Total Seismic Energy Research Articles

The seismicity of the Carpathians in 2023

According to the results of observations at the seismic stations of the Carpathian region of Ukraine in 2023, the main parameters of 81 earthquakes in the range of energy classes KR=5.8÷13.7 were obtained. The parameters of seismometric equipment at active seismic stations are given. A catalog of earthquakes, their distribution by regions and energy classes, a map of epicenters, graphs of seismic energy release and the number of earthquakes in the region by month are presented. A brief description of the seismicity of certain seismically active areas of the Carpathian region is given. The total energy observed in the region was ΣЕ=9.06·1013 J, which is slightly higher than the last year’s level of ΣЕ=5.06·1013 J. This year, increased seismic activity was observed in three seismically active areas. Thus, 19 earthquakes of energy class KR=5.7÷13.7 were recorded in the North-Western region. Their total seismic energy was ΣЕ=5.02∙1013 J. The two strongest in this area were the earthquake that occurred on October 9 at 18:23 on the territory of Slovakia, near the town of Humenne, with KR=13.7 at a depth of h=8.8 km and intensity at the epicenter of I0=8 points and the earthquake in Transcarpathia, near the village of Dovge, on January 3 at 01:28 with magnitude MSH=3.1, KR=10.7 at a depth of h=9.6 km and intensity at the epicenter of about 5 points. In the Southern Carpathians, 29 earthquakes with KR=8.8÷13.0 were registered at a depth of 2―35 km with a total seismic energy of ΣЕ=3.72∙1013 J. This year, in terms of seismic activity after a long seismic lull, the Krishan region was the third. There were 8 earthquakes with KR=7.6÷12.3 with total seismic energy ΣЕ=2.56∙1012 J. The foci of earthquakes are located in the earth’s crust at depths h=2.0÷15.1 km. This year, compared to last year, the Vrancea district was less active. For the whole year, 19 events with KR=8.4÷11.5 were recorded, the total seismic energy of which is ΣЕ=6.41∙1011 J. In the territory of Bukovyna this year, there is also a decrease in seismic activity compared to 2022. A total of 4 earthquakes with an energy class of KR= 5.8÷7.8 had total seismic energy ΣЕ=1.05∙108 J. The foci of earthquakes were located in the earth’s crust at depths h=1.1÷5 km. Only 2 weak earthquakes were recorded in the Bacau region in 2023, and none in the Banat and Transylvania regions. The regional Carpathian hodograph was used to determine the main parameters of earthquakes in Transcarpathia, and the Jeffreys-Bullen hodograph was used for earthquakes in the Vrancea zone and other six districts.

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.

Determination of the Advanced Mining Influence Range in Coal Mines Based on the Statistical Analysis of Mining-Induced Seismicity

Determining the advanced mining influence range of an underground working face is crucial for preventing dynamic disasters, such as coal bursts and gas outbursts. In this study, the occurrence of advanced seismicity before the working face as well as its correlation with the acoustic emission (AE) activity of coal and rocks under axial loading was analyzed. Based on the results, a novel statistical method to determine the advanced mining influence range based on advanced seismicity data was proposed and then validated with a case study. The results show that advanced seismicity is caused by the combined effects of static and dynamic stresses at the working face. This seismicity can be used to assess the mining influence degree of the working face on the advanced coal and rock mass, and determine the advanced mining influence range. Using the novel statistical method, the normalized curves for the total number and total energy of the advanced mining-induced seismicity can be plotted. Then, the advanced mining influence range can be determined using thresholds. The thresholds can be established based on the AE activities observed in coal and rock samples under axial static loading. In the case study in this research, the thresholds for the total seismic number and total seismic energy are 0.076 and 0.052, respectively. The corresponding advanced mining influence ranges are 275 m and 245 m, respectively. Field monitoring confirms an advanced mining influence range of 255 m, which validates the results obtained using the novel statistical method.

