progress report 2019 - nnsn.geo.uib.no
TRANSCRIPT
Progress Report 2019
for
Norwegian National Seismic Network
January to September, 2019
Supported by
Norwegian Oil and Gas Association
and
University of Bergen, Department of Earth Science
Prepared by
Department of Earth Science
University of Bergen
Allegaten 41, N-5007 Bergen
October 2019
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CONTENTS
1 Introduction ......................................................................................................................... 3
2 Operation ............................................................................................................................. 3 3 Field stations and technical service ..................................................................................... 7 4 Seismicity .......................................................................................................................... 10 5 NNSN plans ...................................................................................................................... 12
5.1 Achievements in 2019 ............................................................................................... 12 5.2 Plans for remainder of 2019 ...................................................................................... 13
6 References ......................................................................................................................... 13
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1 Introduction
This annual report describes the operation of the Norwegian National Seismic Network
(NNSN) for the first part of 2019. The network is financially supported by the oil industry
through the Norwegian Oil and Gas Association and the University of Bergen (UiB). UiB
has the main responsibility to run the NNSN. This report covers operational aspects for all
seismic stations operated by the Department of Earth Science at the UiB and includes the
financial report.
2 Operation
In Norway, UiB operates 38 of the seismic stations that form the Norwegian National
Seismic Network (NNSN). NORSAR operates seismic arrays, which also include broadband
instruments, and three single seismometer stations (JMIC, JETT and AKN) (Figure 1). In
total, NORSAR provides data from 14 broadband stations to the NNSN. The station HSPB is
operated jointly between NORSAR and the Geophysical Institute, Polish Academy of
Sciences, Warsaw, Poland and the stations located in Barentsburg (BRBA and BRBB) are
operated jointly between NORSAR and the Kola Regional Seismological Centre of
Geophysical Service, Russia.
As seen in Figure 1 and Figure 2, data from several Swedish, Finish, Icelandic and Danish
stations are also included. As part of the EPOS project data from more stations are available
and data from five additional seismic stations in Sweden are from September 2019 available
in real-time. Data from the Danish stations located on the east coast of Greenland (Figure 2)
operated by GEUS, contribute to the location of earthquakes in the Greenland Sea and Artic
Sea. The Icelandic Meteorological Office (IMO) operates the seismic stations on Iceland. At
present, NNSN receives data from one station (BORG).
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Figure 1. Stations delivering data to the NNSN database. UiB operates 38 stations (red) and NORSAR
contributes 14 stations (blue), including the three arrays and station JMIC. AKN and JETT are operated
by NORSAR on behalf of NVE.
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Figure 2 Seismic stations in the artic area from were data are included into NNSN. Three stations located
on Greenland operated by GEUS, Denmark and one seismic station on Iceand operated by IMO, Iceland.
UiB has been upgrading the NNSN by installing new stations and changing short period (SP) to
broadband (BB) seismometers. A further effort is made to install additional high quality
digitizers. The current use of seismometers is shown in Figure 1. As of today the numbers of SP,
BB stations and stations with real time transmission are listed in Table 1.
Table 1. Overview of UiB seismic stations
Short Period Broadband
(natural period greater
than 100 sec)
Real time
Number of stations 2 36
38
The operational stability for each station is shown in Table 2. The downtime is computed
from the amount of data that are missing from the continuous recordings at UiB. The statistics
will, therefore, also show when a single component is not working. This is done as the goal is
to obtain as complete continuous data from all stations as possible. Also, communication or
computing problems at the centre will contribute to the overall downtime. In the case of
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communication problems, a station may not participate in the earthquake detection process,
but the data can be used when it has been transferred. Thus, the statistics given allow us to
evaluate the data availability when rerunning the earthquake detection not in real-time.
The downtime for the majority of stations is below 5%. Larger down time was observed for the
following stations: DOMB, FOO, KTK1, JNW and SUE (see Table 2 and technical service
overview for details).
Table 2. Data completeness in % for January to September 2019 for all stations of the NNSN operated by
UiB.
