Arrival Phase Research Articles

A surrogate model to assess the whole body SAR induced by multiple plane waves at 2.4 GHz

The assessment of the exposure to electromagnetic waves is nowadays a key question. Dealing with the relationship between exposure and incident field, most of previous investigations have been performed with a single plane wave. Realistic exposure in the far field can be modeled as multiple plane waves with random direction of arrival, random amplitude, and random phase. This paper, based on numerical investigations, studies the whole body specific absorption rate (SAR) linked to the exposure induced by five random plane waves having uniformly distributed angles of arrival in the horizontal plane, log-normal distributed amplitudes, and uniformly distributed phases. A first result shows that this random heterogeneous exposure generates maximal variations of ±25% for the whole body specific absorption. An important observation is that the exposure to a single plane wave arriving face to the body, used for the guidelines, does not constitute the worst case. We propose a surrogate model to assess the distribution of the whole body SAR in the case of an exposure to multiple plane waves. For a sample of 30 values of whole body SAR induced by five plane waves at 2.4 GHz, this simple approach, considering the resulting SAR as the sum of the SAR induced by each isolated plane wave, leads to an estimated distribution of whole body SAR following the real distribution with a p value of 76% according to the Kolmogorov statistical test.

Gravity-assisted maneuvers applied in the multi-objective optimization of interplanetary trajectories

In this work, the problem of optimization of interplanetary trajectories with minimum fuel consumption, but with a time limit is studied. It was used a methodology known as the Patched Conics, where the trajectory is divided into three parts: (1) departure phase, inside of the sphere of influence of the departure planet; (2) heliocentric phase, during the journey between the planets; and (3) arrival phase, inside of the sphere of influence of the arrival planet. Furthermore, the possibility of gravitational assisted maneuvers (swing-by) was considered to reduce fuel consumption. In this case the full trajectory would be divided into more parts, depending on the number of maneuvers. Therefore, the goal of this work is to find a combination of conical trajectories, using gravitational assisted maneuvers, which perform the transfer close to the departure planet to the vicinity of the arrival planet, spending minimal fuel with minimal time for the journey. Considering the minimization of time, the solution cannot be the solution of minimum fuel consumption, because the minimization of time and the minimization of fuel are conflicting objectives. Thus, a multi-objective problem must be solved. Hence, a methodology based on the Non Inferiority Criterion (Pareto, 1909 [2]) and the Smallest Loss Criterion (Rocco et al., 2002 [6]) was used, capable of considering multiple objectives simultaneously, without reducing the problem to the case of optimizing a single objective as occur in most methods found in the literature. A mission to Pluto, similar to NASA’s New Horizons Mission, was studied considering gravitational assisted maneuvers in Mars, Jupiter and Saturn. Simulating the trajectories and the maneuvers using the Transfer Trajectory Design Programs (Sukhanov, 2004 [13]), several possibilities were analyzed for many combinations of fuel consumption, time of departure, time of arrival and planet used for the swing-by. Then, using the Multi-objective Optimization Program (Rocco et al., 2002 [6]) the problem was solved seeking the best combination. The results can provide good assistance for mission analysis reducing the cost and time.

Effective-one-body waveforms calibrated to numerical relativity simulations: Coalescence of nonprecessing, spinning, equal-mass black holes

