scholarly journals BARENTS-EURO/ARCTIC

2019 ◽  
pp. 232-239
Author(s):  
Sergey Baranov ◽  
Sergey Petrov
Keyword(s):  
Remote Monitoring ◽  
Seismic Energy ◽  
Seismic Events ◽  
Maximum Magnitude ◽  
Seismic Emission ◽  
Murmansk Region ◽  
Tectonic Earthquakes ◽  
The Baltic ◽  
Strong Seasonality ◽  
Digital Equipment

Continuous seismic monitoring of the Kola Peninsula and the Spitsbergen archipelago with adjacent water areas was carried out. Seismic events were recorded using digital equipment. Operational catalogs of earth-quakes were compiled. Great attention is paid to the improvement of systems for seismic and infrasonic monitoring. Seventeen seismic events with magnitudes from 0.8 to 2.8 which can be interpreted as tectonic earthquakes were recorded in the Baltic Shield area. The strongest earthquakes were recorded in the Arkhangelsk region (28.03.2013, M=2.9), in northern Norway (09.02.2013, MLрег=2.8), and in northern Finland (21.11.2013, MLрег=2.7). The maximum magnitude of the event in the Murmansk region was 2.3. The seismic activity in 2013 was the lowest over the last five-year period (from 2009 to 2013). The Spitsbergen archipelago was characterized by the smallest number of earthquakes in all ranges of magnitudes and by the smallest amount of released seismic energy for the five-year period from 2009 to 2013. The experimental research to monitor seismic and infrasonic emissions generated by glaciers was carried out using a seismic and infrasonic system installed before in the Spitsbergen archipelago. In particular, the seismic emission generated by the Isfjord glaciers has a strong seasonality. Activation is observed in the second half of summer and continues until the 20th of September. As a result of the studies, the possibility of remote monitoring of the destruction of glaciers by the seismic and infrasonic method was convincingly demonstrated

scholarly journals Modern seismological surveys in Latvia from 2008 to 2019 and prospects for their development

2020 ◽  
Vol 2 (1) ◽  
pp. 27-39
Author(s):  
Valerijs Nikulins
Keyword(s):  
Energy Transport ◽  
Sedimentary Cover ◽  
Seismic Monitoring ◽  
Seismic Events ◽  
Adjacent Part ◽  
Geological Conditions ◽  
Tectonic Earthquakes ◽  
Kaliningrad Region ◽  
The Baltic ◽  
National Networks

In Latvia, seismological monitoring has been carried out at Slitere station since 2006. Slitere station is part of the GEOFON international network, with its center at GFZ Potsdam. The use of other stations of the GEOFON network and some stations of national networks of Finland and Estonia allows monitoring the entire East Baltic Region (VBR), including Estonia, Latvia, Lithuania, the Kaliningrad Region of Russia, and the adjacent part of the Baltic Sea (Lat=53.9°N - 59.7°N; Lon=19.4°E - 29.6°E). The impetus for the development of seismological monitoring was the Kaliningrad earthquakes of 2004 with Mw 5.0 and 5.2. The main object of research, in addition to tectonic earthquakes, is man-made seismicity, which prevails in Latvia and in EBR. Because of seismic monitoring for the period from 2008 to 2019, 8 tectonic earthquakes were localized, as well as more than 5640 man-made seismic events. The total number of seismic events localized by the BAVSEN network is 13328, including 1096 teleseismic events. The relevance of seismological monitoring is increasing due to unfavorable geodynamic conditions in the area where some large energy, transport facilities, and agglomerations are located, which requires a study of the seismic regime of the territories around these objects. The main problems of EBR seismic monitoring are associated with the identification of relatively weak seismic events, with a rare network of seismic stations, adverse seismic and geological conditions of the sedimentary cover, and low activity of EBR tectonic earthquakes. The lack of promising methods for recognizing the genesis of seismic events puts this problem in the first place. The prospects for seismological research in Latvia are related to the study of the seismic and geological properties of grounds, seismic micro zoning, monitoring of hydraulic structures, as well as the possibility of creating a National Data Center, within which seismological monitoring can become one of the main methods for radiation safety of EBR.

