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Fault stability analysis plays an important role in assessing the potential hazard of faults and in studying the mechanism of earthquake occurrence. Fault stability depends on the magnitude of the normal and shear stresses imposed on the fault by the tectonic stress and rock friction, while the magnitude of the normal and shear stresses is related to the spatial orientation of the fault normal with respect to the three principal stress axes, so it is easier to understand the variation of fault stability with its orientation by expressing the stability of different faults in the principal axis coordinate system. In this paper, we first developed a method to plot the stability of faults with different orientations in the principal stress axis coordinate system, then investigated the influence of the magnitude of principal stresses and friction on fault instability, and reached the conclusion that the instability is mainly affected by the relative magnitude of principal stresses (shape ratio). Finally, we proposed to use fault stability as an indicator to evaluate the quality of inverted stress obtained from fault slip data or earthquake focal mechanisms, that is, to evaluate the reliability of the inverted stress according to the compatibility of stress and fault stability. It is described in detail in terms of measured fault slip data from two regions. [ABSTRACT FROM AUTHOR]

This paper describes the behavior of several seismic precursors prior to the 2016–2019 activation in an area of a complex geodynamic setting at the boundary of the Pacific, North American, and Eurasian plates. We used an integrated approach to combine identified precursors with a view to getting more accurate locations of possible rupture zones of future large earthquakes. The precursors include quiescence based on the RTL parameter and the "Z-function", variations in the slope of the earthquake recurrence graph (γ-value), and the areas of seismic ruptures dS. For the first time in Kamchatka, we analyze anomalies in the parameter dS interpreted as seismic activations to show the presence of a precursory component before the onset of the foreshock activation. Examples include increases in the values of that parameter before events that were the largest for the areas where they occurred: the Near-Islands Aleutian earthquake of July 17, 2017, Mw = 7.8 and the Uglovoe Podnyatie earthquake of December 20, 2018, Mw = 7.3. The overall extent of the anomalous area, which still exists and includes consecutive quiescence and foreshock phases, is ~900 km, which creates conditions for possible occurrence of a new great earthquake in the junction zone of the three plates with a magnitude that can exceed whatever has been recorded in the region so far. [ABSTRACT FROM AUTHOR]

The Chuya earthquake of 2003 exerted an appreciable influence on the seismicity of the entire Altai. This paper presents data on variations in the Altai seismicity from 2003 to 2021. It is shown that earthquakes of the first half-year after the major earthquake of 2003 had their rupture zones in the epicentral zone, while the other Altai structures were aseismic. After 2009 we saw changes both in the near zone that encompasses geological structures that were adjacent to the epicenter (with distances of 60‒80 km from the mainshock epicenter), such as the Aigulak, Kurai, South Chuisky and North Chuisky mountain ranges, and in the far zone at distances of 250‒450 km from the epicenter and in different directions from it. The Aigulak earthquake of 2019 gave rise to an aftershock process that displaced the center of Altai seismicity to the eponymous mountain range. There are no data on large earthquakes during the historical period for many Altai structures which have been activated following the Chuya earthquake, either from seismological or from paleo-geological evidence. One could explain the evolution of seismicity around the rupture zone of the Chuya earthquake in space, and with time delays of some years, invoking the influence of a large earthquake on a medium involving plasticity. We know of nonlinear models that hold promise for future research concerning the influence of large earthquakes on the evolution of seismicity in geological media. [ABSTRACT FROM AUTHOR]

This paper reports results from an analysis of swarm seismic events that were recorded in 2018 in the area of the Elbrus Volcanic Center (EVC) by the North Caucasus Seismological Network of the Federal Research Center, Geophysical Survey, Russian Academy of Sciences (FRC GS RAS). The standard location procedure was used to find the hypocenters of recorded events in the EVC area. In the LOS program package, a complex combined location algorithm, methods for minimizing the time residuals at the source, and search over a grid with several trial depth values, were used to relocate the hypocenters of seismic events in swarm sequences. This approach enhances location reliability due to incorporation of the uncertainties related to erroneous onset identification and insignificant deviations of travel times that depend on the earth velocity model used here. A study of earthquake mechanisms for the larger earthquakes has determined the type of slip in agreement with the kinematics in the Elbrus–Mineralnye Vody normal-oblique fault zone. Correlation analysis of waveforms on the vertical component that have been filtered in the frequency range 1‒10 Hz, which includes P and S waves, at the nearest station shows a high agreement among the data under analysis (the correlation coefficient is R ≥ 0.85), thus indicating a high probability of all events having similar sources and propagation paths of seismic waves. Comparison of power spectral densities for individual earthquakes in the swarm sequences also demonstrates a high similarity. [ABSTRACT FROM AUTHOR]

In this paper, we present the first results of complex geological and geophysical studies of active tectonics in the northeast of Taymyr that were carried out during the expedition of the Northern Fleet and the Russian Geographical Society in 2020. At the foot of the Byrranga Mountains, a wide zone of active fault-folded tectonic deformations was identified and studied. The general kinematics of displacements is reverse-thrust with signs of shear. The structural style of young tectonic deformations bears a direct resemblance to well-studied structural analogues of the Central Asian seismic belt. The Taymyr seismotectonic zone reveals both spatial and genetic isolation. It has an individual model of the Late Cenozoic geodynamic evolution and modern seismotectonic regime, which differs sharply from the Laptev Sea rift zone adjacent to the east. A complex of geological and geophysical methods showed the high efficiency of application in the Arctic to identify young fault-fold structures, which are potential sources of strong earthquakes. [ABSTRACT FROM AUTHOR]

In this paper, we determine the location of the hypocenter and the magnitude of the earthquake of September 11/23, 1888 based on macroseismic data published in the Russian periodic in Russian, Armenian, and Georgian languages. Calculations showed that the magnitude of the earthquake was previously significantly underestimated, due to which it was not included in the catalog of strong earthquakes in the Caucasus test region (Shebalin and Tatevossian, 1997). The accuracy of the location of the hypocenter makes it possible to identify the active fault, with which the source of the 1888 earthquake is associated. The earthquake with Mw = 6.6 that occurred almost 100 years later confirms the long-term activity of the Western branch of the East Anatolian fault zone. [ABSTRACT FROM AUTHOR]

In this paper, we kinematically analyze the movements of plates and blocks of the region of southeastern Turkey, where strong earthquakes occurred on February 6, 2023, based on a homogeneous database of displacement velocities of GNSS permanent monitoring stations. Along the East Anatolian fault zone from 2008 to 2018, the Arabian Plate was established to shift relative to the Anatolian Plate, which corresponds to a left shift (without a normal component) at a rate from 1 cm/yr in the eastern part to 0.8 cm/yr in the western part. Along the Chardak fault, displacements corresponding to the left shift occurred at a rate of less than 0.7 cm/year. The revealed kinematics is confirmed by focal mechanisms and cosesismic displacements of the studied earthquakes. The M7.5 earthquake that occurred directly on the Chardak fault is not an aftershock of the M7.8 earthquake, but is a relatively independent event. An analysis of the seismic regime shows that the stresses on the East Anatolian fault after the main M7.8 event are relieved by the first large latitudinal fault zone (the Chardak fault). The results of our study suggest that the counterclockwise rotation of the Anatolian and Arabian plates associated with the opening of the Red Sea Rift is most likely decisive for the general kinematics of the plates in the region. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to present the damage features of masonry structures and engineering seismology studies after the 19–22 November 2021 Köprüköy earthquakes (Mw 5.1 and Mw 4.7). The masonry structures damaged near the epicenter have been examined. Damages have been detected that such as vertical cracks in the walls of the masonry structures, out-of-plane bending of the walls, splits in the joints of the walls, and separation of the floors from the elements such as walls and roofs. The fact that the structures in the region do not receive an engineering service and that they are constructed without complying with the relevant earthquake regulations are thought to cause such damage. The damage in Topçu village of Köprüköy district in Erzurum is more than in other settlements. Microtremor measurements have been applied in Topçu Village to investigate dynamic soil features. The soil amplification factor and soil predominant period have been obtained ~ 6.8 and ~ 1.3 s for the first measurement and ~ 9.4 and ~ 1.3 s for second location, respectively. Also, Vs30, bedrock depth, vulnerability index, and shear strain parameters have been calculated using some empirical relations. High bedrock depth and low Vs30 values are obtained for both measurements. The vulnerability index and shear strain values also indicate that the vulnerability of the soil is high. In order to remain in the safe zone for structures in a possible future earthquake, it has been suggested that it should comply with the earthquake-soil-structure relationship and should be designed in accordance with the earthquake regulation standard. [ABSTRACT FROM AUTHOR]

