Seismicity of Norway and surrounding areas for 2012nnsn.geo.uib.no/reports/2012/seismicity_2012_final.pdfstations (red) and in addition the data are transferred from Ekofisk (EKO1),

Seismicity of Norway

and surrounding areas for

2012

Prepared by

Department of Earth Science

University of Bergen

Allegt. 41

N-5007 Bergen

e-mail: [email protected]

Phone: (+47) 55 58 36 00

Fax: (+47) 55 58 36 60

March 2013

CONTENTS

1 Introduction ............................................................................................................ 1 2 Data availability to the public ................................................................................ 2

3 Velocity models and magnitude relations .............................................................. 3 4 Events recorded by the NNSN ............................................................................... 5 5 The seismicity of Norway and adjacent areas ...................................................... 10

5.1 Seismicity in Nordland .................................................................................. 15 5.2 Seismicity in the arctic area .......................................................................... 17

5.3 Seismicity in the Jan Mayen area .................................................................. 17 5.4 Seismicity in Storfjorden, Svalbard .............................................................. 22 5.5 Haugesund earthquake .................................................................................. 24 5.6 Fedje earthquake ........................................................................................... 26

5.7 Voss earthquake ............................................................................................ 27 5.8 Earthquakes north of the Faroe isles ............................................................. 29

6 Felt earthquakes ................................................................................................... 30

7 Use of NNSN data during 2012 ........................................................................... 32 References .................................................................................................................... 34

Seismicity of Norway, January – December 2012 Department of Earth Science, UiB

1

1 Introduction This annual report on the seismicity of Norway and adjacent areas encompasses the

time period January 1st - December 31

st, 2012. The earthquake locations have been

compiled from all available seismic stations operating on the Norwegian territory

including the Arctic islands of Spitsbergen, Bjørnøya, Hopen and Jan Mayen.

In Norway, the University of Bergen (UiB) operates the Norwegian National Seismic

Network (NNSN) consisting of 32 seismic stations where 20 have broadband

sensors. NORSAR operates three seismic arrays and two seismic stations (Figure 1).

One station with real-time data is provided from the Ekofisk field by ConocoPhillips.

Data from temporarily installed local networks are also included whenever data are

made available. In addition to the NNSN stations, waveform data from other selected

stations in Norway (operated by NORSAR), Finland, Denmark, Poland and Great

Britain are transferred in real time and included in the NNSN database. In total data

from 15 stations located in or operated by neighbouring countries are recorded

continuously in Bergen and can be used for locating earthquakes.

Phase data from arrays in Russia (Apatity), Finland (Finess), Sweden (Hagfors) and

stations operated by the British Geological Survey (BGS) are also included when

available. All phase data are collected by UiB, and a monthly bulletin is prepared

and distributed. All local and regional earthquakes recorded on NNSN stations are

presented on the web pages and the largest are also e-mailed to the European-

Mediterranean Seismological Centre (EMSC) to be published on the EMSC web

pages. A brief overview of the events published in the monthly bulletins is given in

this annual report. Macroseismic data for the largest felt earthquakes in Norway are

collected, and macroseismic maps are presented.

Local, regional and teleseismic events that are detected by the UiB network are

included. The merging of data between NORSAR and UiB is based on the following

principles:

i) All local and regional events recorded by NORSAR that are also detected

by the NNSN network are included.

ii) All local and regional events with local magnitude larger than 2.0 detected

by NORSAR and not recorded by the NNSN are included.

iii) All teleseismic events recorded by NORSAR and also detected by the

NNSN are included.

iv) All teleseismic events with NORSAR magnitude Mb5.0 are included

even not detected by the NNSN.

Data from the British Geological Survey (BGS) are included in the database in

Bergen following similar criteria as mentioned above, however only events located

in the prime area of interest, shown in Figure 1, are included.

Starting from 2008, the NNSN stations were upgraded to provide continuous data in

real time. This has resulted in more effective monitoring of earthquake activity in the

region.


2

2 Data availability to the public

All the data stored in the NNSN database are also available to the public via Internet,

e-mail or on manual request. The main web-portal for earthquake information is

www.skjelv.no. It is possible to search interactively for specific data, display the data

locally (waveforms and hypocenters) and then download the data. Data are processed

as soon as possible and updated lists of events recorded by Norwegian stations are

available soon after recording. These pages are automatically updated with regular

intervals.

Figure 1. Stations included in Norwegian National Seismic Network (NNSN). UiB operates the 31

stations (red) and in addition the data are transferred from Ekofisk (EKO1), and NORSAR

operates the stations marked in blue including the 3 arrays. Data from stations marked in yellow

are received continuously in Bergen, but are operated by institutions in neighbouring countries.

http://www.skjelv.no/


3

3 Velocity models and magnitude relations

The velocity model used for locating all local and regional events, except for the

local Jan Mayen events, is shown in Table 1 (Havskov and Bungum, 1987). Event

locations are performed using the HYPOCENTER program (Lienert and Havskov,

1995) and all processing is performed using the SEISAN data analysis software

(Havskov and Ottemöller, 1999).

Table 1. Velocity model used for locating all local and regional events, except for the local Jan

Mayen events (Havskov and Bungum, 1987).

P-wave velocity

(km/sec)

Depth to layer

interface (km)

6.2 0.0

6.6 12.0

7.1 23.0

8.05 31.0

8.25 50.0

8.5 80.0

Magnitudes are calculated from coda duration, amplitudes or displacement source

spectra. The coda magnitude relation was revised in 2006 (Havskov & Sørensen

2006). The coda wave magnitude scale (MC) is estimated through the relation

MC = -4.28 + 3.16 log10(T) +0.0003 D

where T is the coda length in seconds and D is the epicentral distance in km. The

new scale made MC more consistent with ML since MC in general is reduced. For this

report all data are updated using the new magnitude scale. When instrument

corrected ground amplitudes A (nm) are available, local magnitude ML is calculated

using the equation given by Alsaker et al. (1991):

ML= 1.0 log(A) + 0.91 log(D) + 0.00087 D - 1.67

where D is the hypocentral distance in km.

