scholarly journals MUYAKAN EARTHQUAKE SEQUENCE in 2015 (Northern Baikal Region)

2021 ◽  
pp. 245-257
Author(s):  
N. Gileva ◽  
V. Melnikova ◽  
A. Filippova ◽  
Ya. Radziminovich ◽  
E. Kobeleva
Keyword(s):  
Baikal Region ◽  
Seismic Station ◽  
Local Stress ◽  
Baikal Rift Zone ◽  
Focal Mechanisms ◽  
Macroseismic Data ◽  
The North ◽  
Macroseismic Effects ◽  
North Eastern ◽  
Spatio Temporal

We present the results of studies of the seismic regime, focal mechanisms, and macroseismic data in the area of the largest Muyakan activation in 2015 (northern Baikal region). Due to the deployment of a network of temporary seismic stations, the number of registered earthquakes (KR≥3) increased significantly in 2015 and reached  30 thousand. Spatio-temporal development of the considered activation is characterized by stable low values of earthquake hypocenters and dividing the epicentral field into two clusters – eastern and north-western ones. Both clusters are connected with local stress-strain field (rift type and strike-slip, respectively), while the general regime of seismotectonic deformations of the crust in the activation area, calculated from the statistical analysis of 77 focal mechanisms of Muyakan earthquakes (KR≥9.2), demonstrates the predominance of submeri-dional horizontal extension. Macroseismic effects from the largest earthquakes of the Muyakan sequence were felt, predominantly, in Severomuysk settlement (=10–15 km, I=5). New data on strong motions, obtained from the records of the seismic station with the same name, have significantly complemented the database for the territory of the north-eastern flank of the Baikal rift zone. In general, the obtained results could be used to clarify the seismic hazard of the considered area and to improve the instrumental part of seismic scales.

Upper-plate structural controls on the segmentation of the Kefalonia Fault (Ionian Sea, Greece)

2021 ◽  
Author(s):  
Emmanuel Skourtsos ◽  
Haralambos Kranis ◽  
Spyridon Mavroulis ◽  
Efthimios Lekkas
Keyword(s):  
Eastern Mediterranean ◽  
Source Parameters ◽  
Plate Boundary ◽  
Temporal Distribution ◽  
Western Coast ◽  
African Plate ◽  
Plate Structure ◽  
The North ◽  
Macroseismic Effects ◽  
Spatio Temporal

<p>The NNE-SSW, right-lateral Kefalonia Transform Fault (KTF) marks the western termination of the subducting Hellenic slab, which is a part of the oceanic remnant of the African plate. The inception of the KTF, described as a STEP fault, is placed in the Pliocene. KTF is considered to be the most active earthquake source in the Eastern Mediterranean. During the last two decades, four significant earthquakes (M>6.0) have been associated with the KTF. These events are attributed to the reactivation of different segments of the KTF, which are (from North to South) the North Lefkada, South Lefkada, Fiskardo, Paliki and Zakynthos segments: the North Lefkada segment ruptured in the 2003 earthquake, the 2014 Kefalonia events are associated with the Paliki segment and the 2015 Lefkada earthquake with the South Lefkada (and possibly the Fiskardo) segments.</p><p>The upper plate structure in the islands of Lefkada and Kefalonia is characterized by the Ionian Unit, thrusted over the Paxi (or Pre-Apulian) Unit. The Ionian Thrust, which brings the Ionian over the Paxi Unit, is a main upper-plate NNW-SSE, NE-dipping structure. It runs through the island of Lefkada, to be mapped onshore again at the western coast of Ithaki and at SE Kefalonia. Two other major thrusts are mapped on this island: the Aenos thrust, which has a WNW-ESE strike at the southern part of the island and gradually curves towards NNW-SSE in the west and the Kalo Fault in the northern part. These Pliocene (and still active) structures developed during the late-most stages of thrusting in the Hellenides, strike obliquely to the KTF and appear to abut against it.</p><p>We suggest that these thrusts control not only the deformation within the upper plate, but also the earthquake segmentation of the KTF. This suggestion is corroborated by the spatio-temporal distribution and source parameters of the recent, well-documented earthquake events and by the macroseismic effects of these earthquakes. The abutment of the Ionian thrust against the KTF marks the southern termination of the Lefkada earthquake segment, which ruptured in the 2003 earthquake, while the Aenos, (or the Kalo) thrust mark the southern end of the Fiskardo segment. The spatial distribution of the Earthquake Environmental Effects related to the four significant events in the last 20 years displays a good correlation with our interpretation: most of the 2003 macroseismic effects are located in the northern part of Lefkada, which belongs to the upper block of the Ionian thrust; similarly, the effects of the 2014 earthquakes of Kefalonia are distributed mainly in the Paliki Peninsula and the southern part of the island that belong to the footwall of the Aenos thrust and the 2015 effects are found in SW Lefkada, which is part of the footwall of the Ionian thrust.</p><p>We suggest that correlation between upper-plate structure and plate boundary faulting can provide insights in the understanding of faulting pattern in convergent settings, therefore contributing to earthquake management plans.</p>

scholarly journals OGS improvements in 2012 in running the North-eastern Italy Seismic Network: the Ferrara VBB borehole seismic station

