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Today's earthquakes are the most direct manifestation of the latest tectonic activity and are the most powerful tool to understand the characteristics of nonrigid deformation within a continent. Particularly, the newly formed faults that have been active since the Late Pleistocene are characterized to have low development maturity, poor connectivity in geometric structure, and obvious difference in strike/depth dip in different sections. Therefore, earthquakes can reveal their three-dimensional space changes, especially the characteristics of brittle-ductile transition depth. Earthquakes can also promote the understanding of the preparation and earthquake generation process of newly formed active faults. The newly formed strike-slip active faults in the Bohai Bay Basin have experienced many strong earthquakes, including the Tangshan MS7.8 and the three Ninghe MS≥ 6.2 earthquakes. The crustal brittle-ductile transition depth revealed by these earthquakes has an important practical significance to understanding the seismogenic mechanism and activity of the region. In this paper, the new fault in the Baodi Miaozhuang uplift in the Bohai Bay Basin is taken as the target fault. In addition, the 2012 Baodi MS4.0 and MS3.5 earthquakes in the Baodi uplift and the 1976 Ninghe MS6.2 and MS6.9 and the 1977 Ninghe MS6.2 earthquakes in the Miaozhuang uplift are taken as the research objects. Finally, the CAP method is used to study the source mechanism solution and the source depth of the Baodi MS4.0 and MS3.5 earthquakes based on the waveform data from the Capital Circle Digital Seismic Network. The double difference method is used to locate the source positions of two earthquake sequences by employing the Sp converted wave of near earthquakes to accurately determine the source depth. Moreover, combined with other data, the seismogenic mechanism of earthquakes in this area and the brittle-ductile transition depth of new fractures are discussed. The following results were found. (1) The source properties of the Baodi MS4.0 and MS3.5 earthquakes are not completely consistent with the known faults on the exposed surface of the Baodi Miaozhuang uplift. Combining the research results of the source parameters of the three Ninghe earthquakes having an MS ≥ 6.2, it is inferred that they all occurred in the Baodi-Ninghe deep fault. (2) Based on the models of electrical structure and rheological structure in the focal area, the five significant earthquakes in Baodi Miaozhuang uplift reveal that the brittle-ductile transition depth of the Baodi-Ninghe deep fault is about 15 km. (3) Based on the dynamic evolution process of the Bohai Bay Basin and relevant deep geophysical exploration data, it is hypothesized that the seismic activity in this area is mainly the result of the Baodi-Ninghe deep fault and deep fluid actions. [ABSTRACT FROM AUTHOR]

Different catalogues of earthquakes are available for the Indian region besides regional catalogues for the Gujarat region. The limitations of these and other historical catalogues have been discussed in this paper for earthquake hazards and other studies. Keeping in view that these historical catalogues have been successful in explaining the recent occurrence of a few earthquakes like Coimbatore (1900), Hyderabad (1983), Bangaluru (1985) and Jabalpur (1997), the study has been extended to the Gujarat region. In this paper, therefore, an attempt has been made to correlate the historical data of the felt earthquakes in the Gujarat region from all the available sources with instrumental data to examine the recurrence of the earthquakes. It has been found that in addition to the seismically active Kutch region and Narmada and Cambay rifts, there is a tendency for earthquakes to recur in many districts of Gujarat for which felt data from historical times is available. The seismicity map prepared by the Institute of Seismological Research (ISR), Gandhinagar based on the Seismic Telemetry (2006–2020) shows scattered seismicity over the whole of Gujarat region besides active seismicity in the Kutch region. This data when combined with that from the catalogue prepared by the National Centre of Seismology provides greater confidence for earthquake hazard studies It has also been found that the coastal regions of Saurashtra and south Gujarat are more prone to swarm types of earthquakes. [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]

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]

Soil plug formation in open-ended piles due to pile driving is a widely studied phenomenon in onshore applications. The narrow diameters of traditional onshore piles ranging from 0.5 to 1.5 m facilitate plug generation during installation and transfer of enhanced confining stresses across the whole body of the soil plug. Offshore wind monopiles with larger diameters and smaller aspect ratios may not enhance confining stress within the soil plug as effectively as their onshore counterparts. Monopiles are currently the most widespread foundation in the offshore wind sector including in seismic areas. Earthquake shaking can lead to accumulation of excess pore pressure and subsequent liquefaction of the soil retained inside the plug. This research investigates the influence of monopile diameter and confining stress on the development of earthquake-induced excess pore pressure within the soil plug using fully coupled time domain Finite Element Analysis. The results presented in this paper reveal lower accumulation of earthquake-induced excess pore pressure in soil plugs subjected to confining stress. However, the influence of additional horizontal stress caused by monopile driving on the generation of excess pore pressure within the soil plug diminishes as the monopile diameter is progressively increased. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the identification of potential seismic damage in an area called Tanah Patah, Bengkulu City, Indonesia. This study is initiated by conducting site investigation and geophysical measurements. Ground motion prediction is conducted to estimate peak ground acceleration which is then used to estimate the damage intensity level during a large earthquake. A spectral matching method to generate ground motion at investigated sites is conducted. Seismic ground response analysis to observe ground response and soil behaviour is performed. The results show that peak ground acceleration in the study area is about 0.255–0.342 g during a large earthquake. IX is this area's Modified Mercalli Intensity (MMI) level scale. Since sandy soils dominate the study area, several sites could be more vulnerable to undergoing liquefaction. The thickness of potentially liquefiable soils is about 8.6–12.8 m. The results could help local governments develop spatial plans in the study area. [ABSTRACT FROM AUTHOR]

This paper reports results of mathematical modeling applied to the stress and strain in epicentral zones before and after the large earthquakes that occurred on June 22, 2002 in the Qazvin Province, northwestern Iran (Mw = 6.4) and the Gujarat, India earthquake of January 26, 2001 (M = 6.9). The modeling relied on a method for calculating stress and strain in a blocky elastic isotropic heterogeneous medium disturbed by a set of faults that are due to an external tectonic stress field. The boundary conditions were specified based on geological and seismological data. It has been shown that the epicenters of large crustal earthquakes occur in zones of high stress concentration at the ends of tectonic faults. Rupture occurs when the relationship between acting tectonic stresses satisfies the requirement σyy/σxx >3, thus connecting zones of high stress. The evolution of the aftershock process is controlled by the stress drop caused by a new rupture, while the resulting aftershock clusters are in spatial correlation with the stress drop zone. The new rupture propagates in the direction of dominant tectonic fault orientation in the region. We show a relationship to exist between rupture length and the possible retrospectively predicted location and magnitude of the earthquake depending on the elastic energy buildup and its possible release under specified structural tectonic conditions. [ABSTRACT FROM AUTHOR]