The moment magnitude Mw is calculated from the seismic moment M0 using the

relation (Kanamori, 1977)

Mw = 0.67 log(M0) – 6.06

The unit of M0 is Nm. The seismic moment is calculated from standard spectral

analysis assuming the Brune model (Brune, 1970) and using the following

parameters:


4

Density: 3.0 g/cm2

Q = 440 f 0.7

P-velocity = 6.2 km/s

S velocity = 3.6 km/s

For more computational details, see Havskov and Ottemöller, (2003).

For the Jan Mayen area, a local velocity model (see Table 2) and coda magnitude

scale is used (Andersen, 1987).

Table 2. Velocity model used for locating local Jan Mayen events.

P-wave velocity

(km/sec)

Depth to layer

interface (km)

6.33 18

8.25 50

The coda magnitude scale for Jan Mayen which is used in this report is given by

Havskov & Sørensen (2006). This scale was implemented in 2006 but all events used

in this report are updated during April/May 2006.

MC = 3.27 log(T) 2.74 + 0.001 D

where T is the coda duration and D is the epicentral distance in km.

The regional and teleseismic events recorded by the network are located using the

global velocity model IASPEI91 (Kennett and Engdahl, 1991).

Body wave magnitude is calculated using the equation by Veith and Clawson

(1972):

Mb = log(A/T) + Q(D,h)

Here h is the hypocentre depth (km), A is the amplitude (microns), T is period in

seconds and Q(D,h) is a correction for distance and depth.

Surface wave magnitude Ms is calculated using the equation (Karnik et al., 1962):

Ms = log(A/T) + 1.66 log(D) + 3.3

where A is the amplitude (microns), T is period in seconds and D is the hypocentral

distance in degrees.

Starting from January 2001, the European Macroseismic Scale, EMS98, (Grünthal,

1998) has been used. All macroseismic intensities mentioned in the text will refer to

the EMS98 instead of the previously used Modified Mercalli Intensity scale. The two

scales are very similar at the lower end of the scale for intensities less than VII.


5

4 Events recorded by the NNSN

Based on the criteria mentioned in section 1, a total of 5254 local and regional events,

were detected by the NNSN during 2012. Of these local and regional events, 64%

were large enough to be recorded by several stations and hence could be located

reliably. The numbers of local/regional and teleseismic events, recorded per month in

2012 are shown in Figure 2. The average number of located local and regional events

recorded per month is 438. The number of recorded local/regional events is higher

than previous years much due to the large number of fore and aftershocks of the

magnitude 6.7 (MW GCMT) earthquake west of Jan Mayen.

A total of 957 teleseismic events were recorded in 2012 and the monthly average of

teleseismic earthquakes in the NNSN database, is 80. In addition to the locations

determined at UiB and NORSAR, also preliminary locations published by the USGS

(United States Geological Survey) based on the worldwide network are included for

earthquakes also registered by NNSN stations.

0

100

200

300

400

500

600

700

JAN MAR MAY JUL SEP NOV

L/R

D

Figure 2. Monthly distribution of local/regional and distant events, recorded during 2012.


6

Figure 3. Epicentre distribution of earthquakes with M3.0, located by the Norwegian Seismic

Network from January to December 2012. Teleseismic events recorded only by NORSAR have

M5.0.

UiB, as an observatory in the global network of seismological observatories, reports

secondary phases from the teleseismic recordings. All events (teleseismic, regional

and local) recorded from January to December 2012 with M 3 are plotted on

Figure 3.

Monthly station recording statistics from January to December 2012 are given in

Table 3. This table shows, for each station, local events recorded on more than one

station and recorded teleseismic events. The statistics are based on the analysed data

and are taken from the database.

Table 3 shows both earthquakes and explosions, and that the large number of

detections at KTK mainly is due to explosions at the Kirruna/Malmberget mines in

Sweden. The MOR station also records the Kirruna/Malmberget explosions, but in

addition the station records a large number of local earthquakes. These earthquakes

are also recorded on the stations STOK and KONS and, therefore, the number of

recorded earthquakes in this region is higher.

The following was observed from Table 3:

The seismic activity in the Jan Mayen area was higher between July and

September. Some of the activity between June and August was in the same

area as the MW=6.7 earthquake on 30 August 2012. Aftershocks from this

event spread all the way to Jan Mayen and even across south of Jan Mayen.

TBLU and OSL are recording mostly teleseismic earthquakes, which is as

expected due to their location in noisy environment. Stronger local

earthquakes will however be detected.

The arctic stations, in particular KBS and SPITS, are recording a much larger

number of earthquakes than the mainland stations. The seismic activity

around Spitsbergen will be presented in a separate section later in this report.

Four stations are located at Jan Mayen. Data from the BB station JMIC are,

together with other BB stations, collected for all teleseismic earthquakes


7

recorded at any of the NNSN stations. Therefore, the number of recorded

teleseismic earthquakes is higher than for the other stations at Jan Mayen.

DOMB is detecting teleseismic earthquakes quite well. However, no

detections were made in November and December due to communication

problems.

The stations KONS, STOK and MOR8 continue to record a relatively large

number of small earthquakes in the area.


8

Table 3a. Monthly statistics of events recorded at each station for January-June 2012.

Abbreviations are: LM = Number of local events recorded at more than one station and D =

Number of teleseismic events.