Station Data completeness
in %
Explanation
Askøy (ASK) 99
Bergen (BER) 100
Bjørnøya (BJO) 100
Blåsjø (BLS) 100
Dombås (DOMB) 91 Faulty digitizer
Florø (FOO) 93 Faulty digitizer
Fauske (FAUS) 100
Hammerfest (HAMF) 100
Homborsund (HOMB) 100
Hopen (HOPEN) 100
Høyanger (HYA) 100
Jan Mayen (JMI) 100
Jan Mayen (JNE) 100
Jan Mayen (JNW) 92 Insufficient power due to
problem with wind generator
Karmøy (KMY) 99
Kautokeino (KTK1) 94 Faulty digitizer
Kings Bay (KBS) 98
Kongsberg (KONO) 98
Konsvik (KONS) 99
Leirfjord (LEIR) 100
Lofoten (LOF) 100
Mo i Rana (MOR8) 99
Molde (MOL) 99
Namsos (NSS) 100
Odda (OOD1) 100
Oslo (OSL) 100
Rausandaksla (RAUS) 100
Røst (ROEST) 100
Skarslia (SKAR) 98
Snartemo (SNART) 95
Stavanger (STAV) 100
Steigen (STEI) 100
Stokkvågen (STOK) 100
Sulen (SUE) 94 Faulty digitizer
Trondheim N/A
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(TBLU/ODLO)
Tromsø (TRO) 96
Vadsø (VADS) 100
Vågaholmen (VAGH) 100
3 Field stations and technical service
The technical changes for each seismic station are listed below. It is noted if these changes are
carried out by the respective local contact and not by the technical staff of UiB. When a
station stops working, tests are made to locate the problem. The different equipment
components can be restarted from Bergen, and this sometimes helps to resolve the issue.
Major changes during this reporting period of 2019 were:
Ask
(ASK)
No visit or technical changes.
Bergen
(BER)
No visit or technical changes
Bjørnøya
(BJO1)
11.03.19: Timestamp from the GPS antenna does not work. Local personnel
notified.
26.03.19: Two GPS antennas shipped.
08.05.19: New GPS antenna mounted. The problem remains.
09.05.19: Digitizer sent from Bergen.
17.07.19: New digitizer installed, but still no GPS signal
19.07.19: Error detected as a disconnected cable, timing was missing 3 March-
19 July.
Blåsjø
(BLS)
No visit or technical changes
Blussuvoll
(TBLU)
14.05.19: The station, located at a high school, is closed permanently. The
school was no longer interested in hosting the station and maintenance
during school holidays was difficult. A new temporary station was
established at NGU in Trondheim.
Dombås
(DOMB)
23.07.19: Station down since 18.07.19. Power cycling restarted the station.
Data was backfilled, but some data is lost.
22.08:19: Station down since 28.07.19. GPS rollover problem. The PC is
removed, a new Guralp EAM digitizer has been installed.
Communication is changed from ICE 4G to Telia 4G. The GPS
rollover problem caused false timing in the data, which as a
consequence not could be used. Data lost.
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Fauske
(FAUS)
No visit or technical changes.
Florø
(FOO)
09.10.19: Station upgraded with new digitizer and communication by the
local operator. Station down since 12.09.19. Data lost.
Hammerfest
(HAMF)
No visit or technical changes.
Homborsund
(HOMB)
No visit or technical changes.
Hopen
(HOPEN)
19.02.19: Mass centering done from Bergen.
10.06.19: Two new spare GPS units arrived at Hopen.
July 2019: Vault inspected by local personnel.
Høyanger
(HYA)
No major changes.
Jan Mayen
(JMI)
No major changes.
JNE No major changes.
JNW 27.07.19: Rear-blade on wind generator had broken off, this was replaced.
Some intermittent power loss between 23 May to 26 August.
Karmøy
(KMY)
No visit or technical changes
Kautokeino
(KTK)
10.05.19: Station down since 23.04.19 due to a malfunctioning digitizer.
New digitizer and GPS installed. Data lost for this time period.
Kings Bay
(KBS)
No visit or technical changes.