Abstract—The paper presents the results of many years of research on the compilation of a consolidated, refined, unified earthquake catalog for the western sector of the Russian Arctic for the entire instrumental observation period, in particular for the period from 1908 to 2020. The catalog includes data on recent seismicity in areas previously unavailable for detailed seismic monitoring. Based on the results of the study, we were able to more accurately determine the spatial distribution of seismicity in the region and compare the instrumental data with parameters of lineament-domain-focal (LDF) models of the General Seismic Zoning maps (GSZ, from Russian term abbreviated as OSR)—OSR-97 and OSR-2016. In the western sector of the Russian Arctic, the highest seismicity is observed in the continent-ocean transition zone, in the Belyi (Kvitøya) Island, Novaya Zemlya and Severnaya Zemlya archipelagos. The very shelf of the Barents and Kara Seas is characterized by rare and scattered seismicity. The configuration, the maximum possible magnitudes, and the depths of the seismogenic layers in the LDF models of OSR-97 and OSR-2016 maps are not always consistent with the instrumental data and need a correction. The consolidated refined earthquake catalog can be used as a basis for the further research aimed at seismic hazard assessment of the territory, construction of geodynamic models, and study of the stress-strain state of the Earth's crust. [ABSTRACT FROM AUTHOR]

This paper is the first in a series of studies generalizing the Map of Expected Earthquakes (MEE) medium-term earthquake forecast method and analyzing the prospects for its further improvement. Over the past 35 years, the MEE method has been used in seismically active regions around the world with different tectonic conditions and seismic regimes. The average prognostic efficiency of the algorithm was shown to be 2.5 times higher than for random guessing. The MEE can be further improved and upgraded. The new methods of data processing to be implemented into the upgraded MEE will significantly increase the amount of analyzed data, take into account the specific signs of the seismic process at different depths, use lineament–domain–focal (LDF) models of the structure of seismically active zones as stationary prognostic criteria, and build three-dimensional distributions of the probability of strong earthquakes. The improvement will involve an expansion of the list of used seismological precursors that have a physically justified link with the earthquake preparation process and the development of formalized techniques for identifying these precursors in the prognostic practice. [ABSTRACT FROM AUTHOR]

It is a key to know mechanical environment (ME) of pre- and post-rupture fault of giant earthquakes at subduction zones for predicting earthquake and tsunami disaster. However, we know little about its details till now. In this paper, using the inverted stress change three hours before and three hours after the mainshock in the rupture zone of the 2011 Tohoku-Oki Mw 9.0 earthquake, we show a quantitative integrated ME in the rupture zone, including principal stress, pore-fluid pressure and friction strength. We discover from this environment a large asperity composed of two asperities induced by relatively high friction coefficients and relatively lower pore-fluid pressures. The integrate ME quantitatively explained the reasons of the overshoot and relatively lower shear strength of the trench, which caused huge displacement and tsunami at the trench. We suggest that the asperities favor the horst and graben structure system which provides a geology environment for interseismic stress accumulation and thus for breeding the megathrust tsunami earthquake. [ABSTRACT FROM AUTHOR]

We consider some characteristics of seismicity in the region of Southwest Alaska. The aftershock zones of the Simeonof (July 22, 2020, Mw = 7.8) and Chignik (July 29, 2021, Mw = 8.2) earthquakes are identified. The characteristics of ring-shaped seismicity structures, which formed in a few decades prior to the Chignik earthquake, are described. The location and magnitude of a large event, which could be prepared to the east of the Simeonof earthquake rupture zone, was predicted in (Kopnichev and Sokolova, 2021a) based on the parameters of these structures. An estimate of the expected magnitude (Mw = 8.2 ± 0.2) was obtained using correlation dependences between the parameters of ring-shaped structures and the magnitudes of large and great earthquakes that occurred in the East Pacific region. This forecast, which was made on the basis of the data obtained prior to October 21, 2020, was presented in the mentioned paper, which was accepted for publication before July 29, 2021. We consider possible changes of the parameters of ring-shaped structures immediately prior to the Chignik earthquake and discuss geodynamic processes that can lead to the formation of ring-shaped structures. [ABSTRACT FROM AUTHOR]

Central Tibet constitutes part of the central part of the Qinghai–Tibetan Plateau, which is one of the highest seismically active areas in China. This paper discusses the regularity of seismic activity in this area. Based on a stratified viscoelastic earth model, we calculated the Coulomb stress changes imparted from four strong earthquakes (M ≥ 6.3) along the Bengco–southeastern piedmont of the Nyainqentanglha mountain fault zone in this region. The result shows that the study area may be entering a new active period from 2020. There was a trigger between the strong earthquakes (M ≥ 6.3) on the Bengco fault zone. The post-seismic viscous relaxation effect of a strong earthquake had a significant impact on subsequent earthquakes (M ≥ 6.3). In the next 100 years, the Coulomb stress loading is more than 1.0 MPa in the northwest section of the Bengco fault and the central part of Nimu segment of the southeastern piedmont of the Nyainqentanglha mountain fault. Thence, strong earthquakes may occur along these fault segments. The maximum magnitude of the earthquake could be M6.7 in the next 100 years. [ABSTRACT FROM AUTHOR]

A destructive earthquake, especially if it occurs in areas of high seismic risk, in the form of certain factors, has a significant impact on the environment, including biodiversity. These factors (earthquake effects) are determined by the strength of the earthquake (manifestations of intensity on the earth's surface), local conditions (geomorphological, geological structure, level of urbanization and seismic risk, etc.), disaster-zone recovery processes (fast and effective recovery, localization and prevention of secondary consequences, environmental protection, state opportunities and political decisions, etc.). It is clear that these three important basic conditions of effects are different in different seismic regions and countries, which means that the impact of an earthquake on the environment is different. To consider the features and factors of the impact of an earthquake on the environment, the 1988 Spitak earthquake—one of the most detailed and comprehensively studied earthquakes in the world—was taken as a test object. The main purpose of this article is to highlight in more detail and more fully the possible natural and human factors of the impact of a strong earthquake on the environment and predict the extent of these impacts. Thirty-six major earthquake factors affecting the environment have been identified, which are conditionally divided into three main groups according to the time of formation and genesis: (a) purely seismic, (b) secondary seismic, and (c) post seismic. The paper also attempts to assess possible changes in these factors depending on global warming and a decrease in precipitation. [ABSTRACT FROM AUTHOR]