We present the first attempt at calibrating the effective-one-body (EOB) model to accurate numerical-relativity simulations of spinning, non-precessing black-hole binaries. Aligning the EOB and numerical waveforms at low frequency over a time interval of 1000M, we first estimate the phase and amplitude errors in the numerical waveforms and then minimize the difference between numerical and EOB waveforms by calibrating a handful of EOB-adjustable parameters. In the equal-mass, spin aligned case, we find that phase and fractional amplitude differences between the numerical and EOB (2,2) mode can be reduced to 0.01 radians and 1%, respectively, over the entire inspiral waveforms. In the equal-mass, spin anti-aligned case, these differences can be reduced to 0.13 radians and 1% during inspiral and plunge, and to 0.4 radians and 10% during merger and ringdown. The waveform agreement is within numerical errors in the spin aligned case while slightly over numerical errors in the spin anti-aligned case. Using Enhanced LIGO and Advanced LIGO noise curves, we find that the overlap between the EOB and the numerical (2,2) mode, maximized over the initial phase and time of arrival, is larger than 0.999 for binaries with total mass 30-200Ms. In addition to the leading (2,2) mode, we compare four subleading modes. We find good amplitude and frequency agreements between the EOB and numerical modes for both spin configurations considered, except for the (3,2) mode in the spin anti-aligned case. We believe that the larger difference in the (3,2) mode is due to the lack of knowledge of post-Newtonian spin effects in the higher modes.

Moving Through Social Networks: The Case of Armenian Migrants in the Czech Republic

AbstractThis paper brings attention to the role of social networks in the migration of asylum seekers and explores how the embeddedness of the migrants in social networks both facilitates and constrains their mobility in different phases of the migration process. It reconstructs the migration paths of eight Armenian migrant families who arrived in the Czech Republic as asylum seekers during the 1990s and the beginning of the twenty‐first century. By examining the narrated stories of the Armenian migrants it shows that social networks formed an important context for employing various migration strategies in all phases of the migration process, and that the meaning and character of migrants’ social networks changed over time. In the initial phase of decision‐making about migration as well as on their journey, it was mainly weak ties of random acquaintances that played a dominant role. The position of the migrants in those networks was rather insecure. They held a little control over the information they received, but in these vulnerable situations they had to rely on their weak ties, which strongly influenced their mobility. In the arrival and settlement phases the social context of the refugee camp hindered the cultivation of social ties outside the migrants’ circle on one hand, and facilitated development of bonding ties among the migrants on the other. Bonding social networks enabled inclusion of the Armenian migrants into various social spheres especially at the beginning of the settlement process. However, the bounded character of these networks was also recognized as excluding them from access to resources of the dominant society and preventing their social mobility in later phases of their settlement. Thus, bridging networks that provide access to certain resources of the dominant society were sought.

Using a Fractal Analysis and Polarization Method for Phase Identification in Three-Component Seismograms

This study presents the automatic P-wave and S-wave arrivals picking algorithm which is essentially based on the fractal dimension and polarized method. With an estimate of the spectral exponent γ in a 1/f process, an interval that indicates the preferred intersection containing both noise and the P-wave is well-detected by corresponding to the minimum absolute spectral exponent γ value along the trace. Based on the different properties of background noise and deterministic signal, the fractal dimension technique can detect the position of the P-wave. The place where the fractal dimension value changes suddenly within the intersection interval indicates the location of arrival of the P-wave. Testing that adds various levels of noise to the seismic signal shows the method can prove able to tolerate noise to a signal-to-noise (S/N) ratio 1.5. Based on the P-wave arrival, the polarized P-wave could be detected by a genetic algorithm (GA) with the strength of polarization and phase difference between the vertical and horizontal components as constraints. Using the first arrival phase as the basis phase, this study combines a polarization filter including rectilinearity functions, linear polarization, phase difference and directionality with GA to detect polarized S-wave of seismograms. Finally, the technique was applied to teleseismic data and near-field motion to verify the accuracy and wide applicability of this method. To conclude, this proposed method, an efficient and brand-new method of associating signal processing technique with physical wave motion properties, may be of importance in finding P-wave and S-wave phase arrivals accurately using three-component seismograms.

Plasmon-assisted terahertz imaging inside metal-filled media

We present the application of THz plasmonics in imaging dielectric objects embedded in metal-filled media. By exploiting the time domain information from the transmitted pulse, signatures of the objects were observed. To enhance the low quality images acquired through THz time domain spectroscopy, a super-resolution image processing technique was applied. It is shown that pulse arrival time and phase magnitude information compared to the integrated instantaneous power of the transmitted pulse provides more detailed images of the embedded object.