Development and application of out-of-plane deformable X-shaped brace for energy dissipation and thermal stress mitigation: An experimental and numerical study

Exoskeleton systems are increasingly employed in both new and existing buildings to enhance seismic performance. Addressing the critical challenges of energy dissipation and thermal stress mitigation in these systems, an out-of-plane deformable X-shaped energy dissipation brace (OPD-XEDB), integrating an out-of-plane X-shaped brace with a shear-type metallic damper, was proposed in this study. A seismic design methodology for OPD-XEDB was firstly developed, ensuring effective energy dissipation of the damper before any potential brace buckling. Following this methodology, two specimens, exhibiting distinct failure modes of damper shear fracture and brace buckling, were designed and subjected to quasi-static loadings to explore their energy dissipation mechanisms. Upon these experimental results, a numerical model incorporating buckling and pinching behaviors was proposed and calibrated, effectively capturing the hysteretic responses of the specimens. This model was then employed in a comprehensive numerical analysis, validating the effectiveness of design methodology and determining the optimal specifications for the OPD-XEDB in a prototype building. Ultimately, thermal analysis and nonlinear time history analysis were conducted on the prototype building. The thermal analysis proved the effectiveness of the OPD-XEDB's out-of-plane configuration in mitigating thermal stress by out-of-plane deformation, significantly mitigating thermal stress in braces and interconnected moment frames by 96.59–96.66 %. The time history analysis revealed that the dampers in OPD-XEDBs dissipated 11.6–23.2 % of total seismic energy, effectively preventing substantial buckling in the X-shaped braces. This energy dissipation mechanism led to a remarkable 79.7 % reduction in steel consumption for post-earthquake retrofitting, thereby significantly enhancing the seismic resilience of the primary structure.

South China Sea Typhoon Hagibis enhanced Xinfengjiang Reservoir seismicity

There was an evident increase in the number of earthquakes in the Xinfengjiang Reservoir from June to July 2014 after the landing of Typhoon Hagibis. To understand the spatial and temporal evolution of this microseismicity, we built a high-precision earthquake catalog for 2014 and relocated 2275 events using recently developed methods for event picking and catalog construction. Seismicity occurred in the southeastern part of the reservoir, with the preferred fault plane orientation aligned along the Heyuan Fault. The total seismic energy peaked when the typhoon passed through the reservoir, and seismicity correlated with typhoon energy. In contrast, a limited seismic response was observed during the later Typhoon Rammasun. Combining data regarding the water level in the Xinfengjiang Reservoir and seismicity frequency changes in the Taiwan region during these two typhoon events, we suggest that typhoon activity may increase microseism energy by impacting fault stability around the Xinfengjiang Reservoir. Whether a fault can be activated also depends on how close the stress accumulation is to its failure point.

The seismicity of the Carpathians in 2022

According to the results of observations at the seismic stations of the Carpathian region of Ukraine in 2022, the main parameters of 50 earthquakes in the range of energy classes KR=5.7÷13.7 were obtained. The parameters of seismometric equipment at active seismic stations are given. A catalog of earthquakes, their distribution by regions and energy classes, a map of epicenters, graphs of seismic energy release, and the number of earthquakes in the region by month are presented. A brief description of the seismicity of certain seismically active areas of the Carpathian region is given. The total energy allocated to the region was ΣЕ=5.06·1013 J, which is higher than last year’s level of ΣЕ=3.13·1012 J. This year, increased seismic activity was observed in the Vrancea Mountains, where 20 earthquakes of energy class KR=9.1÷13.7 were recorded. Their total seismic energy was ΣE=5.06·1013J. The foci of the Vrancea earthquakes are concentrated at a depth of h=80÷152 km (18 events) and h=20 km (2 events). 10 earthquakes with energy class KR=5.8÷8.0 were registered in Transcarpathia. Their total seismic energy was ΣE=2.78·108 J. The strongest was recorded on March 28 with KR=8.0 at 05h01m at a depth of h=2.4 km. For the past seven years, Transcarpathia has been practically in a seismic lull. On the territory of Bukovyna this year, there is also a decrease in seismic acti­vity compared to 2021. A total of 9 earthquakes with energy class KR=6.9÷8.4 and total seismic energy ΣЕ=8.41·108 J were registered here. The foci of earthquakes are in the earth’s crust at a depth of h=1.8÷15 km. In seismically active areas such as the Southern Carpathians, Transylvania, and Bacau, only one earthquake was recorded in 2022, while no event was recorded in the Kryšana and Banat regions. The regional Carpathian hodograph was used to determine the main parameters of earthquakes in Transcarpathia, and the Jeffreys-Bullen hodograph was used for earthquakes in the Vrancea zone and six other regions.