JANUARY FEBRUARY MARCH APRIL MAY JUNE STATION LM D LM D LM D LM D LM D LM D ASK 41 11 17 8 38 19 29 19 23 25 24 15 BER 17 12 10 22 18 16 8 22 12 21 14 19 BJO1 5 4 7 2 9 3 16 12 39 5 9 9 BLS5 39 13 36 25 43 23 30 24 27 26 22 19 DOMB 15 14 11 28 26 27 20 24 13 28 4 21 FOO 17 8 16 15 34 10 22 17 12 13 0 0 HAMF 14 10 10 16 14 18 14 21 32 18 8 27 HOMB 19 8 19 20 22 20 14 18 18 18 11 17 HOPEN 26 7 20 1 16 6 49 13 24 3 7 6 HYA 35 9 30 17 52 14 41 20 19 26 20 17 JMI 11 0 13 0 15 0 8 0 22 0 53 0 JMIC 28 2 16 1 17 4 18 7 38 3 70 6 JNE 24 0 17 0 16 0 16 0 34 0 61 0 JNW 28 0 16 0 16 0 17 0 35 0 66 0 KBS 66 9 108 18 119 15 117 17 167 15 106 23 KMY 21 5 25 11 26 11 20 18 7 13 16 13 KONO 22 14 16 26 32 25 18 27 19 24 13 20 KONS 35 11 41 12 45 16 69 18 61 17 37 24 KTK1 5 1 0 0 87 8 47 23 50 18 36 13 LOF 31 9 28 16 21 12 21 18 48 12 30 21 MOL 6 9 5 15 14 15 8 19 8 18 5 16 MOR8 43 15 41 24 67 21 58 28 61 26 40 30 NSS 1 5 12 19 6 19 6 20 12 17 5 21 ODD1 48 13 37 23 30 24 32 23 18 24 13 19 OSL 2 12 1 19 4 19 3 20 1 24 2 18 SNART 29 12 23 20 26 21 20 22 22 25 12 17 STAV 12 13 13 11 15 11 11 20 11 23 10 19 STEI 22 13 19 21 19 20 11 21 11 13 50 29 STOK 32 10 34 9 43 17 67 22 26 6 16 2 SUE 30 9 25 13 45 11 37 19 17 17 20 14 TBLU 1 7 1 12 0 8 1 17 4 19 0 16 TRO 30 13 16 21 22 23 18 26 43 23 20 32 NORSAR 25 70 29 61 48 66 30 81 44 77 27 65 ARCES 60 0 68 0 70 0 55 0 78 0 41 0 SPITS 87 11 126 24 135 21 130 18 183 13 117 26


9

Table 3b. Monthly statistics of events recorded at each station for July-December 2012.

Abbreviations are: LM = Number of local events recorded at more than one station and

D = Number of teleseismic events.

JULY AUGUST SEPT OCT NOV DEC

STATION LM D LM D LM D LM D L

M

D LM D ASK 28 30 38 25 35 18 45 17 38 12 29 18 BER 12 28 23 27 8 16 15 15 18

9

10 16 19 BJO1 12 6 1 6 12 9 6 2 4 2 13 5 BLS5 21 30 36 26 46 19 43 22 39 18 37 23 DOMB 8 32 17 27 8 12 3 7 0 0 0 1 FOO 0 0 10 15 22 10 24 12 30 6 14 8 HAMF 11 33 15 24 17 28 13 27 12 22 19 25 HOMB 10 23 16 20 21 9 20 12 3 5 6 7 HOPEN 14 1 12 4 14 6 13 3 6 1 17 5 HYA 26 28 45 21 32 13 46 18 42 10 17 8 JMI 79 0 252 5 153 9 51 0 48 0 15 0 JMIC 167 4 279 8 180 10 57 3 43 2 21 0 JNE 159 0 230 2 130 9 43 0 38 0 16 0 JNW 160 0 282 4 179 8 55 0 49 0 21 0 KBS 124 26 131 19 191 25 157 12 10

3

13 85 16 KMY 8 4 7 9 20 9 33 11 0 0 33 10

KONO 12 24 22 25 29 17 41 16 30 16 25 19 KONS 40 31 33 25 25 23 10 29 28 15 56 20 KTK1 26 35 46 29 52 36 52 43 57 35 79 41 LOF 24 37 40 21 28 18 13 18 13 10 31 18 MOL 9 19 7 22 5 12 7 17 9 12 7 19 MOR8 39 34 21 11 0 0 4 7 31 25 61 37 NSS 8 38 5 30 1 21 2 27 5 24 6 29 ODD1 15 16 27 23 12 12 29 14 30 17 41 21 OSL 2 23 1 16 1 12 1 16 3 10 2 19 SNART 13 31 17 18 27 17 25 20 12 15 23 22 STAV 4 16 3 6 5 11 13 7 6 11 12 9 STEI 59 42 55 28 29 27 24 35 34 26 69 33 STOK 5 0 13 2 2 1 2 1 16 0 36 3 SUE 23 20 43 24 30 11 46 12 45 7 45 13 TBLU 0 14 2 9 1 14 0 10 1 8 1 18 TRO 38 46 24 28 22 32 11 35 13 29 27 39 NORSAR 18 82 36 71 28 90 20 89 23 61 21 82 ARCES 42 1 39 4 45 6 29 1 30 1 43 0 SPITS 136 35 141 23 195 38 166 23 11

2

22 96 24


10

5 The seismicity of Norway and adjacent areas

A total of 3366 of the recorded events are located inside the NNSN prime area,

54N-82N and 15W-35E. We also show the seismicity for the Arctic region

including the Barents Sea defined by the coordinates 65-85°N and 20°W-50°E.

During analysis and using the explosion filter (Ottemöller, 1995), 31% of these

events were identified as probable explosions. Figure 4 shows all local/regional

events in the prime area, analyzed and located during 2012.

Figure 4. Epicentre distribution of events analyzed and located in 2012. Earthquakes are plotted

in red and probable and known explosions in blue. For station locations, see Figure 1.

Figure 5 and Table 4 show the 180 local and regional earthquakes (known and

probably explosions are removed) located in the prime area, with one of the calculated

magnitudes greater than or equal to 3.0. Among these, 95 are located in the vicinity of

Jan Mayen.

It should be emphasized that the magnitude calculation for the earthquakes located

on the oceanic ridge in the Norwegian Sea uses the same formula as for mainland

Norway. As the scale is not appropriate for this region, the magnitudes for these


11

earthquakes are underestimated. Most of the recorded earthquakes in this area have

magnitudes above 3.0 if they are recorded on Norwegian mainland stations.

Figure 5. Epicentre distribution of located events with one of the calculated magnitudes above or

equal to 3.0. All earthquakes are listed in Table 4. for station location, see Figure 1.


12

Table 4.

Local and regional events in prime area with any magnitude above or equal to 3.0 for the time period

January through December 2012. Only magnitudes reported by the University of Bergen are included.

In cases where all BER magnitudes are below 3 but the event still is included in the list, NORSAR of

BGS has reported a magnitude of 3.0 or larger. Abbreviations are: HR = hour (UTC), MM = minutes,

Sec = seconds, L = distance identification (L=local, R=regional, D=teleseismic), Latitud = latitude,

Longitud = longitude, Depth = focal depth (km), F = fixed depth, AGA = agency (BER=Bergen),

NST = number of stations, RMS = root mean square of the travel-time residuals, Ml = local

magnitude and Mw = moment magnitude.