Identification and inversion of converted shear waves: case studies from the European North Atlantic continental margins

Wide-angle shear wave arrivals, converted from compressional to shear waves at crustal interfaces, enable crustal Vp/Vs ratios to be determined which provide valuable constraint on geological interpretations. Analysis of the converted shear wave phases represents the next logical step in characterizing the crustal structure and composition following multichannel seismic structural imaging and tomographic inversion of the wide-angle compressional wave phases. In this offshore study across two passive margins extending from stretched continental to fully oceanic crust, the high-data density (2–10 km ocean bottom seismometer, OBS, spacing) and a consistent, efficient conversion interface produced shear wave data sets suitable for traveltime inversion. The shear waves were recorded by three orthogonal geophones in each OBS. Arrival phases, visible to 180 km offset, were identified using their arrival times, moveout velocities and particle motions. Across the North Atlantic volcanic rifted continental margins studied, breakup was accompanied by the eruption of large volumes of basalts of the North Atlantic Igneous Province. The interface between post-volcanic sediments and the top of the basalts provides the dominant conversion boundary across the oceanic crust and the continent—ocean transition. However, the shear wave data quality was significantly diminished at the continental ends of the profiles where the thick basalt flows and hence this conversion interface feathers out and crustal attenuation increases. Initial modelling of the converted shear wave phases was carried out using a layer-based approach with arrivals converted on the way up used to constrain the Vp/Vs ratio of the post-volcanic sedimentary sequence beneath each OBS. To produce a model with continuous crustal S-wave velocities, the compressional wave velocities beneath the sediment-top basalt interface were transformed into starting shear wave velocities using a constant value of Vp/Vs and the inversion carried out by specifying the appropriate ray path. Once the data set had been fully interpreted, correction of the traveltimes to effective symmetric ray paths enabled us to apply a regularized grid inversion. Such inversions are less subjective than the layer-based approach and yield more robust minimum structure results with quantifiable errors, except in the vicinity of a known subbasalt low-velocity zone encountered on the Faroes margin. Monte Carlo analyses were performed for this approach; the average model from multiple inversions using randomized starting models and traveltimes shows the structure required by the traveltimes and the model standard deviation gives an estimate of uncertainty. Model and inversion parametrizations were fully tested and optimum parameters chosen for compressional and shear wave inversions. This allows, after appropriate model smoothing, an estimate to be made of the spatial variation of the Vp/Vs ratio within the crust. There are marked gradients in Vp, Vs and Vp/Vs ratio across the continent—ocean transition, which may result from intrusion of high magnesium mafic igneous material into the crystalline continental crust. The Vp/Vs ratio, used in conjunction with Vp, also provides constraints on the subbasalt lithologies forming the low-velocity zone. We conclude from such an analysis that this zone is unlikely to be composed entirely of igneous hyaloclastite material; some proportion of clastic sedimentary rocks is likely to be present. The Vp/Vs and Vp properties of the units underlying the low-velocity zone are inconsistent with crystalline continental basement and this unit is likely to represent a sill-intruded Mesozoic sedimentary sequence from a pre-breakup sedimentary basin.

Effective-one-body waveforms calibrated to numerical relativity simulations: Coalescence of nonspinning, equal-mass black holes