Kongsberg
(KONO)
USGS plans to move the site to a different location in the mine. This work
will be done during October/November 2019.
Konsvik
(KONS)
13.03.19: Visit. The station was visited to see how it can be upgraded.
Leirdalen
(LEIR)
No visit or technical changes.
Lofoten
(LOF)
No visit or technical changes.
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Mo i Rana
(MOR8)
No visit or technical changes.
Molde
(MOL)
22.06.19: Visit. The station was upgraded with a Nanometrics Trilliun
QA120 sensor, Nanometrics Centaur digitizer and the communication
was changed to mobile broadband communication.
Namsos
(NSS)
01.10.19: Visit. Station is upgraded with a Nanometrics Trillium 120 QA
sensor, Nanometrics Centaur digitizer and mobile broadband
communication.
Odda
(ODD1)
No visit or technical changes.
Oslo
(OSL)
No visit or technical changes.
Rausandaksla
(RAUS)
25.06.19: Visit. New station site constructed as part of the EPOS project.
11.09.19: Visit. Station installation between 9-11 September. The station was
set into operation.
Røst
(ROEST)
01.05.19: Visit. A new station was constructed as part of the EPOS project
20.05.19: Visit. Station installation between 20-23 May. The station was
set into operation 23.05.19.
Skarslia
(SKAR)
08.07.19: Visit. Inspection of vault and installation of over-voltage
protection unit.
23.09.19: Station down due digitizer problem. Data lost.
Snartemo
(SNART)
17.08.19: Station down since 06.08.19 due to a defective PC. The existing
Guralp digitizer is connected directly to the Digi router. Data are lost.
Stavanger
(STAV)
No visit or technical changes.
Steigen
(STEI)
No visit or technical changes.
Stokkvågen
(STOK)
14.08.19: Centaur firmware upgraded to version 4.3.20.
Sulen
(SUE)
12.09.19: Station down since 28.08.19 due to a broken digitizer. New Guralp
EAM digitizer installed by the local operator. Data lost.
Tromsø
(TRO)
No visit or technical changes.
Trondheim 14.05.19: Temporary installation to replace TBLU. This will run until a
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(ODLO) permanent site is found.
Vadsø
(VADS)
No visit or technical changes.
Vågaholmen
(VAGH)
11.02.19: Visit. A new station was constructed as part of the EPOS-N project
11.03.19: Visit. Station installation between 11-14.03.19. The station was
set into operation 14.03.19.
4 Seismicity
The seismicity detected by the network is processed at UiB, but also NORSAR integrates
their results in the joint database at UiB. Seismicity maps for the reporting period are shown
in Figure 3 and Figure 4.
Figure 3. Seismicity map showing earthquakes (red) and explosions (blue) for the period January to
September 2019.
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Figure 4. Seismicity in the artic area for the period January to September 2019. Known and probable
explosions are excluded.
The seismic activity in 2019 matches known active seismic areas. Under the EPOS-N project
four additional seismic stations are installed in Nordland. As a consequence, an increased
number of small earthquakes are registered and located in the area north of Mo i Rana (65N,
12E in Figure 2). After the major upgrade of the seismic stations at Jan Mayen during 2018,
an increased number of earthquakes are located in the area and also the detection level is
slightly reduced due to better S/N ratio.
As in 2018 some earthquakes are located to the area west of the Knipovich ridge as seen on
Figure 4. In Svalbard five seismic active areas are clearly seen on Figure 2. Compared to 2018
there is an increased number of earthquakes in Nordaustlandet. This areas has been seismic
active for some years. Since the M=6.0 earthquake in Storfjorden in 2008, continuous seismic
activity has been seen in several areas of Storfjorden. This year the area north in Storfjorden,
between Kap Lee to the east and Heer Land to the west, shows higher seismic activity than
before. During July 2019 three Ocean Bottom Seismographs were deployed in Storfjorden
intended to record for one year. It will be interesting to use this data to improve the location of
the earthquakes in Storfjorden to better understand the seismicity in the area.
