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  • Latest Data - NORSAR
    data files in near real time to NORSAR and forwarded to a basic automatically processing In order to get a rough overview on the status of the network we compute the signal amplitudes averaged over a 16 second time window This allows us to see immediately the noise conditions within the network Signals large enough to be seen on all geophones show up as vertical lines and may be indicative for a seismic event or man made noise within the network Once we have received the data for a full day we run a more sophisticated event detection procedure Currently we assign an event if we observe a seismic signal with a signal to noise ratio better than 2 5 on at least 4 geophones within a common time window of 0 5 seconds Overview on current seismicity The figure shows the latest plot of the seismic signal level in the network Signal amplitudes averaged over a 16 second time window The figure shows the amplitude level of the 24 channels of the 8 geophones as a function of time GMT The local time is GMT 1 hour or GMT 2 hours during the daylight saving period in summer High amplitudes are in red low amplitudes are in blue Vertical lines represent signals that are observed at all instruments and may be indicative for a larger seismic event or man made noise For older plots click here The figure shows daily seismic activity The height of the columns indicate the number of seismic events within a certain hour of the day The times are given in Greenwich Mean Time The colors indicate on how many channels a particular event was recorded Black blue green magenta and red means the events was observed on more than 9 12 15 18 and

    Original URL path: http://www.norsar.no/seismology/Projects/AKN/Latest-Data/ (2016-02-03)
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  • Waveform Correlation - NORSAR
    a given sensor is like a geophysical fingerprint for earthquakes or explosions at a given site In the same way that a human fingerprint at the scene of a crime which matches a fingerprint record can identify a likely suspect a seismic signal which closely matches a previous observation can be used as evidence that the newly observed event must have occurred very close to the event which generated the first observation The principle is demonstrated in the plot to the right The signal from a magnitude 3 5 earthquake in northern Norway in June 2005 recorded at a station in southern Norway was extracted and used as a template The template is then cross correlated with continuous data from the same sensor and any new occurrences of a similar signal will result in a relatively high value of the correlation coefficient Two peaks within a minute of each other were detected in December of the same year and data from a much closer station was able to confirm that there were in fact two separate events at the times indicated by these peaks very close to the June 2005 event Full details of this study are given by Gibbons et al 2007 Click on image for larger version There may be many situations where waveform correlation can be used to characterize aftershock sequences or to detect very small explosions see Stevens et al 2006 Most of the stations operated by NORSAR are arrays with many closely spaced seismometers Stacking the cross correlation traces from all the sites in an array or even over many arrays or large networks can lead to a very large improvement to the detectability of small events see Gibbons and Ringdal 2006 The reason for this is that when two seismic events are co located

    Original URL path: http://www.norsar.no/seismology/Projects/WaveformCorrelation/ (2016-02-03)
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  • International Centre for Geohazards - NORSAR
    for Geohazards NERA International Polar Year Barents Sea 3D Model SEISMOLOGY PROJECTS International Centre for Geohazards International Centre for Geohazards 2003 2012 NORSAR is one of 5 partners in a Norwegian Centre of Excellence called the International Centre for Geohazards ICG The Norwegian Centres of Excellence are an initiative from the Research Council of Norway to provide funding for internationally leading research groups in Norway The Partners of ICG are Norwegian Geotechnical Institute NGI host institution Geological Survey of Norway NGU NORSAR University of Oslo Norwegian University of Science and Technology in Trondheim ICG carries out research on the assessment prevention and mitigation of geohazards and contributes to the education of researchers and specialists in these fields NORSAR participates in ICG with expertise in geophysics especially in seismology seismic risk micro seismic monitoring near surface geophysics and seismic modelling and imaging in petroleum and near surface applications NORSAR is responsible of the ICG Project 3 Seismic hazard risk and loss which performs research on quantification of earthquake hazard including the influence of soil amplification characteristics seismic vulnerability of the built and populated environment development of models and software tools for risk quantification and loss modeling at different scales The term earthquake hazard refers to the occurrence probabilities of damaging ground motions exclusively relating to natural phenomena and processes while risk and loss results from combining the earthquake hazard with the vulnerability of the building stock NORSAR is also leading ICG Theme 1 Geophysics for Geohazards since 2005 to better include geophysics as one of the 3 G at ICG i e beside geotechnique and geology all 3 expertise domains working in a cross disciplinary manner ICG T1 is continuously working towards a best practice approach in using geophysics for geohazard assessment quick clay rock slides submarine slides etc with integration

