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Uphole refraction survey of the velocity regimes in South-Eastern part of Niger Delta, Nigeria was carried out using a 12-channel seismograph: Mc SEIS 160M Model 1115. The study presents a regional weathering structure of the area, the velocities and depths of the weathered layers were calculated from the travel time of the seismic waves. The data were interpreted using the time -- intercept method which revealed that the low velocity layer was fairly variable in thickness in the region, varying between 24.5m and 25.8m, with a regional average value of 25.12m. The weathered and consolidated layers have average Compressional wave velocities of 944.0m/s and 1907.69m/s respectively. The knowledge from the result of this study can be applied in oil and ground water exploration plans. [ABSTRACT FROM AUTHOR]

This paper describes a new method for automatic preparation of a noisy seismic record for further analysis using expert information systems. The method is based on seismogram fingerprints, which, due to their concise but informative pattern, allow the development of a reliable algorithm for finding important noise characteristics. The search for the optimal cutoff frequency for a high-pass filter is especially important under conditions of partial overlap of the signal and noise spectra, when the latter have high intensity. It is precisely this difficult case that this study aims to address. The article analyzes the methodology developed here in application to several hundred records of regional earthquakes and explosions. The analysis showed that reliable results can be achieved in more than 90% of the cases. In addition, the defects and limitations of the method are mentioned, which are logical consequences of its advantages. The Appendix to this article contains a detailed description of the algorithm underlying the method. [ABSTRACT FROM AUTHOR]

The recent earthquake in the Kahramanmaraş region on 06.02.2023 in Turkey and Syria had a magnitude of Mw 7.8, its intensity in some areas of Turkey reached XI points on the modified Mercalli scale. The earthquake caused catastrophic consequences, leading to the death of more than 52,800 people, as well as numerous destructions of infrastructure. The article analyzes the consequences of the appearance in the seismogram of an earthquake of an unusually strong delta pulse, associated with the arrival of a horizontally polarized S-wave. The issues of creating seismic protection systems against high-intensity delta-shaped pulses are discussed. [ABSTRACT FROM AUTHOR]

Proper regulative in earthquake risk reduction, hazard assessment, earthquake resistant design and construction of structures, should be under perpetual improvement. They are mainly the result of earthquake study and analysis of post-seismic effects. In this context, a new frame for seismogram analysis is proposed, based on its decomposition into elementary and single (positive and negative) fluctuations (EF/SF). Decomposition enables rearrangement, both providing the frame for defining new attributes, where several main ones are proposed and elaborated in the paper: fan diagram of EFs structural axes; R- or RQ-envelope, formed over positive and over negative peaks of ordered SFs; two forms of difference functions of positive and negative R/RQ-envelopes, as a measure of seismogram's (a)symmetry, in respect to t-axis; distributions of SFs durations. Several others are in perspective. Analogy between R-envelope and seismogram's spectrum is considered from the aspects of arranged elements, and asymptotic behavior of these two functional attributes. More objective definition of seismogram duration is proposed, determined by linear regression across the scatter plot of SFs peaks. R-envelope showed itself as an invariant in the seismogram population, and the distribution of SFs durations as well. Results are presented through extensive graphics, backed with mathematical description. Thorough discussion of the concept and results is given. [ABSTRACT FROM AUTHOR]

This paper proposes a method to reduce seismogram variability as a determining factor in its interpretation, processing, and clustering. By introducing the concept of single fluctuations (SFs), the seismogram can be parsed into a sequence of random impulses with subsequent ordering. This rearrangement of SFs, if they are assigned by positive integers, represents the formal mapping of a regular string of integers into a random one, which can be represented with a bipartite random graph (bigraph). Due to its specific randomness, such a bigraph is considered a new type of random balanced bigraph. The R-envelope and RQ-envelope, its equidistant version, are defined by tracing the peak envelope over ordered SFs. The equivalence and complementariness of the RQ and bigraph are considered and discussed, forming a combined characteristic of the seismogram. The R/RQ provided a considerable reduction in seismogram variability, which was confirmed by creating and analyzing an ensemble of RQ from several seismograms. In the RQ domain, distance is defined as a possible basis for metrics and clustering, but the ensemble variability was quite narrow and not as suitable for this purpose. Otherwise, the ensemble shows high redundancy hidden in the seismogram population. As for the bigraph, the mesh of its edges is structuralized in bundles, forming a skeleton, which reflects the internal structural content of the seismogram. The distance over the domain of bigraphs is proposed to show the possibility of clustering. This means that only a combined RQ and bigraph provides a suitable frame for seismogram representation with reduced variability and, thus, the potential for more effectively organizing seismic databases and a deeper interpretation of seismograms; therefore, RQs and bigraphs can be considered as a transform of a seismogram. Many aspects of these concepts are thoroughly discussed. The similarity between concepts of SF and wavelets is briefly considered. This very complex theme is new and promises broad further research. All issues considered in the paper are abundantly illustrated. [ABSTRACT FROM AUTHOR]

