Seismic Monitoring and Data Processing at the Norwegian National Seismic Network

Ottemöller, Lars; Strømme, Marte Louise; Storheim, Berit M.

doi:10.31905/1m97csyl

Cited by 16 publications

(15 citation statements)

References 7 publications

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“…This includes the detection of additional events based on the OBSs, combining the OBS arrival times with the regional catalog, single event location and magnitude estimation. All processing is done with the Seisan software (Havskov et al, 2020) and we considered the NNSN catalog (Ottemöller et al, 2018) as baseline information. Note that data from the Danish database DNK, here the Greenland events, is routinely incorporated into NNSN.…”

Section: Earthquake Catalog Improvementmentioning

confidence: 99%

Improved Seismic Monitoring with OBS Deployment in the Arctic: A Pilot Study from Offshore Western Svalbard

Jeddi

Ottemöller

Sørensen

et al. 2021

Seismological Research Letters

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The mid-ocean ridge system is the main source of earthquakes within the Arctic region. The earthquakes are recorded on the permanent land-based stations in the region, although, smaller earthquakes remain undetected. In this study, we make use of three Ocean Bottom Seismographs (OBSs) that were deployed offshore western Svalbard, along the spreading ridges. The OBS arrival times were used to relocate the regional seismicity, using a Bayesian approach, which resulted in a significant improvement with tighter clustering around the spreading ridge. We also extended the regional magnitude scales for the northern Atlantic region for OBSs, by computing site correction terms. Besides location and magnitude improvement, the OBS network was able to detect hundreds of earthquakes, mostly with magnitude below Mw 3, including a swarm activity at the Molloy Deep. Our offshore observations provide further evidence of a low-velocity anomaly offshore Svalbard, at the northern tip of Knipovich ridge that was previously seen in full-waveform inversion. We conclude that even a single permanent OBS near the ridge would make a significant difference to earthquake catalogs and their interpretation.

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Section: Earthquake Catalog Improvementmentioning

confidence: 99%

Improved Seismic Monitoring with OBS Deployment in the Arctic: A Pilot Study from Offshore Western Svalbard

Jeddi

Ottemöller

Sørensen

et al. 2021

Seismological Research Letters

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“…Finally, we point out that further investigations on the difference between M w from GCMT and regional agencies are desirable, although several papers (e.g. Patton, 1998;Patton and Randall, 2002;Hjörleifsdóttir and Ekström, 2010;Konstantinou and Rontogianni, 2011) considered this aspect. Addressing such discrepancies may have significant impacts in different types of studies (e.g.…”

Section: Resultsmentioning

confidence: 97%

“…We have seen in previous sections that M w GCMT and several regional M w providers fit well for strong and major earthquakes, whereas for moderate and smaller earthquakes the variability of the differences between GCMT and regional M w values is higher, with GCMT nearly always larger than regional M w values. This observation is not new as, for example, Patton (1998) and Patton and Randall (2002) showed the tendency of GCMT to overestimate seismic moments (hence of M w ) in central Asia, particularly for lowermagnitude earthquakes. It is not the scope of this work to further investigate the reasons for such differences (Hjörleifsdóttir and Ekström, 2010), as our main aim is to highlight some features of the M w from the ISC Bulletin as an instrumental resource for further research into M w .…”

Section: Comparisons Of M S and M B From The Isc With M Wmentioning

confidence: 91%

Complementing regional moment magnitudes to GCMT: a perspective from the rebuilt International Seismological Centre Bulletin