Year Date HRMM Sec L Latitud Longitud Depth FF AGA NST RMS Ml Mb Mw

2012 1 1 2228 20.8 L 70.938 -6.095 3.9 BER 11 0.5 3.6 BER

2012 1 9 2332 24.3 L 73.302 7.200 15.0 BER 19 0.6 2.4 BER

2012 112 1231 41.0 L 76.985 18.778 15.0 BER 7 0.5 2.9 BER

2012 112 1702 31.9 L 76.915 18.791 15.0 BER 8 0.3 2.8 BER

2012 114 1245 41.5 L 81.451 -3.111 0.0 BER 7 0.7 2.5 BER

2012 114 2111 27.0 L 70.920 -6.284 10.9 BER 9 0.3 2.7 BER

2012 115 0211 15.0 L 71.687 -2.244 20.8 BER 24 0.7 2.6 BER

2012 115 1445 59.3 L 71.785 -1.455 0.0 BER 32 1.1 3.1 BER

2012 115 1801 30.7 L 72.097 0.084 0.0 BER 19 1.0 2.6 BER

2012 116 0837 13.6 L 71.753 -1.692 0.0 BER 19 0.8 2.7 BER

2012 117 1802 43.4 L 71.669 -2.393 0.0 BER 10 0.7 2.4 BER

2012 119 1715 47.3 L 78.255 8.078 4.7 BER 5 0.2 2.7 BER

2012 120 0341 31.5 L 70.961 -6.924 1.9 BER 4 0.1 3.3 BER

2012 122 1626 26.7 L 72.669 4.015 22.2 BER 23 0.9 3.1 BER

2012 122 1633 24.7 L 72.657 4.893 82.2 BER 8 0.8 3.0 BER

2012 2 3 0039 41.4 L 79.322 4.453 15.0 BER 9 0.7 3.0 BER

2012 2 5 0034 21.9 L 66.066 13.131 0.1 BER 11 0.6 1.8 BER

2012 2 7 2337 5.1 L 77.074 8.187 15.0 BER 18 1.4 3.5 BER

2012 210 1356 24.9 L 71.165 -8.230 0.0 BER 4 0.2 3.4 BER

2012 210 1543 54.2 L 73.353 7.800 15.0 BER 18 0.8 2.8 BER

2012 213 1136 30.8 L 80.901 0.632 23.0 BER 7 0.4 2.6 BER

2012 215 1558 59.3 L 71.628 -2.494 0.0 BER 17 0.8 2.6 BER

2012 216 1840 58.5 L 71.904 -2.859 23.2 BER 18 1.0 2.6 BER

2012 0217 1558 51.2 L 71.631 -1.168 * NAO 4 0.5 3.4 NAO

2012 217 1608 49.3 L 71.810 -1.965 0.0 BER 17 0.8 2.6 BER

2012 217 1630 22.3 L 71.666 -2.219 15.0 BER 3 0.1 3.2 NAO

2012 217 1634 59.0 L 77.656 14.556 15.0 BER 3 7.1 3.4 NAO

2012 217 1652 26.9 L 71.852 -1.328 0.0 BER 25 1.0 2.9 BER

2012 217 1800 10.3 L 71.640 -1.412 11.4 BER 7 0.2 3.5 NAO

2012 220 0858 0.7 L 71.716 -1.156 10.0 F BER 6 0.8 3.0 NAO

2012 222 1641 52.7 L 76.920 18.270 15.0 BER 7 0.5 2.7 BER

2012 226 0018 53.2 L 76.902 18.377 20.9 BER 10 0.7 3.1 BER

2012 229 1555 22.0 L 76.956 18.882 16.1 BER 7 0.7 3.2 BER

2012 3 2 1459 0.8 L 59.460 -1.569 9.5 F BER 30 0.8 2.7 BER

2012 312 0158 38.1 L 77.031 18.829 23.0 BER 7 0.4 3.8 BER

2012 312 1057 44.9 L 71.270 -8.912 10.0 F BER 4 0.3 3.0 BER

2012 314 1922 27.9 L 59.524 5.578 13.7 BER 41 0.5 3.2 BER

2012 317 2300 16.9 L 71.986 19.423 15.0 F BER 19 0.7 2.2 BER

2012 319 1849 55.4 L 71.138 -6.520 8.9 BER 4 0.2 3.1 BER

2012 319 2315 42.5 L 71.740 -2.088 10.0 F BER 26 1.1 2.6 BER

2012 321 1830 40.2 L 71.884 0.306 0.0 BER 4 0.2 3.2 NAO

2012 322 2120 24.5 L 70.959 -7.164 0.0 BER 4 0.1 3.5 BER

2012 324 1106 30.5 L 60.634 6.401 15.3 BER 51 0.4 3.0 BER

2012 329 0521 37.5 L 73.818 7.806 0.0 BER 5 0.4 3.4 NAO

2012 330 1119 23.7 L 80.343 4.828 10.0 F BER 30 1.6 4.0 BER 4.9 PDE

2012 331 2130 6.8 L 70.786 -6.769 11.9 BER 25 0.6 3.4 BER 4.1 PDE

2012 4 3 1952 50.3 L 75.717 8.950 0.0 BER 6 0.7 2.1 BER

2012 4 5 2129 18.8 L 70.750 -6.358 2.8 BER 35 0.7 3.2 BER 4.0 PDE

2012 4 6 1245 30.3 L 71.040 -5.694 10.0 F BER 4 0.1 3.5 NAO

2012 4 6 1510 28.6 L 70.806 -6.143 0.0 FF NAO 3 1.1 2.4 BER

2012 4 6 1527 2.0 L 70.983 -5.899 7.3 BER 5 0.3 3.0 NAO

2012 411 2053 39.9 L 71.802 -1.699 11.9 BER 15 0.6 2.5 BER

2012 419 0240 57.8 L 71.172 -6.783 10.0 F BER 4 0.3 3.4 BER

2012 420 1518 25.5 L 73.874 9.278 9.3 BER 11 0.7 2.1 BER

2012 421 2016 3.3 L 73.037 6.091 15.0 BER 11 0.2 3.1 NAO

2012 425 1009 36.7 L 73.060 6.270 15.0 BER 24 0.7 2.8 BER

2012 427 2207 18.1 L 72.084 0.306 15.0 BER 7 0.3 3.6 NAO

2012 428 1712 0.5 L 73.017 5.895 10.0 F BER 18 0.7 2.7 BER

2012 430 2015 30.9 L 71.338 -9.661 0.0 BER 7 0.8 2.9 BER

2012 5 1 1529 8.7 L 79.978 21.029 15.0 BER 7 0.8 2.9 BER


13

2012 5 3 2343 33.0 L 73.143 6.667 0.0 BER 11 0.4 2.1 BER

2012 519 2102 39.8 L 73.120 6.143 10.0 F BER 11 0.5 3.0 NAO

2012 524 2247 48.1 L 73.094 6.149 10.0 F BER 43 1.6 4.2 BER 5.7 PDE 6.1WCM

2012 524 2258 40.6 L 72.965 5.316 15.0 BER 14 0.6 2.5 BER

2012 524 2346 19.3 L 73.022 6.445 10.0 F BER 28 1.1 2.6 BER

