Seismoactive Zone Research Articles

Сейсмотектоническая активность Ляховичского разлома в Припятском прогибе

The main result of the work was the identification of the present-day seismotectonic regime of an active zone of the Lyakhovichi regional fault. The areal and space-time distribution of the earthquake epicenters along the fault line was reconstructed. The coordinates of the seismically active fault zone located within an area of 52.738—53.037° N and 26.830—28.034° E were determined. It was found that the distribution of earthquakes along the fault line occurred non-uniformly in space and time. The period from 2012 till 2021 was the most active one by the quantity of occurred earth quakes (169) and released total seismic energy (4.5929•109 J). The strongest earthquake with a magnitude M = 2.9 was recorded in the eastern part of the fault on September 03, 2021. Our reconstructions determined the value of seismic dislocation along the fault, which corresponded to the kinematic slip fault. To characterize the modern seismogeodynamic activity in the Lyakhovichi fault zone, a comprehensive technique based on long-term monitoring of seismic events was used. Based on the performed studies, the seismotectonic potential of the seismoactive zone of the Lyakhovichi fault was determined.

Technological Solution for Improving Structural Performance and Resilience of Buildings in Seismic Zone

Its purpose is to assess novelty materials and technologies to increase the stability of structures in seismo-active zones. The research relates to the post-earthquake requirement for reconstructing structures and infrastructures that could stand the deadly phenomena that have ravaged many parts of the world. New and improved materials were researched and experimented with, including high-performance concrete, FRP or fiber reinforced polymers, self-healing concrete, and hi-tech anchorages. The compressive strength of the reinforced concrete slab was determined through a universal testing machine. In contrast, the tensile strength and % elongation at the Break of FRP were determined using an Instron machine. Data analyses involved variance analysis (ANOVA) and regression to analyze the performance of the used material. The healing efficiency of the self-healing materials, as identified in the study, ranged from 85 percent. 123% to 99. 789%, while the healing time varies between 7-21 days. 123 to 11. 789 days. The observed enhancement of tensile strength of all FRPs under investigation ranged between 180 and 240: 789 and high UV resistance scores with an average of 9. 456. EI-based and PB anchoring systems demonstrated that Von Mises' stress load capacity variations stood between 100. 123 kN to 240. This was 789 kN, while corrosion resistance scores for all the tires examined in this study averaged 8. 567. The breakdown of the cost difference indicated an inconsistency that ranged between N50. 123/kg to N68. 789/kg. From the findings, it is evident that there is an understanding of how the improved materials promoted can improve structural capacity in cases of seismic activity. Therefore, the study offers valuable information on material choice and use while urging building officials to incorporate these components in their codes and standards for constructing earthquake resistant structures in the regions most vulnerable to this phenomenon.

ICDP drilling of the Eger Rift observatory: magmatic fluids driving the earthquake swarms and deep biosphere

Abstract. The new in situ geodynamic laboratory established in the framework of the ICDP Eger project aims to develop the most modern, comprehensive, multiparameter laboratory at depth for studying earthquake swarms, crustal fluid flow, mantle-derived CO2 and helium degassing, and processes of the deep biosphere. In order to reach a new level of high-frequency, near-source and multiparameter observation of earthquake swarms and related phenomena, such a laboratory comprises a set of shallow boreholes with high-frequency 3-D seismic arrays as well as modern continuous real-time fluid monitoring at depth and the study of the deep biosphere. This laboratory is located in the western part of the Eger Rift at the border of the Czech Republic and Germany (in the West Bohemia–Vogtland geodynamic region) and comprises a set of five boreholes around the seismoactive zone. To date, all monitoring boreholes have been drilled. This includes the seismic monitoring boreholes S1, S2 and S3 in the crystalline units north and east of the major Nový Kostel seismogenic zone, borehole F3 in the Hartoušov mofette field and borehole S4 in the newly discovered Bažina maar near Libá. Supplementary borehole P1 is being prepared in the Neualbenreuth maar for paleoclimate and biological research. At each of these sites, a borehole broadband seismometer will be installed, and sites S1, S2 and S3 will also host a 3-D seismic array composed of a vertical geophone chain and surface seismic array. Seismic instrumenting has been completed in the S1 borehole and is in preparation in the remaining four monitoring boreholes. The continuous fluid monitoring site of Hartoušov includes three boreholes, F1, F2 and F3, and a pilot monitoring phase is underway. The laboratory also enables one to analyze microbial activity at CO2 mofettes and maar structures in the context of changes in habitats. The drillings into the maar volcanoes contribute to a better understanding of the Quaternary paleoclimate and volcanic activity.