One earthquake had one of the reported magnitudes above 5.0. The earthquake is located to
the Malloy transform fault west of Kings Bay.
The largest of the earthquakes in the vicinity of the Norwegian mainland, with estimated
magnitude 3.3, occurred on 22 May 2019 at 07:33 (UTC) located at the continental slope west
of Lofoten. The majority of the earthquakes reported felt during the first nine months of 2019
are west of the Svartisen glacier in Nordland.
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In the North Sea (area 54-60N 0-5E, Figure 3), an earthquake occurred on 24 September 2019
with magnitude ML(BER)=3.4, MW(BER)=4.2 and ML(BGS) =4.2. It was located at 57.066N 1.778E,
which is in the vicinity of the Elgin and Franklin fields. The event was felt.
5 NNSN plans
The overall purpose of the NNSN is to provide data both for scientific studies, but equally
important is the routine observation of earthquakes. This in principle means that broadband
seismometers are desired at all sites, and this is now achieved except for two sites. A general
goal for the future development has to be to maintain standardization in particular with the
seismometers and digitizers. The total number of stations will remain mostly stable for now,
but it is important to improve the overall network performance. However, additional stations
will become available through the EPOS-Norway project in the coming years.
5.1 Achievements in 2019
Four of the new seismic stations in the Nordland area under EPOS-Norway are
operational. All of these provide high quality data.
The two seismic stations deployed close to Mannen recorded the landslide in
September, and are now removed. Data from several minor rock falls and of the main
landslide are recorded.
The upgrade of the seismic stations at Jan Mayen was finalized.
Stations NSS and MOL have been upgraded with broadband sensors and new
digitizers. Only two short-period stations remain in the network (KONS and SNART).
Three OBS stations were deployed in Storfjorden, Svalbard under the EPOS-Norway
project. The OBSs will be retrieved during summer 2020 and will give one year of
data to improve the understanding of the seismicity in the area.
The TBLU station located at the Blussuvoll skole, Trondheim has been closed and a
temporary station (ODLO) is now located at the Geological survey of Norway (NGU)
until a permanent site is found.
The work for a new site in the Kongsberg silver mine started in October. The
construction work is done under the supervision of Norsk Bergverks Museum
following plans given by USGS. The construction work is expected to be finalized in
October/November.
Data from an additional five seismic stations in Sweden (SNSN) are now included in
the daily processing.
Under a temporary deployment, two profiles with 22 stations from the Norwegian
broadband pool (20 stations) and UiB (2 stations) were deployed across the
Hardangerfjord. Data is recorded on site and is merged into the NNSN database when
collected. This will result in improved detection and location of the smaller
earthquakes in the region.
Data from Grane and Oseberg are received at UiB in real-time.
An EIDA node for improved data distribution of Norwegian seismic data has been
established, and is approved by ORFEUS.
UiB and NORSAR arranged a meeting to coordinate the research activities.
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Felix Halpaap has been employed as a 4-year Postdoc and started on 14 October. His
research at the start will focus on improved detection in southern Norway, including
offshore areas, and interpretation of the seismicity.
The work on attenuation tomography was accepted for publication (Demuth et al.,
2019).
Improved automatic detection was implemented in spring 2019.
skjelv.no has seen minor improvements and spectrograms are now made available
together with the helicorder plots.
5.2 Plans for remainder of 2019
Sysselmannen approved installation of two seismic stations at Svalbard under the
EPOS-Norway project. The stations are planned to be installed during August 2020.
Upgrade station KONS with broadband seismometer.
Integrate data from the fifth EPOS-N station in Nordland into the NNSN. Finalizing
the installation depends on the weather conditions in the mountain area where the
station is located.
Start research work on the 24 September event in the North Sea into source
mechanism, location and detection. This work will later be extended to the broader
region.
Collaboration with Equinor on the Grane and Oseberg data. Implement detection of
offshore and coastal stations.
6 References
Demuth, A., Ottemöller, L. & Keers, H. (2019). QLg wave tomography beneath Norway, J
Seismol 23: 151. https://doi.org/10.1007/s10950-018-9798-x