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Receiver function (RF) inversion is a well-established method to quantify a horizontally layered approximation of the S-wave velocity structure beneath a seismic station. It is well-known that the RF inverse problem is highly non-unique, and various tools such as joint inversion with other seismological observations exist that may overcome this problem. We present a joint inversion framework along with a Python package that implements the joint inversion of RF and the apparent S-wave velocity (VS,app). Our implementation includes a pseudo-initial model estimation, which helps address the inherent non-uniqueness of the joint inversion of RFs and VS,app. This implementation enhances the resolving power, enabling estimation of S-wave velocities with resolution approaching that of deep controlled source seismic methods. As an illustration, we showcase an example from a permanent station in the Makran subduction zone southeast of the Iranian Plateau and two other stations in the supplementary material. We compare our joint inversion results with several S-wave velocity models obtained through a deep seismic sounding profile and joint inversion of surface wave dispersion and RFs. This comparison shows that although we note a slightly lower sensitivity of our proposed method at greater depths (beyond 50 km), the method yields much better results for shallow structures. Our inversion code provides a powerful, accessible software package that has superior resolving power at shallow depth compared to RFs-surface wave inversion codes. Furthermore, the fact that only one data-derivative is used, makes this inversion code extremely easy to use, without the need for complementary datasets. [ABSTRACT FROM AUTHOR]

The launch of a rocket requires an energy comparable to the energy of many natural processes. For large rockets, the energy release reaches 10–100 TJ, and the power of engines reaches 0.1–1 TW. The energy release per unit volume is much higher than the specific energy content and energy release of all natural processes. During the launch and flight of a large rocket, disturbances in the substratum, the atmosphere, the ionosphere, and even in the magnetosphere occur. Effects from rocket engine burns have been studied for more than 60 years. Research results have been published in hundreds of articles, handbooks, and monographs. It turns out that the effects produced exhibit diverse geophysical phenomena. The effects near the rocket trajectory, namely, the regions of depressed electron density (ionospheric holes), and the generation of infrasound and atmospheric gravity waves (density waves) are investigated better than other effects. Great attention has been paid to studying the geomagnetic effect. The following methods have been used in studies: the Doppler effect, the Faraday, incoherent scattering, ionosonde, magnetometric methods, etc. The effects accompanying the launches and flights of rockets are being actively studied even now. For many years, large-scale (1 to 10 Mm) disturbances that occur after rocket launches have been studied. Their study makes it possible to better understand the mechanisms of the propagation of disturbances from a rocket over global distances, the interaction of subsystems in the Earth–atmosphere–ionosphere–magnetosphere system, and the ecological consequences of rocket engine burns. Disturbances occurring in the atmosphere and geospace substantially depend on the state of the atmospheric–space weather, time of day, season, and phase of the solar cycle. Even with the launch of two identical rockets, disturbances in the mentioned system can be very different. It should be borne in mind that rockets differ in power, trajectories, fuel composition, and the location of cosmodromes. Therefore, studying the response of subsystems to rocket launches and flights remains an urgent problem. The purpose of this study is to describe the results of an analysis of the ionospheric effects of the Soyuz and Proton rockets launched during the 24th cycle of solar activity from the Baikonur Cosmodrome. To observe the effects in the ionosphere caused by the launch of the Soyuz and Proton rockets from the Baikonur Cosmodrome, a vertical sounding Doppler radar was used. As a rule, measurements are carried out at two fixed frequencies of 3.2 and 4.2 MHz. The smaller of them is effective when studying the dynamic processes in the E and F1 layers, and the larger one is effective when studying the F1 and F2 layers. The parameters of ionospheric disturbances that followed the launches of 81 Soyuz rockets and 53 Proton rockets from the Baikonur Cosmodrome in 2009–2021 are analyzed. It is confirmed that there are several groups of delay times for the possible reaction of the ionosphere to the launch and flight of the rockets. These delay times varied widely (from 10 to 300 min). The delay time groups correspond to several groups of apparent horizontal velocities of disturbance propagation (100–200, 390 ± 23 m/s, 0.97 ± 0.10, 1.28 ± 0.13, 1.68 ± 0.13, 2.07 ± 0.13 km/s, and approximately 8 km/s). Slow atmospheric gravity waves, atmospheric gravity waves of man-made origin, density shock waves, slow, and ordinary MHD waves have such velocities. As a rule, the generated perturbations (except for shock waves) are quasi-periodic in behavior with a period in the range from 5 to 20 min. The amplitude of the Doppler shift is 0.1–0.3 Hz. The relative amplitude of quasi-periodic variations in the electron density is typically 1‒10% and rarely reaches 20%. [ABSTRACT FROM AUTHOR]