Earthquake indicators provide a huge advantage in the preparation for the calamity and its aftermaths. Total electron content (TEC) is an ionospheric measurement that varies before the possible happenstance of an earthquake. In this research paper, ordinary kriging based surrogate model (OKSM) which is used for forecasting ionospheric TEC variation is adapted as an earthquake indicators in low-latitude and mid-latitude regions. Seven International GNSS Service (IGS) stations from the mid-latitude and low-latitude region are chosen for observation. The stations are from different countries such as Indonesia (BAKO), Ecuador (RIOP), Greece (ORID), Cyprus (NICO), Hawaii (HNLC) and Italy (MATE & MAT1). The OKSM prediction program is performed with previous 2 months of TEC data from the observed date and its accompanying solar parameters such as Planetary K and A index (Kp & Ap), Radio Flux at 10.7 cm (F10.7) and disturbance storm time (DST) index acquired from OMNIWEB data servers. The performance of the model is evaluated using statistical metrics such as root mean square error (RMSE), normalized – RMSE (NRMSE), mean absolute error (MAE), Pearson's correlation coefficient (PCC) and chi-squared goodness of fit test. The evaluation of the prediction model on the same date shows that the performance deviation of OKSM is in the range of 2–5 TECU and also establishes the fact that the prediction capability of the OKSM is accurate. Application of the OKSM constructed with previous days data collected from high earthquake prone areas by omitting effects of solar storms and solar activities will act as a highly economical and simple early warning indicator of an earthquake. [ABSTRACT FROM AUTHOR]

Static and dynamic frictional properties of rock discontinuities are of great importance in the evaluation of the initiation of failure and post-failure motions of rock engineering structures as well as the rupture and strong motions induced by earthquake faults in earthquake science. Nevertheless, experiments on static and dynamic frictional properties of rock discontinuities are very rare. In this study, the authors describe tilting and stick–slip experiments on various natural rock discontinuities and saw-cut surfaces to determine their static and dynamic frictional properties. Furthermore, these experimental results are compared with each other to discuss the static and dynamic frictional properties of rock discontinuities from tilting and stick–slip tests. Experimental results show that peak (static) friction angle for discontinuity surfaces obtained from tilting tests and stick–slip experiments are very close to each other. Highlights: In this paper, it is demonstrated that the static and dynamic frictional properties of rock discontinuities can be determined from tilting and stick-slip tests. Experimental results confirm that peak (static) friction angle for discontinuity surfaces obtained from tilting tests are very close to those obtained from stick-slip experiments. The experimental results could be useful for researchers dealing with the estimation of post-failure motions of failed bodies in Rock Mechanics and Rock Engineering as well as strong motion simulations in Earthquake Science and Engineering. [ABSTRACT FROM AUTHOR]

With the increase in the pace of development, the demand for tunnels has increased in recent years. Analysing the stability of a tunnel in a fractured rock mass is a very challenging and cumbersome activity. The tunnel stability depends on the strength of the rock, joints bolt strength, in-situ stresses, and their orientation. This paper focuses on constructing tunnels in fractured/jointed rock mass. Three different software namely Rocscience Phase2 (finite element based), FLAC3D (finite volume based) and PFC3D (distinct element based), were used to analyse the performance and stability under static and dynamic loading conditions. The geomaterial properties used for the analysis were taken from data obtained after laboratory testing and based on available literature. The effect of joint orientation and bolt length was analysed using Phase 2 assuming plain strain conditions. The effect of earthquake and performance of fully grouted, energy absorbing and deformation-controlled bolts under seismic loading conditions were compared using FLAC3D. While the 3D distinct element analysis of geometry was performed using PFC3D to evaluate the effect of joints and their orientation. The performance of the different types of bolts was also analysed numerically. The behaviour of bolts can be customised using the 'fish'function. The results indicate that analysis must incorporate the fusion of various numerical simulation techniques like finite element-, finite volume- and distinct element-based methods for more reliable results. [ABSTRACT FROM AUTHOR]

This paper reports the obtained analysis data on the focal mechanisms and general distribution of earthquake epicenters in the Laptev Sea region. The principal stress axes directions were calculated by the formal stress inversion method for four groups of event clusters with known focal mechanisms. The distributions of the earthquake epicenters and crust thickness were compared. According to the seismological data, the extension axis of the Gakkel Ridge on the Laptev Sea shelf currently continues in the vicinity of the group of extension detachments located along the eastern boundary of the Anisin, Zarya, and Belkovskii–Svyatonosskii rift chains. The more ancient extension axis located along the group of detachments marking the eastern boundary of the Ust'-Lena and Omoloi rift systems and continuing the Gakkel Ridge axis is currently much less active. It carries residual stresses near its intersection with the Khatanga–Lomonosov fault zone in the northwestern parts of the shelf area and with the Lena–Taimyr zone of boundary uplifts, in the southwestern part. The axes oriented along the Olenyok and Bykovskii channels and the Siberian Platform boundary form extension conditions in the eastern part and strike–slip conditions in the western part of the Lena delta area. [ABSTRACT FROM AUTHOR]

The existence of several magnitude scales in the compiled earthquake catalogs of a specific region has made the development of regional relations connecting magnitude scales a necessity, especially for creating a homogeneous seismic catalog in which all magnitudes should be converted to a preferred magnitude scale. To consistently estimate all magnitude ranges and avoid the saturation problem for large earthquakes, the preference is always given to the moment magnitude Mw scale, wherein the most complete and reliable catalog used worldwide is the Global Centroid Moment Tensor (GCMT). However, to our knowledge, no study has yielded regional (in Algeria) relationships for converting different magnitudes to the moment magnitude (Mw,GCMT). The main reason is typically due to the lack of data pairs of different magnitude scales with Mw (GCMT). To overcome this issue, in this research paper, the moment magnitudes data used for northern Algeria (the area bounded by 32° to 39° N and 3° W to 10° E) have been taken principally from the GCMT catalog and enhanced with the European–Mediterranean Regional Centroid Moment Tensor catalogs RCMT and ZUR-CMT. Regarding this latter, it has been demonstrated in the literature that for the Mediterranean regions, a minor correction should be addressed before merging its data with the GCMT and RCMT catalogs, which are perfectly correlated. To accomplish this task, the magnitude scales tested against Mw are the surface wave magnitude, MS, and the body wave magnitude mb issued from the international seismological sources of ISC and NEIC for the same boundaries. As long as the earthquake magnitudes, in general, are affected by errors of comparable size, the best and most reliable regression method that considers the errors in both dependent and independent variables for linear conversion problems is the General Orthogonal Regression, which is adopted and applied herein to develop the regional relations. [ABSTRACT FROM AUTHOR]