Statistical Global Investigation of Pre-Earthquake Anomalous Geomagnetic Diurnal Variation Using Superposed Epoch Analysis

Recent studies reported that the diurnal variation of the geomagnetic field exhibited anomalous characteristics several months before earthquakes (EQs). However, the statistical significance of such anomalies detected using the diurnal variation range ratio (DVRR) method still requires verification as only a limited number of EQs occurring in certain seismoactive zones were included. In this study, the DVRR method was employed in conjunction with the superposed epoch analysis (SEA) to perform a large-scale study. A total of 157 EQs that occurred between 2000 and 2019 were investigated using vast geomagnetic field data collected from 92 ground-based magnetometer stations spread across multiple global regions. The case study conducted on the May 13, 2011, M6.1 Honshu (Japan) EQ showed that the diurnal variation of the vertical geomagnetic component disappeared around a week before the EQ. The case study also demonstrated the effectiveness of the DVRR method in minimizing solar disturbance influences, further proving that the observed anomalies were not caused by the Sun. The subsequent SEA revealed statistically significant increases in anomaly counts before the occurrence of EQs for all three geomagnetic components. The number of anomalies gradually increased approaching the day of EQs with temporal lags between the components. Furthermore, a control group analysis confirmed the findings by demonstrating that the increases were not coincidental and several explanations have been suggested, focusing primarily on the emergence and generation mechanisms of the anomalies. Results from this study showed that the anomalies were significant and were potentially precursors to the succeeding EQs.

S-Wave Attenuation Field and Seismotectonics of Eastern Anatolia

This work studies the characteristics of seismic coda waves attenuation in Eastern Anatolia. The short-period coda waves from about 400 earthquakes that occurred in Eastern Anatolia between 1989 and 2018 are analyzed. The three-component digital records of seismic events with M ≥ 3.5, recorded at epicentral distances of 10–600 kilometers, are used. S-wave attenuation was estimated from short-period coda envelopes (including those of Lg wave coda) at a frequency of ~1 Hz. The structural features of the S-wave attenuation field in the upper mantle of the Lake Van area are similar to those for other seismoactive zones. The attenuation field is represented by blocks, which have weak attenuation and are subisometric in plan view, and strong attenuation zones; in the case of blocks, attenuation decreases in the direction from the boundaries to the central of these blocks (Q-factor is up to 300–700). Among the zones of strong attenuation, which are usually linearly elongated, the most noticeable are the en echelon zone (north of 39° N), associated with the North Anatolian Fault; here, QS ~ 80–110 (up to QS ~ 60 in the north); and the Bitlis-Zagros fold and thrust belt (QS ~ 60–70). Sources of the strongest earthquakes with M > 6.0, including the 1976 Caldiran–Muradiye and 2011 Van earthquakes, are confined to the boundaries of the blocks. The attenuation field structure corresponds to the velocity field structure: low-velocity anomalies correspond to low-Q zones. Vertically elongated volumes, with which intensive localized seismicity (earthquake swarms) is associated and along which deep fluids can migrate, are revealed. Seismic activation in such volumes precedes large seismic events (for example, the 2011 Van earthquake). It is assumed that such volumes can be interpreted as local seismogenic sources.