scholarly journals Analysis of Petrinja 2020 Earthquake (Croatia) and First 500 Aftershocks >M1.0, Identification of Their Sources and Seismogenic Faults

2021 ◽  
Author(s):  
Tihomir Marjanac ◽  
Marina Čalogović ◽  
Karlo Bermanec ◽  
Ljerka Marjanac
Keyword(s):  
Hanging Wall ◽  
Normal Fault ◽  
Seismic Energy ◽  
Seismic Events ◽  
Surface Cracks ◽  
Surface Phenomena ◽  
Slip Mechanism ◽  
Seismogenic Faults ◽  
Water Activation ◽  
Major Fault

Abstract Strong earthquake of M6.4 stroke Petrinja and neighbouring cities of Sisak and Glina in Croatia on December 29th 2020. It was preceded by two foreshocks of M5.2 and M5.0, and followed by a series of aftershocks of various magnitudes and intensities. We have analysed first 500 earthquakes and aftershocks of > M1.0 which occurred from December 28th 2020 to January 19th 2021, their frequency, focal depths, and coseismic surface phenomena. Correlation of focal depths revealed the source of earthquakes was faulting of hanging wall of a listric normal fault with NW-SE strike and dip towards NE. Major fault seems to have caused earthquakes with only minor magnitudes. The strongest two earthquakes of M6.4 and M5.2 were initiated on synthetic fault, whereas M5.0 earthquake was initiated on an antithetic fault. Almost 50% of all seismic energy of the first 500 analysed seismic events over M1.0 was released on 1 km and 10 km deep hypocentres. Focal mechanisms of major earthquakes and strong fore- and aftershocks indicate dextral-slip mechanism, which is also in accordance with the orientation of surface cracks, land faulting and sand volcano trains. Co-seismic surface phenomena are land cracks and fissures, land faults, sand volcanoes, eruptive springing of ground water, activation of landslides, and formation of dozens of collapse sinkholes which continued to form and grow for about a month following the major earthquake.

Which Earthquakes are Expected to Exceed the Design Spectra?

2019 ◽  
Vol 35 (3) ◽  
pp. 1465-1483 ◽  
Author(s):  
Iunio Iervolino ◽  
Massimiliano Giorgio ◽  
Pasquale Cito
Keyword(s):  
State Of The Art ◽  
National Level ◽  
Seismic Events ◽  
Maximum Magnitude ◽  
Probabilistic Measure ◽  
Design Spectra ◽  
Earthquake Resistant Design ◽  
Safety Margins ◽  
Earthquake Resistant ◽  
Elastic Design

Extended recording coverage of contemporary seismic events allows a comparison of observed seismic actions with their counterparts used for design. Said comparison shows actions systematically exceeding design spectra. This paper discusses: (1) that considered exceedances can be anticipated by the probabilistic seismic hazard on the basis of which design actions are determined, (2) exceedances of elastic design actions are expected for earthquakes occurring close to the site even if their magnitude is far from the maximum magnitude considered in the hazard assessment, and (3) design spectra are likely to be exceeded in epicentral areas of earthquakes that occur frequently in the region where the code is enforced, but rarely occur close to the site under consideration. In fact, code-mandated protection against these earthquakes is factually warranted by the rarity with which they are expected to occur near the structure and other safety margins implicit to earthquake-resistant design. All these issues, addressed with reference to Italy, are discussed with the intent not to criticize the way spectra are determined, but rather to raise awareness and give a probabilistic measure about what to factually expect from state-of-the-art design at a national level.

scholarly journals Estimation of relative source locations from seismic amplitude: application to earthquakes and tremors at Meakandake volcano, eastern Hokkaido, Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Masashi Ogiso ◽  
Kiyoshi Yomogida
Keyword(s):  
Amplitude Ratio ◽  
Linear Equations ◽  
Site Amplification ◽  
New Method ◽  
Seismic Events ◽  
Arrival Times ◽  
Event Location ◽  
Tectonic Earthquakes ◽  
The Difference ◽  
Seismic Amplitudes