Background: The Bangkok Basin has been known from non-instrumental observations of the local population to be subject to ground motion amplification due to the deep alluvial sediments and basin geometry. This study analyzes available seismic data to confirm that basin effects are significant in the Bangkok Basin. The paper contributes to the evaluation of basin effects by characterizing the engineering ground motion parameters and HVSR curves for the Bangkok basin which produce lengthening of ground motion duration with respect to nearby rock sites, albeit with very low ground motions. For this purpose, we analyzed ground motion records from seismic stations located within the Bangkok alluvial basin from 2007 to 2021. Recorded peak horizontal ground acceleration (PGA) for seismic stations inside the basin always exceeded 1 cm/s2 during eight earthquakes with Mw ≥ 5.5. Of these, two were intraslab events and six were shallow crustal earthquakes. These recorded ground motions shook high-rise buildings in Bangkok even though their epicentral distance exceeded 600 km. Methods: Several time and frequency domain analyses (such as analysis of residual, HVSR, Hodogram plots, etc.) are used on the ground motion records in the Bangkok basin to determine the frequency content of recorded ground motion and to demonstrate the significance of surface waves induced by the deep basin in altering the engineering ground motion amplitudes. In addition, centerless circular array microtremor analysis is used to determine the depth of sedimentary basin to the bedrock. Results: Based on comparisons from those stations located outside the Bangkok basin, we observed the capability of alluvial deposits in the Bangkok basin to amplify ground motion records by about 3 times. We observed that there is a unique site amplification effect between 0.3 and 0.1 Hz due to local surface waves and other moderate amplifications between 2 and 0.5 Hz due to a soft layer like other deep alluvial basins in other metropolitan areas. Conclusion: We noticed that there is a unique site amplification effect between 0.1 and 0.3 Hz and smaller peaks around 2 and 0.5 Hz consistent with expectations for site amplification effects associated with deep basins. Moreover, we noticed the presence of low frequencies content of the surface wave generated within the basin which deserved further studies using the 2D/3D ground motion modelling through basin topography and velocity models. [ABSTRACT FROM AUTHOR]

Predicting individual large earthquakes (EQs)' locations, magnitudes, and timing remains unreachable. The author's prior study shows that individual large EQs have unique signatures obtained from multi-layered data transformations. Via spatio-temporal convolutions, decades-long EQ catalog data are transformed into pseudo-physics quantities (e.g., energy, power, vorticity, and Laplacian), which turn into surface-like information via Gauss curvatures. Using these new features, a rule-learning machine learning approach unravels promising prediction rules. This paper suggests further data transformation via Fourier transformation (FT). Results show that FT-based new feature can help sharpen the prediction rules. Feasibility tests of large EQs ( M ≥ 6.5) over the past 40 years in the western U.S. show promise, shedding light on data-driven prediction of individual large EQs. The handshake among ML methods, Fourier, and Gauss may help answer the long-standing enigma of seismogenesis. [ABSTRACT FROM AUTHOR]

In this paper a novel passive device defined as the tuned mass damper inerter (TMDI) is studied to control the response of a base-isolated nuclear power plant containment (BI-NPPC) structures under stochastic horizontal ground motions. A new method of connecting TMDI to the isolation foundation is proposed. Recently, the TMDI has been introduced as a generalization of the classical TMD to achieve enhanced performance. Consider the case of a base-isolated structure equipped with a TMDI device, which is served as a base-isolated nuclear power plant containment. A particular arrangement of mechanical gearings (inerter) attached to TMD is set, optimum parameters of this system are found based on a simplified two degree of freedom model that reflects the dynamic properties of both the isolation structure and the TMDI. A straightforward numerical approach is developed for the optimal design of this device considering a white noise ground excitation, and a simplified analytical solution for the optimal design of TMDI parameters are introduced and compared with the numerical results in terms of the optimum frequency ratio, the optimum damping ratio and enhanced performance. Within a probabilistic framework, the influence of soil conditions is investigated by modeling the seismic ground motion as a filtered Gaussian random process. Different filter parameters are considered that may be associated with firm, medium or soil conditions depending on the frequency content of the power spectral density function. Several natural recorded accelerograms are also selected to scrutinize the effectiveness of the TMDI isolated-base structure via time-domain analyses. Properties of the BIS are considered in respect of its damping and stiffness. It can be concluded that higher control performances are achieved when lower values of base isolation sub-system damping ratio are used, however, the control performances of the TMDI are basically not affected by small variation of the natural frequency of the isolated-base structure. [ABSTRACT FROM AUTHOR]

This paper focuses on the lack of income opportunities for Dalits in Nepal, as they are the most affected group in any disaster. The presence of vulnerable family members in Dalit households may further increase their income deprivation. We therefore studied Dalit households' income sources and identified income determinants in Gandaki Rural Municipality in Gorkha District—the epicentre of the 2015 earthquake. We observed a higher dependency of Dalit households on daily wages, livestock sales, social security allowances, and vegetables sales; however, remittance and seasonal job earnings represented the largest share of household incomes. We observed a significant difference in per capita income between farm (US$46) and non-farm (US$273) income sources, with the difference smallest in the lowest income quantile and the largest in the highest quantile. When the household head was a single woman, we observed a reduction in non-farm (by 29%) and total incomes (by 23%). Likewise, when the household head had a chronic health problem, or the household included an elderly family member, there was a reduction in the household's income. We suggest economic interventions for Dalit households to prevent increased social exclusion in the development process, specifically focusing on vulnerable individuals and households in the lowest income quantile. [ABSTRACT FROM AUTHOR]

This paper presents the first example of how to systematically identify the submarine landslide source of a tsunami using an innovative hybrid approach. This ground-breaking method is developed to resolve the puzzle around the source mechanism of the mysterious tsunami observed on 6th February 2023 in the Eastern Mediterranean Sea. The tsunami followed the two inland Mw 7.8 and Mw 7.5 Türkiye–Syria earthquakes, which occurred consequently with a 9 h interval on this day. The first earthquake (Mw 7.8) had an epicentral distance of 90 km from the nearest coast, which is closer than the second one (Mw 7.5) to the coast and yet its crustal deformation was almost entirely limited to inland. Therefore, the co-seismic surface displacement generated by the earthquake was ruled out as the source of the tsunami, confirmed by numerical modelling. Here, we hypothesized that the tsunami was most likely generated by a submarine landslide triggered by the earthquake. Analysis of tide gauge observations revealed that the waves arrived from 27 min to 48 min after the first earthquake (Mw 7.8) at different coastal locations, implying that the potential submarine landslide was triggered by the first earthquake (Mw 7.8). Backward tsunami travel time mapping using tide gauge observations guided us to constrain the area of the potential landslide. We approximated the dimensions of the landslide using spectral analysis of the tsunami observations. Consequently, an iterative trial-and-error approach was employed to confirm the landslide source of the tsunami by defining various informed alternative landslide scenarios and applying numerical modeling. Modelling showed that a submarine landslide can reproduce the tsunami observations reasonably well. It is located on a steep slope of the seafloor approximately 50 km from Arsuz. The submarine landslide is estimated to have caused a seafloor deformation measuring approximately 16 km in length and 4.0 km in width. [ABSTRACT FROM AUTHOR]