Giacomo¹,

Harris²,

Storchak³

2021

Earth Syst. Sci. Data

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Abstract. Seismologists and geoscientists often need earthquake catalogues for various types of research. This input usually contains basic earthquake parameters such as location (longitude, latitude, depth, and origin time), as well as magnitude information. For the latter, the moment magnitude Mw has become the most sought after magnitude scale in the seismological community to characterize the size of an earthquake. In this contribution we provide an informative account of the Mw content for the newly rebuilt Bulletin of the International Seismological Centre (ISC, http://www.isc.ac.uk, last access: May 2021), which is regarded as the most comprehensive record of the Earth's seismicity. From this data, we extracted a list of hypocentres with Mw from a multitude of agencies reporting data to the ISC. We first summarize the main temporal and spatial features of the Mw provided by global (i.e. providing results for moderate to great earthquakes worldwide) and regional agencies (i.e. also providing results for small earthquakes in a specific area). Following this, we discuss their comparisons, by considering not only Mw but also the surface wave magnitude MS and short-period body wave magnitude mb. By using the Global Centroid Moment Tensor solutions as an authoritative global agency, we identify regional agencies that best complement it and show examples of frequency–magnitude distributions in different areas obtained both from the Global Centroid Moment Tensor alone and complemented by Mw from regional agencies. The work done by the regional agencies in terms of Mw is fundamental to improve our understanding of the seismicity of an area, and we call for the implementation of procedures to compute Mw in a systematic way in areas currently not well covered in this respect, such as vast parts of continental Asia and Africa. In addition, more studies are needed to clarify the causes of the apparent overestimation of global Mw estimations compared to regional Mw. Such difference is also observed in the comparisons of Mw with MS and mb. The results presented here are obtained from the dataset (Di Giacomo and Harris, 2020, https://doi.org/10.31905/J2W2M64S) stored at the ISC Dataset Repository (http://www.isc.ac.uk/dataset_repository/, last access: May 2021).

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“…3) was downloaded from the Norwegian National Seismic Network webpage http://nnsn.geo.uib.no/nnsn/#/, which belongs to the University of Bergen. More details about location and processing can be found in its 2018 annual report (Ottemöller et al, 2018;Norwegian National Seismic Network, 2018). The original catalogue consists of 27,477 regional seismic events, for which local magnitude was previously calculated through the scale proposed by Alsaker et al (1991).…”

Section: Methodsmentioning

confidence: 99%

Frictional energy patterns related to the temperature increases due to intraplate seismicity, southern Norway, 2000–2019 catalogue

Pavez¹,

Estay²,

Brönner³

et al. 2021

NJG

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Low-magnitude seismic events (0 ≤ Mw ≤ 3.8) recorded in southern Norway during the period 2000-2019 were used to calculate the sudden co-seismic temperature increases using a simple stress-drop model. The maximum temperature increase associated with an Mw = 3.5 earthquake was ~122°C. Simultaneously, we added 13 historical earthquakes to our study data, which occurred between 1657 and 1989. Here, the maximum temperature rise was ~560°C for an Mw = 5.6 event. The temperature values were analysed to derive local thermo-mechanical effects, such as thermal fracturing, frictional drop and the possible formation of cataclasites and pseudotachylites. Using the Kanamori's equations, we estimated the thermal energy released by individual events and in 2D and 3D cumulative patterns. To identify possible correlations between frictional energy, seismicity distribution and regional geology, the results were spatially correlated with a lineament zone located along the southwestern coastline and a heat flux map.Areas with high thermal energy values seem to be spatially linked with zones that exhibit a high density of lineaments and high heat flux located along the whole of the southwestern Norwegian coast.

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Seismic Monitoring and Data Processing at the Norwegian National Seismic Network

Abstract: Lars Ottemöller, Marte Louise Strømme and Berit Marie Storheim report on Seismic Monitoring and Data Processing at the Norwegian National Seismic Network for the Summary of the Bulletin of the International Seismological Centre.

Cited by 16 publications

References 7 publications

Improved Seismic Monitoring with OBS Deployment in the Arctic: A Pilot Study from Offshore Western Svalbard

Improved Seismic Monitoring with OBS Deployment in the Arctic: A Pilot Study from Offshore Western Svalbard

Complementing regional moment magnitudes to GCMT: a perspective from the rebuilt International Seismological Centre Bulletin

Frictional energy patterns related to the temperature increases due to intraplate seismicity, southern Norway, 2000–2019 catalogue

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