    Original URL path: http://www.norsar.no/seismology/Projects/ICG/ (2016-02-03)
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  • NERA - NORSAR
    and seismic hazard earthquake risk and engineering seismology related topics and offers as one of four TAs access to its facility within the EC project NERA The infrastructure at NORSAR consists primarily of a data center and field installations consisting of different seismic arrays with apertures ranging from 1 to 75 km equipped with 1C or 3C short period or broadband sensors NORSAR provides access to a unique database of seismic recordings from its arrays reaching back to April 1971 NORSAR operates a test facility for seismic arrays and station equipment and has an extensive bilateral real time data exchange with other institutions operating seismic arrays and stations in Northern Europe and the European Arctic NORSAR s technical facilities are complemented with a group of scientists and engineers that capture 40 years of experience and world renowned research in Array seismology Automatic on line data processing Near real time seismic monitoring in various scales from regional seismicity over aftershock sequences and mining induced seismicity to microearthquakes associated with ground instabilities or hydrothermal activities Seismic hazard earthquake risk engineering seismology and earthquake engineering Seismic hazard and earthquake risk quantification has been research topics at NORSAR since the mid 1970s During the last years the group have broadened its activities into research engineering seismology By offering access to its infrastructure NORSAR contributes within NERA its knowledge on the aforementioned research topics array seismology automatic on line data processing monitoring of seismic active areas seismic hazard and earthquake risk analysis and engineering seismology and supports further developments and applications of these techniques in Europe During the next years until 2014 in all 12 visiting months are financed by NERA which are planned as about 3 visits per year each with a duration of approximately one month How to apply for access grants Applicants

    Original URL path: http://www.norsar.no/seismology/Projects/NERA/ (2016-02-03)
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  • International Polar Year - NORSAR
    of the Barents Sea near Bear Island and the mid Atlantic along the Knipovich Ridge We will study the Earth s structure and dynamics at this margin from its top sedimentary cover to its imprint in the upper mantle The continental margin in this region includes an extremely thick sedimentary wedge and steep slopes with at least one major paleo fracture zone cutting through the wedge Recent studies in this area indicate very low seismic velocities in the lithosphere which may be explained by a subcrustal extension of Mohns Ridge The stress field undergoes an extensional compressional transition in the region of the margin It is therefore of particular interest to understand the structural architecture the stress and the dynamics of the whole region because of its natural hazard exposure and the processes involved in the formation of the margin and opening of the Atlantic The collection of deep seismic sounding data and detailed monitoring and analysis of the seismicity between margin and mid Atlantic ridge system using temporary broadband stations are necessary for providing such information Data from existing seismic stations in the European Arctic ARC ARA0 Bear Island BJO KBS JMI JMIC and SPI SPA0 will also be analysed A concentrated active and passive seismological experiment is proposed along the continental margin of the Barents Sea near Bear Island and the mid Atlantic along the Knipovich Ridge We will study the Earth s structure and dynamics at this margin from its top sedimentary cover to its imprint in the upper mantle The continental margin in this region includes an extremely thick sedimentary wedge and steep slopes with at least one major paleo fracture zone cutting through the wedge Recent studies in this area indicate very low seismic velocities in the lithosphere which may be explained by a subcrustal

    Original URL path: http://www.norsar.no/seismology/Projects/IPY/ (2016-02-03)
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  • Project Organization - NORSAR
    Geohazards NERA International Polar Year Project Organization Barents Sea 3D Model SEISMOLOGY PROJECTS International Polar Year Project Organization Project Organization The Continental Margin project is part of the Norwegian contribution to the International Polar Year IPY activities organized by the Norwegian IPY Committee and mainly financed by the Norwegian Research Council Contract Number 176069 S30 All IPY projects are organized in international project clusters The Continental Margin project is part