2012 525 0025 56.6 L 73.036 5.518 14.2 BER 27 0.9 3.3 BER

2012 525 0401 38.3 L 73.068 6.128 10.0 F BER 34 1.1 3.0 BER

2012 525 0413 16.3 L 73.037 6.129 10.0 F BER 12 0.8 2.4 BER

2012 525 0736 35.7 L 72.967 5.785 10.0 F BER 8 0.7 2.5 BER

2012 525 0818 19.3 L 72.940 5.155 10.0 F BER 12 0.6 2.6 BER

2012 525 1253 9.7 L 73.158 5.561 10.0 F BER 18 0.7 3.3 NAO

2012 525 1921 50.7 L 73.137 5.890 10.0 F BER 7 0.9 2.5 BER

2012 526 1118 39.2 L 73.014 5.281 10.0 F BER 19 0.7 3.2 NAO

2012 526 1118 50.4 L 73.008 5.409 10.0 F BER 15 0.7 3.6 NAO

2012 527 0319 50.9 L 73.030 5.923 10.0 F BER 21 0.8 2.4 BER

2012 528 0838 24.3 L 80.752 0.914 16.0 BER 5 0.6 2.0 BER

2012 530 0736 11.7 L 77.215 18.130 15.0 BER 5 0.4 2.4 BER

2012 530 1512 4.9 L 73.074 6.556 10.0 F BER 14 0.6 2.4 BER

2012 6 4 1920 23.2 L 73.035 5.979 10.0 F BER 16 0.8 2.4 BER

2012 6 4 2037 6.6 L 73.117 5.901 10.0 F BER 17 0.9 2.2 BER

2012 6 6 0758 11.1 L 54.360 -11.091 3.4 F BER 23 1.6 3.6 BER

2012 610 0630 58.0 L 70.740 -6.808 9.1 BER 7 0.3 3.5 BER

2012 613 0545 54.0 L 71.269 -9.909 0.0 BER 13 1.0 2.9 BER

2012 613 1247 4.3 L 71.270 -9.788 0.1 BER 12 0.8 2.9 BER

2012 621 0938 51.2 L 76.113 24.626 14.1 BER 6 0.5 2.7 BER

2012 630 0100 48.2 L 72.000 -0.133 2.4 BER 16 0.7 2.4 BER

2012 7 2 0455 52.6 L 78.862 4.690 10.0 F BER 8 1.1 2.7 BER

2012 7 2 2236 16.6 L 66.063 13.349 0.0 BER 25 0.6 2.4 BER

2012 7 3 0435 17.2 L 71.375 -9.302 3.0 BER 4 0.3 3.1 BER

2012 7 4 0708 32.2 L 76.119 24.497 17.2 BER 7 0.5 3.0 NAO

2012 7 4 0909 36.4 L 73.194 6.715 10.0 F BER 13 0.6 3.5 NAO

2012 7 9 1845 28.4 L 81.610 -0.781 15.0 BER 11 0.4 3.6 BER

2012 711 1619 33.8 L 81.800 -1.081 15.0 BER 13 0.8 2.8 BER

2012 713 1914 44.2 L 71.348 -9.270 10.0 F BER 24 1.2 3.2 BER

2012 714 1211 40.4 L 71.241 -9.817 15.0 BER 11 0.5 3.1 BER

2012 714 1308 56.2 L 71.249 -9.887 0.1 BER 14 0.7 3.3 BER

2012 714 1941 19.0 L 71.206 -9.921 10.0 F BER 11 0.8 3.1 BER

2012 714 1954 13.8 L 71.300 -9.936 10.0 F BER 32 0.9 3.8 BER 4.5 PDE

2012 715 0213 38.5 L 71.259 -9.829 15.0 BER 22 0.5 3.5 BER

2012 715 0234 51.9 L 71.338 -9.361 20.8 BER 14 0.5 3.2 BER

2012 715 1146 31.9 L 71.243 -10.089 8.1 BER 20 0.5 3.7 BER

2012 715 1224 36.6 L 71.305 -9.412 0.0 BER 4 0.2 3.0 BER

2012 715 1302 42.3 L 71.266 -10.076 7.8 BER 29 0.8 3.9 BER

2012 715 1311 23.5 L 71.369 -8.534 10.0 F BER 14 1.0 3.5 BER

2012 717 1442 51.8 L 79.687 5.019 1.1 BER 4 0.3 3.3 NAO

2012 721 1327 17.5 L 81.044 1.188 0.0 BER 5 0.6 2.3 BER

2012 723 0438 45.8 L 79.479 4.708 0.0 BER 8 0.6 3.2 BER 4.7 PDE

2012 728 1014 40.2 L 80.043 3.608 10.0 F BER 25 1.4 3.7 BER

2012 728 1123 46.6 D 81.176 -1.036 10.0 F BER 18 1.1 4.8 NAO 5.1 BER

2012 730 1940 49.5 L 71.091 -6.245 15.0 BER 9 0.2 3.0 BER

2012 8 5 2119 59.4 L 64.406 -4.416 10.0 F BER 45 2.0 2.7 BER

2012 8 6 0257 16.3 L 56.664 12.029 1.7 BER 39 0.8 3.9 BER

2012 8 7 0441 31.4 L 70.933 -6.886 0.0 BER 4 0.2 3.0 BER

2012 8 7 0522 52.2 L 71.089 -7.013 0.0 BER 8 0.1 3.2 BER

2012 820 1505 35.8 L 78.085 8.125 21.9 BER 3 0.3 2.6 BER

2012 830 1343 26.9 D 71.437 -10.048 20.3 BER 44 0.7 6.2 NAO 5.9 PDE 6.8WCM

2012 830 1351 3.3 D 70.760 -8.160 5.0 F BER 29 1.6 5.6 NAO

2012 830 1357 29.5 D 71.451 -10.604 13.5 BER 5 0.2 3.3 BER

2012 830 1357 33.9 D 71.673 -9.791 15.4 BER 4 0.1 3.8 NAO

2012 830 1408 11.3 L 71.305 -8.986 10.0 F BER 4 0.3 3.1 BER

2012 830 1437 44.0 L 71.016 -8.812 0.0 BER 4 0.1 3.4 BER

2012 830 1439 5.1 L 71.207 -9.112 0.0 BER 4 0.1 3.0 BER

2012 830 1452 48.9 L 70.288 -7.184 0.0 BER 4 0.2 3.0 BER

2012 830 1726 57.6 L 71.230 -8.895 0.0 BER 4 0.1 3.1 BER

2012 830 2100 46.9 L 71.013 -9.560 0.1 BER 3 0.0 3.2 BER

2012 830 2128 23.8 L 71.312 -9.518 3.0 BER 4 0.2 3.8 BER

2012 830 2355 42.2 L 71.363 -9.543 3.0 BER 4 0.2 3.0 BER

2012 831 1430 24.7 L 71.280 -9.380 3.0 BER 4 0.1 3.0 BER

2012 9 1 0631 51.0 L 71.363 -9.528 0.0 BER 9 0.7 3.2 BER

2012 9 1 2107 29.9 L 71.359 -10.360 0.0 BER 9 0.6 3.0 BER

2012 9 1 2129 5.0 L 71.494 -9.930 1.1 BER 4 0.2 3.2 BER

