Progress Report 2019 - nnsn.geo.uib.no

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

Norwegian National Seismic Network Progress report 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)


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)


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)


Homborsund

(HOMB)


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)


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)


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)


Lofoten

(LOF)



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Mo i Rana

(MOR8)


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)


Oslo

(OSL)


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)


Steigen

(STEI)


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)


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)


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

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