2014 ◽  
Vol 36 ◽  
pp. 61-67
Author(s):  
D. Pesaresi ◽  
M. Romanelli ◽  
C. Barnaba ◽  
P. L. Bragato ◽  
G. Durì
Keyword(s):  
Real Time ◽  
Seismic Station ◽  
Broad Band ◽  
Seismic Monitoring ◽  
Seismic Network ◽  
Research Centre ◽  
Seismic Stations ◽  
The North ◽  
North Eastern ◽  
Borehole Seismic

Abstract. The Centro di Ricerche Sismologiche (CRS, Seismological Research Centre) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the North-eastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data centre in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of North-eastern Italy. The south-western edge of the OGS seismic network (Fig. 1) stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML = 5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on 20 May 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the North-eastern Italy Seismic Network, including details of the Ferrara VBB borehole station configuration and installation, with first results.

scholarly journals Macroseismic and instrumental studies of the Verkhniy Fiagdon earthquake on January 26, 2020

2020 ◽  
pp. 113-123
Author(s):  
И.Ю. Дмитриева ◽  
А.А. Саяпина ◽  
С.С. Багаева ◽  
С.В. Горожанцев
Keyword(s):  
Seismic Station ◽  
Comfort Level ◽  
Kinematic Characteristic ◽  
Macroseismic Data ◽  
North Caucasus ◽  
Tectonic Earthquake ◽  
P Waves ◽  
The North ◽  
Tectonic Position ◽  
The Republic

Изучение землетрясений территории Северного Кавказа не просто актуальная задача. Ее решение является насущной необходимостью, требует ежедневного, кропотливого труда для повышения уровня комфортности жизни населения. Целью работы является представить достаточно подробный анализ ощутимого тектонического землетрясения, случившегося 26января 2020 года в 21h01m по Гринвичу с интенсивностью сотрясений в эпицентре 4-5 баллов, произошедшего на территории Республики Северная Осетия-Алания. Методы исследования включали: определение параметров гипоцентра сейсмического события с помощью программно-вычислительных комплексах WSG и HYPO71; описание геолого-тектонической позиции очага; расчет и графическое представление механизма очага землетрясения по знакам первых вступлений P-волн; сбор макросейсмических данных путем выездов на места проявления землетрясения для определения интенсивности сотрясений земной поверхности в баллах; рассмотрение историческойи современнойсейсмичности в области исследуемого землетрясения. В результате получено следующее решение параметров гипоцентра землетрясения: φ=42,69°N, φ=44,15°E, h=6 км, Кр=11,2. Очаг землетрясения находился вблизи зоны возникновения очагов землетрясений (ВОЗ) Главного хребтав сейсмотектоническом блоке, расположенном между Главным Кавказским и АдайкомКазбекским разломами. По знакам первых вступлений продольных P-волн на 20 станциях рассчитан механизм очага землетрясения. Согласно полученному решению очаг землетрясения возник в верхней части земной коры под действием сжимающих напряжений, тип движения – взбросо-сдвиг, что согласуется с кинематической характеристикой зоны Главного хребта. Землетрясение, получившее название Верхне-Фиагдонское, характеризуется отсутствием заметного афтершокового процесса, однако анализ имеющихся волновых форм ближайшей сейсмической станции показал наличие последовательности слабых сейсмических событий. Макросейсмический эффект землетрясения был исследован сотрудниками Северо-Осетинского филиала ФИЦ ЕГС РАН в 25 населенных пунктах. Согласно результатам опроса, максимальная интенсивность сотрясений составила 4-5 балла. По результатам оценки интенсивности построена соответствующая карта пунктов-баллов землетрясения. Приведены сведения по истории сейсмичности очаговой зоны исследуемого землетрясения за более чем 150 лет The earthquakes study in the North Caucasus is not just an urgent task. Its solution is an urgent need. It requires daily, painstaking work to increase the comfort level of the population’s life. The aim of the work is to present a sufficiently detailed analysis of the tangible tectonic earthquake on January 26 at 21h01m GMT, which occurred on the territory of the Republic of North Ossetia-Alania. Intensity of the shok equaled 4-5 in the epicenter. Research methods included: determination of the parameters of the seismic event hypocenter using the WSG and HYPO71 software complexes; description of the geological and tectonic position of the source; calculation and graphical presentation of the earthquake source mechanism by the signs of the first arrivals of P-waves; collection of macroseismic data by visits to the places of earthquake manifestation to determine the intensity of shaking the earth’s surface in points; consideration of historical and modern seismicity in the area of the investigated earthquake. As a result, the following solution of parameters of an earthquake is received: φ=42,69°N, φ=44,15°E, h=6 km, KР=11,2. The epicenter of the earthquake occurs near the Main ridge zone. In more detail, the earthquake happened in the seismotectonic block located between the Main Caucasian and Adaykom-Kazbek faults. For the earthquake, the mechanism of the focus was calculated according to the signs of the first arrivals of longitudinal P-waves at 20 stations. According to the solution, the earthquake occurred in the upper part of the earth’s crust under the action of compressive stresses, the type of motion is upthrust-strike-slip, which is consistent with the kinematic characteristic of the Main Ridge Zone. The earthquake, called Verkhniy Fiagdon earthquake, is characterized by the absence of a noticeable aftershock process, but the analysis of the available wave forms of the nearest seismic station showed the presence of a sequence of weak seismic events. The macroseismic effect of the earthquake was investigated in 25 settlements by the staff of the North Ossetian branch of the Geophysical Survey of the Russian Academy of Sciences. According to the survey results, the maximum intensity of concussions was 4-5 points. A map of earthquake manifestations in localities constructed based on the results of the intensity assessment. The history of seismicity of the focal zone of the investigated earthquake for the last 150 years is studied