SEISMICITY of the AMUR and PRIMORYE, SAKHALIN and the KURIL-OKHOTSK REGION in 2018-2019

A review of the Amur and Primorye, Sakhalin, and the Kuril-Okhotsk region seismicity for 20182019 is presented on the basis of data from the regional network of stationary seismic stations of the Sakhalin branch of the Geophysical Survey RAS with the involvement of data from adjacent seismological Russian and foreign agencies, as well as ten stations of the local network operating in the south Sakhalin. Parameters of 4989 seismic events have been determined, 193 of them are explosions. Focal mechanisms were calculated for 88 earthquakes. 116 earthquakes have shown a macroseismic effect. A map of the epicenters is presented, the distribution of the number N of crustal and deep-focus earthquakes by a magnitude, a total seismic energy ∑E for seismically active regions of three regions are given, in comparison with the average parameters N and ∑E for 20012017. For each region, an analysis of the parameters of the seismic regime in 20182019 is given in comparison with long-term averages, the maximum and significant seismic events are described. The seismicity of the Priamurye and Primorye, Sakhalin, and the Kuril-Okhotsk region in 20182019 can be characterized as a moderate one.

SEISMICITY of NORTHERN EURASIA in 2018–2019

An overview of seismicity in 16 regions of Russia and neighboring countries in 2018–2019 is presented. Seismic monitoring of this territory was carried out by networks of seismic stations of Russia, Azerbaijan, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Turkmenistan, Tajikistan, Uzbekistan, Ukraine. In most regions, the seismic process occurred in the background. In Northern Eurasia as a whole, the total seismic energy in 2018 (Еan=17∙1016 J) remained unchanged compared to that for the previous year, and in 2019 fell to Еan=0.65∙1016 J, with annual values of released energy for 2018 and 2019 were significantly lower than its average annual level for the period 2006–2017. (Еan=5.3∙1016 J). The “Angular Uplift earthquake” on December 20, 2018 at 17h01m with MS=7.4 (MwGCMT=7.2), localized in the surface layer of the seismofocal zone of the Commander segment of the Aleutian arc with the epicenter in the Pacific Ocean was the strongest for the period 2018– 2019. Maximum shaking intensity on the tyerritory of Northern Eurasia (I=6–7) was caused by earthquake on July 6, 2018 at 01h40m with MwGCMT=6.2, h=75 km in the seismofocal zone of the Kuril Islands–Southern Kamchatka and Katav-Ivanovsk earthquake on September 4, 2018 at 22h58m in the Chelyabinsk oblast (Ural and Western Siberia region). The Katav-Ivanovsk earthquake is also unique in that it was accompanied by a significant number of aftershocks, which is the first known case for tectonic events within the Urals. In addition, it demonstrated that the natural seismic potential of the Urals exceeds the man-made component by orders of energy

SEISMICITY of the ALTAI and SAYAN region in 2018–2019

The seismicity of the Altai-Sayan region in 2018–2019 is considered. The stationary seismic network within the reporting period consisted of 55 stations. Upgrading the recording equipment and retrofitting the stations with strong motion sensors was continued. In addition to the stationary network, five local networks functioned in the region. One of them investigated the seismic process and accumulated data for constructing the Moho boundary using the method of receiving functions in the Altai Republic, the other four were focused on the study of technogenic seismicity in the area of coal minings of the Kemerovo and Novosibirsk regions. During the reporting period, 15405 earthquakes were registered in the region, 52 % of them occurred in the Chui-Kurai zone of the Altai Mountains, for which a brief description of seismicity is given separately. The total seismic energy released in earthquake foci was 2.191012 J in 2018 and 1.171013 J in 2019. The slope of the linear part of the earthquake recurrence chart for 2018–2019 has not undergone significant changes compared to previous reporting periods. The largest earthquake on the territory of the Altai-Sayan region for the reporting period (ML=6.2) occurred on February 1, 2019 at 21h54m in China, 70 km south of the Zaisan lake

