Frequently long-span bridges provide deep valley crossings, which require special consideration due to the possibility of local amplification of the ground motion as a consequence of topographical irregularities and local soil conditions. This does in fact cause locally enhanced seismic input with the possibility for the bridge piers to respond asynchronously. This introduces special design requirements so that possible out-of-phase ground displacements and the associated large relative displacements of adjacent piers can be accommodated without excessive damage. Assessment of the local variability of the ground motion due to local lateral heterogeneities and to attenuation properties is thus crucial toward the realistic definition of the asynchronous motion at the base of the bridge piers. We illustrate the work done in the framework of a large international cooperation to assess the importance of non-synchronous seismic excitation of long structures. To accomplish this task a complete SYNTHETIC accelerogram dataset was computed by using as input a set of parameters that describes, to the best of our knowledge, the geological structure and seismotectonic setting of the investigated area. The results show that lateral heterogeneities can produce strong spatial variations in the ground motion even at small incremental distances. In absolute terms, the differential motion amplitude is comparable with the input motion amplitude when displacement, velocity and acceleration domains are considered. Thus, on the base of the existing empirical regression relations between Intensity and peak values of ground motion a general result of our modeling is that the effect of the differential motion can cause an increment greater than one unit in the seismic intensity experienced by the bridge, with respect to the average intensity affecting the area where the bridge is built.

The ray series method may be generalized using a ray centered coordinate system for general 3D-heterogeneous media. This method is useful for Amplitude Versus Offset (AVO) seismic modeling, seismic analysis, interpretational purposes, and comparison with seismic field observations. For each central ray (constant ray parameter), the kinematic (the eikonal) and dynamic ray tracing system of equations are numerically solved. Then, the ray impulse and the ray SYNTHETIC SEISMOGRAMS are efficiently computed. The reflected, refracted, critically diffracted multiples and converted P-waves and/or S-waves are computed and evaluated at the ray endpoints. The central Ray Method application to two-dimensional models is investigated and comparison with seismic wave field is successfully done. Two examples of the ray field and SYNTHETIC SEISMOGRAMS for the complex models are presented here both for surface seismic profiling (SSP) and vertical seismic profiling (VSP).

The purpose of this work is to evaluate the regional seismic hazard for Morocco, following the deterministic approach proposed by Costa et al [1], based on the computation of complete P-SV and SH SYNTHETIC SEISMOGRAMS. The input for the computations is represented by source and structural models. Seismic sources are parameterized using the knowledge about past seismicity and the tectonic regime. The regional structural model we adopted is the one proposed by Cherkaoui [2], modified in its shallower part to account for the effects of the uppermost sedimentary layers. Maps of peak acceleration, velocity, and displacements are used for the general representation of the hazard. Accelerations are in good agreement with the values determined by Jimenez et al [3] with the standard probabilistic approach.

Seismometers and accelerometers pick up velocity and acceleration of seismic events and have different applications, which are mostly used by seismologists and engineers, respectively.Therefore, they are not regularly installed in the same location. It is believed that acceleration and velocity records can be calculated by each other, regarding that acceleration is the derivative of velocity. However, this belief has not been confirmed yet. For example, calculated acceleration, through the derivative of the seismometer record, has not been validated by comparing with the recorded accelerograms. This paper tries to find an answer for this challenge by having a comparison between the recorded accelerograms and the one calculated from seismometer records. For this, an accelerometer and a seismometer, both from the same factory, were installed in Mormori after the main earthquake of this city on August 18, 2014, to record aftershocks. Four events with considerable accelerations were selected among the events and recorded by these two instruments. All recorded data were corrected, and then the recorded accelerograms are compared with those obtained from differentiating of the corresponding SEISMOGRAMS. Some quantitative parameters, as well as response spectrum and Fourier amplitude spectrum have been used for the comparison. The parameters indicate that there are some ignorable differences between the records, the average of the parameters, Cave, is greater than 9.0 for all records, therefore, there is an excellent fit between the compared records.Response spectrums of the recorded accelerograms and the one obtained by differentiating respective SEISMOGRAMS are almost consistent for Tn<1.0 sec, however, they are different for longer vibrational periods. Therefore, for structures with a natural period of vibration (Tn) less than 1 sec, the required acceleration records for time history analysis can be calculated by differentiating the recorded SEISMOGRAMS.However, for structures with a longer natural period of vibration, accelerograms should be applied, and it is better not to rely on the acceleration record calculated by SEISMOGRAMS.

The work done in the framework of a large international cooperation, showing the very recent numerical experiments carried out within the framework of the EC project "Advanced methods for assessing the seismic vulnerability of existing motorway bridges" (VAB) to assess the importance of non-synchronous seismic excitation of long structures have been illustrated. The definition of the seismic input at the Warth bridge site, i.e. the determination of the seismic ground motion due to an earthquake with a given magnitude and epicentral distance from the site, has been done following a theoretical approach. In order to perform an accurate and realistic estimate of site effects and of differential motion it is necessary to make a parametric study that takes into account the complex combination of the source and propagation parameters, in realistic geological structures. The results for the final local model, characterized by an exaggeratedly thick and low velocity layer, demonstrate that a deep source excites lower frequencies than a shallow one and that the effect of increasing the epicentral distance is to attenuate high frequencies, making the resonant peaks, present at frequencies around 0.8 Hz, the dominant features of the entire spectra. The main practical conclusion of our analysis, verified by laboratory experiments, is that the Warth bridge is likely to well stand the most severe seismic input compatible with the seismic regime of the Eastern Alps.