The 1923 Kanto earthquake (MJ=7.9) has great significance for seismic hazard assessments of the Tokyo metropolitan area, because it caused extensive damage to the area. To deepen our understanding of the strong ground motion of the Kanto earthquake, this paper reviewed studies on its observed strong ground motion and found that 1) seismic intensity VI on the Japanese scale (IX or X on the M. M. scale) was widely distributed in an area of approximately 8,000 km2, which is equivalent of that of the 2011 M9 Tohoku earthquake, 2) strong effects of soil amplification on ground motion were suggested by the correlation of the damage distribution with surface geology, 3) the restoration of the scaled-out seismogram indicated that the ground motion at the upland of Tokyo would be roughly 50 cm/s for maximum velocity and 50 cm for maximum displacement, and 4) the ground motion in the epicentral area is unclear, but would be roughly twice or more as strong as that at Tokyo. [ABSTRACT FROM AUTHOR]

The first seismic station of the Seismic Network of Sofia University (SNSU) was built in 2023 with funding from the Scientific Research Fund of Sofia University "St. Kliment Ohridski". The station is operating in the Faculty of Physics since September 2023. The equipment consists of a seismometer Geophone 4.5 Hz and a digitiser PSNADC24. A portable computer is used for data recording and archiving. During the month of station operation several earthquakes in Bulgaria and neighbouring countries were analysed. The spectrum of the seismic noise from the station was analysed for different periods. The characteristics of the terrain of station installation were also determined using the method H/V. Although the equipment has modest capabilities, it allows students and young scientists to work directly with the seismic equipment and to do scientific investigations. The possibility of scientific research will be expanded renewing the equipment (purchased in October 2023). [ABSTRACT FROM AUTHOR]

It is favorable to re-evaluate the seismic hazard for a given territory, since in the course of time new methods are developed and new data are gathered that can enable more sophisticated (physically sound) and reliable assessment of the seismic hazard. Therefore, it is mandatory to re-evaluate the seismic hazard for Kosovo, considering the seismic sources in Kosovo. The data of this article influence the reduction of seismic risk for the territory of Kosovo.

In this paper, we propose a new approach based on the fitting of a generalized linear regression model in order to detect points of change in the variance of a multivariate-covariance Gaussian variable, where the variance function is piecewise constant. By applying this new approach to multivariate waveforms, our method provides simultaneous detection of change points in functional time series. The proposed approach can be used as a new picking algorithm in order to automatically identify the arrival times of P- and S-waves in different seismograms that are recording the same seismic event. A seismogram is a record of ground motion at a measuring station as a function of time, and it typically records motions along three orthogonal axes (X, Y, and Z), with the Z-axis being perpendicular to the Earth's surface and the X- and Y-axes being parallel to the surface and generally oriented in North–South and East–West directions, respectively. The proposed method was tested on a dataset of simulated waveforms in order to capture changes in the performance according to the waveform characteristics. In an application to real seismic data, our results demonstrated the ability of the multivariate algorithm to pick the arrival times in quite noisy waveforms coming from seismic events with low magnitudes. [ABSTRACT FROM AUTHOR]

Proper regulative in earthquake risk reduction, hazard assessment, earthquake resistant design and construction of structures, should be under perpetual improvement. They are mainly the result of earthquake study and analysis of post-seismic effects. In this context, a new frame for seismogram analysis is proposed, based on its decomposition into elementary and single (positive and negative) fluctuations (EF/SF). Decomposition enables rearrangement, both providing the frame for defining new attributes, where several main ones are proposed and elaborated in the paper: fan diagram of EFs structural axes; R- or RQ-envelope, formed over positive and over negative peaks of ordered SFs; two forms of difference functions of positive and negative R/RQ-envelopes, as a measure of seismogram’s (a)symmetry, in respect to t-axis; distributions of SFs durations. Several others are in perspective. Analogy between R-envelope and seismogram’s spectrum is considered from the aspects of arranged elements, and asymptotic behavior of these two functional attributes. More objective definition of seismogram duration is proposed, determined by linear regression across the scatter plot of SFs peaks. R-envelope showed itself as an invariant in the seismogram population, and the distribution of SFs durations as well. Results are presented through extensive graphics, backed with mathematical description. Thorough discussion of the concept and results is given.