Tectonic Fracturing of the Lithosphere of the Priamurye Region by Submeridional and Sublatitudinal Faults (from Geophysical Data and Relief Analysis)

Based on the data of relief analysis, the gravity and magnetic anomaly axes, earthquake foci sequences, and Vp/Vs ratio values, tectonic fracturing of the lithosphere is studied and tectonic submeridionally and sublatitudinally oriented fracturing zones are distinguished in the Priamurye region. Separate segments of extended submeridional and sublatitudional fracturing zones are evidenced from the regional faults detected using the geological methods. Submeridionally oriented tectonic fracturing zones are mostly revealed, which do not correlate with the regional faults. Fracturing zones of similar orientation which are displayed in lineaments of different type and correlate with the seismoactive zones may be considered as hidden faults.

Fault Tectonics and Deep Structure of Seismic Zones in the Eastern Priamurye Region

This paper is concerned with spatial relationships between seismic zones in the eastern Priamurye region (М ≥ 5) on the one hand and, on the other, regional faults and zones of hidden faults as indicated by axes of gravity and magnetic anomalies. The seismoactive zones where М ≥ 5 earthquakes occurred are mostly confined to regional faults, while there are two cases where no such relationship has been detected. Seismic zones are observed both at intersections of regional faults and at intersections of regional faults with hidden faults of different rank. The seismic zones comprise inclined and subvertical deep-seated faults as identified by deep seismic sounding (DSS), the earthquake converted wave method (ECWM), and magnetotelluric sounding (MTS) surveys. The seismoactive zones were studied by geophysical techniques to identify indication of fluid saturation, as follows: the seismoactive faults frequently control low velocity and low resistivity inhomogeneities in the Earth’s crust and upper mantle; some seismoactive faults have displaced the Moho interface; there are dome-shaped flexures of crustal interfaces and of the Moho interface; and the crust is found to contain numerous conversion interfaces. The deep occurrence of seismoactive faults and the indications of fluid saturation suggest that the seismoactive faults in the eastern Priamurye region provide supply of fluids from the mantle to the crust.

The features of fault tectonics and deep structure of the seismoactive zones in Eastern Priamurye

The paper examines the spatial relationship between the seismoactive zones in eastern Priamurye (М ≥ 5) and the regional faults and hidden fault zones identified from the gravity and magnetic anomaly axes. The seismoactive zones where earthquakes with М ≥ 5 occurred are mostly confined to the regional faults, though such a relationship has not been validated in two cases. The seismoactive zones are detected both at the regional fault intersection and in areas where the regional faults intersect with the hidden faults of various ranks. According to the data obtained by deep seismic sounding (DSS), earthquake converted wave method (ECWM) and magnetotelluric sounding (MTS), the seismoactive zones are formed by deep inclined and subvertical faults. The indications of fluid saturation are found in the seismoactive zones from geophysical data which show that the seismoactive faults often control low-velocity and low-resistivity anomalies in the crust and upper mantle. In some cases, the Moho displacement and the dome-like flexures of the crustal and Moho boundaries are observed along these seismoactive faults and the abundance of the conversion boundaries in the crust is also noted. The deep pattern of the seismoactive faults and the revealed indications of fluid saturation allow us to consider the seismoactive zones in eastern Priamurye as the channels providing fluid supply from the mantle to the crust.

Can low-magnitude earthquakes act as a triggering factor for landslide activity? Examples from the Western Carpathian Mts, Poland