For the first time, a numerical comparison of the General Seismic Zoning (GSZ) maps with the effect of earthquakes that actually occurred after the publication of the maps was carried out. The area of zones of expected intensity on the GSZ map is compared with the area of isoseists from actual earthquakes. It turned out that the isoseist area is on average by an order less than expected according to the GSZ. This paper describes possible reasons for such an overestimation and proposes ways to improve seismic hazard assessments. [ABSTRACT FROM AUTHOR]

This paper presents the effects of October 30, 2020 Samos-Aegean Sea earthquake on hydraulic structures, lifelines and industrial facilities which mainly located in the western cost of Turkey, within the borders of Izmir and Aydin Cities. These two highly populated cities are known for their importance in contributing country's economics by their industrialized areas. In addition, Izmir is the third largest city of Turkey with its high seismic hazard zone. Although some disruptions in the aftermath of the earthquake were occurred in gas and electricity services, these issues immediately identified, and all systems were managed to reoperate. Damages to the infrastructures were mainly due to the collapse of buildings and tsunami effects. No significant damages were reported on lifeline systems, large industrial facilities, and dams due to relatively low shaking intensity. [ABSTRACT FROM AUTHOR]

The goal of this paper is to describe cluster analyses of the focal mechanism solutions estimated from local and teleseismic measurements and stress inversions to support the recent and previously published studies in the investigated region, that is the Vrancea seismic zone. We have applied different established clustering methods—e.g. hierarchical density-based clustering for applications with noise (HDBSCAN) and agglomerative hierarchical analysis—to the geographical coordinates, focal depths and parameters of the focal mechanism solutions of the gathered seismic events. We have attempted to develop a fully automated algorithm for the classification of earthquakes and to support the further investigation of stress inversions. This algorithm does not call for the setting of hyper-parameters by the users, thus the contribution from any bias of the user can be reduced significantly and the time required to carry out the clustering can also be decreased. In most cases, the resulting stress tensors are in close agreement with those we found in the literature. [ABSTRACT FROM AUTHOR]

The Philippines, as part of the Circum-Pacific belt, is considered as one of the most seismically active countries in the world. Earthquake occurrence is frequent and its effects vary depending on its size. Understanding how the occurrences happen is therefore important. Stochastic models of earthquake occurrence have been used to study seismic activities in various active earthquake zones globally. In this paper, we apply Poisson hidden Markov models (PHMM) using the January 1, 1960 to January 20, 2019 earthquake data of Metro Manila, Philippines. The parameters in the models are estimated using expectation-maximization (EM) algorithm. We determine using various statistical tests that the 5-state PHMM best represents the earthquake data and implement bootstrap algorithm to validate the acceptability of its parameter estimates. Moreover, we investigate the forecasting capability of the 5-state PHMM by comparing it to the ARIMA model. Using unscaled mean bounded relative absolute error (UMBRAE), we find that the 5-state PHMM gives closer one-step ahead forecasts and is a better forecasting model for the considered data. [ABSTRACT FROM AUTHOR]

The present paper gives a scale of earthquake energy class KF that is to standardize the relevant data based on the existing scales: MS, MW, mb, KS, among many others. The conceptual novelty of the scale we propose consists in shifting the emphasis from seismometric issues that are traditional in such cases, which are concerned with the recording of seismic waves, as well as with issues arising in discussions of their generation and propagation, toward an effective use of basic energy properties of the seismic process (the Gutenberg–Richter law). In the most general case, this approach can significantly simplify the development of regression relations between different earthquake size scales, but the most promising problem consists in developing a single generalized scale. A particular solution of the problem is presented as the development of such a scale for earthquakes of Kamchatka. The KF scale rests on the energy class proposed by S.A. Fedotov (KS at the Kamchatka Branch (KB) of the National Seismological Centre, Geophysical Survey, Russian Academy of Sciences (NSC GS RAS) and on the generally accepted mb magnitude (ISC). [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]

Abstract—In this paper, we explore the findings of monitoring the components of the Earth's natural electromagnetic (EM) field obtained in 2020–2021, as well as their link with rather strong seismic events within Baikal Rift Zone (in particular, the Kudarin earthquake (Dec. 9, 2020, Mw = 5.5)). During the observations of the magnetotelluric field more than one month prior to the seismic event, the increased conductivity of the tensor-sensitive parts of the sounded soil was recorded due to the displaced release of conducting fluid to the weak crust zones before the earthquake. 24 hours before the seismic event, the anomalous behavior of the electrical field vertical component (Ez) was observed as U-shaped oscillations every 5-30 s due to the electrical charge excitation and relaxation from the compression of quartz-containing rock. The first approximation showed that the analysis of magnetotelluric (MT) monitoring data could help identify medium- and short-term precursors of seismic events. [ABSTRACT FROM AUTHOR]

The Mw 7.8 earthquake that struck Kahramanmaras on February 6, 2023, caused significant damage to hydrocarbon and water transmission lines due to permanent ground deformations. Explosions occurred in the Kahramanmaras–Gaziantep Natural Gas transmission pipeline causing disruption of gas in the cities of Gaziantep and Hatay Fault Displacement Hazard. Water transmission pipelines were also damaged due to extreme fault offsets. This paper presents the findings from the earthquake affected zones. Particular attention was given to the performance of the 2600 mm diameter Duzbag–Gaziantep water transmission pipeline due to three reported challenges: (#1) The behavior of the pipe in the Duzbag tunnel, (#2) The pipe bend behavior at the fault crossing, and (#3) The pull-out of the pipe at valve room. Based on field observations, extreme damage forms at pipes were presented. A three-dimensional nonlinear numerical analysis was performed to simulate the observed damage of the reoriented water pipe at the fault crossing for Case #2. The nonlinear finite element model was able to capture the complex nature of the post-yield behavior of steel pipe as well as the damage locations along the pipe and their sequence of occurrences. As a mitigation measure for new pipes, the need for using flexible connections at critical crossings was highlighted. For existing pipes, the importance of developing secondary (by-pass) lines was emphasized. [ABSTRACT FROM AUTHOR]