We calibrate the effective-one-body (EOB) model to an accurate numerical simulation of an equal-mass, nonspinning binary black-hole coalescence produced by the Caltech-Cornell Collaboration. Aligning the EOB and numerical waveforms at low frequency over a time interval of ~1000M, and taking into account the uncertainties in the numerical simulation, we investigate the significance and degeneracy of the EOB-adjustable parameters during inspiral, plunge, and merger, and determine the minimum number of EOB-adjustable parameters that achieves phase and amplitude agreements on the order of the numerical error. We find that phase and fractional amplitude differences between the numerical and EOB values of the dominant gravitational-wave mode h_22 can be reduced to 0.02 radians and 2%, respectively, until a time 20M before merger, and to 0.04 radians and 7%, respectively, at a time 20M after merger (during ringdown). Using LIGO, Enhanced LIGO, and Advanced LIGO noise curves, we find that the overlap between the EOB and the numerical h_22, maximized only over the initial phase and time of arrival, is larger than 0.999 for equal-mass binary black holes with total mass 30–150 M☉. In addition to the leading gravitational mode (2, 2), we compare the dominant subleading modes (4, 4) and (3, 2) for the inspiral and find phase and amplitude differences on the order of the numerical error. We also determine the mass-ratio dependence of one of the EOB-adjustable parameters by calibrating to numerical inspiral waveforms for black-hole binaries with mass ratios 2:1 and 3:1. The results presented in this paper improve and extend recent successful attempts aimed at providing gravitational-wave data analysts the best analytical EOB model capable of interpolating accurate numerical simulations.

Hypocenter location of mixed events in real-time processing systems

Automatic pickings in earthquake real-time monitoring systems often contain noise bursts and/or phases of different event(s) occurring almost simultaneously. Typically, a locator uses these picks as P and S waves arrival times coming from a single event and, therefore, should be complemented by a distinctive phase association logic. The method we propose manages to automatically associate data related to different events and eliminates the influence of spoiled data from single events. The method is based on “network beamforming”, a robust and stable algorithm, which utilizes a hypocenter grid search for the stack maximum of a set of complex exponents applied to the P phase readings. The algorithm separates the residual outliers and then uses them for location. If successful, a hypocenter is established for the interfering event. The solutions obtained are overall robust and independent from the estimate of origin times. The preliminary epicenter for the grid search is provided by the intersection of perpendicular bisectors in the modified “arrival order algorithm” or by the modified “Tnow” algorithm, which uses non-arrival information. We applied this method to automatic first arrival phase readings of 915 events registered by the Hi-net Japan seismic network and our results are statistically promising. Here, we present two interesting and complicated examples.

Effects of native vegetation on invasion success of Chinese tallow in a floating marsh ecosystem

Summary Interactions between resident and exotic species have been shown to control the biotic resistance of communities to invasion. With different life stages of the exotic species, each sequential interaction may dampen or strengthen previous ones, thereby influencing invasion success. We assessed the effects of resident vegetation type on the arrival and performance of Triadica sebifera (Chinese tallow), a widespread invader in freshwater floating marshes, using a combination of field studies and glasshouse experiments. Our results indicated that Triadica abundance was positively associated with native woody species, particularly the native actinorhizal shrub Morella cerifera (wax myrtle). Seed dispersal and germination of Triadica were generally low but suggestive that Morella has weak, facilitative effects on the spread of Triadica by channelling its dispersal by birds into shrub thickets and promoting germination upon arrival. Triadica seedling growth was greatest where light and total inorganic N were higher. Growth of Triadica trees was greater in marsh sites without Morella and did not exhibit any detectable responses to elevated N levels in substrates from Morella thickets. Morella may facilitate the spread of Triadica in floating shrub communities, yet inhibit its growth once established. The few individuals that establish in herbaceous marshes grow faster and may therefore reach maturity sooner than in Morella shrub thickets. Synthesis. Our work suggests that the net effects of facilitation and inhibition by native, resident species on exotics can influence invasion success. In this case, weak, facilitative effects operating in the arrival and establishment phases of invasion are not completely negated by subsequent negative interactions between the same species, enabling the invader to persist. Models that quantify the relative strength and cumulative effects of these interactions are needed to improve predictions of community invasibility.