There are numerous examples of the impact of strong earthquakes on landslide activity. There is however very little information about the ability of low-magnitude earthquakes (M < 5.0) to affect the stability of pre-existing landslide slopes. Two landslides were studied (Hołowiec and Kamień, Western Carpathians, Poland). These are located 20–30 km from seismoactive zones where earthquakes of M ≤ 4.4 occur. We have used tree rings to date past landslide movements possibly caused by earthquakes. We have dated events of tree tilting by landslide activity, after which the trees developed eccentric rings and reaction wood, in a sample of 40 Norway spruces (Hołowiec) and 51 European silver firs (Kamień). The results of dendrochronological dating were compared with the occurrence of earthquakes in the study area (magnitudes, epicentral distance, etc.). We have also analysed precipitation data to help to disentangle the impact of rainfall and earthquakes as triggering factors. We were able to distinguish: earthquake-triggered landsliding with no impact of precipitation, precipitation-triggered landsliding with no seismic impact and landsliding triggered by the overlapping impact of precipitation and earthquakes. The results show that the combination of both triggering factors has the strongest influence on the stability of landslides under study. The study demonstrates the ability of low-magnitude (M < 5.0) earthquakes to trigger landslide activity, even at distances larger than appears from limiting curves published for co-seismic landslides. The results also suggest that the activity of the Kamień landslide can possibly be influenced by the long-distance (over 500 km) influence of strong earthquakes (M 6.8–7.4) from outside of the study area. The study demonstrates that the seismic factor, both local, low-magnitude earthquakes and distant, strong earthquakes, can be an important trigger of landslide activity. Their role may be underestimated in the study area and other areas considered as seismically non-active or of low seismic activity.

Some Probabilistic and Statistical Properties of the Seismic Regime of Zemmouri (Algeria) Seismoactive Zone

Statistical tests have been used to adjust the Zemmouri seismic data using a distribution function. The Pareto law has been used and the probabilities of various expected earthquakes were computed. A mathematical expression giving the quantiles was established. The extreme values limiting law confirmed the accuracy of the adjustment method. Using the moment magnitude scale, a probabilistic model was made to predict the occurrences of strong earthquakes. The seismic structure has been characterized by the slope of the recurrence plot γ, fractal dimension D, concentration parameter Ksr, Hurst exponents Hr and Ht. The values of D, γ, Ksr, Hr, and Ht diminished many months before the principal seismic shock (M = 6.9) of the studied seismoactive zone has occurred. Three stages of the deformation of the geophysical medium are manifested in the variation of the coefficient G% of the clustering of minor seismic events.

Seismicity of the Central Kuril Islands before and after the catastrophic M = 8.3 (November 15, 2006) and M = 8.1 (January 13, 2007) earthquakes

The data on foreshocks and aftershocks of the strongest earthquakes occurred in the area of Kuril island arc on November 15, 2006 (Mw = 8.3) and January 13, 2007 (Mw = 8.1) are compared. In 2006, two months before the catastrophic earthquake in November, the detailed seismological investigations were carried out with the use of bottom stations in the area of seismic gap in the Central Kuril arc. The maps of epicenters and vertical cross sections for the equal time intervals are compared. The clear difference between distributions of hypocenters in the periods of foreshocks and aftershocks is revealed. Earthquakes were not distributed within the limits of the seismoactive block in the Kuril arc during the foreshocks period; instead, boundaries of seismoactive zone abruptly narrowed and hypocenters concentrated largely within the Benioff zone.

Seismoactive morphostrctures of the east of Eurasia

The comparison of materials of morphostructural and paleoseismogeological investigations for the East of Eurasia was made. As a result the series of previously unknown seismoactive morphostructures, morphostructural zones and regions were discovered. These data testify to the more high level of seismic danger in this region than it was considered earlier. Therefore, compiling new maps of seismic zoning on the morphostructural-and-paleoseismogeological base as well as actions for people and economy protection from possible strong earthquakes are the most actual now.

Possible influence of telluric current on seismicity of the Earth’s crust in seismoactive zones

A physical model is proposed for the possible effect of telluric currents on macrofracturing in the Earth’s crust and the triggering of earthquakes via the interaction of telluric currents with the geomagnetic field. For implementation of the considered processes, a an escalated regime due to positive feedback between the decrease in electrical conductivity of the developing earthquake source and the increases in current and pressure in this source was established. Estimates of characteristic earthquake-triggering time that agree with the experimental data were obtained. The model explains the interrelationship between some observed electromagnetic phenomena and earthquake development processes in seismoactive zones.