We systematically investigate the identification and statistical characteristics of foreshock sequences in the North–South seismic belt (21 ~ 43°N, 97 ~ 107°E), which is the test area of China under the "Collaboratory for the Study of Earthquake Predictability (CSEP)," so as to provide data support for foreshock probability forecasting and monitoring deployment. In this paper, we use a stochastic declustering method based on a space–time epidemic-type aftershock sequence (ETAS) model to fit the real catalogs in the North–South seismic belt, and separate each catalog into stochastic versions of family trees, so as to identify the foreshock sequences and analyze their space–time characteristics and statistical characteristics. The results show that the proportion of foreshock sequences of ML ≥ 3.0 earthquakes in the North–South seismic belt is not significantly higher than that in other regions of the world (New Zealand, Southern California) without considering the difference in cutoff magnitude. The number of foreshock sequences in the North–South seismic belt displays obvious regional differences, with the number in the middle section distinctly lower and in the south section distinctly higher, while accounting for nearly 50% in all earthquake sequences except for a few areas. The foreshock sequence duration is mostly one to one hundred days, without displaying obvious correlation between the duration of sequences and foreshock sequences and latitude. The background earthquakes have a high b value, approximately 0.89. The b value of foreshock sequences, especially foreshock sequences in the strict sense, is low, approximately 0.72. The b value of aftershock sequences is the lowest, approximately 0.69. The duration of foreshocks in most earthquake sequences is lower than that of aftershocks, especially in sequences with large numbers of events. Meanwhile, sequences that last for more than 1 year have shorter foreshock sequences and longer aftershock sequences. [ABSTRACT FROM AUTHOR]

Nowcasting refers to the use of proxy data to estimate the current dynamic state of driven complex systems such as earthquakes, neural networks, or the financial markets. In previous papers, methods to nowcast earthquakes have been presented based on the natural time count of small earthquakes after the last large earthquake in a defined, seismically active geographic region. In this method, a large geographic region is identified in which a local region of interest is embedded. The primary assumption in the method is that the frequency-magnitude statistics of the local region are the same as the frequency-magnitude relation of the large region. The nowcasting technique relies on seismic catalogs that are complete in the sense that all events whose magnitude is larger than a completeness threshold have been detected. For this reason, the previous papers have been limited to nowcasting large earthquakes with magnitudes of approximately M7.5. In this article, we extend the nowcasting method to great global earthquakes of magnitudes as large as M9 by defining the surrounding large region as the entire earth. We then analyze the current hazard of a number of selected "local" regions and rank the regions in terms of current risk of great earthquakes. These great events also present significant hazards for generating mega-tsunamis as well as local damage due to intense shaking. We also perform a sensitivity analysis to establish the reliability of the nowcasts. One of our main results is that the eastern Aleutian Islands, site of the M8.6 earthquake of 1 April 1946, is currently the region most at current risk of a great earthquake larger than M8.0. We finish by presenting comments on the applicability of our methods for anticipating the occurrence of great destructive earthquakes and tsunamis. [ABSTRACT FROM AUTHOR]

This paper presents a causal relationship between thoron anomaly and earthquakes along the Indo-Burman subduction line. A 15 min cycle thoron data was generated at Mizoram University, Aizawl, Mizoram (India) between January, 2019 and December, 2019 for correlation with earthquakes. All earthquakes within 150 km from the monitoring station were correlated with an average precursory time of 7 ± 5 days. The empirical mode decomposition (EMD) based Hilbert–Huang transform (HHT) analysis shows that thoron anomaly of the monitoring station specifically responds to those earthquakes along the subduction line and the region was seismically active. [ABSTRACT FROM AUTHOR]

The paper presents the results of modeling the stress–strain state of the epicentral zone of the strong crustal Hanshin–Awaji earthquake, which occurred in the area of Kobe (Japan) on January 17, 1995, with a magnitude M of 6.9. In this work the author's method for modelling and analyzing the stress–strain state of the epicentral zones of crustal earthquakes was used. The geological, tectonic, and seismological data for the earthquake region are used as input data and boundary conditions for modeling. In this work it is shown that the main rupture arising at the origin of the earthquake is generated in a zone of high stress intensity at a certain ratio of the main tectonic stresses and propagates through areas of anomalously high stress concentration, causing maximum displacements in these zones. The results provide new insights into the focal mechanism of an earthquake, aimed at predicting the location and magnitude of strong crustal earthquakes in earthquake-prone areas. [ABSTRACT FROM AUTHOR]

According to theory, earthquakes may produce disturbances in surrounding areas and affect the major earthquake occurrence rate of surrounding faults. The MS 6.6 Jinghe Earthquake on 9th August, 2017 occurred in the Tienshan Seismic Belt where there is much tectonic activity and many strong earthquakes occur. The impact of this earthquake on major earthquake activity of surrounding areas is worth studying. This paper attempts to combine two models: the Brownian passage-time (BPT) model, which describes the quasi-periodic recurrence of major earthquakes, and the Coulomb Failure Stress model, which describes rock failure on faults. The amount of change in the rate of major earthquake occurrence caused by a nearby earthquake was calculated, and changes in major earthquake activity in the surrounding areas after the Jinghe Earthquake were re-estimated. There are few differences in major earthquake occurrence rate change by stress disturbances calculated with the BPT model or the Coulomb Failure Stress model. Calculation results are consistent with actual earthquake cases. The 2017 Jinghe Earthquake increased major earthquake activity on the Boluokenu Fault and Yili Basin North Fault, and the expected major earthquake recurrence times of the two faults were advanced by 11 years and 59 years, respectively. Conclusions of this paper provide a reference for time-dependent seismic hazard assessments in related areas. [ABSTRACT FROM AUTHOR]