Although Myanmar is an earthquake-prone country, there has not been proposed an official national seismic hazard map. Thus, this study conducted a probabilistic seismic hazard assessment for Myanmar and some of its metropolitan areas. Performing this assessment required a set of databases that incorporates both earthquake catalogs and fault parameters. We obtained seismic parameters from the International Seismological Centre, and the fault database includes fault parameters from paper reviews and the database. Based on seismic activities, we considered three categories of seismogenic sources—active fault source, shallow area source, and subduction zone source. We evaluated seismic activity of each source based on the earthquake catalogs and fault parameters. Evaluating the ground-shaking behaviors for Myanmar requires evaluation of ground-shaking attenuation; therefore, we validated existing ground motion prediction equations (GMPEs) by comparing instrumental observations and felt intensities for recent earthquakes. We then incorporated the best fitting GMPEs into our seismic hazard assessments. By incorporating the Vs30 (the average shear velocity down to 30 m depth) map from an analysis of topographic slope, we utilized site effect and assessed national probabilistic seismic hazards for Myanmar. The assessment shows highest seismic hazard levels near those faults with high slip rates, including the Sagaing Fault and along the Western Coast of Myanmar. We also assessed seismic hazard for some metropolitan cities, including Bagan, Bago, Mandalay, Sagaing, Taungoo and Yangon, in the forms of hazard curves and disaggregation by implementing detailed Vs30 maps from micro-tremor surveys. The city-scale assessments show higher hazards for sites close to an active fault or/and with a low Vs30, demonstrating the importance of investigating site conditions. The outcomes of this study will be beneficial to urban planning on a city scale and building code legislation on a national scale. [ABSTRACT FROM AUTHOR]

Maoxian Country in Sichuan Province, China is a quake-prone mountainous area. Within 300 km of it, there have been more than ten strong earthquakes higher than Ms6.0 on record. The nearest one is the Diexi Earthquake of 1933, 8.7 km from Maoxian County. A catastrophic scale landslide, the Xinmo landslide, took place on the steep cataclinal slope of Xinmo Village on June 24, 2017. Shear failure happened to the phyllite layer of rich fissures during the landslide. In this paper, shaking table tests have been conducted on the Xinmo landslide as a prototype, and a non-contact deformation measurement based on the digital image correlation (DIC) technique has been made to analyze the dynamic response and deformation of the slope under accumulated seismic actions. As the results, stress amplification is found at the end of joints on the potential slide face. Failure starting from the middle of the potential slide face in the beginning extends upwards and downwards along the face, and leads to a steep tension crack on the top of the slope and a buckling failure of radial-arc cracks at the foot. A semi-steep radial crack in buckling part has a shear failure. The tensile stress amplification on the discontinuous face contributes to the failure accumulation of it and asymptotic failure of the slope. It proposed that the closure and downward displacement of tensile crack on the top of slope, buckling phenomenon at the foot of slope and shear failure of semi-steep crack are all the bad omens of landsliding. [ABSTRACT FROM AUTHOR]

This paper provides an overview of inverse studies that estimate earthquake source processes using tsunami-related data. Methods and techniques developed with those data associated with the 2004 Sumatra and 2011 Tohoku-oki earthquakes were reviewed. These events significantly impacted subsequent studies that focused on great historical earthquakes. Thus, recent advancements from studies on great historical earthquakes (M > 8) using old tsunami data, including documents and non-digital tsunami waveforms, have been reviewed. Another key earthquake was the 1700 Cascadia earthquake, and its source process was revealed using geological tsunami deposit data, which have led to a recent surge in prehistorical earthquake studies using tsunami deposit data. Considering this, the advancements in prehistorical earthquake studies have been reviewed. Finally, expected advancements in earthquake source process studies using tsunami-related data in the near future have been discussed. [ABSTRACT FROM AUTHOR]

Load reduction methods (LRMs) for the deeply buried structure such as a high-filled cut-and-cover tunnels (HFCCTs) under seismic loads are complex when compared with cases under static loads. The soil arching effect (SAE) for load reduction mechanisms is ambiguous. Unfortunately, very limited related research focused on these LRMs subjected to earthquake loads. This paper mainly focused on investigating the SAE induced by different LRMs under dynamic loads. Parametric studies were conducted using FLAC3D to assess the effectiveness of these LRM based on the variations of the SAE in soils under three different seismic waves. Several proven effective LRMs such as the inclusion of expanded polystyrene (EPS) and combined with concrete wedges were analyzed. Considering the variations of vertical soil pressure (VSP) and lateral soil pressure (LSP), the results show that the SAE is significantly related to the height and thickness of the soil arching zone (SAZ) that develops, which in turn affects the soils pressure distribution (SPD) around the CCT's structures. In addition, the use of EPS above and on both sides of a CCT to reduce both VSP and LSP simultaneously was found to resist seismic loads more effectively. [ABSTRACT FROM AUTHOR]

Phenomenology is the unity of principles and methods employed for investigating the essence of things. The present paper is a brief review of the series of publications that these authors carried out over the past decade. The general thrust of these publications consists in the idea that phenomenological ideas of physics are used to analyze earthquakes. One conspicuous example of a phenomenological theory is thermodynamics. Maxwell's electrodynamics is also a perfect example of a phenomenological theory. The phenomenology of earthquakes is still far from reaching that high level of excellence. A look at the rational knowledge of geodynamics shows that we have so far reached a preliminary stage where we are aware of the subject-matter, methods, and problems faced by the future phenomenological theory of earthquakes. Nevertheless, we already clearly see that our approach to the construction of such a theory has promise. We are using concrete examples to show that phenomenological concepts of general physics are helpful in the search for the principles of the theory, in the processing and analysis of concrete manifestations of seismicity. [ABSTRACT FROM AUTHOR]

The paper presents the studies of the Khuvsgul earthquake on January 11, 2021 at 21:32 UTC (January 12, 2021 at 05:32 local time), MW = 6.7, ML = 6.9, and the seismicity structure in the aftershock period for the Altai-Sayan mountain region and the Baikal rift zone, where the epicenter of this earthquake was located. Two faults are seismically activated, diverging from the southern end of the aftershock area at an acute angle: one in the northeast and one in the northwest direction, as well as transverse faults between them. According to the epicenter position and studies of the source area by other authors, the main event corresponds to the northeastern fault, and large aftershocks occurred at the junction of the northwestern fault with transverse faults feathering from the east. The main event was immediately followed by a series of large aftershocks, the strongest of which occurred on March 31, 2021 with ML = 6.2 and on May 3, 2021 with ML = 6.4. Spatial changes in the seismic regime of the aftershock region led to the predominant activity of its southern end. The junction area of the collisional structures of the Altai–Sayan folded zone and the rift structures of the Baikal depressions system is distinguished in seismicity as a block structure with increased seismicity near the block boundaries. First of all, these are the Tuva-Mongolian block and the eastern part of the Sayano-Tuva block. After the Khuvsgul earthquake of 2021, a block structure with the activation of the epicentral zones of the 1991 Busingol earthquake, the 2011–2012 Tuva earthquakes, and other structures seismically active until 2021 has increased seismic activity. It is proved that the 2014 Khuvsgul earthquake occurred under the basin of the same name and is associated with other faults than the 2021 earthquake and is not a direct precursor of the 2021–2022 activation. [ABSTRACT FROM AUTHOR]

On February 6, 2023, an Mw7.8 earthquake hit the south of Kahramanmaras prefecture, Turkey, followed by another Mw7.5 earthquake after nine hours in the middle region of the Kahramanmaras prefecture. More than 84,000 buildings collapsed or were severely damaged, and more than 50,000 lives were lost in Turkey and Syria. Some of the authors, as members of Chinese rescue team, entered Antakya, Hatay prefecture, and investigated the damaged buildings. This paper first summarizes the damage patterns of buildings and provides three reasons for the massive number of collapsed buildings; i.e., the lack of seismic measures for better ductility, site effects such as liquefaction and surface rupture, and pronounced low-frequency components of the ground motions. Next, the seismic responses of two typical buildings are calculated based on the geometric data estimated by visual inspection. The results imply that the resonance of the whole structure and the poorer ductility of key members resulted in the collapse of buildings. Finally, some conclusions are drawn. Note that although a large number of buildings were seriously damaged to collapse, the majority of buildings in the areas of extreme shaking were lightly or moderately damaged, which implies that well designed and constructed buildings were able to survive and protect human lives even in over-design earthquakes. [ABSTRACT FROM AUTHOR]