This paper proposes a method to reduce seismogram variability as a determining factor in its interpretation, processing, and clustering. By introducing the concept of single fluctuations (SFs), the seismogram can be parsed into a sequence of random impulses with subsequent ordering. This rearrangement of SFs, if they are assigned by positive integers, represents the formal mapping of a regular string of integers into a random one, which can be represented with a bipartite random graph (bigraph). Due to its specific randomness, such a bigraph is considered a new type of random balanced bigraph. The R-envelope and RQ-envelope, its equidistant version, are defined by tracing the peak envelope over ordered SFs. The equivalence and complementariness of the RQ and bigraph are considered and discussed, forming a combined characteristic of the seismogram. The R/RQ provided a considerable reduction in seismogram variability, which was confirmed by creating and analyzing an ensemble of RQ from several seismograms. In the RQ domain, distance is defined as a possible basis for metrics and clustering, but the ensemble variability was quite narrow and not as suitable for this purpose. Otherwise, the ensemble shows high redundancy hidden in the seismogram population. As for the bigraph, the mesh of its edges is structuralized in bundles, forming a skeleton, which reflects the internal structural content of the seismogram. The distance over the domain of bigraphs is proposed to show the possibility of clustering. This means that only a combined RQ and bigraph provides a suitable frame for seismogram representation with reduced variability and, thus, the potential for more effectively organizing seismic databases and a deeper interpretation of seismograms; therefore, RQs and bigraphs can be considered as a transform of a seismogram. Many aspects of these concepts are thoroughly discussed. The similarity between concepts of SF and wavelets is briefly considered. This very complex theme is new and promises broad further research. All issues considered in the paper are abundantly illustrated.

On May 29, 2017, the MW6.6 Poso earthquake occurred in Central Sulawesi, Indonesia, causing moderate damages. The mainshock rupture and primary aftershock cluster occurred in the active Palolo-Sausu tectonic zone, and some aftershocks also took place around the Tokararu fault. However, the rupture mechanism of this earthquake and its relation to regional tectonics are not clear. In this study, the rupture process of the Poso mainshock is estimated by finite-fault waveform inversion, which is constrained by teleseismic bodies and surface waves. The rupture propagates upward unilaterally in a southwest-dipping moderate-angle (∼34°) normal fault beneath Tokorondo Mountains, with a notable ∼15% initial moment release at the first 4s of the ∼12s rupture duration. The average and peak slip are 0.5 m and 1.5 m, respectively. The rupture velocity is relatively slow (less than 2.5 km/s), and the Coulomb stress changes due to the mainshock are obtained using the inverted coseismic slip.

It is well known that seismic events at sea can lead to severe effects on marine facilities. A seismic event can generate amplifications due to local conditions of the place, that is, site effects. In this work, we show numerical results of seismic amplifications on the seabed where there is the presence of deposits formed by soft soils. We formulate the problem using an Indirect Boundary Element Method. In this formulation, we consider that the total field of displacements can be expressed in terms of an incident and another diffracted field. Specifically, the diffracted field is expressed in terms of Fredholm integral equations of second kind and zero order. This conceptualization can also be understood as the implementation of the Huygens Principle because the waves are constructed at the boundary from which they are irradiated. We study five geometries of soft deposits. In general, we found that P (compressional) waves can generate seismic amplifications of up to 45 times while SV (shear) waves cause amplifications up to 65 times. [ABSTRACT FROM AUTHOR]

Mechanical methods of deployment of permanent, continuous analog visible recording of signals complicate the design of analog recorders and light-beam oscilloscopes with the continuous visible recording of low-frequency processes and periodic output of recording frames, reduce their reliability and accuracy, make it difficult to adjust deployment steps, increase power and dimensions, and also lead to additional geometrical and optical errors in light-beam oscilloscopes. To eliminate these shortcomings, electronic methods for deployment of continuous analog visible recording are proposed and analysed, on the basis of which corresponding devices are also developed, created, and tested, with the help of which the proposed electronic methods are tested and verified based on ASEO type Automatic seismic electrographic oscilloscopes. [ABSTRACT FROM AUTHOR]