To understand steeply dipping events in seismic reflection interferometry (SRI), we derived an expression that describes the difference in travel time (Δτ) from a diffractor to two receivers in two dimensions. For a fixed receiver interval, the expression shows that Δτ is zero when the diffractor is at the midpoint of the paired receivers, increases with an apparent velocity of half the medium velocity as the diffractor moves toward either receiver, and remains constant for a diffractor located on the same side of both receivers. The horizontal portion of Δτ is slightly skewed during the normal moveout correction, yielding a maximum peak of the horizontally stacked trace at a slightly smaller time than Δτ. Accordingly, the diffracted waves have an apparent velocity slightly higher than half of the medium velocity in a horizontally stacked image. This conformed to virtual data for an elastic two-layer model with a vertical boundary. We then generalized the expression to three dimensions, in which listric travel time curves were predicted for an oblique edge diffractor, a vertex diffractor offline from the receiver pair, or a buried diffractor. Based on both two- and three-dimensional analyses of the edge diffractor, we tentatively interpreted the linear and listric dipping events observed in the passive SRI image across the Korean Peninsula to have been caused by diffractors near the intersection of the profile and geologic boundaries. [ABSTRACT FROM AUTHOR]

Depending upon the surface wave methods, the measured surface wave velocities are either normal mode velocities or apparent velocities. The "apparent" surface wave velocity corresponds to the superposed mode combining the available normal modes. The spectral-analysis-of-surface-waves (SASW) method measures the apparent surface wave velocities. However, these velocities render SASW analyses complicated because of the mode jumps induced by several wave groups. To alleviate such complications, this study introduced a beamforming technique and produced information on unwrapped wavenumber, which is vital in unwrapping the phase spectrum in SASW analyses. Additionally, incoming wave directions filtered out multiple reflections and irrelevant seismic events to retain only the surface waves directly propagating from the source. The proposed wavenumber unwrapping technique was verified using field applications, dynamic finite element analysis, and synthetic waveforms. Notably, an optimal beamforming technique was established using four geophones, making the proposed method highly practical and reducing the hardware requirements. Hopefully, the proposed analysis technique provides SASW practitioners with a more comfortable and more reliable environment in utilizing the SASW technique. • Unwrapped wavenumbers were proposed as a guide in SASW velocity calculations. • Wave directions were used as a filter for measured irrelevant stress waves. • Beamforming tests coupled with SASW analysis was optimized by using four receivers. • The proposed method was validated by seismograms, FEA and three field applications. [ABSTRACT FROM AUTHOR]

We consider equations and algorithms describing the operation of strapdown inertial navigation systems (SINS) intended for determining the inertial attitude parameters (the Rodrigues-Hamilton (Euler) parameters) and the apparent velocity of a moving object. The construction of these equations and algorithms is based on the Kotelnikov-Study transference principle, Hamiltonian quaternions and Clifford biquaternions, and differential equations in four-dimensional (quaternion and biquaternion) orthogonal operators. [ABSTRACT FROM AUTHOR]

The crustal velocity structure of southern Guatemala is estimated using the methods of Minimum Apparent Velocity and Converted Waves, applied to local seismic data. The results are tested by relocating a random sample of events and by the generation of synthetic seismograms. The velocity model obtained has a roughly constant gradient throughout the crust, underlain by an intermediate layer ~ 15 km in thickness. Mantle velocities are approximately 8.0 km/sec. This is an aver¬age model for southern Guatemala with the limitations of the complex tectonics.