2012 9 1 2149 34.0 L 71.255 -9.157 12.5 BER 8 0.2 3.4 BER

2012 9 2 0840 2.9 L 71.293 -9.297 0.0 BER 4 0.1 3.1 BER

2012 9 2 1244 2.5 D 78.301 8.027 10.0 F BER 20 1.1 4.5 BER

2012 9 2 1758 59.0 L 71.288 -9.404 0.0 BER 8 0.2 3.2 BER

2012 9 2 1905 49.9 L 78.422 7.812 0.0 BER 4 0.7 3.3 BER

2012 9 5 1344 55.9 L 70.549 -7.952 3.1 BER 10 0.5 3.4 BER


14

2012 9 6 1159 17.5 D 71.486 -9.274 10.2 BER 14 1.6 3.4 BER

2012 9 9 0139 23.0 L 78.328 8.688 0.0 BER 5 0.6 3.3 NAO

2012 911 1015 54.7 D 73.325 8.602 10.0 F BER 27 1.3 3.3 BER

2012 914 1115 45.3 L 71.197 -6.846 10.0 F BER 4 0.2 3.0 BER

2012 914 1922 55.0 D 72.392 3.462 10.0 F BER 11 0.4 2.1 BER

2012 915 0241 34.3 L 76.759 8.669 0.0 BER 11 1.0 2.4 BER

2012 915 1722 47.3 L 72.382 2.733 6.6 BER 16 0.6 2.3 BER

2012 916 0211 59.9 L 72.304 2.357 0.0 BER 4 0.2 3.1 NAO

2012 916 2155 60.0 L 72.456 3.034 10.0 F BER 18 0.8 2.7 BER

2012 917 1339 24.9 L 72.401 2.666 10.0 F BER 17 0.6 2.4 BER

2012 917 1608 47.5 L 72.449 2.942 0.0 BER 19 0.6 2.9 BER

2012 917 1853 8.5 L 72.410 2.471 0.0 BER 15 0.5 2.2 BER

2012 918 0035 24.2 L 72.481 2.148 0.0 BER 15 0.5 4.1 NAO

2012 920 0420 5.9 L 73.157 7.052 15.0 BER 13 0.5 3.0 NAO

2012 920 0732 31.0 L 71.247 -9.063 0.1 BER 4 0.1 3.0 BER

2012 921 0842 27.2 D 71.258 -7.991 10.0 F BER 18 1.1 3.0 BER

2012 923 1612 5.8 D 71.435 -8.909 11.5 BER 13 1.1 3.4 BER

2012 924 1431 29.1 D 71.542 -11.083 12.9 BER 7 0.3 3.0 BER

2012 926 1717 1.3 L 74.700 9.597 3.1 BER 12 1.0 2.2 BER

2012 10 6 0119 36.3 L 76.074 7.975 16.8 BER 18 1.8 2.9 BER

2012 1023 1545 16.7 L 78.608 7.101 0.0 BER 5 0.4 3.0 BER

2012 1026 0020 40.8 L 71.644 -0.675 10.0 F BER 5 0.4 3.3 NAO

2012 1029 1454 53.6 L 81.137 -1.369 14.9 BER 12 0.5 3.0 BER

2012 1030 0724 48.3 L 62.189 5.174 12.1 BER 20 0.4 3.0 BER 2.9BER

2012 11 1 0633 39.6 L 72.091 0.507 0.0 BER 29 1.0 3.0 BER

2012 11 8 1601 23.0 L 80.758 1.435 10.0 F BER 5 0.6 3.0 NAO

2012 1120 0954 31.2 L 71.811 -0.448 15.0 F BER 18 0.8 3.8 NOA

2012 1123 0717 57.3 L 70.973 -6.867 3.0 BER 4 0.2 3.1 BER

2012 1124 2025 30.4 L 70.912 -6.683 3.0 BER 3 0.1 3.5 BER

2012 1126 1131 38.5 L 76.513 16.937 15.0 BER 7 0.8 3.1 NAO

2012 1129 0136 48.2 L 70.805 -6.810 2.0 BER 7 0.2 3.4 BER

2012 1129 0223 59.6 L 70.969 -7.085 10.0 F BER 38 1.2 4.6 BER

2012 1129 0224 45.3 L 71.037 -6.947 10.0 F BER 4 0.1 3.5 BER

2012 1129 0239 48.4 L 71.132 -7.009 10.0 F BER 4 0.2 3.5 BER

2012 1129 0436 8.9 L 71.072 -6.996 10.0 F BER 4 0.2 3.3 BER

2012 12 1 1823 29.6 L 73.451 7.722 22.0 BER 25 0.9 2.2 BER

2012 12 1 1824 49.1 L 73.222 7.081 26.1 FF NAO 6 0.6 3.2 NAO

2012 12 2 1213 20.9 L 73.441 8.172 10.0 F BER 14 0.5 1.9 BER

2012 12 3 0917 22.4 L 73.462 7.900 10.0 F BER 23 0.7 2.3 BER

2012 1222 2109 19.6 L 67.660 33.499 0.0 BER 13 0.7 1.8 BER

2012 1224 1236 8.4 L 71.021 -7.105 0.1 BER 4 0.1 3.6 BER

2012 1225 0344 35.8 L 72.978 15.658 10.0 F BER 25 0.8 2.6 BER

2012 1229 0953 42.4 L 70.401 -7.937 0.0 BER 4 0.5 3.1 BER

The largest local or regional earthquake in 2012, recorded on Norwegian stations and

within the prime area, occurred on August 30 at 13:43(UTC) northwest of Jan

Mayen. The earthquake had a magnitude of MW=6.7 (GCMT) and was strongly felt

at the island 74 km away. Another large earthquake occurred on the Mohns Ridge on

May 24 at 22:47 with a magnitude MW=6.3 (MW GCMT).

The most significant earthquakes in the vicinity of the Norwegian mainland were:

14 March 2012, 19:22 (UTC): The earthquake was located northeast of

Haugesund, Rogaland, with a magnitude of ML=3.2. This earthquake was

reported felt in a large area in Hordaland and Rogaland.

24 March 2012, 06:05 (UTC): The earthquake occurred about 18 km

southwest of the Fedje island and 15 km west of Øygarden, Hordaland. The

earthquake had a magnitude ML=2.9. This earthquake was reported felt in

northern parts of Hordaland and in Gulen, Sogn og Fjordane.

24 March 2012, 11:06 (UTC): An earthquake was felt in the Voss area with a