Implementation of complex signal-processing algorithms for position-sensitive microcalorimeters

We have recently reported on a theoretical digital signal-processing algorithm for improved energy and position resolution in position-sensitive, transition-edge sensor (PoST) X-ray detectors [Smith et al., Nucl. Instr. and Meth. A 556 (2006) 237]. PoST's consists of one or more transition-edge sensors (TES's) on a large continuous or pixellated X-ray absorber and are under development as an alternative to arrays of single-pixel TES's. PoST's provide a means to increase the field-of-view for the fewest number of read-out channels. In this contribution we extend the theoretical correlated energy-position optimal filter (CEPOF) algorithm (originally developed for 2-TES continuous absorber PoST's) to investigate the practical implementation on multi-pixel single TES PoST's or Hydras. We use numerically simulated data for a nine-absorber device, which includes realistic detector noise, to demonstrate an iterative scheme that enables convergence on the correct photon absorption position and energy without any a priori assumptions. The position sensitivity of the CEPOF implemented on simulated data agrees very well with the theoretically predicted resolution. We discuss practical issues such as the impact of random arrival phase of the measured data on the performance of the CEPOF. The CEPOF algorithm demonstrates that full-width-at-half-maximum energy resolution of<8 eV coupled with position-sensitivity down to a few 100 eV should be achievable for a fully optimized device.

The Chemokine Receptor CXCR4 and the Metalloproteinase MT1-MMP Are Mutually Required during Melanoma Metastasis to Lungs

Melanoma is the most aggressive skin cancer once metastasis begins; therefore, it is important to characterize the molecular players involved in melanoma dissemination. The chemokine receptor CXCR4 and the membrane-bound metalloproteinase MT1-MMP are expressed on melanoma cells and represent candidate molecules for the control of metastasis. Using human melanoma transfectants that either overexpress or silence CXCR4 or MT1-MMP, or that have a combination of overexpression and interference of these proteins, we show that CXCR4 and MT1-MMP coordinate their activities at different steps along melanoma cell metastasis into the lungs. Results from in vivo xenograft mouse models of melanoma lung colonization and mice survival and short-term, homing nested polymerase chain reaction experiments from lung samples indicated that CXCR4 is required at early phases of melanoma cell arrival in the lungs. In contrast, MT1-MMP is not needed for these initial steps but promotes subsequent invasion and dissemination of the tumor with CXCR4. Investigation of potential cross talk between CXCR4 and MT1-MMP revealed that MT1-MMP accumulates intracellularly after melanoma cell stimulation with the CXCR4 ligand CXCL12, and that this process involves the activation of the Rac-Erk1/2 pathway. Subsequent to cell contact with specific basement membrane proteins, MT1-MMP redistributes to the cell membrane in a phosphatidylinositol 3-kinase-dependent manner. These results suggest that combination therapies that target CXCR4 and MT1-MMP should improve the limitations of the current therapies for metastatic melanoma.

한국형 달탐사 임무 예비 설계 소프트웨어의 개발

향후 우리나라의 달탐사 임무에 대비하여 순간 추력을 이용한 한국형 달탐사 예비 임무 설계 소프트웨어를 개발하였다. 달 탐사 임무 수행을 위한 지구 출발 단계, 달 천이 단계, 달 도착 및 임무 수행 궤도 단계를 포함한 임무 설계가 이루어 졌다. 이 소프트웨어를 이용하면 순간 추력을 사용한 최적의 달탐사 비행궤적을 설계할 수 있다. 이를 바탕으로 우리나라의 우주 발사체인 KSLV-II를 사용할 때의 발사 가능한 달 탐사선의 최대 질량을 산출하여 보았다. 아울러 심우주 추적망을 이용하여 탐사선의 추적 가능 여부에 대한 해석이 이루어 졌으며 탐사선과의 통신, 태양 전지판의 지향점 해석 그리고 식기간의 분석을 위한 지구-달-탐사선-태양 간의 기하학적 위치에 대한 해석도 함께 이루어졌다. Preparing for future Korean Lunar missions, preliminary Lunar mission design software is developed using a impulsive thrusting method. Developed software is capable of design and analysis every required mission phases to design Lunar mission, including the Earth departure, Lunar transfer, Lunar arrival and mission operation phases. Also, assuming that KSLV-II is selected as a launch vehicle, future Korean Lunar explorer's mass budget is estimated based on driven optimal trajectory characteristics. Tracking analysis is also performed using Deep Space Network including angle geometry analysis between Earth - Moon - Lunar explorer - Sun which are very important for communication, solar panel pointing strategy and eclipse analysis when Lunar missions are under designing phase.