Rapid detection of landslides using remote sensing images plays a key role in hazard assessment and mitigation. Many deep convolutional neural network-based models have been proposed for this purpose; however, for small-scale landslide detection, excessive convolution and pooling process may cause potential texture information loss, which can lead to misclassification of landslide target. In this paper, we present a novel UNet model for the automatic detection of landslides, wherein the reversed image pyramid features (RIPFs) are adapted to mitigate the information loss caused by a succession of convolution and pooling. The proposed RIPF-Unet model is trained and validated using the open-source landslides dataset of the Bijie area, Guizhou Province, China, wherein the precision of the proposed model is observed to increase by 3.5% and 4.0%, compared to the conventional UNet and UNet + + model, respectively. The proposed RIPF-Unet model is further applied to the case of the Longtoushan region after the 2014 Ms.6.5 Ludian earthquake. Results show that the proposed model achieves a 96.63% accuracy for detecting landslides using remote sensing images. And the RIPF-Unet model is also advanced in its compact parameter size; notably, it is 31% lighter compared to the UNet + + model. [ABSTRACT FROM AUTHOR]

The temporal distribution of earthquakes provides important basis for earthquake prediction and seismic hazard analysis. The relatively limited records of strong earthquakes have often made it difficult to study the temporal distribution models of regional strong earthquakes. However, there are hundreds of years of complete strong earthquake records in the North China Seismic Zone, providing abundant basic data for studying temporal distribution models. Using the data of M ≥ 6.5 earthquakes in North China as inputs, this paper estimates the model parameters using the maximum likelihood method with Poisson, Gamma, Weibull, Lognormal and Brownian passage time (BPT) distributions as target models. The optimal model for describing the temporal distribution of earthquakes is determined according to Akaike information criterion (AIC),and Kolmogorov–Smirnov test (K–S test). The results show that Lognormal and BPT models perform better in describing the temporal distribution of strong earthquakes in North China. The mean recurrence periods of strong earthquakes (M ≥ 6.5) calculated based on these two models are 8.1 years and 13.2 years, respectively. In addition, we used the likelihood profile method to estimate the uncertainty of model parameters. For the BPT model, the mean and 95% confidence interval of recurrence interval μ is 13.2 (8.9–19.1) years, and the mean and 95% confidence interval of α is 1.29 (1.0–1.78). For the Lognormal model, the mean value and 95% confidence interval of v is 2.09 (1.68–2.49), the mean value exp (v) corresponding to earthquake recurrence interval is 8.1 (5.4–12.1) years. In this study, we also calculated the occurrence probability of M ≥ 6.5 earthquakes in the North China Seismic Zone in the future, and found that the probability and 95% confidence interval in the next 10 years based on the BPT model is 35.3% (26.8%-44.9%); the mean value and 95% confidence interval of earthquake occurrence probability based on the Lognormal distribution is 35.4% (22.9%-49.7%); the mean probability and 95% confidence interval based on the Poisson model is 53.1% (41.1%-64%). The results of this study may provide important reference for temporal distribution model selection and earthquake recurrence period calculation in future seismic hazard analysis in North China. [ABSTRACT FROM AUTHOR]

The paper is devoted to the assessment and forecast of the occurrence of submarine landslides on the shelf of southeastern Vietnam. The prediction is based on the analysis of the existence of slip tendency on known faults, studying the magnitude of possible relative vertical and horizontal displacements in the Earth's crust, considering the slope steepness of bottom relief and surface of landslide deposits, as well as assessing the probability of reactivation of faults and likely earthquake zones. The results of the study allow making decisions on combating submarine landslides, reducing damage to people and property in coastal areas. Based on the information obtained, not only submarine landslides but also other geological hazards in areas of the Vietnamese continental shelf can be predicted. [ABSTRACT FROM AUTHOR]

This paper discusses continuum models for simulating earthquake sequences on faults governed by rate-and-state dependent friction. Through detailed numerical analysis of a conventional strike-slip fault, new observations regarding the use of various continuum earthquake models are presented. We update a recently proposed plasticity-based model using a consistently linearized formulation, show its agreement with discrete fault models for fault thicknesses of hundreds of meters, and demonstrate mesh objectivity for slip-related variables. To obtain a fully regularized fault width description with an internal length scale, we study the performance and mesh convergence of a plasticity-based model complemented by a Kelvin viscosity term and the phase-field approach to cohesive fracture. The Kelvin viscoplasticity-based model can introduce an internal length scale and a mesh-objective response. However, on grid sizes down to meters, this only holds for very high Kelvin viscosities that inhibit seismic slip rates, which renders this approach impractical for simulating earthquake sequences. On the other hand, our phase-field implementation for earthquake sequences provides a numerically robust framework that agrees with a discrete reference solution, is mesh objective, and reaches seismic slip rates. The model, unsurprisingly, requires highly refined grids around the fault zones to reproduce results close to a discrete model. Following this line, the effect of an internal length scale parameter on the phase-field predictions and mesh convergence are discussed. [ABSTRACT FROM AUTHOR]

On December 29, 2020, nine months after the March Mw 5.4 Zagreb earthquake and amidst the COVID-19 lockdown, a devastating Mw 6.4 earthquake struck near the town of Petrinja, about 50 km SE from the country's capital Zagreb. It was preceded by the Mw 4.9 foreshock from the day before. The main shock claimed 7 fatalities and caused widespread damage. Historical centers of nearby cities with invaluable heritage buildings were significantly affected as were the many residential buildings, built mainly of unreinforced masonry. Damage was observed as far as 60 km from the epicenter. This paper summarizes the seismological aspects of the Mw 6.4 Petrinja earthquake, the emergency response and the main impacts to people and buildings. The description and findings are based on the field observations and a series of post-earthquake activities led by the team of the Faculty of Civil Engineering, University of Zagreb. Typical damage to buildings and usability data are presented with examples based on 50,000 inspection results. By far the most affected were the unreinforced masonry buildings, followed by confined masonry, whereas reinforced concrete buildings were the least affected. The total direct and indirect losses are estimated to 4.8 billion EUR. The provided information represents a useful basis and impetus for improving emergency action and long-term disaster reduction plans in other regions with similar building exposure and seismotectonic settings. [ABSTRACT FROM AUTHOR]

The estimation of seismic damages and debris at the urban scale—at a building-by-building level- is challenging for several reasons. First, commonly used methodologies for seismic damage estimation rarely take into account the local site effects, precisely at the building-level. Second, the available methods for debris estimation fail to estimate at the same time the quantity of debris generated per building according to its damage level and the distribution of the debris (extent and height) around buildings. Finally, the lack of comprehensive data on the building stock and the relevant building properties and their taxonomy further increases the complexity of assessing possible earthquake consequences at an urban scale. This paper addresses these challenges and proposes improvements to the assessment of seismic damages and debris from building-level simulations, along with the development of a 3D building model based on satellite images and heterogeneous data. These developments, applied to the city of Beirut, Lebanon, highlight the control of the site effects on the seismic damage's spatial distribution throughout the city and the large volume and extent of debris to be expected in the city for a strong earthquake. [ABSTRACT FROM AUTHOR]