The paper addresses the issue of researching into the engineering characteristics of rotational strong ground motion components and rotational effects in structural response. In this regard, at first, the acceleration response spectra of rotational components are estimated in terms of translational ones. Next, new methods in order to consider the effects of rotational components in seismic design codes are presented by determining the effective structural parameters in the rotational loading of structures due only to the earthquake rotational components. Numerical results show that according to the frequency content of rotational components, the contribution of the rocking components to the seismic excitation of short period structures can never be ignored. During strong earthquakes, these rotational motions may lead to the unexpected overturning or local structural damages for the low-rise multi-story buildings located on soft soil. The arrangement of lateral-load resisting system in the plan, period, and aspect ratio of the system can severely change the seismic loading of wide symmetric buildings under the earthquake torsional component. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Summary: Groundwater age has become a fundamental concept in groundwater hydrology, but ages originating from isotopic analyses are still identified with a lack of clarity and using models that occasionally are unrealistic. If the effect of advection and dispersion on water ages has already been extensively identified, very few studies address the reliability of using radiometric ages as derived from isotopic data to estimate aquifer properties such as average velocities. Using simple one-dimensional and two-dimensional analytical solutions for single-site and two-sites mobile–immobile systems, we compare the radiometric ages to the mean ages (or residence times) as deduced from a direct, physically-based simulation approach (using the mean age equation), and show that the competition between isotope decay rate and dispersion coefficient can generate important discrepancies between the two types of ages. A correction for the average apparent velocity originating from apparent isotopic ages is additionally provided. The particular case of the tritium age dating method is also addressed, and a numerical example is finally given for illustrating the analysis considering a more complex and heterogeneous aquifer system. Our results suggest that age definitions based on the radioactivity of isotopes may not be representative for the mean age of the sample or for the groundwater velocity at given locations, and may not always be suitable for constraining the calibration of hydrogeological models. [ABSTRACT FROM AUTHOR]

The apparent velocity of the incident wave is an important parameter for simulating rotational ground motion with theoretical methods, but it is difficult to estimate effectively when there is only a single record. This paper discusses a P-SV ratio method based on elastodynamic theory in a multi-layer isotropic elastic half space. The apparent velocities of four earthquakes in the SMART1 array are calculated with this method. The result is close to a method that uses travel time analysis. Furthermore, the factors that impact the apparent velocity and equivalent incident angle are considered according to records from the Chi-Chi earthquake. There is no obvious relationship between the equivalent incident angle and epicenter distance. However, the equivalent incident angle is obviously dependent on the site conditions. [ABSTRACT FROM AUTHOR]

Two design methods of a filter in a frequency-spatial frequency (f-k) domain have been developed for bistatic ground penetrating radar. The proposed methods suppress the direct wave, which causes significant artifacts in radar images, and are evaluated by laboratory measurements. Because the geometric positions of a transmitting antenna and a receiving antenna are not fixed, the suppression of a direct wave is an important issue. Then, we propose an f-k filtering approach for the solution, and present two methods to design the f-k filter. Both methods use a difference of an apparent horizontal velocity between a direct wave and a reflection from a target, and work automatically from position information of a transmitting antenna and a receiving antenna. One method is to mask an f-k spectrum in a region where a spectrum of the direct wave is distributed. The region is defined from the maximum and the minimum apparent horizontal velocity of the direct wave, which are calculated from the location of the transmitting antenna and the scanning area of the receiver. As for the other method, the most essential point is applying a time shift to eliminate a difference of an arrival time of a direct wave, where the time shift is calculated beforehand from the location of the transmitting antenna and the receiving antenna. Then, anapparent horizontal velocity of the direct wave becomes infinitely large due to the time shift. Thus, the f-k spectrum of the direct wave concentrates around a frequency axis because its slope is infinitely large. Then, a filter to reject the dc component in the spatial frequency direction is applied. Both methods are applied to an experimental data set which is acquired by a bistatic radar measurement to detect a buried landmine model with a depth of 10 cm. In addition, it is confirmed that they can suppress the undesired fluctuation of the images nearly one-tenth and help the reliable detection of a buried object. [ABSTRACT FROM AUTHOR]