SEISMICITY of the CARPATHIANS in 2018–2019

The article describes seismic observations in the Carpathian region in 2018–2019, which were carried out, as before, by two organizations from two states: in Ukraine – the Seismicity department of the Carpathian region of the Institute of Geophysics of the National Academy of Sciences of Ukraine, in Moldova – the seismology laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. The monitoring of seismicity was carried out 21 stationary digital and 3 temporary stations of Ukraine with a processing centre in Lviv and six stations of Moldova with a processing centre in Chisinau. The consolidated catalog of earthquakes was created in Lviv. The total number of Carpathian earthquakes in 2018–2019 was NΣ=99 in the range KR=4.5–13.6 within the interval of hypocenter depths h=0.4–157.5 km, with total seismic energy ΣE=4.2·1013 J. The maximum earthquake with KR=13.6, MSH=5.3 and hрР=150.6 km was registered on October 28, 2018 in the Vrancea zone. The epicentral zone was subjected to shaking with an intensity up to Ii=V by MM (Mercally) scale. The earthquake was felt by the population of Romania, Bulgaria, Ukraine, Moldova and other European countries. In the Precarpathian and Transcarpathian regions, all earthquakes were weaker. For Transcarpathia, their energy class was in the range of KR=5.5–7.9, and the depths was in the range of h=0.6–8.0 km. The strongest event in Precarpathian was a tangible earthquake that occurred in the Drohobych district of the Lviv region on September 27, 2018 with KR=7.3 at a depth of 1.7±0.9 km. The strongest event in Bukovina was an earthquake of March 24, 2018 with KR=9.4, МSH=2.4 and h=1 km near Novodnestrovsk city, Ukraina, which was felt by the population of the village of Lomachintsy with an intensity of 4 points. In Novodnestrovsk, the earthquake was felt only on the upper floors. In general, in 2018–2019 there was a slight decrease in the level of seismicity in seismically active areas: № 1 (North-Western), № 2 (Vrancea), № 5 (Bukovina) and № 8 (Bacau), compared with that in the previous period 2016–2017. In areas № 3 (South Carpathians), № 4 (Banat) and № 7 (Transylvania) there was no earthquakes, and in area № 6 (Krishana) only there was one earthquake with КР=10.8, MSH=3.2.

SEISMICITY of the NORTH-EAST of RUSSIA in 2018–2019

The results of seismic monitoring of the Magadan region, Chukotka Autonomous Area and the shelf of adjacent Okhotsk, Chukchi, Bering and East Siberian seas are considered. There were 14 seismic stations working in the region. The catalog includes information about 644 earthquakes with energy classes KR=4.8–13.2. As usual, most of them (77 %) are localized in the Kolyma region (area № 2).The additional catalog contains information about 12 earthquakes in the Chukchi. The total seismic energy released within the region’s borders was ΣЕ=2.671013 J. The classification of Russian North-East earthquakes was performed using energy classes KR of T.G. Rautian’s scale. According to the earthquake energy representativeness map, the regional network of stations records without omissions the earthquakes with Kmin=7on the territory of Magadan region, with Kmin=8 in the Okhotsk sea and with Kmin=10 in the Chukchi. The strongest earthquake of 2018–2019 with KR=13.2 (MPSP=5.1, MS=4.0) occurred on July 5, 2019 in in the Kolyma area. 14 earthquakes with intensity I=2–5 of the Russian Seismic Intensity Scale (SIS-2017) were felt in North East settlements. Epicenters of Magadan region earthquakes were plotted on the tectonic zoning scheme. Most earthquakes are confined to the largest deep faults in the northwestern and sublatitudinal directions. All hypocenters are located within the earth's crust. The seismicity level of the North-East of Russia in 2018–2019 according to the “SOUS’09” scale was assessed as "background average one" for the observation period from 1968 to 2019. Spatially, all earthquakes in the North-East of Russia are traditionally concentrated in large seismogenic belts: Chersky, North-Okhotsk and Trans-Beringian.

SEISMICITY of the AMUR AND PRIMORYE, SAKHALIN and the KURIL-OKHOTSK REGION in 2016–2017

A review of the Amur and Primorye, Sakhalin, and the Kuril-Okhotsk region seismicity for 20162017 is presented on the basis of data from the regional network of stationary seismic stations of the Sakhalin branch of the Geophysical Survey RAS with the involvement of data from adjacent seismological Russian and foreign agencies, as well as ten stations of the local network operating in the south Sakhalin. Parameters of 4561 seismic events have been determined, 114 of them are explosions. Focal mechanisms were calculated for 32 earthquakes. 88 earthquakes have shown a macroseismic effect. A map of the epicenters is presented, the distribution of the number N of crustal and deep-focus earthquakes by a magnitude, a total seismic energy E for seismically active regions of three regions are given, in comparison with the average parameters N and E for 2001-2015. For each region, an analysis of the parameters of the seismic regime in 2016-2017 is given in comparison with long-term averages, the maximum and significant seismic events are described. The seismicity of the Priamurye and Primorye, Sakhalin, and the Kuril-Okhotsk region in 20162017 can be characterized as a moderate one.