Chronology of tsunamis documented in sections of the coastal lowlands in East Primorye

One of the fields in the study of how catastrophic events are manifested is investigation of sediments produced by historical and paleotsunamis. This infor� mation allows researchers to define the age, scale, and frequency of these events in the past. These studies are especially topical for the coasts of the Russian Far East where chronicles have provided almost no evidence and instrumental observations have been carried out only since the second half of the 20th century (1, 2). The longterm works on studying paleotsunamis have been being carried out in the Kuril-Kamchatka Region (3-5), but there are no data on the sediments of the historical and paleotsunamis for the continental coast of the Sea of Japan until the recent time. The Primorye is located in the rare seismoactive zones of Russia, and although most earthquakes in this region are deep focus ones, some strong shallow earthquakes of 5-7 in magnitude have been reported (6). Large tsu� namis in the region are related to the earthquakes whose epicenters are clustered along the narrow band of the shelf and submarine slope of the island of Japan, stretching to Moneron Island (2). Four large tsunamis were reported here during the 20th century: in 1907, 1940, 1983, and 1993; the effects of the last two events were investigated on the coasts of Primorye immedi� ately after the tsunami struck (1, 7, 8). The effects of these tsunamis on the natural and economic objects located in the coastal zone were also assessed, and the zonation of coasts in terms of tsunami hazard was car�

Numerical simulation of tsunami wave height distribution for Turkish Black Sea coast in nonlinear dynamic keyboard model of underwater seismic source

In frames of nonlinear shallow water equations taking into account dissipative effects and bottom friction a numerical simulation of a possible catastrophic tsunami in the Black Sea basin is performed. The computation was performed for seismic sources with various locations in the south-eastern and north-western parts of the Black Sea basin. The location of model sources was selected taking into account more seismoactive zones and proposed recurrence periods of tsunamis for a given region. A seismic source was constructed in frames of a keyboard model of the earthquake source taking into account possible temporal and velocity characteristics of seismic processes in a concrete source. Using a keyboard model of the source, both kinematic and dynamic models of earthquake sources were considered. The keyboard model of an earthquake source with different-time motions of keyboard blocks permits considering various scenarios of processes possible at earthquakes in seismic sources and estimating the influence of these processes on the distribution of maximum wave heights along the coast. Two scenarios for each seismic source were considered: a dynamical model, when the source is divided into keyboard blocks which are shifted in the vertical direction for different times and a single block moving according to certain laws describing unloading in the seismic source on the realization of an earthquake. For each of the scenarios considered, wave characteristics were obtained and a spectral analysis was performed which permits clearing the most dangerous places of the coast for moderate or strong tsunamigenic earthquakes.

Shallow-focus seismicity and tectonic structure of the Sea of Japan

The analysis of the available seismological data on the Sea of Japan region made it possible to prepare the first complete unified catalog of earthquakes with M ⩾ 3.0 and h ⩽ 60 km for the period of 1975–2010. Four maps of epicenters for different depth intervals (0–10, 11–20, 21–30, and 31–60 km) and three sublatitudinal sections 1° wide are constructed. The analysis includes the structural features and the probable tectonic nature of the seismoactive zone along the underwater margin or borderland of the Japan-Sakhalin island arc: the regional or, more exactly, megaduplex of compression faults determined by the crust sliding in the back part of the frontal deep-seated thrust. The crustal seismicity in the southeastern margin of the Korean Peninsula (the Sino-Korean Shield) is likely related to the Tsushima and Ullyndo faults. It is assumed that it may provoke block, potentially thsunamigenic landslides in the southern and eastern cirques of the Ullyndo Basin incised into the underwater delta of the Huanghe River.

Development of inversion methods on fault slip data: Stress state in orogenes of the Central Asia

Algorithm of natural stress reconstruction based on data on slip fault sets is presented. Also additional physical principles following from generalization of experimental geomechanics and theoretical tectonophysics are considered. It gives possibility to define not only orientation of stress tensor principal axis but also the ratio of its spherical and deviatory components. The characteristic feature of the method is that it simultaneously calculates mutually consistent components of stress tensor and increment tensor of seismotectonic deformations, what was missing in previously known methods of tectonophysics. The application of the method is illustrated by two case studies in seismoactive zones of Central Asia: a) Altai and Sayan and b) Northern Tien Shan. Results of stress reconstruction in this intra-plate faulted and folded domains demonstrate that the impact of crust flow and mantle heterogeneity on stresses is great. These processes can contribute much more in generating stresses in crust than interaction of lithosphere plates at distant borders.