This paper is an analysis of the seismic process in the source zones of great (M ~ 8) earthquakes occurring at the Pacific seismic belt and in Southeast Asia. We sought to enhance data homogeneity for different seismic regions by proposing the concept of a generalized energy class of earthquakes. The concept is a promising alternative to the existing procedure for the energy classification of earthquakes. We consider one important characteristic of the source zone of a great earthquake, namely, the energy spectrum of the seismic process; the Gutenberg–Richter law is generally treated as a first approximation to this concept. We have proposed a method for the study of the concept, have identified a significant peaking growth of the slope of the recurrence curve for the period between 5 and 10 years before a great event and a decrease immediately before it. These peaking anomalies are hypothesized to repeat themselves and to be quasi-periodic in character, with the periods of their occurrence prior to a great earthquake being arguably different in different regions. The results of this study can be used both to enhance the reliability of long-term earthquake prediction and for intermediate-term and short-term updating of earthquake hazard. [ABSTRACT FROM AUTHOR]

Abstract—The paper addresses the problems associated with the maximum earthquakes in a seismically active region. Pisarenko and Rodkin (2009; 2010; 2015) proposed an alternative to the ambiguously determined parameter of the maximum regional magnitude Mmax in the form of a clearly defined and statistically substantiated parameter of the maximum possible magnitude of an earthquake in a given region on a given future time interval T. In this work, we study the statistical characteristics of this parameter—quantiles with a given confidence level q. For the first time, the estimates for the bias, standard deviation, and root mean square deviation of these quantiles are conducted on a large set (1000) of independent samples (synthetic catalogs) with known distribution law. This allowed us to compare the true accuracy of the resulting estimates with that obtained in the case of using one catalog for which the distribution law is not known. The real efficiency of the quantile estimates is assessed from the examples with the exact known quantile values, and stability and robustness of these quantiles as an informative and important characteristic of seismic risk is demonstrated. The conducted comparisons make it possible to estimate the scatter of the quantiles in the region of large times T and with very high confidence levels q. The quantile estimates of the maximum possible events in a future time interval are substantially more robust at a stronger downward bend of the frequency–magnitude graph. A relationship is derived between the quantiles of a single earthquake and the quantiles of a maximum earthquake in the future time interval T. This relationship establishes the equivalence between the length of interval T and the level of significance (reliability) q, which in the case of heavy-tailed distributions should be taken into account in seismic risk assessment. The statistical analysis is carried out using two different methods of parameter estimation: by maximum likelihood estimation and by Bayesian approach. Both methods proved to be approximately equally efficient. Based on these methods, it is concluded that the estimate of the long-term seismic hazard for the regions with a distinctly pronounced downward bend of the frequency–magnitude graph is fairly stable and robust. [ABSTRACT FROM AUTHOR]

This paper presents the results of analysis of the spatial distribution of repeated shocks. Data from the world earthquake catalog of USGS/NEIC from 1973 to 2014 were used. Short time intervals, no more than 10 hours after the main shock, and distances from the epicenter of the main shock, no more than 5°, were considered. The dependence of the number of repeated shocks on the distance from the epicenter was studied. Two properties of the spatial distribution of repeated shocks have been identified. The first property is that the curve describing spatial distribution has its maximum at a certain distance (approximately from 10 to 120 km) from the epicenter of the main shock. The logarithm of this distance is directly proportional to the magnitude of the main shock. The second property is that the position of the maximum does not depend on time, i.e., it is a stable spatial characteristic of the earthquake source. Based on these properties, a new way to determine the size of the rupture zone was proposed. [ABSTRACT FROM AUTHOR]

Afghanistan is a tectonically complex zone developed as a result of the collision between the Eurasian plate and the Indian plate to the southeast and the Arabian plate to the south. The active tectonics of the country is distinguished by a wide zone of crustal deformation. There is no large-scale active fault map in Afghanistan, which is essential for seismic hazard mitigation. I, therefore, mapped active and presumed active faults mainly based on interpretation of 1-arcsecond SRTM anaglyph images and shaded relief map. The map reveals that there are significant active faults across the country. In consideration based on the available data and geomorphic criteria, 22 faults are considered seismically active. The result from the mapping represents that three dominant types of structures (left-lateral strike-slip, right-lateral strike-slip, and thrust faults) characterized the interior of Afghanistan. Then the active fault map was combined with earthquake catalog data to interpret the seismic hazard and define earthquake sources based on focal mechanisms and distribution of earthquakes. To contribute to the understanding of seismic hazard, the paper outlines regions with similar neotectonic constraints and observations of type and age of faults that generate background seismicity. I delineated four seismic source zones: (1) east-northeastern, (2) Afghanistan-North Pamir, (3) Northern Afghanistan platform, and (4) middle and southwestern Afghanistan. The east-northeastern seismic zone is the most seismically active and has more crustal earthquakes in the country. This zone is cut by large active and potentially active faults, and Chaman fault is the most significant left-lateral fault that produced five historical surface ruptures. [ABSTRACT FROM AUTHOR]

Satellite measurements are becoming popular among the scientific community to identify earthquake precursors since its spatial coverage is more and round the clock measurements are possible. In this paper, we analyzed Total Electron Content (TEC), Outgoing Longwave Radiation (OLR), Sea Level Pressure (SLP), Surface Latent Heat flux (SLHF) and Sea Surface Temperature(SST) to identify any abnormal anomalies before Taiwan earthquakes which occurred on 4th February 2018 (M = 6.1, depth = 12 km) and 6th February 2018 (M = 6.4, depth = 17 km). The GPS data of International GNSS Service(IGS) stations (TWTF and CKSV) which operated 90 and 200 km away from the epicenter of the earthquake on 6th February 2018 respectively, were used for calculation of VTEC. The locations of these stations are within the preparatory zone of these earthquakes. The global parameters such as Dst, Kp, and IMF are also analyzed for the corresponding period of VTEC. We noticed the raise of temporal variations of 5–8 TECU before few days of the present earthquakes. The VTEC and other parameters such as SLP, SST, SLHF, and OLR were analyzed using the "Sliding Interquartile range method" during the period of 09th Jan to 10th Feb 2018 (33 days) to identify the abnormal signal due to these earthquakes. Strong positive anomalies occurred one day before the earthquake of 4th February and 1st, 3rd and 5th day before the Taiwan earthquake of 6th February 2018 with strong anomalous nature with an absolute amplitude of 5–8 TECU.The Cross wavelet analysis between Kp and TEC is carried out to study the impact of global geomagnetic activity on TEC during the seismic event and we found a negligible influence of global geomagnetic activity. The good raise of SLP on the day of the earthquake on 6th February 2018 have been noticed with the raise of 300 mb, the SLHF anomalies are observed at the interface of the earth's surface and atmosphere. Moreover, anomalous variations in air temperature and OLR were observed 2 days before the occurrence of the earthquake on 6th February 2018. Well co-ordinated scrutiny of various parameters such as TEC, SLHF, and OLR indicates that they can be used as promising precursors to the impending devastating earthquakes with reasonable accuracy. [ABSTRACT FROM AUTHOR]