AbstractAlthough seismic amplitudes can be used to estimate event locations for volcanic tremors and other seismic events with unclear phase arrival times, the precision of such estimates is strongly affected by site amplification factors. Therefore, reduction of the influence of site amplification will allow more precise estimation of event locations by this method. Here, we propose a new method to estimate relative event locations using seismic amplitudes. We use the amplitude ratio between two seismic events at a given station to cancel out the effect of the site amplification factor at that station. By assuming that the difference between the hypocentral distances of these events is much smaller than their hypocentral distances themselves, we derive a system of linear equations for the differences in relative event locations. This formulation is similar to that of a master event location method that uses differences in phase arrival times. We applied our new method to earthquakes and tremors at Meakandake volcano, eastern Hokkaido, Japan. Comparison of the hypocentral distributions of volcano-tectonic earthquakes obtained thereby with those obtained from phase arrival times confirmed the validity of our new method. Moreover, our method clearly identified source migration among three source regions in the tremor on 16 November 2008, consistent with previous interpretations of other geophysical observations in our study area. Our method will thus be useful for detailed analyses of seismic events whose onset times are ambiguous.

Forecast of the Pyroclastic Volume by Precursory Seismicity of Merapi Volcano

2019 ◽  
Vol 14 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Masato Iguchi ◽  
Haruhisa Nakamichi ◽  
Kuniaki Miyamoto ◽  
Makoto Shimomura ◽  
I Gusti Made Agung Nandaka ◽  
...  
Keyword(s):  
Seismic Energy ◽  
Volcanic Eruptions ◽  
Pyroclastic Flows ◽  
Energy Calculation ◽  
Cumulative Energy ◽  
Merapi Volcano ◽  
Tectonic Earthquakes ◽  
Order Of Magnitude ◽  
The Difference ◽  
Log Linear

We propose a method to evaluate the potential volume of eruptive material using the seismic energy of volcanic earthquakes prior to eruptions of Merapi volcano. For this analysis, we used well-documented eruptions of Merapi volcano with pyroclastic flows (1994, 1997, 1998, 2001, 2006, and 2010) and the rates and magnitudes of volcano-tectonic A-type, volcano-tectonic B-type, and multiphase earthquakes before each of the eruptions. Using the worldwide database presented by White and McCausland [1], we derived a log-linear formula that describes the upper limit of the potential volume of erupted material estimated from the cumulative seismic energy of distal volcano-tectonic earthquakes. The relationship between the volume of pyroclastic material and the cumulative seismic energy released in 1994, 1997, 1998, 2001, 2006, and 2010 at Merapi volcano is well-approximated by the empirical formula derived from worldwide data within an order of magnitude. It is possible to expand this to other volcanic eruptions with short (< 30 years) inter-eruptive intervals. The difference in the intruded and extruded volumes between intrusions and eruptions, and the selection of the time period for the cumulative energy calculation are problems that still need to be addressed.

scholarly journals Glacial rumblings from Jakobshavn ice stream, Greenland

2009 ◽  
Vol 55 (191) ◽  
pp. 389-399 ◽  
Author(s):  
J.A. Rial ◽  
C. Tang ◽  
K. Steffen
Keyword(s):  
Seismic Activity ◽  
Seismic Energy ◽  
Seismic Events ◽  
Earthquake Activity ◽  
Mass Wasting ◽  
Close Inspection ◽  
Seismic Amplitude ◽  
Ice Stream ◽  
Long Duration ◽  
Seismographic Network

AbstractThe steep increase in Greenland’s glacial earthquake activity detected by the Global Seismographic Network since the late 1990s suggests that a close inspection of these events might provide clues to the nature and origin of such seismic activity. Here we discuss the detection of large, unexpected seismic events of extraordinarily long duration (10–40 min) occurring about once every 2 days, and localized in the ice stream that feeds the Earth’s fastest-moving glacier (Jakobshavn Isbræ) from the east. These ‘glacial rumblings’ represent an ice-mass wasting process that is greater and more frequent than glacial earthquakes have suggested. Probably triggered by calving, the rumblings are all very similar regardless of duration, and all end with a sharp, earthquake-like event in which the largest seismic amplitude is in the rumbling and that might signal the collapse of large ice masses upstream. By calculating the total amount of seismic energy released as rumblings, we estimate that the maximum seasonal amount of ice moved seismogenically down the ice stream is up to 12 km3, or ∼30% of the average annual iceberg discharge in Jakobshavn.