Experimental studies of anomalous radon activity in the Tlamacas Mountain, Popocatepetl Volcano area, México: new tools to study lithosphere-atmosphere coupling for forecasting volcanic and seismic events

This study presents and discusses the results of soil radon monitoring at three different volcano sites and one reference site, from December 2007 to January 2009. This relates to the activity of the Popocatepetl Volcano and a radon survey and gamma-ray spectrometry in the area between Paso de Cortes and Tlamacas Mountain, and in the adjacent regions. The results are applied to the aspects of atmosphere electricity and lithosphere-atmosphere coupling in relation to the forecasting of volcano and earthquake activity. The monitoring of radon release reveals a decrease in radon concentration (down to total suppression) with approaching moderate volcanic eruptions. The behavior of the radon activity at the Tlamacas site is more apparent, compared to other observational sites. The average level of radon release observed at the Tlamacas site is much higher, with some characteristic variations. Both the radon survey and gamma-ray spectrometry indicate intensive diffusion radon emission localized in the area of Tlamacas Mountain. The average radon concentration in the area of Tlamacas is about 10-20-fold greater than the background volcano values. The new concept of lithosphere-atmosphere coupling is presented: intensive radon release in high elevated areas shortens and modifies the Earth-to-thunderclouds electric circuit, which provokes microdischarges into the air close to the ground, attracting lightning discharges. This concept attempts to explain in a new way the noise-like geomagnetic emissions registered before major earthquakes, and it promotes interest for the study of thunderstorm activity in seismo-active zones, as a promising instrument for earthquake forecasting.

The Influence of Earthquakes on Open-Pit Slope Stability

Estimation of stability of natural slopes, embankments, dams and open-pit slopes during earthquakes are complex and non-linear problems, therefore physical modeling is used for decision of it. As a result of physical modeling the pattern of seismic vibrations impact based on the movement process of probable collapse prism delineated by the most stressed plane of sliding has been established. Particular recommendations on the basis of safety factors selection in seismoactive zones are given.

The KVVN-7 multifunction digital measuring station for electromagnetic monitoring of seismoactive zones

The portable highly sensitive measuring station KVVN-7 has been designed. It enables us to perform frequency sounding with controllable sources and audio-magnetotelluric sounding in the field of natural variations in an electromagnetic field within one session. Signal recording is made by seven channels (three magnetic and four electric ones) in a broad frequency spectrum (0.1–2000 Hz) with elimination of frequencies on the edges of the set frequency range and in the odd harmonics of industrial frequency (up to the ninth harmonic). The station incorporates the system of band-stop filters and anti-alias filters at resistors having a low temperature coefficient of resistance (TCR is lower than 25 × 10−6 °C−1) and capacitors having a low temperature coefficient of capacity (TCC is lower than ±30 × 10−6 °C−1). Application of the KVVN-7 station allows the electric conductivity and fluid regime of the upper crust to be studied for both implementation of geological tasks and tasks related to electromagnetic monitoring of seismoactive zones in combination with seismic methods. The example of practical application of the KVVN-7 station in the Lovozero-Pulozero profile (Kola Peninsula) has been presented. A high effectiveness of a station has been demonstrated when study of a fluid-saturated layer with conductivity of a dilatancy-diffuse origin (“DD layer”) in the upper crust. The further perfection of the KVVN-7 measuring station is aimed at the design of a completely automated recording system through data recording to a built-in data medium (flash memory). Additionally, it is suggested to use a built-in analog-to-digital converter of high resolution (24 bit) for every channel in order to broaden the dynamical range of the station.