SEISMICITY of the CARPATHIANS in 2016–2017

The article describes seismic observations in the Carpathian region in 2016–2017, which were carried out, as before, by two organizations from two states: in Ukraine – the seismicity department of the Carpathian region of the Institute of Geophysics of the NAS of Ukraine, in Moldova – the seismology laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. In Ukraine, 20 stationary digital stations and 1 temporary in the area of Stebnik with a processing center in Lviv, in Moldova – six stations with a center in Chisinau. Different programs, local hodographs and magnitudes were used. The consolidated catalog of earthquakes was created in Lviv. A maps of epicenters and a table of the distribution of earthquakes of different classes by region are given. The total number of earthquakes in 2016–2017 was NΣ=140 in the range KR =4.0–14.4 with depths h=1–160 km and the total seismic energy ΣE=2.92·1014 J. The maximum earthquake with KR=14.4, MSH=5.7 and hрР=95 km was registered on September 23, 2016 located in the Vrancea zone. The earthquake was felt by the population in Romania and Moldova. In the cities of Chisinau and Cahul, the earthquake was felt with intensity I=3–4 points. In the Precarpathian and Transcarpathian regions, all earthquakes are weaker. The strongest event in Transcarpathia was a tangible earthquake, which occurred north of the village of Uglya, Tyachevo district, on June 6, 2017 with KR=9.8, of h=5 km. The earthquake was felt by the population of 20 settlements with an intensity ranging from 2 to 4–5 points. The most powerful event in Precarpathian in 2016–2017 there was a tangible earthquake that occurred in the Drohobych district of the Lvov region on September 29, 2017 with KR=9.8 at a depth of 1.9 ± 0.4 km. Perhaps it was a tectonic earthquake that triggered a collapse in the mine, or vice versa – the collapse of the rocks was recorded as a seismic event. The strongest event in Bukovina was an earthquake that occurred on July 12, 2016 at 18h21m with an energy class of KR=9.9 and magnitude МSH=3.0 in the area of the village of Kurazhin, Khmelnitsky region and was felt by the population with an intensity of 3–4 points. In general, in the seismically active zone of Vrancea and Bukovina in 2016–2017 there was an increase in the level of seismicity compared to those in 2012–2015, and in areas № 1, 3 and 8 there was a slight decrease in the level of seismicity.

EARTHQUAKES of 2016–2017 FELT in MOLDOVA (Romania–Moldova)

All earthquakes felt in 2016–2017 on the territory of Moldova occurred outside its borders, in the Vrancea region (Romania), with intermediate depths in the range hрР = 95–135 km. In 2016, the population of Moldova felt 2 earthquakes: September 23th with Mw=5.7, hрР=95 km and December 27th with Mw=5.6, hрР=100 km. For them, data on quakes in 113 and 150 localities, respectively, were collected, according to which isoseismal maps were made. The earthquake of September 23, 2016 was most evident in the eastern and southern parts of Romania. But it was also felt in the north of Bulgaria, in Moldova and the south-west of Ukraine, in Serbia and Macedonia. The echoes of the earthquake reached Istanbul in the south, Tirana in the west, Gomel in the north and Mariupol in the east from the epicenter. The maximum intensity of 6 points on the Mercalli scale was noted in Buzau. The earthquake of December 27, 2016 was most evident in the eastern and southern parts of Romania, as well as in northern Bulgaria, Moldova, southwestern Ukraine and Serbia. The maximum intensity of I=5 on the Mercalli scale was noted in Vanatori. In 2017, the population of Moldova felt 4 earthquakes: February 8th, May 19th, August 1st and 2nd. The earthquake on February 2nd with Mw=4.5 and hрР=126 km manifested itself in Romania and in the Republic of Moldova with an intensity of I=2–3. The earthquake on May 19 with Mw=4.3 and hрР=124 km was felt in the eastern and southern counties of Romania (in 6 localities), in the central and southern regions of the Republic of Moldova. Tremors from the August 1st earthquake with Mw=4.3 and hрР=107 km were felt in the eastern and southern counties of Romania, as well as in the central and southern regions of Moldova (Cahul and Chisinau, I=2–3). The earthquake on August 2nd with Mw=4.9 and hрР=135 km was felt in the eastern and southern counties of Romania, in Cahul with an intensity I=3 and in Chisinau – I=2. The solutions of the focal mechanism given in the article indicate that all the considered earthquakes occurred under the influence of the prevailing compression close to horizontal. It is noted that the value of the total seismic energy released in 2016 in the focal area of Vrancea is the maximum annual energy for this area in the 21st century.