After an earthquake, the goal of emergency rescue work is to minimize the number of casualties and save lives. The most important initial task is the rapid assessment of the number of earthquake casualties. At present, the rapid assessment of casualties relies primarily on census data rather than real-time population data in an earthquake area. Features of the census data, such as their low accuracy and time lag, can easily cause large errors in the assessment result; thus, the assessment result cannot always reflect the actual situation in an earthquake area. In this paper, we use phone signal data to construct a population density model and estimate the real-time population in a seismic area. The results show that the estimated population is consistent with the actual data in the study area. Finally, we obtain a real-time population distribution map of the study area. The real-time distribution of the population is consistent with the actual situation based on the economic and social development of the study area. The population in an urban area is relatively dense, whereas that in a rural area is less dense. The results show that phone signal data can play a useful role in estimating the real-time population when an earthquake occurs and can be used to support earthquake emergency rescue work. [ABSTRACT FROM AUTHOR]

This paper describes a method for calculating the earthquake energy class for the Kamchatka region from coda records in the 0.8–1.8 Hz frequency band. The method is based on an empirical correlative relationship between the coda level and the Fedotov earthquake class. The coda level is found as the mean power of the ground velocity in an interval of 30 s. Five seismic dipping zones have been identified in Kamchatka, each having its own expression for converting the coda level to the energy class. [ABSTRACT FROM AUTHOR]

The 2010 Mw = 8.8 Maule earthquake, which occurred in the subduction contact between the Nazca and the South American tectonic plates off the coast of Chile, represents an important opportunity to improve understanding of the distribution and controls for the generation of landslides triggered by large megathrust earthquakes in subduction zones. This paper provides the analysis of the comprehensive landslide inventory for the Maule earthquake between 32.5° S and 38.5° S. In total, 1226 landslides were mapped over a total area of c. 120,500 km2, dominantly disrupted slides. The total landslide volume is c. 10.6 Mm3. The events are unevenly distributed in the study area, the majority of landslides located in the Principal Andean Cordillera and a very constrained region near the coast on the Arauco Peninsula, forming landslide clusters. Statistical analysis of our database suggests that relief and lithology are the main geological factors controlling coseismic landslides, whilst the seismic factor with higher correlation with landslide occurrence is the ratio between peak horizontal and peak vertical ground accelerations. The results and comparison with other seismic events elsewhere suggest that the number of landslides generated by megathrust earthquakes is lower than events triggered by shallow crustal earthquakes by at least one or two orders of magnitude, which is very important to consider in future seismic landslide hazard analysis. [ABSTRACT FROM AUTHOR]

The Gulf of Aqaba is one of the most active places around Egypt, with several earthquake sequences having occurred there through ancient and modern times. In the last century, four earthquake sequences took place in the gulf (1983, 1990, 1993, and 1995). Recently, on 27 June 2015, a sequence of 96 earthquakes with local magnitudes ranging from 0.7 to 5.2 was recorded by the Egyptian National Seismological Network (ENSN). On 16 May 2016, another earthquake sequence started and continued for several consecutive days, with 95 events with local magnitudes ranging from 1.6 to 5.5 being centered south of the 27 June 2015 sequence. In this paper, we analyse the complete waveform and polarity data set of both earthquake sequences to determine their focal mechanisms and to update our knowledge of the stress field in the Gulf of Aqaba. Through the results obtained, we conclude that, the Gulf of Aqaba is affected by a primary structure of a left-lateral strike-slip fault with a minor normal component in most segments. Our study also infers the presence of a secondary structure, which is indicated to be a right-lateral strike-slip with a minor reverse component. [ABSTRACT FROM AUTHOR]

The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis (GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city (located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region. [ABSTRACT FROM AUTHOR]

Abstract—: This paper reports the results of numerical modeling of the stress-strain state of the epicentral area before and after the August 24, 2014 earthquake in Napa, California, USA, compared to calculated data obtained in instrumental studies in the dilatation areas based on GPS observation results. Numerical modeling has made it possible to calculate the stress-strain state of the epicentral area affected by the tectonic fault system. GPS observation data on the epicentral area of the earthquake and the results of numerical modeling of the stress-strain state before and after the considered earthquake have been analyzed. A trend toward localization of earthquake epicenters in the region of high stress intensity concentration has been confirmed. It has been proved that aftershock development is due to the drop in stress caused by a new fracture and that the aftershock cluster that occurred was localized in the area of decreased stress intensity. [ABSTRACT FROM AUTHOR]

This paper aims at implementing and introducing the use of conditional mean spectrum (CMS) and conditional spectrum (CS) as the main input parameters in the practice of seismic safety evaluation (SSE) in China, instead of the currently used uniform hazard spectrum (UHS). For this purpose, a procedure for M-R-epsilon seismic hazard deaggregation in China was first developed. For illustration purposes, two different typical sites in China, with one to two dominant seismic zones, were considered as examples to carry out seismic hazard deaggregation and illustrate the construction of CMS/CS. Two types of correlation coefficients were used to generate CMS and the results were compared over a vibration period range of interest. Ground motion records were selected from the NSMONS (2007-2015) and PEER NGA-West2 databases to correspond to the target CMS and CS. Hazard consistency of the spectral accelerations of the selected ground motion records was evaluated and validated by computing the annual exceedance probability rate of the response spectra and comparing the results to the hazard curve corresponding to each site of concern at different periods. The tools developed in this work and their illustrative application to specific case studies in China are a first step towards the adoption of CMS and CS into the practice of seismic safety evaluation in this country. [ABSTRACT FROM AUTHOR]