The various tremors coming from inside the Earth, i.e. the earthquake P and Ѕ waves, are registered on appropriate devices called seismometers. The records given by seismometers are called seismograms. The methods for analysis of analog and digitally registered seismic earthquake waves - seismograms and numerical processing of the results of those analyzes in modern seismological practice include the following elements: • Identification of different types of seismic waves on the seismogram, • Determining the exact time of registration of a certain type of seismic wave, • Numerical processing of the registered waves at a number of seismic stations, in order to determine the spatial parameter of the hypocenter of the earthquake and the moment of its occurrence, • Defining the mechanism for protection against earthquakes and dynamic parameters of protection, • Energy characteristics (magnitude) of the earthquake and analysis in the distribution of the macroseismic field, i.e. formation of a mathematical model for distribution of the surface effect of the earthquake, • Determining the structural elements of the Earth's crust based on the interpretation of surface and spatial waveforms, • Calculation of the empirical values of the amplification characteristics of the soil on a local scale and determination of the mathematical laws for those phenomena. [ABSTRACT FROM AUTHOR]

Increasing the resolution of seismic data has long been a major topic in seismic exploration. Due to the effect of high-frequency noises, traditional methods could only improve the resolution limitedly. To end this, this paper newly proposed a high-resolution seismic data processing method based on well–seismic combination after summarizing the research status on high resolution. Synthetic record and seismogram are similar in effective signals but dissimilar in noises. Their effective signals are regular and noises are irregular. And they are similar in adjacent frequency. Based on these “three-regularity” characteristics, the relationship between synthetic record and seismogram was established using the neural network algorithm. Then, the corresponding extrapolation algorithm was proposed based on the self-adaptive geological and geophysical variation of multi-layer network structure. And a model was established by virtue of this method and the theoretical simulation was carried out. In addition, it was tested from the aspects of frequency component and amplitude energy recovery, phase correction, regularity elimination and stochastic noise. And the following research results were obtained. First, this new method can extract high-frequency information as much as possible and remain middle and low-frequency effective information while eliminating the noises. Second, in this method, the idea of traditional methods to denoise first and then expand frequency is changed completely and the limitation of traditional methods is broken. It establishes the idea of expanding frequency and denoising simultaneously and increases the resolution to the uttermost. Third, this new method has been applied to a variety of reservoir descriptions and the high-resolution processing results have been improved significantly in precision and accuracy.

Perceptron is adopted to classify the Ricker wavelets and to detect the seismic anomaly in a seismogram. Three learning rules are used in the training of perceptron to solve the decision boundary. The optimal learning-rate parameter is derived. The lower and upper bounds of the learning-rate parameter are derived. It can provide that the learning can converge when the parameter is within the range. The normalized learning rule is derived also. Combining learning rules, a fusion learning rule is proposed. In the experiments, these rules are applied to the detection of a seismic anomaly in the simulated seismogram and to compare the convergence speed. The fusion learning rule has the fastest convergence and is applied to the real seismogram. The seismic anomaly can be detected successfully. It can improve the seismic interpretation.

In this paper, we propose a new approach based on the fitting of a generalized linear regression model in order to detect points of change in the variance of a multivariate-covariance Gaussian variable, where the variance function is piecewise constant. By applying this new approach to multivariate waveforms, our method provides simultaneous detection of change points in functional time series. The proposed approach can be used as a new picking algorithm in order to automatically identify the arrival times of P- and S-waves in different seismograms that are recording the same seismic event. A seismogram is a record of ground motion at a measuring station as a function of time, and it typically records motions along three orthogonal axes (X, Y, and Z), with the Z-axis being perpendicular to the Earth’s surface and the X- and Y-axes being parallel to the surface and generally oriented in North–South and East–West directions, respectively. The proposed method was tested on a dataset of simulated waveforms in order to capture changes in the performance according to the waveform characteristics. In an application to real seismic data, our results demonstrated the ability of the multivariate algorithm to pick the arrival times in quite noisy waveforms coming from seismic events with low magnitudes.