Earthquakes can generate large volumes of debris which may threaten public health, hinder reconstruction and impact the environment. The present paper aims at investigating how the current Italian regulatory framework may be further developed to improve communities' ability to manage debris from earthquakes. Since the lack of preparedness for managing disaster debris is not confined to Italy, the paper may be valuable to stimulate a broader debate on this issue. The research work is based on selected case studies (L'Aquila 2009, Regione Emilia-Romagna—Circolare n. 2 of 12.06.2012 (2012) "Provisions for the resumption of production activities according to art. 3 paragraphs 7 to 10 of Legislative Decree June 6, 2012 n. 74" and Central Italy 2016–2017 earthquakes) and the review of the relevant literature and legislation. It shows that preparedness could have contributed to reducing or avoiding significant delays and problems in managing debris after the above-mentioned Italian earthquakes. It further suggests that disaster debris management in Italy could benefit from the existence of a comprehensive ex ante regulatory framework including a range of different tools (laws, guidelines, contingency plans and the like) and from the proper implementation of laws that are already part of our legal order. The above findings may directly feed into decision-making addressing disaster debris management. Overall, the paper focuses on a research topic which is becoming increasingly relevant, given the rise in the number and severity of natural disasters, but which is still not widely explored. [ABSTRACT FROM AUTHOR]

The geological activity in Sichuan and Yunnan of China is intense, and large earthquakes such as the Tonghai earthquake in 1970 have caused huge casualties and economic losses. Therefore, it is significant to reduce the long-period earthquake damage of dams and high-rise buildings to reproduce the near-fault long-period ground motion characteristics of the Tonghai earthquake. In this paper, the finite difference method is used to predict the long-period characteristics of the Tonghai Ms 7.8 earthquake. Considering the uncertainty of the initial fracture point, number of asperities, and slip angle, 18 seismic scenarios are established. The predicted results are verified by comparing intensity, attenuation relation and pulse probability distribution. At the same time, based on the velocity pulse recognition method, the pulse probability distribution of the near-field is obtained. We selected six seismic scenarios with high probability from 18 seismic scenarios. Our results show that the spatial distribution and pulse probability distribution of near-field simulated ground motion is significantly affected by the initial rupture positions. After the characteristics of the largest asperity on the fault are determined, the remaining asperities have limited influence on the spatial distribution of simulated ground motion. This study expands the application scope of the finite difference method, which can simulate the seismic intensity characteristics of destructive earthquakes in areas with few seismic records. [ABSTRACT FROM AUTHOR]

This paper documents performance of cast-in-place reinforced concrete (RC) buildings in the Durrës municipality during Albania earthquake of November 26, 2019 (MW 6.4). Both mid- and high-rise RC buildings were affected by the earthquake, experiencing structural and/or non-structural damage and even collapse in some cases. The authors performed a reconnaissance study after the earthquake and were involved in seismic assessment of buildings in the affected area. Besides the observations related to physical damage of RC buildings, the paper also presents results of a statistical analysis of damaged RC buildings in the Durrës municipality. The discussion in the paper is focused on damage patterns and failure mechanisms that are relevant for the seismic response of RC structures. Most common damage pattern observed after the earthquakes was related to masonry infill walls, which experienced damage and failure in some cases, and affected the performance of adjacent RC columns due to the infill/frame interaction. Taller RC framed buildings (10 storeys and higher) were expected to have RC shear walls; however, these walls were reportedly absent in the damaged buildings of this type. In some cases, masonry infill walls (instead of RC shear walls) were used in the elevator shaft areas, which resulted in inadequate seismic performance. A case study has been presented to illustrate seismic behaviour of mid-rise and high-rise cast-in-place RC buildings in the November 2019 earthquake, and is based on post-earthquake field observations and a detailed seismic assessment of two earthquake-damaged buildings. Finally, relevant lessons and recommendations are presented in light of the observed performance of RC buildings. [ABSTRACT FROM AUTHOR]

The paper addresses the investigation of the dynamic characteristics of a case study, the Egyptian church of Abu serga. To this aim some in situ investigations have been conducted and related results are discussed. The paper presents interesting and innovative aspects, mainly related to the characteristics of the church investigated, covering a lack of knowledge in the scientific literature due to the typology of the church. The integrated geotechnical and geophysical investigation techniques assessed the level of seismic and other geo-environmental risks that Abu serga church suffers from. It suffers multiple Geo-environmental hazards. The main objectives of this pilot study are as follows: (1) Identifying the shear velocity Vs analysis profile of the subsoil and also the resonant frequency of soil and the historical building of Abu serga church using ambient noise recordings (microtremors) to assess the level of seismic and other geo-environmental hazards. (2) Understanding the damage to the historic building caused by the recent earthquakes. (3) Offering technical support and advice on intervention retrofitting for the historic damaged structure. In this study, ambient noise recordings have been processed through horizontal to vertical spectral ratios to examine the main frequencies and to examine whether the building has its main frequency close to that of the soil in order to identify potential resonance phenomena. Numerous ambient noise recordings were recorded on the soil, in the basement, and at each floor of the buildings. This study suggests moderate level of earthquake activity at Abu serga church and is in a good agreement with the fact that "Egypt is a part of the stable African Shield", but the existence of old structures such as the Abu serga church may reduce the ability to resist any earthquake shaking. [ABSTRACT FROM AUTHOR]

Nonlinear time domain numerical approaches together with elasto-plastic effective stress soil constitutive models are nowadays available to geotechnical researchers and practitioners interested in geotechnical earthquake engineering. The use of such advanced two- and three-dimensional schemes allows the analysis and design of complex geotechnical structures within a performance-based framework, considering the build-up of excess pore water pressure during the earthquake, dynamic interaction between the soil deposit and the above surface buildings and infrastructures and effects of multi-directional seismic loading. Within this context, the paper focuses on the dynamic finite element (FE) method and presents a review of the key ingredients governing its predictive capabilities. These include i) the description of the fully coupled solid–fluid interaction formulation and time integration, ii) the calibration of Rayleigh damping and the soil constitutive model parameters, iii) prescription of the boundary conditions for the generated mesh and iv) input motion selection/scaling strategies. For each of the above points, the paper summarises the current knowledge and best practice, with the aim of providing protocols for a confident application of nonlinear FE schemes to evaluate the performance of critical geotechnical infrastructures. Useful hints to promote familiarity of advanced nonlinear soil dynamic analysis among geotechnical practitioners and to indicate areas for further improvement are also highlighted. [ABSTRACT FROM AUTHOR]

In the paper, the kinematic analysis is carried out to evaluate the face stability of shallow tunnel in the framework of plasticity theory. In view of the non-uniformity of soil strength parameters, a discretization technique is introduced to generate possible failure mechanisms which respect the associative flow rule and requirement of the non-uniformity of soil strength parameters. As an earthquake situation is considered, a pseudo-dynamic method is adopted to portray the distribution of seismic acceleration. Some comparisons are made to the conventional analysis, including discretization-based pseudo-static analysis and log-spiral-based pseudo-static analysis, to prove the validity of the programming code and accuracy of the proposed method. The soil strength parameters are considered varying in the vertical direction. The effect of distribution of strength parameters is discussed, and distribution form is initially assumed to be linear profile and, then, to be other nonlinear functional profile, including power profile, constant profile and quadratic profile. The results derived from further parametric study show that although the influence of horizontal seismic coefficient is more significant than the vertical one, the vertical effect cannot be ignored in most circumstances, and some factors affect the stability cyclically. In addition, in the linear profile of soil strength parameters, the influence of gradient on supporting pressure is rather small comparing to the average. The influence of non-uniformity of soil strength parameters and seismic parameters on the shape and collapsed area of the failure mechanism is successively studied in this paper. All the optimized solutions are presented in the figures and tables for practical application. [ABSTRACT FROM AUTHOR]