This paper describes a method for calculating the station corrections to earthquake energy class and the acoustic impedance based on records of earthquake codas in the 0.8-1.8 Hz frequency band. The calculation is based on measurements of the relative coda level at two stations, with one of the two being used as the reference. The data were recorded by digital seismometers: CMG-3TB (GURALP), CMG-5TD (GURALP), CMG-6TD (GURALP), and GMS-AC-73i HHV (GeoSIG). We present estimates of class corrections for the Kamchatka network of seismic stations. [ABSTRACT FROM AUTHOR]

This paper presents a seismic hazard map for the southern part of Ghana prepared using the probabilistic approach, and seismic hazard assessment results for six cities. The seismic hazard map was prepared for 10% probability of exceedance for peak ground acceleration in 50 years. The input parameters used for the computations of hazard were obtained using data from a catalogue that was compiled and homogenised to moment magnitude (Mw). The catalogue covered a period of over a century (1615-2009). The hazard assessment is based on the Poisson model for earthquake occurrence, and hence, dependent events were identified and removed from the catalogue. The following attenuation relations were adopted and used in this study—Allen (for south and eastern Australia), Silva et al. (for Central and eastern North America), Campbell and Bozorgnia (for worldwide active-shallow-crust regions) and Chiou and Youngs (for worldwide active-shallow-crust regions). Logic-tree formalism was used to account for possible uncertainties associated with the attenuation relationships. OpenQuake software package was used for the hazard calculation. The highest level of seismic hazard is found in the Accra and Tema seismic zones, with estimated peak ground acceleration close to 0.2 g. The level of the seismic hazard in the southern part of Ghana diminishes with distance away from the Accra/Tema region to a value of 0.05 g at a distance of about 140 km. [ABSTRACT FROM AUTHOR]

On October 21, 2016, an earthquake with Japan Meteorological Agency (JMA) magnitude 6.6 hit the central part of Tottori Prefecture, Japan. This paper demonstrates two notable effects of the surface geology on strong ground motions due to the earthquake. One is a predominant period issue observed over a large area. A seismic intensity of 6 lower on the JMA scale was registered at three sites in the disaster area. However, the peak ground acceleration ranged from 0.3 to 1.4 G at the three sites because of the varying peak periods of observed strong ground motions. The spectral properties of the observations also reflect the damage around the sites. Three-component microtremors were observed in the area; the predominant ground period distributions based on horizontal to vertical spectral ratios were provided by the authors. The peak periods of the strong motion records agree well with predominant periods estimated from microtremor observations at a rather hard site; however, the predominant periods of the microtremors are slightly shorter than those of the main shock at the other two soft sites. We checked the nonlinear effect at the sites by comparing the site responses to small events and the main shock. The peak periods of the main shock were longer than those of the weak motions at the sites. This phenomenon indicates a nonlinear site effect due to large ground motions caused by the main shock. A horizontal component of the accelerogram showed rather pulsating swings that indicate cyclic mobility behavior, especially at a site close to a pond shore; ground subsidence of ~20 cm was observed around the site. The peak periods of weak motions agree well with those of the microtremor observations. This implies an important issue that the predominant periods estimated by microtremors are not sufficient to estimate the effect of surface geology for disaster mitigation. We have to estimate the predominant periods under large ground motions considering the nonlinear site response of soft sediment sites. [ABSTRACT FROM AUTHOR]

The fragility of buried electrical cables is often neglected in earthquakes but significant damage to cables was observed during the 2010-2011 Canterbury earthquake sequence in New Zealand. This study estimates Poisson repair rates, similar to those in existence for pipelines, using damage data retrieved from part of the electric power distribution network in the city of Christchurch. The functions have been developed separately for four seismic hazard zones: no liquefaction, all liquefaction effects, liquefaction-induced settlement only, and liquefaction-induced lateral spread. In each zone six different intensity measures (IMs) are tested, including peak ground velocity as a measure of ground shaking and five metrics of permanent ground deformation: vertical differential, horizontal, maximum, vector mean and geometric mean. The analysis confirms that the vulnerability of buried cables is influenced more by liquefaction than by ground shaking, and that lateral spread causes more damage than settlement alone. In areas where lateral spreading is observed, the geometric mean permanent ground deformation is identified as the best performing IM across all zones when considering both variance explained and uncertainty. In areas where only settlement is observed, there is only a moderate correlation between repair rate and vertical differential permanent ground deformation but the estimated model error is relatively small and so the model may be acceptable. In general, repair rates in the zone where no liquefaction occurred are very low and it is possible that repairs present in this area result from misclassification of hazard observations, either in the raw data or due to the approximations of the geospatial analysis. Along with hazard intensity, insulation material is identified as a critical factor influencing cable fragility, with paper-insulated lead covered armoured cables experiencing considerably higher repair rates than cross-linked polyethylene cables. The analysis shows no trend between cable age and repair rates and the differences in repair rates between conducting materials is shown not to be significant. In addition to repair rate functions, an example of a fragility curve suite for cables is presented, which may be more useful for analysis of network connectivity where cable functionality is of more interest than the number of repairs. These functions are one of the first to be produced for the prediction of damage to buried cables. [ABSTRACT FROM AUTHOR]

This paper begins with a critical assessment of the concept of macroseismic intensity, on which traditional scales, such as MSK and EMS, are based. The main shortcoming identified is the model's failure to consider the spectral features of ground motion. This omission may lead to erroneous seismic zonation, as shown in the paper. As a result, the model is of little interest to engineers who must design and build safe structures while adopting economical solutions. The paper presents a way to radically improve this situation. The starting point for this approach was the experience of the destructive Vrancea earthquake of 1977.03.04, which made it clear that intensity appears to be different for structures having natural periods pertaining to different spectral domains. The solution proposed to the shortcomings of the traditional intensity concept is postulated on a system of analytical expressions, covering definitions of global intensities, of intensities related to oscillation frequency and of intensities related to a definite spectral band. The latter definition lies at the basis of a definition of discrete intensity spectra. Illustrative applications are presented, in relation to global intensities and to discrete intensity spectra. We then analyze an illustrative case in which the use of traditional macroseismic survey techniques led to erroneous seismic zonation. Finally, some conclusions and recommendations are presented. Based on the authors' long-term experience, we strongly recommend close interaction between seismologists and engineers in working groups and joint projects targeted on radical improvement of the basic concepts of seismic intensity and of specific analysis procedures. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study undertaken to evaluate the implications of the newly mapped offshore Mount Lebanon Thrust (MLT) fault system on the seismic hazard of Lebanon and the current seismic zoning and design parameters used by the local engineering community. This re-evaluation is critical, given that the MLT is located at close proximity to the major cities and economic centers of the country. The updated seismic hazard was assessed using probabilistic methods of analysis. The potential sources of seismic activities that affect Lebanon were integrated along with any/all newly established characteristics within an updated database which includes the newly mapped fault system. The earthquake recurrence relationships of these sources were developed from instrumental seismology data, historical records, and earlier studies undertaken to evaluate the seismic hazard of neighboring countries. Maps of peak ground acceleration contours, based on 10 % probability of exceedance in 50 years (as per Uniform Building Code (UBC) 1997), as well as 0.2 and 1 s peak spectral acceleration contours, based on 2 % probability of exceedance in 50 years (as per International Building Code (IBC) 2012), were also developed. Finally, spectral charts for the main coastal cities of Beirut, Tripoli, Jounieh, Byblos, Saida, and Tyre are provided for use by designers. [ABSTRACT FROM AUTHOR]