On the Analysis of Envelope Correlation and Spectra for Rician Fading Channel

Physical fading radio channels encountered in wireless mobile communication are often modeled as a complex Gaussian process whose envelope is statistically described by Rayleigh or Rician probability distribution function (PDF). In most of the literature, the accuracy of the simulation model is estimated by comparing the simulated autocorrelation function (ACF) of inphase (or quadrature phase) component of the fading process and ACF of squared envelope with the analytical ones. In this paper, we examine the performance of a sum of sinusoid (SOS) based Rician fading channel simulator on the basis of the ACF and power spectral density (PSD) of the fading envelope. We obtained simplified approximate expressions for the autocorrelation and mean value of the fading envelope which become more accurate as the value of Rice factor increases. In the simulation, the line-of-sight (LOS) component is modeled as a zero-mean random variable with pre-chosen angle of arrival (AOA) and random initial phase. We showed that the AOA of the LOS component significantly affects the level crossing rate (LCR) and average fade duration (AFD) of the fading envelope. All simulation results are compared with the analytical results and a very good agreement between them is found.

Vajillas de importación no africanas en el noreste peninsular (s. V-VII). Distribución y tipocronología

The present paper deals with the last phases of arrival, in north-eastern Iberian Peninsula, of late Roman fine wares (5 th - 7 th century AD). The author takes into consideration those pottery productions that unlike the ARS wares which represent the majority of the imports in the western Mediterranean contexts for the period (e.g. “D.S.P.”, “Late Hispanic Sigillata”, “Phocaean Red Slip / Late Roman C Ware”). The different productions, their distribution and chronology will be presented in the first part of the paper, whereas their typologies and presence in the area of study will be discussed in the second one. The study, which is based on archaeological contexts dated by through sequences of 25 years, puts forward a chronology of 6 th century AD for the end of the arrival of these productions.

Approaching faithful templates for nonspinning binary black holes using the effective-one-body approach

We present an accurate approximation of the full gravitational radiation waveforms generated in the merger of noneccentric systems of two nonspinning black holes. Utilizing information from recent numerical relativity simulations and the natural flexibility of the effective-one-body (EOB) model, we extend the latter so that it can successfully match the numerical relativity waveforms during the last stages of inspiral, merger, and ringdown. By ``successfully'' here, we mean with phase differences $\ensuremath{\lesssim}8%$ of a gravitational-wave cycle accumulated by the end of the ringdown phase, maximizing only over time of arrival and initial phase. We obtain this result by simply adding a 4-post-Newtonian order correction in the EOB radial potential and determining the (constant) coefficient by imposing high-matching performances with numerical waveforms of mass ratios ${m}_{1}/{m}_{2}=1$, $3/2$, 2 and 4, ${m}_{1}$ and ${m}_{2}$ being the individual black-hole masses. The final black-hole mass and spin predicted by the numerical simulations are used to determine the ringdown frequency and decay time of three quasinormal-mode damped sinusoids that are attached to the EOB inspiral-(plunge) waveform at the EOB light ring. The EOB waveforms might be tested and further improved in the future by comparison with extremely long and accurate inspiral numerical relativity waveforms. They may be already employed for coherent searches and parameter estimation of gravitational waves emitted by nonspinning coalescing binary black holes with ground-based laser-interferometer detectors.