    Original URL path: http://www.norsar.no/seismology/Projects/IPY/Project-Organization/ (2016-02-03)
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  • Barents Sea 3D Model - NORSAR
    km and for each node point two sedimentary and three crystalline layers have been defined in terms of their depths and physical properties The upper mantle model BARMOD Levshin et al 2006 is based on a large dataset of predominantly new surface wave observations from more than 150 local and regional events with travel paths through the greater Barents Sea region These observations of group velocities were first inverted for 2D group velocity maps and subsequently for a 3D S wave velocity model with a nominal resolution of 1 by 1 degree Applying standard conversion relations the model contains also P wave velocities and densities The figure shows a map of the greater Barents Sea region showing the target region for the BARENTS3D model The thick grey line indicates the continent ocean boundary of Eurasia thin grey lines are bathymetric contours In a final step the new crustal model was combined with the new surface wave inversion mantle structure sampled laterally at 50 km resulting in a complete 3D hybrid velocity model BARENTS3D that provides a significantly better resolution and accuracy than previously published models For contents and scientific questions please contact Crustal model Dr Oliver Ritzmann University of Oslo UiO Prof Jan Inge Faleide UiO NORSAR Mantle model Dr Johannes Schweitzer NORSAR Dr Nikolai Shapiro IPG Paris formerly University of Colorado Project manager Prof Hilmar Bungum NORSAR UiO Barents Sea 3D model basis BARENTS50 crustal model O Ritzmann 1 N Maercklin 2 J I Faleide 1 2 H Bungum 2 1 W D Mooney 3 and S T Detweiler 3 BARMOD mantle model A L Levshin 5 J Schweitzer 2 Ch Weidle 1 N M Shapiro 4 5 and M Ritzwoller 5 1 University of Oslo P O Box 1047 Blindern N 0316 Oslo Norway 2 NORSAR P O

    Original URL path: http://www.norsar.no/seismology/Projects/BarentsSea3D/ (2016-02-03)
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  • Barents Sea 3D Model Related Presentations & Publications - NORSAR
    161 Faleide J I O Ritzmann Ch Weidle and A Levshin 2006 Geodynamic aspects of a new 3D geophysical model of the greater Barents Sea region Linking sedimentary basins to the upper mantle structure EGU General Assembly Vienna Austria Levshin A Ch Weidle and J Schweitzer 2005 Surface wave tomography for the Barents Sea and surrounding regions NORSAR Sci Rep 2 2005 37 48 Levshin A J Schweitzer Ch Weidle N Maercklin N Shapiro and M Ritzwoller 2005 Surface wave tomography of the European Arctic EOS Trans Am Geophys Union 86 52 Fall Meet Suppl abstract S51E 1053 Levshin A J Schweitzer Ch Weidle N Maercklin N Shapiro and M Ritzwoller 2006 Surface wave tomography for the Barents Sea and surrounding regions Part II NORSAR Sci Rep 1 2006 36 41 Maercklin N O Ritzmann J I Faleide H Bungum J Schweitzer W D Mooney and S T Detweiler 2004 Development of a 3D velocity model for the crust and upper mantle of the Barents Sea and adjacent regions European Seismological Commission 29th General Assembly Potsdam Germany abstract SCD 1 P189 Maercklin N O Ritzmann H Bungum and J I Faleide 2006 A 3D seismic velocity model for the greater Barents Sea region Reference events and traveltime modelling In preparation for Geophys J Int Maercklin N O Ritzmann H Bungum J I Faleide W D Mooney and S T Detweiler 2005 Construction and testing of a 3D seismic velocity model in the greater Barents Sea region EGU General Assembly Geophys Res Abs 7 06258 Maercklin N O Ritzmann H Bungum J I Faleide W D Mooney and S T Detweiler 2005 Construction and testing of a 3D seismic velocity model in the greater Barents Sea region 36th Nordic Seismology Seminar GEUS Copenhagen Denmark Ritzmann O J I Faleide H Bungum

    Original URL path: http://www.norsar.no/seismology/Projects/BarentsSea3D/Publications/ (2016-02-03)
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