SEISMICITY of the NORTH-EAST of RUSSIA in 2016–2017

The results of seismic monitoring of the region of Magadan, Chukotka Autonomous Area and the shelf of adjacent seas (the Okhotsk, Chukchi, Bering and East Siberian seas) are considered. There were 14 seismic stations working in the region in 2016–2017. The new station “Talon” was opened on the Okhotsk sea coast. The catalog includes information about 577 earthquakes with energy classes KR=4.6–12.7. As usual, most of them (88 %) are located in the Kolyma region (area № 2). The additional catalog contains information about 12 earthquakes in the Chukchi. The total seismic energy released within the region’s borders was equal to ΣЕ=1.861013 J. The energy representativeness map of earthquakes with Kmin=5–10 was built. It shows that the described network of stations records earthquakes with Kmin=7 at the Magadan region, with Kmin=8 in the Okhotsk sea without omissions. In 2016–2017 the strongest earthquake with KR=12.7 (mbMOS=4.8) occurred on November 5 in Chukchi Peninsula. Five earthquakes with the intensity I=2–4 (according to the Russian Seismic Intensity scale introduced in 2017) were felt in the North East settlements. The maximum shaking intensity of I=4 was observed in the Beringovskiy settlement (∆=22 km). Joint map of epicenters of the Magadan region earthquakes and tectonic zoning scheme shows that most earthquakes are confined to the largest deep faults in the northwestern and sublatitudinal directions. All hypocenters are located within the Earth's crust. The seismicity level of the North-East of Russia in 2016–2017 according to the “SOUS-09” scale was assessed as "background average" for the observation period from 1968 to 2017. Spatially, all earthquakes are traditionally concentrated in large seismogenic belts: Chersky, North-Okhotsk and Trans-Beringian.

SEISMICITY of the ALTAI and SAYAN region in 2016–2017

The characteristic features of the seismicity of the Altai-Sayan region in 2016–2017 are considered. The stationary seismic network within the reporting period consisted of 52 stations. Upgrading the recording equipment and retrofitting the stations with strong motion sensors was continued. In addition to the stationary network, four local time networks functioned in the region. One of them investigated the seismic process and accumulated data for constructing the Moho boundary using the method of receiving functions in the Altai Republic, the other three were focused on the study of technogenic seismicity in the area of coal minings of the Kemerovo and Novosibirsk regions. During the reporting period, 11424 earthquakes were registered in the region, 58 % of them occurred in the Chui-Kurai zone of the Altai Mountains, for which a brief description of seismicity is given separately. The total seismic energy released in earthquake foci was 6.141012 J in 2016 and 2.381013 J in 2017. The slope of the linear part of the earthquake recurrence chart for 2016–2017 has not undergone significant changes compared to previous reporting periods. The largest earthquake on the territory of the Altai-Sayan region for the reporting period (ML=6.39) occurred on April 4, 2017 at 15h07m in the Zaisan Depression area of the Kazakhstan Republic.

Estimation of the story response parameters through the seismic input energy for moment-resisting frames

The energy-based seismic design method is considered more reliable as it considers frequency content, duration, and pulse type of the seismic excitation in addition to the hysteretic behavior of the structural members. A comprehensive design can be achieved when the energy capacity of the structure exceeds the energy demand from earthquakes. To reach this goal, the distribution of the total seismic input energy should be determined at floor levels first. A new practical method is proposed in this study to estimate the story-wise distribution of seismic input energy on the moment-resisting frame (MRF) type buildings. Once the input energy distribution is obtained, the displacement, velocity, and acceleration responses at floor levels can be achieved using a reverse calculation. The method was validated by testing nonlinear response history analyses (NRHA) on four benchmark steel MRF-type buildings. Based on the results of the study, it can be stated that the proposed method yields very accurate results for predicting the nonlinear seismic demands of MRF-type buildings without having to perform computationally expensive nonlinear analyses. The mean relative differences between the estimated nonlinear responses based on the proposed methodology and NRHA results were calculated as around 12%, 20%, 17%, and 13% for the total seismic input energy, input energy, relative velocity at floor levels, and story displacements, respectively.