China suffers severe continental earthquakes. The 2008 Wenchuan earthquake (Ms 8.0) and the 2014 Ludian earthquake (Ms 6.5) are two representative examples from the modern era. The Wenchuan earthquake caused considerable economic losses, and the Ludian earthquake caused unexpected losses with only moderate magnitude. Based on disability-adjusted life years (DALYs), this paper first calculates aggregated disaster losses and the contributions of three factors: number of deaths or missing persons, number of people affected, and direct economic losses. Then, the losses per unit energy released or area affected are calculated for each earthquake to investigate which of the two earthquakes caused more damage. The paper finishes by investigating the implications and revealing three results. (1) The Wenchuan earthquake induced more damage than the Ludian earthquake, but the latter had relatively higher losses per unit energy than the former. (2) Injuries and affected people contributed most to the total losses for each earthquake, more than fatalities or direct damage. This outcome means that unnoticed aspects have the most severe disaster impacts. In addition, long-term impacts of earthquakes are more serious than usually acknowledged, and more attention needs to be paid to these. (3) The damage from moderate earthquakes can exceed expectations, meaning that disaster mitigation policies in all regions are necessary, regardless of the degree of anticipated hazard. [ABSTRACT FROM AUTHOR]

Earthquake casualty prediction is crucial for efficient and effective emergency management and response. In order to improve prediction reliability of earthquake casualties, correlation analysis and principal component analysis are used to select prediction covariates. Finally, five key indexes, including magnitude, epicenter intensity, population density, earthquake occurrence time and damaged building area, are chosen. According to the "two-stage" rule of earthquake casualties, a prediction model based on the modified partial Gaussian curve is proposed. In order to improve its prediction accuracy, the paper looked epicenter intensity and the casualty as the variables. And the partial Gaussian curve prediction model is modified by using the magnitude coefficient, population density coefficient, earthquake occurrence time coefficient and damaged building coefficient. The cross-validation experimental results show that the modified partial Gaussian curve has the advantages of good stability and high prediction accuracy comparing with the high-order nonlinearity, logarithmic curve, multivariate linearity, artificial neural network and so on. It can be used in practice from earthquake casualty prediction. [ABSTRACT FROM AUTHOR]

Rock slopes with planar joints or weak structural planes are vulnerable in nature, especially suffering from the natural hazards, instabilities of slopes are more prone to occur. Therefore, concerning to the influence of earthquakes, this paper performs a new procedure to evaluate slope stability in a geomaterial governed by Hoek–Brown strength criterion. A rotational failure mechanism determined by 21 dependent angle variables is introduced to respect the Hoek–Brown strength criterion. The earthquake load is characterized by a modified pseudo-dynamic method that does not violate the zero boundary condition and considers the damping properties of geomaterials. A slice approach is adopted to calculate the earthquake-induced inertial force work rate. The stability number of rock slope is considered to measure the safety. The stability number is formulated as a classical optimization problem controlled by 21 dependent angle variables and a time variable which need to be optimized by the genetic algorithm toolbox. Comparisons with the literature are made to prove rationality and accuracy of the proposed procedure. Parametric study is carried out to reveal the influence of dynamic properties. For engineering application, stability charts are provided for a quick assessment of slope safety. [ABSTRACT FROM AUTHOR]

The present paper aims at earthquake prediction assessment in Iran using VLF radio signal sounding and space-based ULF emission observation. VLF subionospheric data using the Denizkoy transmitter in Turkey at 26.7 kHz and a receiving station in Tehran are incorporated. Three earthquake events during 2019 located at different distances to the signal propagation path are used in this study. The short-term variations in the VLF signal for the 5 days averaged amplitude, as well as the deviation of the VLF signal against the 30 days averaged signal to monitor the alternation in the trend, are employed in this study to perform earthquake prediction assessment using VLF radio signal sounding. Several characteristic parameters of the VLF signal such fall-time, minimum 1 and minimum 2 throughout the day are used. A threshold over the standard deviation of the signal is used to determine the signal anomaly. The signal anomalies associated with three selected events and the correlation of prediction with the distance are discussed. A decision-making procedure for the detection of EQ-related anomalies based on the assessment of the proposed approach is introduced. The ULF emissions recorded by the China Seismo-Electromagnetic Satellite (CSES) are provided and associated with the two analyzed earthquakes using the VLF data due to lack of time coverage for the third case. The space-based detected ULF signals are presented and discussed. The proximity of the detected ULF emission with respect to the earthquake epicenter is discussed. [ABSTRACT FROM AUTHOR]

The characteristics of aftershocks can be quite different from those of mainshocks. However, most of the works in the past have generally focused on the aftershocks of strong earthquakes, while some moderate earthquakes can cause aftershocks with magnitudes close to the mainshocks. This paper focuses on the aftershocks characteristics of the 2012 Varzaghan–Ahar Doublet event (Mw = 6.4, 6.2), northwest of Iran. Numerous aftershocks with magnitudes 3.7–5.5 recorded by the local seismic stations provide useful data to study the spectral characteristics at various periods. The predictive capability of the 2008 Next Generation Attenuation along with two regional models has been examined by several aftershock records obtained during these events. This paper is the first attempt made to compare the predictive capability of modern models based on significant aftershock data obtained for these two moderate events. Results confirmed that the ground motion models which have been derived based on larger-magnitude events should not directly be extrapolated to predict aftershock ground motions with magnitude smaller than 5.5, especially when we use relationships that developed without considering aftershock data. The residual analysis showed that the model of Abrahamson and Silva (Earthq Spectra, 24(1): 67–97, 2008) performed the best overall predictions in this study. However, this model performs poorly in the short period of 0.2 s at distances greater than 50 km which underestimates the spectral values for this case. [ABSTRACT FROM AUTHOR]

The earthquake cycle of stress accumulation and release is associated with the elastic rebound hypothesis proposed by H.F. Reid following the M7.9 San Francisco earthquake of 1906. However, observing details of the actual values of time- and space-dependent tectonic stress is not possible at the present time. In two previous papers, we have proposed methods to image the earthquake cycle in California by means of proxy variables. These variables are based on correlations in patterns of small earthquakes that occur nearly continuously in time. The purpose of the present paper is to compare these two methods by evaluating their information content using decision thresholds and Receiver Operating Characteristic methods together with Shannon information entropy. Using seismic data from 1940 to present in California, we find that both methods provide nearly equivalent information on the rise and fall of earthquake correlations associated with major earthquakes in the region. We conclude that the resulting timeseries can be viewed as proxies for the cycle of stress accumulation and release associated with major tectonic activity. Article Highlights: The current state of the earthquake cycle of tectonic stress accumulation and release is unobservable We review two methods for visualizing the current state of the earthquake cycle from correlation in small earthquake patterns Machine learning techniques indicate that signals in a correlation time series corresponding to future large earthquakes can be detected [ABSTRACT FROM AUTHOR]

This paper presents a topology optimization approach for the seismic design of multiple-rocking self-centering concentrically braced frames (SC-CBFs). SC-CBFs have been recently developed as damage-free seismic lateral load-resisting systems. In these systems, rocking sections are potentially designed in several locations over the height due to several modes. The design of multiple-rocking SC-CBFs is a demanding task due to their highly non-linear behavior. The vertical irregularity, caused by the non-continuous stiffness over the height of these systems, makes the prediction of their behavior a challenging task, especially when subjected to dynamic ground accelerations. In this paper, an efficient and general design approach for these systems is developed utilizing gradient-based topology optimization. An optimization problem is formulated such that the construction cost of the SC-CBF is minimized while simultaneously considering the topology of the frame, cables, energy dissipation (ED) material, and the location of the rocking sections. The performance of the building is limited to acceptable limits by formulating the constraints of the optimization problem based on the results obtained from non-linear time history analysis (NLTHA). An efficient numerical integration scheme based on the mixed lagrangian formalism (MLF) was adopted to conduct the NLTHA. The proposed method was used for the design of 5- and 10-story buildings. The results show that efficient designs could be achieved with a reasonable number of iterations using a personal computer. This makes the proposed approach desirable for the design of multiple-rocking SC-CBFs by researchers and engineers. [ABSTRACT FROM AUTHOR]