magnitude of ML=3.0.


15

Offshore, an earthquake occurred north of the Faroe Islands on 5 August. The

earthquake was located to 64.406˚N 4.416˚W with magnitudes MLBER =2.7

and MLBGS=3.6. The earthquake was registered both on Norwegian and

British seismic stations.

5.1 Seismicity in Nordland

Figure 6 shows the seismicity in Nordland since 2000. The area includes the locations

of earthquake swarm activity such as Meløy, Steigen and Stokkvågen. The latter two

areas are clearly visible on the map.

Steigen was active between 2007 and 2008, but has been relatively quiet since then.

The activity in the Stokkvågen area has been nearly continuous, but specific clusters

in time and space have occurred. The temporal distribution shows the cluster in 2005,

which is when the three station network was installed. The number of events during

and after 2011 was lower than in previous years, probably reflecting that the station

FLOS was closed in February 2011. This also reduced the number of very small

earthquakes that are located in this area, as can be seen for 2012.


16

Figure 6. Seismicty in the Nordland area. Bottom: Red circles show seismicity for 2000-2011,

and blue circles show seismicity for 2012. Explosions are excluded. The green triangles give the

station locations. Top: Seismicity in the same area is plotted as latitude versus time of

occurrence.


17

5.2 Seismicity in the arctic area

With the mainland stations on the Lofoten, in Tromsø and Hammerfest, the network

on Jan Mayen, and stations on Bjørnøya, Hopen and Svalbard, the network detection

capability in the arctic area is relatively good. We define the arctic area as the region

65-85°N and 20°W-50°E. Most of the activity falls into three areas: Jan Mayen, the

Mid-Atlantic ridge and Storfjorden southeast of Svalbard, as can be seen in Figure 7.

The two largest earthquakes of the year (Mohns Ridge and Jan Mayen) fall into the

arctic area.

Figure 7. Seismicity in the Norwegian arctic area during 2012. A total of 2132 located

earthquakes.

5.3 Seismicity in the Jan Mayen area

Jan Mayen is located in an active tectonic area with two major structures, the Mid

Atlantic ridge and the Jan Mayen fracture zone, interacting in the vicinity of the

island. Due to both tectonic and magmatic activity in the area, the number of recorded

earthquakes is higher than in other areas covered by Norwegian seismic stations.

During 2012 a total of 2136 earthquakes were located as seen in Figure 8 and of these,

196 had a magnitude equal or above 3.0. The largest earthquake in the Jan Mayen

region in 2012 occurred on 30 August at 13:43 (UTC). This earthquake was located at

71.44N and 10.05W with a magnitude of 6.7. The earthquake was strongly felt by the

population on the island only 74 km from the hypocenter. The earthquake had a strike


18

slip mechanism as determined through global moment tensor inversion (Figure 9).

The NW-SE striking nodal plane is an alignment with the Jan Mayen fracture zone.

Figure 8. Earthquakes located in the vicinity of Jan Mayen during 2012. The two yellow stars

mark the two major earthquakes, the M6.7 northwest of the island and the M5.3 to the southeast.

201208301343A JAN MAYEN ISLAND REGION Date: 2012/ 8/30 Centroid Time: 13:43:35.4 GMT

Lat= 71.44 Lon= -9.84

Depth= 23.6 Half duration= 5.7

Centroid time minus hypocenter time: 10.2

Moment Tensor: Expo=26 -0.011 1.100 -1.090 -0.050 0.230 1.190

Mw = 6.7 mb = 5.9 Ms = 6.8 Scalar Moment = 1.63e+26

Fault plane: strike=111 dip=83 slip=-5

Fault plane: strike=202 dip=86 slip=-173

Figure 9. Moment tensor solution provided by the Global CMT project (taken from

http://www.globalcmt.org).

http://pubweb.parc.xerox.com/map/color=1/lat=71.44/lon=-9.84/mark=71.44,-9.84


19

0

50

100

150

200

250

300

350

Jan Mar May Jul Sep Nov

Located

earthquakes

Figure 10. Monthly distribution of the earthquakes recorded on Jan Mayen during 2012.