This paper aimed at assessing gravity variations as precursors for earthquake prediction in the Tibet (Xizang)-Qinghai-Xinjiang-Sichuan Region, western China. We here take a statistical approach to evaluate efficiency and possibility of earthquake prediction. We used the most recent spatiotemporal gravity field variation datasets of 2002-2008 for the region that were provided by the Crustal Movement Observation Network of China (CMONC). The datasets were space sparse and time discrete. In 2007-2010, 13 earthquakes (> M 6.0) occurred in the region. The observed gravity variations have a statistical correlation with the occurrence of these earthquakes through the Molchan error diagram tests that lead to alarms over a good fraction of space-time. The results show that the prediction efficiency of amplitude of analytic signal of gravity variations is better than seismicity rate model and THD and absolute value of gravity variation, implying that gravity variations before earthquake may include precursory information of future large earthquakes. [ABSTRACT FROM AUTHOR]

In this paper, significant variations in rate of moderate-large earthquake occurrence during the last two centuries at the north of Persia (Alborz, Azarbaijan, and Kopeh Dagh seismotectonic provinces) were chronically investigated. Depths of some historical and instrumental earthquakes were reasonably estimated using macroseismic data. Also, empirical relationships were developed between the maximum intensity and magnitude of the earthquakes in the north of Persia. Two centuries of earthquake data (M ≥5.0) reliably demonstrates that quite periods with durations of about a few years to two decades have happened and have been subsequently followed by active periods with durations of about 10 to 70 years. The time variation of seismic hazards (achieved by the macroseismic maximum intensity, I ≥IV) almost displays a similar behavior at the study area. According to both patterns of the time variations of seismicity and the seismic hazards, it may conclude that we are within a low rate of seismic period, and we may expect a higher rate of seismicity at the Alborz in the next decades. Finally, in both the Azarbaijan and Kopeh Dagh areas, we discovered considerable migrations of the seismicity from the east to the west. [ABSTRACT FROM AUTHOR]

Work was performed in 2008-2014 on the long-term prediction of great earthquakes at the Kuril-Kamchatka arc based on patterns that are observable in the locations of the rupture zones of great earthquakes (seismic gaps) and in the seismic cycle for such earthquakes. The prediction method has been successfully developed and applied to the region since 1965 (the LTEP method). This paper presents a long-term seismic forecast for the September 2013 to August 2018 period for the Kuril-Kamchatka arc earthquake-generating zone. The forecast predicts the following quantities for 20 constituent segments: phases of the seismic cycle, the normalized rate of small earthquakes A, the magnitudes of moderate-size earthquakes to be expected with probabilities 0.8, 0.5, and 0.15, the maximum possible magnitudes and probabilities of occurrence for great (M ≥ 7.7) earthquakes in the most active depth interval, viz., 0-80 km. We also discuss the seismic process in this region for the 2008-2013 period, namely, the patterns that are observable in the locations of earthquake swarms, the values of and changes in several characteristics of the seismic process in the Kuril-Kamchatka seismic zone during the period 2008-2013, which occurred in relation with great shallow earthquakes beneath the Sea of Okhotsk (July 5, 2008, M = 7.7; August 14, 2012, M = 7.7; May 24, 2013, M = 8.3, and the giant Tohoku earthquake of March 11, 2011 with M = 9.0). The results corroborate the high seismic hazard for the area of Petropavlovsk-Kamchatskii and the urgent necessity of continuing and intensifying the ongoing work on seismic retrofitting and seismic safety. [ABSTRACT FROM AUTHOR]

This paper presents results from a study of variations in short-period shear-wave attenuation in the lithosphere of the Baikal Rift Zone (BRZ). We used earthquake records made at the Ulan-Bator station (ULN) at epicentral distances of ∼400-1300 km. The ratios of maximum amplitudes in the Sn and Pn waves were considered. We show that these ratios are on the whole considerably higher than those in other areas of Central Asia. It was found that zones of low shear wave attenuation coincide with the rupture zones of large earthquakes that occurred during the 19th and 20th centuries. We identified zones of high attenuation where no large (M∼ > 7.0) seismic events have occurred during at least 180 years. The hypothesis we propose is that precursory processes before future large earthquakes may be occurring in these zones. We discuss the question of whether wave attenuation characteristics may be related to seismicity. [ABSTRACT FROM AUTHOR]

The area of western Transbaikalia is characterized by moderate seismic activity. Nevertheless, there is historical and instrumental evidence to show that rather strong seismic events have occurred in the area and caused considerable material damage to the population centers around their epicenters. Seismological knowledge of the region is scant. The earthquake catalogs for the area and for the historical period of time need to be corrected and supplemented. The present paper considers the earthquake of October 9, 1864, which has not been included in any parametric catalog thus far. New primary data that were found in the regional periodic press were used to determine the epicenter and magnitude (M = 5.1) for the event. The earthquake of October 9, 1864 is a 'forgotten' event, but is a significant addition to the catalog for western Transbaikalia. The materials presented here can be used to assess earthquake hazard for the area, as well as to aid in the search for other unknown or 'forgotten' earthquakes. [ABSTRACT FROM AUTHOR]