Spatiotemporal Distribution of Strong Earthquakes and the Time Course of the Parameters of the Seismic Regime of the Bishkek Seismic Research Site of Kyrgyzstan

This paper analyzes spatiotemporal distribution of strong historical earthquakes within the Bishkek seismic research (BSR) site. The main focus is on the spatial and temporal characteristics of crustal earthquakes in the instrumental period of observation, particularly the last 30 years (1991-2020). This period was the time of transition from the analog earthquake recording system to a digital one. Available epicenter maps of weak to moderate earthquakes were analyzed to identify areas of high and low seismic density. The analysis uses such parameters as the total number of earthquakes, magnitude, slope of the recurrence curve, and total seismic energy. The time course of seismic parameters was the main factor used to assess the current seismic setting of the Bishkek seismic research site. The slope of the earthquake recurrence curve was calculated using two methods: the least squares method and the maximum likelihood method. The analysis identified a downward trend showing a decrease in the number of earthquakes in the past 30 years (1991-2020). The results of this research can help develop a methodology for strong earthquake prediction and seismic hazard assessment of the BSR area.

SEISMICITY of the AMUR and PRIMORYE, SAKHALIN, and the KURIL-OKHOTSK REGION in 2015

A review of the Amur and Primorye, Sakhalin, and the Kuril-Okhotsk region seismicity for 2015 is presented on the basis of data from the regional network of stationary seismic stations of the Sakhalin branch of the Geophysical Survey RAS with the involvement of data from adjacent seismological Russian and foreign agencies, as well as ten stations of the local network operating in the south Sakhalin. Parameters of 1643 seismic events have been determined, 126 of them are explosions. Focal mechanisms were calculated for 62 earthquakes. 48 earthquakes have shown a macroseismic effect. A map of the epicenters is presented, the distribution of the number N of crustal and deep-focus earthquakes by a magnitude, a total seismic energy ∑E for seismically active regions of three regions are given, in comparison with the average parameters N and ∑E for 20012014. For each region, an analysis of the parameters of the seismic regime in 2015 is given in comparison with long-term averages, the maximum and significant seismic events are described. The seismicity of the Priamurye and Primorye, Sakhalin, and the Kuril-Okhotsk region in 2015 can be characterized as a moderate one.

SEISMICITY of the CARPATHIANS in 2015

The article describes seismic observations in the Carpathian region in 2015, which were carried out, as before, by two organizations from two states: in Ukraine – the Seismicity department of the Carpathian region of the Institute of Geophysics of the NAS of Ukraine, in Moldova – the Seismology laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. 20 stationary digital stations with a processing center in L'viv and six stations with a center in Chisinau operated in Ukraine and Moldova respectively. Different programs, local hodographs and magnitudes were used. The consolidated catalogue of earthquakes was created in L'viv. The total number of earthquakes in 2015 was NΣ=164 in the ranges: KR=4.7–12.2, h=1–160 km. The total seismic energy ΣE=5.381012 J. 23 earthquakes with depths h=50–160 km were located in the Vrancea zone. The maximum earthquake with KR=12.2 was registered on January 24 in the Vrancha mountains with hрР=89 km. In the Precarpathian region, nine events with energy classes KR=4.7–8.9 were registered, the total seismic energy of which is ΣЕ=1.25109 J. Increased seismic activity was observed in Transcarpathia. A series of tangible earthquakes with aftershocks was recorded in the Tyachiv area. Their total number was NΣ=77. The strongest tangible earthquake occurred in the area of Okrugla village on July 19 with KR=11.1. The earthquake source is located in the Earth's crust at a depth of h=7.7 km. The earthquake was felt by the population in the epicentral area with an intensity of I=6. In addition, this earthquake, like 5 others, was felt in the territory of northern Romania. In general, a decrease in the seismicity level in the Carpathians in 2015 was observed compared to that in 2013 and 2014.