Structure of the crust beneath the southeastern Tibetan Plateau from teleseismic receiver functions

Southeastern Tibet marks the site of presumed clockwise rotation of the crust due to the India–Eurasian collision and abutment against the stable Sichuan basin and South China block. Knowing the structure of the crust is a key to better understanding of crustal deformation and seismicity in this region. Here, we analyze recordings of teleseismic earthquakes from 25 temporary broadband seismic stations and one permanent station using the receiver function method. We find that the crustal thickness decreases gradually from the Tibetan Plateau proper to the Sichuan basin and Yangtze platform but that significant (intra-)crustal heterogeneity exists on shorter lateral scales (<1000 km). Most receiver functions reveal a time shift of ∼0.2 s in the direct P arrival and negative phases between 0 and 5 s after the first arrival. Inversion of the receiver functions yields S-velocity profiles marked by near-surface and intra-crustal low-velocity zones (IC-LVZs). The shallow low-velocity zones are consistent with the wide distribution of thick surface sedimentary layers. The IC-LVZ varies laterally in depth and strength; it becomes thinner toward the east and southeast and is absent in the Sichuan basin and the southern part of the Yangtze platform. Results from slant-stacking analysis show a concomitant decrease in crust thickness from ∼60 km in the Songpan-Ganze fold system to ∼46 km in the Sichuan basin and ∼40 km in the Yangtze platform. High Poisson's ratios (>0.30) are detected beneath the southeastern margin of Tibet but in the Sichuan basin and southeastern Yangtze platform the values are close to the global average. Combined with high regional heat flow and independent evidence for mid-crustal layers of high (electric) conductivity, the large intra-crustal S-wave velocity reduction (12–19%) and the intermediate-to-high average crustal Poisson's ratios are consistent with partial melt in the crust beneath parts of southeastern Tibet. These results could be used in support of deformation models involving intra-crustal flow, with the caveat that significant lateral variation in location and strength of this flow may occur.

Detecting abrupt changes in a piecewise locally stationary time series

Non-stationary time series arise in many settings, such as seismology, speech-processing, and finance. In many of these settings we are interested in points where a model of local stationarity is violated. We consider the problem of how to detect these change-points, which we identify by finding sharp changes in the time-varying power spectrum. Several different methods are considered, and we find that the symmetrized Kullback–Leibler information discrimination performs best in simulation studies. We derive asymptotic normality of our test statistic, and consistency of estimated change-point locations. We then demonstrate the technique on the problem of detecting arrival phases in earthquakes.

The phase relations between the first arrivals of compressional and shear waves, and their signification to full wave logging

This paper describes the three phenomena observed in full wave experiments: 1. the amplitudes (absolute value) of the first compressional and shear arrivals have the same variation rules; 2. the phases of the first compressional and shear arrivals are always opposite to each other; and 3. the amplitude variation periods of the first compressional and shear arrivals are 2π. A full analysis and interpretation points out that these phenomena should appear under the full wave logging condition. Hence, the basis of using phase differences to extract useful information from the full wave is found.

Finite Difference Numerical Simulation of Trapped Waves in the Kunlun Fault Zone

AbstractIn this paper, we simulated the trapped waves generated by explosions in the Kunlun fault zone, using the three‐dimensional staggered‐grid finite difference algorithm. In order to improve the reliability of final fault‐zone model, we use the data of three components. The simulations indicate that the region above the depth of 1.0 km in the Kunlun fault zone produces main effects on the characteristics of the trapped waves. The S‐wave velocities and the width of fault zone have more effects on arrival times, waveforms, amplitudes and phases of the trapped waves. By simulation, the detailed structure parameters of the Kunlun fault zone are as follows: the width of shallow fault zone is 300m, and 250m in deep; The S‐wave velocity inside the fault zone is 0.98 km/s in the layers above the depth of 400 m, and that of surrounding rock is 1.70 km/s, and the Q value is 13.8. The S‐wave velocities and Q increase with depth. Beneath the depth of 1000 m, the S‐wave velocity inside the fault zone is 2.80 km/s and that of surrounding rocks is 3.3 km/s.