In the year 1999, two devastating earthquakes (Mw 7.4 Kocaeli earthquake in August and Mw 7.2 Düzce earthquake in November) occurred in Northwest Türkiye. These two earthquakes led to a very large number of casualties and building collapses. When the 1999 earthquakes occurred, most of the structures in the earthquake-impacted region were not designed according to modern seismic design codes. During the 25 years following those earthquakes, there have been significant advances in building construction in the light of earthquake engineering, including adequate seismic codes, new regulations, and effective code enforcement in the earthquake impacted region. These advances have been reflected in the construction of new structures in the region and the retrofitting of existing ones. As a result, 70–80% of the current building stock in Düzce was designed, constructed, or retrofitted after the 1999 earthquakes. Almost 23 years later, in 2022, an Mw 6.1 earthquake occurred in Düzce, with ground shaking close to the seismic design code life safety performance level. The 2022 earthquake provided a great opportunity to evaluate the effectiveness and consequences of the advances in earthquake engineering and the relevant policy-making and regulations. This paper provides a comparative overview of the 1999 and 2022 earthquakes that struck the city of Düzce in terms of hazard, vulnerability, and consequences. Furthermore, other key lessons learned from the 2022 Düzce earthquake are documented based on field reconnaissance and numerical simulations. The lessons learned are expected to provide useful guidance for the reconstruction efforts after the 2023 Kahramanmaraş Türkiye earthquake sequence or in similar efforts in other parts of the world. [ABSTRACT FROM AUTHOR]

This paper presents the physics based ground motion synthetics and its earthquake engineering consequences in the National Capital Territory (NCT) Delhi, India due to the Mw8.2 scenario earthquake on the Nahan segment of the western Himalaya. In order to fulfill the aim, a state-of-the-art pseudo-dynamic rupture is implemented in a 3D fourth-order staggered-grid viscoelastic time-domain finite-difference code. The ground motion is simulated in a frequency bandwidth of 0–2.5 Hz at the basement level at 158 locations of the NCT Delhi. The computed transverse component of velocity time series at the basement level is numerically transferred to the free surface taking into account the rheological parameters of the sediment deposit. Upon first inspection, the estimated range of peak ground acceleration, between 0.017–0.12 g, indicates that all the buildings in the NCT Delhi will remain safe in the event of an Mw8.2 Nahan earthquake, provided they are constructed in accordance with Indian building codes. But, the computed acceleration response spectra (Sa) depicts that some of the high-rise buildings of the NCT Delhi may suffer minor damage to collapse under partial or complete double resonance condition due to Sa exceeding the DBE and MCE levels. The obtained range of pseudo-spectral displacements (Sd) reveals the need of performance-based design for high-rise buildings in the NCT Delhi, so that they can withstand under partial or complete double resonance condition during the occurrence of Nahan earthquakes. The developed contour maps of Sa and Sd at different periods can be used for the retrofitting and forced-based and displacement-based designs of the high-rise buildings. [ABSTRACT FROM AUTHOR]

Earthquake is one of the main factors causing structural disasters in current buildings. Under earthquake action, adjacent building structures are generally in different vibration stages, and collisions may occur in the structures, which may cause serious damage to the structure. In order to prevent certain earthquakes from damaging the designed buildings, this article mainly introduced the design and analysis of a numerical algorithm for seismic nonlinear structural dynamic response based on the HVSR algorithm. This article evenly divided the acceleration response time series into 15 time periods and then selected the position corresponding to the peak point of instantaneous amplitude within each period as the selected data point position. The same seismic load can be applied at the bottom of the established nonlinear model to extract the dynamic response data of the top layer of the structure, and then, the instantaneous amplitude and corresponding instantaneous phases and frequencies of the main components of the structural dynamic response can be extracted through the time-varying filter and Hilbert transform based on the discrete analytic mode decomposition. Under the influence of these four ground motions, the collision force within the range of 0–50 kN accounted for over 87% of the total number of collisions. In the comparison results of collision response to peak displacement, the four ground motions all led to structural collision, and the collision inhibited the positive peak displacement response of node 1512. Compared with noncollision, the peak displacement was reduced by 27.273, 33.675, 27.727, and 37.248%, respectively. The peak displacement of 1512 nodes was suppressed and reduced by 18.856%. The results indicate that the HVSR algorithm can obtain the instantaneous characteristic parameters of nonlinear structural dynamic response and achieve model correction. [ABSTRACT FROM AUTHOR]

Although most of the previous studies focused on the effect of liquefaction on clean sandy soils, new observations revealed that silty soils are also prone to liquefaction. Therefore evaluating the liquefaction hazard at silty soil sites is also of particular importance. The primary objective of this research paper was to assess the liquefaction occurrence of a fine-grained silty profile at a specific site in southern Iran. This assessment was conducted through a combination of numerical analysis and the application of liquefaction susceptibility criteria. To achieve this, a finite element model incorporating the PM4Silt advanced constitutive model was employed. The findings of our study revealed that the liquefaction susceptibility criteria exhibited a higher likelihood of predicting liquefaction compared to numerical modeling when applied to the case study site. Therefore in some depths, despite the prediction of liquefaction by susceptibility criteria, in the numerical modeling results, liquefaction has not been observed even by relatively strong earthquakes. Furthermore, the numerical modeling results reveal that one of the most important parameters affecting soil liquefaction in addition to earthquakes' amplitude is the input motion frequency content so that earthquakes with lower PGA but larger Fourier amplitude at low frequencies have a greater effect on the liquefaction of fine-grained soils. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical modeling and analysis of the stress–strain state of the epicentral zone of a strong earthquake in Northeast China that occurred on July 27, 1976, with Ms = 7.8. Many present-day works continue to discuss the reasons for such a strong earthquake, which occurred in tectonic conditions: far from interplate boundaries, inside the Tangshan tectonic block bounded by tectonic faults. However, new published geodynamic, seismological, geophysical, and geodetic data provide confidence in the determining role of fault tectonics in this region. Based on an analysis of the results of modeling of the stress–strain state preceding the Tangshan earthquake with coseismic geophysical and geodetic data, we propose an earthquake rupture formation model. The results of comparing independent shear stress estimates with the results of modeling in the sources of strong earthquakes suggest that areas of tectonic stress concentration are localized in the interfault rupture of the Tangshan fault, reaching maximum values at the termination of fault ruptures σi ≈ 50 MPa and τxy ≈ 20 MPa. The hypocenter of the main seismic event (taking into account the coordinate determination error) is located in the region of stress intensity 35‒50 MPa and a ratio of main stresses σxx/σyy ≈ 8–10. It should be expected that these zones are the rupture initiation site, the extent of which depends on the amount of accumulated elastic potential energy of tectonic stresses in the adjacent region. For the Tangshan earthquake, this area corresponds to high-intensity stresses in a band with a length exceeding 30 km and width reaching 4.5 km, exceeding 30 MPa. [ABSTRACT FROM AUTHOR]

Abstract—In many aspects, the deep fluid regime plays a key role in seismicity, aseismic deformation of the lithosphere, and ore and oil genesis processes. An informative detailed analysis of the hydrogeology of shallow fault zones is presented in (Kocharyan and Shatunov, 2024), where it is noted that little is known about the character of the fluid dynamics of deep faults. This paper focuses mainly on the challenges of describing deep fault zones and highlights a number of inconsistencies that arise in this consideration. It is shown that the difficulties inherent in such a description are largely overcome by accounting for the processes of metamorphism and associated anomalies in the physical properties of the Earth's interior. Further refinement is given to the proposition that earthquakes occurring at different depths have different physical mechanisms. [ABSTRACT FROM AUTHOR]