE activity was dependent on the nerve stump length. The rate of loss of AChE activity was not significantly different for MEP or DEP regions after either high or low nerve transection and averaged a rate of 1.54%/h. Loss of AChE activity in the NEP region was independent of nerve stump length and enzyme activity decreased at a rate of 0.62–0.63%/h, beginning immediately after nerve transection. AChE activity in phrenic nerve was also measured and was found to contribute significantly to measurements of endplate enzyme activity in diaphragm. Data indicate a nerve length-dependent loss of AChE in MEP and DEP regions of muscle with an apparent velocity of 300 mm/day, suggesting a relationship to fast axoplasmic transport of either AChE itself or a trophic factor.

Pion spectra from asymmetric heavy-ion collisions at intermediate energies are studied in the slab geometry. The effect of pion absorption is treated in a phenomenological way. The shadowing of outgoing pions explains the apparent velocity of “the pion emitting source”.

The survival and growth of developing salmonid embryos are strongly influenced by the rate of oxygen supply to the redd. Oxygen supply is determined as the product of the groundwater velocity (apparent velocity) and dissolved oxygen content. A modified standpipe technique is presented to measure groundwater velocity. It differs from earlier colour dilution methods in that the colour solution is replaced by an electrolyte, thus allowing remote sensing of conductivity changes and dilution rates. Up to 8 standpipes in a single spawning bed may be operated simultaneously in this way and the method offers considerable advantages in allowing systematic or randomized grid sampling designs. Accuracy compares favourably with that of earlier methods.

The perceived rate of movement of sine wave gratings has been measured over a range of contrasts. At temporal frequencies below about 8 Hz a decrease in contrast reduces apparent velocity. At 16 Hz a reduction in contrast increases perceived velocity.

We give a statistical method which will estimate the true rotational velocity V of a Be star from its observed apparent velocity U = V sin i . We show that Be stars do not rotate with the critical velocity and that the ratio between their real velocity and the critical velocity is about 0.7.

Ocean bottom seismograph (OBS) long-range explosion experiments were carried out in the Mariana Basin in 1973 and 1976. Seven large shots (8.5–1.5 ton) as well as several tens of small shots were fired. The maximum range of observation was about 1900 km. As many as 25 OBS stations were deployed in an array of about 800 km. It is found that the sub-Moho P-wave velocity structure is of stratified nature, being composed of alternating high- and low-velocity layers. High-velocity layers with apparent velocities of 8.1, 8.2, 8.4, 8.6 and 8.7 km/s are identified. Low-velocity layers, sandwiched between the high-velocity layers of 8.4, 8.6 and 8.7 km/s, are very prominent. The sub-Moho high-velocity lid with an apparent velocity of 8.4 km/s is very thin. Thinning of this lid, thickening of the low-velocity layer, and the presence under it of another high-velocity layer (8.6 km/s) appear to characterize the uppermost mantle structure beneath the Mariana Basin.

Seismic observations of the travel times from explosions in Lake Superior on profiles both north and south of the lake show an increase in apparent velocity at a distance of about 650 km. These observations imply that there is a seismic discontinuity at which the velocity increases from about 8.05 to 8.3 to 8.45 km/sec at a depth of 80–90 km. It is suggested that this change may arise from the transition from spinel to garnet peridotite.

Summary Interborehole acoustic measurements are made by transmitting a pulse of sound energy from one borehole to another. Analysis of the recorded signals can provide useful information on ground conditions between and beneath the boreholes. This includes the location of boundaries between different rock and soil types, and an assessment of geotechnical properties in certain cases. A sparker source of energy has been developed for use in boreholes, giving a repetitive pulse shape. The received signal may contain direct, refracted and reflected arrivals, which can be timed. These times are converted to apparent velocities and a vertical scan of two boreholes presented as an apparent velocity versus depth curve. Two case histories from the Dinorwic hydro-electric scheme in North Wales and from Whatley Quarry near Frome in Somerset, illustrate the nature of the interpretation process, and the quality and distribution of the additional geological data that can be achieved. Interborehole scanning has certain advantages over conventional surface seismic refraction; for example, in the detection of low velocity layers at depth. It does of course have its limitations, in the theoretical, interpretational and the practical senses. With these limitations minimized, interborehole acoustic measurements can be a very useful addition to site investigation.