Two design methods of a filter in a frequency--spatial frequency (f-k) domain have been developed for bistatic ground penetrating radar. The proposed methods suppress the direct wave, which causes significant artifacts in radar images, and are evaluated by laboratory measurements. Because the geometric positions of a transmitting antenna and a receiving antenna are not fixed, the suppression of a direct wave is an important issue. Then, we propose an f-k filtering approach for the solution, and present two methods to design the f-k filter. Both methods use a difference of an apparent horizontal velocity between a direct wave and a reflection from a target, and work automatically from position information of a transmitting antenna and a receiving antenna. One method is to mask an f-k spectrum in a region where a spectrum of the direct wave is distributed. The region is defined from the maximum and the minimum apparent horizontal velocity of the direct wave, which are calculated from the location of the transmitting antenna and the scanning area of the receiver. As for the other method, the most essential point is applying a time shift to eliminate a difference of an arrival time of a direct wave, where the time shift is calculated beforehand from the location of the transmitting antenna and the receiving antenna. Then, an apparent horizontal velocity of the direct wave becomes infinitely large due to the time shift. Thus, the f-k spectrum of the direct wave concentrates around a frequency axis because its slope is infinitely large. Then, a filter to reject the dc component in the spatial frequency direction is applied. Both methods are applied to an experimental data set which is acquired by a bistatic radar measurement to detect a buried landmine model with a depth of 10 cm. In addition, it is confirmed that they can suppress the undesired fluctuation of the images nearly one-tenth and help the reliable detection of a buried object. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

For assessing the radionuclide transport parameters, the apparent diffusion coefficient and the rock capacity factor η R (being the product of the accessible porosity η and the retardation factor R) in host rocks used for nuclear waste disposal, mainly two classes of experiments are used: pure diffusive experiments e.g. through-diffusion, and experiments where next to a concentration gradient also a pressure gradient is applied e.g. pulse injection experiments. In Boom Clay, through-diffusion and pulse injection experiments lead to similar values for the accessible porosity of tritiated water (HTO), while for another unretarded tracer, iodide, significantly higher values are obtained by pulse injection. Similarly, in recompacted Na-illite, for chloride (another unretarded anion), lower accessible porosity values are observed by through-diffusion than by pulse injection. The difference increases while lowering the ionic strength. The reason for the discrepancy lies in the models used for analysing the migration experiments with a pressure gradient. Experiments with a pressure gradient allow fitting the apparent velocity V app of a tracer. The rock capacity factor is estimated as the ratio V Darcy / V app of the Darcy velocity V Darcy and V app. This is correct for HTO, but not for anions because the water flow through anion inaccessible porosity is neglected. Making a correct water flow mass balance by taking the water flow through inaccessible porosity into account, demonstrates that the rock capacity factor is given by the product F V V Darcy / V app with F V the fraction (0 ≤ F V ≤ 1) of the Darcy velocity flowing through tracer accessible porosity. Previously determined η R values are in reality the ratio η R / F V and overestimate η R. In agreement with the experimental results, a lower ionic strength leads for (unretarded) anions to a lower accessible porosity η and consequently a lower F V and more overestimation of η. Besides charge related inaccessible porosity, porosity can also be inaccessible because of the size of the transported species: the accessible porosity becomes zero in case the particle size approaches the pore throat. Because the intention of experiments with a pressure gradient is to know η R , we propose two models, which are basically two tracer distributions over a pore, for estimating F V. Considering Poiseuille flow, we calculate a typical pore radius, the hydraulic conductivity and for both distributions the accessible porosity, the fraction F V and the fitted ratio η R / F V. Application to experimental data shows anisotropy in the pore radius, corresponding to the observed anisotropy in hydraulic conductivity. For anion exclusion, the model describes qualitatively the experimentally observed evolution as a function of double layer width. Because also for cations there is presently no valid relation between V app and η R , migration experiments with a pressure gradient only provide a reasonable estimate for the rock capacity factor η R in case of small (with respect to the average pore size) neutral particles like HTO. • Pressure gradient experiments may not allow determining the accessible porosity. •Flow changes concentration in the accessible porosity when entering/ leaving a core. •Anisotropy of clay pore radius explains anisotropy of hydraulic conductivity. •It can be unclear what is the length in the Péclet number. •Typical distance of back diffusion is ratio of dispersion coefficient and velocity. [ABSTRACT FROM AUTHOR]