scholarly journals Spatio-temporal variation of nitrate and nitrite levels in groundwater samples from Romania

2020 ◽  
Vol 2 (2) ◽  
pp. 56-63
Author(s):  
Florinela Pirvu ◽  
Iuliana Paun ◽  
Florentina Laura Chiriac ◽  
Marcela Niculescu ◽  
Nicoleta Vasilache ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Nitrite Concentration ◽  
The North ◽  
Groundwater Samples ◽  
Geographical Regions ◽  
North Eastern ◽  
Spatio Temporal ◽  
Seasonal Indices ◽  
Nitrate And Nitrite

This study investigated the spatial and temporal distribution of nitrate and nitrite concentration in groundwater from different geographical regions, in Romania. A special emphasis was put on a descriptive statistical analysis of data, namely on the determination of seasonal indices during dry and wet seasons. Nitrate and nitrite concentrations were monitored in 24 groundwater sources situated in different areas, between January 2016 and February 2020. The obtained data showed that the values of nitrate concentrations were situated between 8.03 mg/L in the North-Eastern part of Romania, 6.37 mg/L in the South-Eastern part of the country, and 3.55 mg/L in the Western part towards the center of the country. Nitrite concentration values were situated under the national maximum admitted limit, 0.5 mg/L, in all the investigated areas. The obtained data shows small changes in water quality during the monitoring period, which leads to the conclusion that, in this long interval of time, there were no significant groundwater contaminations with nitrate and nitrite. For adequate control of water pollution and rigorous management of groundwater sources, seasonal indices were calculated.

scholarly journals STRONG EARTHQUAKES in the NORTH of the LAKE BAIKAL REGION (Mw=4.6–4.7) in 2015

2021 ◽  
pp. 276-290
Author(s):  
Ya. Radziminovich ◽  
V. Melnikova ◽  
N. Gileva ◽  
A. Filippova
Keyword(s):  
Lake Baikal ◽  
Baikal Region ◽  
Moment Tensor ◽  
Seismic Hazard Assessment ◽  
Normal Fault ◽  
Seismic Moment Tensor ◽  
Macroseismic Data ◽  
Strong Earthquakes ◽  
The North ◽  
Lake Baikal Region

The paper considers three relatively strong earthquakes that occurred in 2015 in the northern Lake Baikal region: July 7 Upper Akuli earthquake (Mw=4.6) with the epicenter at the headwaters of the Akuli River, and September 25 Gulonga-I (Mw=4.7) and December 13 Gulonga-II earthquakes (Mw=4.6) with the epicenters near the mountain lakes Gulonga. Instrumental and macroseismic data on these seismic events are reported. A seismic moment tensor, calculated from surface wave records, shows normal fault focal mechanisms for Upper Akuli and Gulonga-II earthquakes and strike-slip movements in the source of the Gulonga-I seismic event. The results obtained could be used in further studies of seismic zoning and seismic hazard assessment in the northern Lake Baikal region.

scholarly journals THE SEPTEMBER 2, 2015, КR=14.0, Mw=5.1, I0=7–8 TALLAY EARTHQUAKE at the NORTH-EASTERN FLANK of the BAIKAL RIFT

2021 ◽  
pp. 305-313
Author(s):  
V. Melnikova ◽  
N. Gileva ◽  
Ya. Radziminovich ◽  
A. Filippova
Keyword(s):  
Seismic Event ◽  
Ground Motions ◽  
Moment Tensor ◽  
Seismic Moment Tensor ◽  
Macroseismic Data ◽  
Eastern Flank ◽  
The North ◽  
North Eastern ◽  
Amplitude Spectra ◽  
Strong Ground

We consider September 2, 2015, Mw=5.1 Tallay earthquake occurred in the previously aseismic area of the North-Muya Ridge adjoining to the Muya-Kuanda basin from the north. Instrumental and macroseismic data on this seismic event are presented. Its seismic moment tensor is calculated from surface wave amplitude spectra. New data on strong ground motions are obtained within the north-eastern flank of the Baikal rift. The Tallay earthquake is found to be connected with seismogenic renewal of the second-order multidirectional faults activated in the rift stress field.

Sign in / Sign up

Export Citation Format

Share Document