A complex study of the structure and rock composition of an exploited oil and gas field on the Yamal Peninsula (Russia) has been performed. The experimental equipment, based on an original deep ground-penetrating radar (GPR) GROT 12, included also a seismic sensing complex. GPR transects and hodograph images have been obtained. The GPR data are compared with seismic data in the general processing system. This complex study of the electromagnetic and acoustic parameters of a layered deposit to actual depths of more than 500 m has been performed for the first time in the engineering practice. The key advantage of the electromagnetic method over the seismic method (higher sensitivity to changes in the saturated bed content (water, oil, gas, condensate) over depth) is implemented. [ABSTRACT FROM AUTHOR]

Traditionally, sonic and density logs are vital components during the generation of synthetic seismogram. However, sonic logs as observed in many studies, often have poor quality or even absent in some cases. This work is a case study for the transformation of resistivity logs to pseudo sonic logs for the generation of pseudo synthetic seismogram considering the effect of gas. This research studies the relationship between resistivity and sonic logs in order to utilize the former for the generation of pseudo synthetics when sonic log is absent or poor. Standard synthetic seismograms were first created conventionally using sonic and density logs as inputs. The sonic log values were then plotted against the corresponding resistivity values for each well to derive their relationship using both linear and polynomial functions. Generally, the crossplot shows a fair correlation but some scattered plots were observed. Further probe into these observed anomalies revealed the areas to be gas saturated. A better correlation was achieved within affected zones by doing independent crossplots for previously gas delineated units. The standard synthetic generated were used as control for the pseudo synthetics and better correlation is observed when compared with the previous pseudo synthetics that does not acknowledge gas-effect. [ABSTRACT FROM AUTHOR]

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When recording seismic ground motion in multiple sites using independent recording stations one needs to recognize the presence of the same parts of seismic waves arriving at these stations. This problem is known in seismology as seismic phase picking. It is challenging to automate the accurate picking of seismic phases to the level of human capabilities. By solving this problem, it would be possible to automate routine processing in real time on any local network. A new machine learning approach was developed to classify seismic phases from local earthquakes. The resulting model is based on spectrograms and utilizes the transformer architecture with a self-attention mechanism and without any convolution blocks. The model is general for various local networks and has only 57 k learning parameters. To assess the generalization property, two new datasets were developed, containing local earthquake data collected from two different regions using a wide variety of seismic instruments. The data were not involved in the training process for any model to estimate the generalization property. The new model exhibits the best classification and computation performance results on its pre-trained weights compared with baseline models from related work. The model code is available online and is ready for day-to-day real-time processing on conventional seismic equipment without graphics processing units.

Abstract Three mysterious explosion sounds were heard in the coastal towns of Tamsui, west of Taipei in northern Taiwan, in the early evening of December 5, 2013. The event left clear signals that are identified in the recordings of 12 regional seismometers and 3 infrasound sensors and processed by means of travel time analysis. The apparent velocity of ~330 m/s of the signals confirms that the energy transmission was through the atmosphere, and the characteristics of the waveforms suggest the meteor-generated shockwaves. We use the graphical method as well as the Genetic Algorithm optimization approach to constrain the trajectory of the meteor and to locate its projected intercept with the ground—(25.33 N, 121.26 E), approximately 20 km off the coast of Tamsui. The trajectory has azimuth (measured from north in a map view in the clockwise direction) of 303° and (near-vertical) elevation angle of 70°. From the observed period of 1.3 s at the maximum amplitude of the infrasound signal, we estimate by conventional scaling law that the meteor in question had impact energy on the order of 5 × 1010 J (equivalent to an earthquake of local magnitude 4) or roughly a size of ~0.5 m across.

In a seismogram, there exist many kinds of wavelets. The reflected wavelet from the gas sand zone has a different shape with other layers. Usually, the information of each wavelet is weak and unknown, and the unsupervised classification method is applied to the clustering of the wavelets. Using the shape structure of the wavelet, syntactic pattern recognition is applied to the clustering. The extracted wavelets can be represented as strings of symbols. Levenshtein distance is used to calculate the distance between the two strings. Bottom-up and top-down hierarchical clustering methods are used in the construction of the dendrogram. The top-down hierarchical clustering by the recursive method is proposed. A new pseudo F-statistics is proposed to decide the optimal number of clusters. From the experimental results in simulated and real seismograms, the wavelets on the gas sand zone can be detected successfully. It can improve the seismic interpretation. [ABSTRACT FROM AUTHOR]