scholarly journals Statistical moments of power spectrum: a fast tool for the classification of seismic events recorded on volcanoes

2020 ◽  
Vol 52 ◽  
pp. 67-74
Author(s):  
Danilo Galluzzo ◽  
Lucia Nardone ◽  
Mario La Rocca ◽  
Antonietta M. Esposito ◽  
Roberto Manzo ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Signal Amplitude ◽  
Low Noise ◽  
Seismic Events ◽  
Spectral Moments ◽  
Spectral Parameters ◽  
Seismic Stations ◽  
Event Classification ◽  
Tectonic Earthquakes

Abstract. Spectral analysis has been applied to almost thousand seismic events recorded at Vesuvius volcano (Naples, southern Italy) in 2018 with the aim to test a new tool for a fast event classification. We computed two spectral parameters, central frequency and shape factor, from the spectral moments of order 0, 1, and 2, for each event at seven seismic stations taking the mean among the three components of ground motion. The analyzed events consist of volcano-tectonic earthquakes, low frequency events and unclassified events (landslides, rockfall, thunders, quarry blasts, etc.). Most of them are of low magnitude, and/or low maximum signal amplitude, therefore the signal to noise ratio is very different between the low noise summit stations and the higher noise stations installed at low elevation around the volcano. The results of our analysis show that volcano-tectonic earthquakes and low frequency events are easily distinguishable through the spectral moments values, particularly at seismic stations closer to the epicenter. On the contrary, unclassified events show the spectral parameters values distributed in a broad range which overlap both the volcano-tectonic earthquakes and the low frequency events. Since the computation of spectral parameters is extremely easy and fast for a detected event, it may become an effective tool for event classification in observatory practice.

scholarly journals BELARUS

2020 ◽  
pp. 208-215
Author(s):  
T. Aronova ◽  
G. Aronov ◽  
T. Protasovitskaya ◽  
V. Aronov
Keyword(s):  
Seismic Event ◽  
Seismic Energy ◽  
Mining Area ◽  
Activity Level ◽  
Seismic Events ◽  
Average Value ◽  
Long Time ◽  
Event Distribution ◽  
Time Average ◽  
Seismicity Analysis

. The review of annual seismicity in the territory of Belarus based on the data of two analog and seventeen digital stations is presented. 57 events with Кd=4.6–8.8 are recorded, all of them are located in the southern part of the territory, including the Soligorsk mining area. The maximum seismic energy released in March, August, October and November. The maximum number of earthquakes was observed from July to August and from October to November. The N(K) andΣE functions in 2014 were compared with those within 1983–2013. The number of events in 2014 is 1.34 times more than its average value for previous 31 years. The level of the seismic energy released in 2014 is 2.43 times more than in 2013 and 2.05 times lower than its long-time average value. The distributionof earthquakes by depth intervals showed that the earthquake foci are mostly located in the upper 20 km part of the Earth’s crust. However, the foci of 47 earthquakes are located at depths below 10 km. A slope of the graph showing the recurrence of the events with representative energy classes Кd=6–8 in 2014 was calculated. Its modulus γ=|0.48| is lower than the value γ=|0.5| in 2013. The distribution of all the events in 2014 is represented in real time. Quiet seismic periods and seismic activation periods were determined. The distribution of the seismic events by the hourly intervals showed the periods of the daytime and nighttime increase of the seismic event number. The maximum and minimum values N in the seismic event distribution by the days of the week were determined. The seismicity analysis has shown that the seismic activity level in 2014 was higher than that in 2013, but lower than its long-time average value.

scholarly journals KAZAKHSTAN

2019 ◽  
pp. 131-138 ◽  
Author(s):  
N. Neverova ◽  
N. Mikhailova ◽  
Inna Sokolova
Keyword(s):  
Urban Areas ◽  
Seismic Energy ◽  
Focal Mechanisms ◽  
Tien Shan ◽  
Seismic Events ◽  
Ministry Of Education ◽  
Geophysical Research ◽  
Seismic Arrays ◽  
The Republic ◽  
Northern Tien Shan