Lg phase is a regional phase and short period guided wave composed mainly of a sequence of multiple reflected post critical S-waves trapped in the crustal wave guide. Lg phase also can be described as superposition of a higher mode of Love and Rayleigh waves. The mechanisms proposed to explain the excitation of Lg phase by explosions are: shear waves generated by inhomogeneity near the source, scattering effects that transfer P-wave or surface wave (Rg) energy into Lg, S-wave energy generated by spall which is an efficient source of Lg, nongeometrical S* phase and P-wave converted S-wave trapped in the crustal wave guide. Lg phase is one of the main phases produced by an underground nuclear explosion even with low yield. This phase has a sharp beginning with high amplitude in the short period SEISMOGRAMS in regional distances. The group velocity of Lg phase is about 3.5 km/s. Lg phase is a proper phase for yield estimation of underground nuclear explosions because of having a symmetric and radial pattern, lack of high attenuation and less scattering of mb (Lg) compared with the magnitude derived from other phases. In this paper, 16 underground nuclear explosions at Semipalaninsk Test Site (STS, in east Kazakhstan) recorded by SRO, Mashhad, have been investigated. The yields of these explosions were announced by Stevens and Murphy (2001). Maximum peak to peak amplitude for periods of 1 to 1.5 seconds was read in the group velocity window of 3.2 to 3.6 km/s as the amplitude of Lg phase. Then mb(Lg) was determined by using the formula presented by Nuttli (1986a). The relationship between computed mb(Lg) and announced yield (Y in kt TNT) of 16 explosions of STS was derived as mb(Lg) = 0.564 log (Y) + 4.863. This relationship is recommended for yield estimation of STS nuclear explosions from SRO, Mashhad.      

All the earthquakes are transient and nonstationary. For lack of alternatives, in seismology as well as earthquake engineering, most data are still processed by using the Fourier analysis. The most difficulties in the Fourier spectral analysis are associated with nonlinearity and non-stationary nature of the data. Such methods cannot reveal the detailed information in the dispersion properties, the wave form deformation, and the energy-frequency distribution. In this study, a new technique based on the time-domain empirical mode decomposition has been explained, which enables us to analyze both short-term information and long-term structures in seismic waves. It provides insight into long term memory and local time behavior of seismic signals. Oscillation modes of Earthquakes and Explosions are compared to each others, relationships between each group of the same data and differences between different data are obtained based on the produced IMFs. With respect to the advanced methods such as discrete stochastic non-Markov process it has been shown that this technique gives better identification. Plotting the maximum frequency of different IMFs via position of them, gives an effective identification tool. In this study first the technique is explained and then the obtained results are illustrated and discussed.

Well logs and seismic sections provide main data for oil reservoir modeling. Generating SYNTHETIC seismogram is a method to calibrate these data. Characterization of Bangestan reservoir by well log analysis and seismic modeling was the goal of the present study. Bangestan is one of the Ahwaz Oil Field reservoirs. Ahwaz Field is located at the north side of Ahwaz city in the south of Iran. The major reservoirs in this field are Asmari, Bangestan and Khami Formations. In the first step of this study, several well logs (Neutron, Density, Sonic and Gamma ray) were digitized for more than fifty wells. These logs provided petrophysical information. SEISMOGRAMS were generated by Geosyn software using sonic and density logs along the field on a seismic line. Petrophysical parameters calculated for this study using Excel software. Finally a SYNTHETIC seismic section was created and compared with petrophysical data such as porosity, volume of shale, lithology, etc. Interpretation of reflector's behavior, study of the level of seismic parameters to capture geologic heterogeneities in SYNTHETIC SEISMOGRAMS, recognizing problems and prevents, analysis of the petrophysical parameters along the section and giving guidance for next studies on this reservoir constitute main results of this study. Porosity variation was recognized the most important factor in appearance of reflectors on the section and reflectors were shown that present zonation of Bangestan reservoir might be changed.

A linear superposition method was used for modeling the time history of the production blast vibrations and optimizing the blast sequence to reduce vibration levels in Sar-Cheshmeh copper mine, Kerman, Iran. A single-hole blast for modeling and two double-hole blasts with time delays of 25 and 65 ms between two holes for modeling validation were carried out. The generated vibrations were measured at seven points with different distances and directions around the blasts. These records contain information about the complex mechanism of seismic energy radiation from an explosive source as well as the filtering effect of the signal travel path. Totally, 40 SEISMOGRAMS were synthesized (3 components for each point) for two blasts using the linear superposition method. The results obtained presented a good correlation between the SYNTHETIC and measured SEISMOGRAMS. Also, a comparison was made between the measured peak particle velocities (PPVs) and those obtained from the scaled-distance method and linear superposition modeling. This shows the merits of linear superposition modeling to predict PPVs. Moreover, the recorded SEISMOGRAMS of the single-hole blast were used to simulate the vibrations produced by a production blast at seven points. Furthermore, by using a systematic variation of firing delay in the modeling procedure, the effect of delay on the production blast vibrations was studied. The production blast simulations showed that for Sar-Cheshmeh copper mine, the blasts carried out with the inter-row delays more than 40 ms can significantly reduce vibration levels.