In 2013, seismic monitoring in Kazakhstan was conducted by two organizations: the Seismological Experience-Methodical expedition of the Ministry of Education and Science of the Republic of Kazakhstan (SEME), and the Institute of Geophysical Research of the Ministry of Energy of the Republic of Kazakhstan (IGR). The station network consists of three-component stations and seismic arrays. The work presents detailed information on seismic observation networks. The catalogue of seismic events of Kazakhstan is made by da-ta of above mentioned Organizations. It includes 1036 earthquakes with energy class КР=6.6–14.7. The catalog contains several additional sheets with Attachments: Microseismic data on felt earthquakes, parameters of focal mechanisms of 55 earthquakes, information on coordinates of 29 urban areas with felt shakes, parameters of 1123 aftershocks, and two forshocks of Saryzhas (Narynkol) earthquake in the range of energy classes КР=4.5–11.8. Two maps of earthquake epicenters are shown in the paper: for the whole Kazakhstan territory with КР≥8.6 and for Northern Tien Shan territory with КР≥6.6. The largest earthquake of the year was the Saryzhas earthquake that occurred in Northern Tien Shan on January 28, MS=6.0, КР=14.7. The earthquake was felt on the territory of Kazakhstan and China and was followed by numerous aftershocks. For the first day, only its number exceeded 500. It was noted that the total released seismic energy in 2013 exceeded significantly the same parameter of 2012.

scholarly journals SEISMICITY of NORTHERN EURASIA in 2015

2021 ◽  
pp. 10-30
Author(s):  
A. Malovichko ◽  
N. Petrova ◽  
I. Gabsatarova ◽  
R. Mikhailova ◽  
V. Levina ◽  
...  
Keyword(s):  
Seismic Station ◽  
Seismic Energy ◽  
Annual Number ◽  
Northern Eurasia ◽  
Middle Urals ◽  
Induced Earthquakes ◽  
Seismic Regime ◽  
East European ◽  
Tectonic Earthquakes ◽  
Seismic Networks

The review of the Northern Eurasia seismicity for 2015 includes a description of seismic networks, the results of analysis of the seismic regime and individual noticeable earthquakes in 16 regions of Russia and neighbouring countries. Seismic monitoring was carried out by the networks of seismic station of Russia, Azerbaijan, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Latvia, Moldova, Turkmenistan, Tajikistan, Uzbekistan, Ukraine, including 599 digital, 7 analogue stations and eight seismic groups. In 2015, these networks registered about 27 thousand tectonic earthquakes, over 6 thousand volcanic earthquakes, 599 explosions, 23 mountain-tectonic shocks and induced earthquakes. Focal mechanisms of 592 earthquakes were determined, the information on manifestations of 449 perceptible earthquakes was collected. 26 shocks were felt in settlements of Northern Eurasia with an intensity Ii≥5. According to estimates of the annual number and released seismic energy in 2015 in comparison with the long-term characteristics of the seismic regime, the seismic process in most regions of Northern Eurasia proceeded in the “background” regime. An exception is Tajikistan and adjacent territories, where two strong earthquakes occurred – the Hindu Kush earthquake on October 26 with Mw=7.5, h=230 km in northern Afghanistan, near the border with Tajikistan, and the Sarez earthquake on December 7 with Mw=7.2, Ms=7.6, h=20 km in Tajikistan. Both earthquakes were accompanied by numerous aftershocks and were felt in Tajikistan with intensities Imax=7 and Imax=7–8 respectively, on the MSK-64 scale. Notable event on the territory of Northern Eurasia in 2015 is the emergence of the Muyakan sequence of earthquakes, the largest for the period of instrumental observations in the region "Baikal and Transbaikalia", as a result of which the number of recorded earthquakes in the region quadrupled concerning 2014. The other interesting fact is occurrence of tangible earthquakes in the regions, traditionally considered weakly seismic – near the Semipalatinsk test area in Eastern Kazakhstan (Chingiz earthquake on January 20, Ms=4.1, I0=5–6), in the Middle Urals (Middle Ural earthquake on October 18 with ML=4.7, I0=6) and in the southwest of East -European platform (Poltava earthquake on February 3 with KR=10.7, I0=6).

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