The monthly distribution of located earthquakes in the area (Figure 10) shows the

increase during July, August and September related to the activity around the

mainshock location before and after the event occurred. Figure 8 shows that

aftershocks were located along the mainshock fault plane, but also continued across

the island to the south-east. This may be significant as only few earthquakes have

been recorded from here in the past. Also the ML=5.3 aftershock occurred away from

the mainshock fault south of Jan Mayen.

The number of recorded earthquakes in the Jan Mayen area has varied over the last

years (Figure 11). The number of relative strong earthquakes (M≥3) shows smaller

time variation than for the smaller earthquakes. The increases in 2004 and 2005 were

due to the M=6.0 earthquake in 2004 and its aftershocks (Sørensen et al., 2007). The

same is true for 2011, where the M=6.0 earthquake on 29 January was followed by a

sequence of aftershocks. The 30 august 2012 earthquake with its fore and aftershocks

clearly increases the number of recorded events in 2012 compared with previous

years, making it the largest number of recorded events since 2001. There are twice as

many large earthquakes but more than four times as many smaller events recorded in

the vicinity of the island.

0

500

1000

1500

2000

2500

2001 2003 2005 2007 2009 2011

Total number of

recorded earthquakes

Number of events with

magnitude equal to or

above 3.0

Figure 11. Yearly distribution of earthquakes located in the Jan Mayen area since 2001.


20

The daily numbers of earthquakes recorded in 2012 are shown in Figure 12. The

figure shows a relative low activity during the first 5 months of 2012 and then an

increase in the activity with three significant peaks. The biggest peak is following the

major earthquake on august 30, when 350 earthquakes were recorded on the Jan

Mayen stations within a few days. This earthquake was strongly felt on Jan Mayen,

where the staff members reported things were falling from shelves and small rock

falls occurred, as illustrated by the photos in Figure 13.

Figure 12. Daily distribution of the earthquakes recorded on the stations at Jan Mayen during

2012.

Figure 13. The photos shows damages on Jan Mayen after the august 30 earthquake. (Photos are

printed with permission by the staff at Jan Mayen).


21

Waveform data of the 30 August, 2012 earthquake are presented in Figure 14. The

earthquake was recorded on all NNSN stations. The data recorded on the Jan Mayen

stations are saturated. To obtain onscale recordings in the future, an accelerometer has

been installed next to the broadband seismometer at station JMI in the beginning of

2013. Further analysis of this major earthquake will be done.

Figure 14. The Jan Mayen earthquake recorded on some of the stations in the NNSN database.


22

5.4 Seismicity in Storfjorden, Svalbard

The Storfjorden area southeast of Svalbard has been seismically active since the

Mw=6.0 earthquake on 21 February 2008. A preliminary study was presented by Piril

et al. (2008). One of the main objectives from this study was to resolve the source

mechanism, which was found to be oblique-normal. This result was found from the

inversion of both regional and teleseismic data. The earthquake had a high number of

aftershocks.

A total of more than 20 earthquakes with magnitude larger than M=4 have occurred

in the area since 2008. An interesting question is whether the earthquakes now are

aftershocks to the event in 2008. From the monthly number of all detected

earthquakes, shown in Figure 15, it seems that the activity had decreased until the

start of 2009 and then remained relatively low until late 2009. In 2010 the number

had increased again and remained mostly stable in 2011. This is mostly explained by

an increase in the number of smaller earthquakes as seen by the almost constant

levels of earthquakes with M>2.5 since 2008. The better detection was due to usage

of the data from the Hornsund (HSPB) station. In 2012, it appears as if the overall

activity is finally decreasing. The total number of events detected in the Storfjorden

area in 2012 was 267.

Figure 15. Monthly number of earthquakes in the Storfjorden area since January 2008. The

colours show: grey – all events, red – M>2.5, blue M>4.0.

Figure 16 shows both a map with the seismicity since 2000 and the distribution of

events over time. The onset of the activity in the Storfjorden area in February 2008 is

obvious from the time plot. The seismicity in 2011 and 2012 is mostly concentrated in

the southwestern half of the area that has been active since 2008.


23

Figure 16. Seismicty in the Svalbard area. Bottom: Red circles show seismicity for 2000-2012

yellow circles and blue circles show seismicity for 2011 and 2012, respectively. The blue triangles

give the station locations. Top: Seismicity in the same area is plotted as latitude as function of

time.


24

5.5 Haugesund earthquake

The most widely felt earthquake on mainland Norway occurred 14 March 2012 at

19:22 (UTC, 20:22 local time). The earthquake was located to 59.52°N and 5.58°E

with a depth of 13.8km and a magnitude MW=3.5. The seismograms recorded are

shown on Figure 17.

Figure 17. Seismograms for the earthquake occurring on 14 March, 2012 at 19:22 (UTC) and

located northeast of Haugesund, Rogaland. The seismograms are filtered between 5-10 Hz. The

horizontal time scale is minutes, first marking at 19:22(UTC).


25

The epicenter is about 22 km northeast of Haugesund and the earthquake was felt by a

large number of people in Rogaland and Hordaland with a maximum intensity of

MMI=V. On the web site skjelv.no questionnaires were published for the public to fill

in and send to NNSN. A total of 690 questionnaires were received, being the basis of

the macroseismic map presented in Figure 18.

Figure 18. Macroseismic map of the March 14, 2012 earthquake northeast of Haugesund. The

reported intensities have not been manually evaluated.


26

Figure 19. Three-component traces of station DOMB, filtered 3-8 Hz.

For several of the stations, it is possible to read direct Pn and Sn waves besides the

larger amplitude Pg and Sg direct arrivals. The seismograms for station DOMB are

shown in Figure 19. Sn (here marked as ES) is often weak and not recognizable in the

signal-generated noise of scattered P waves. Reading different phases with different

take-off angle from the source, such as Pg/Pn and Sg/Sn, significantly improves the

depth determination (13.8 km).

5.6 Fedje earthquake

The 24 March 2012 at 07:05 (local time) an earthquake occurred about 18 km

southwest of Fedje island and 15 km west of Øygarden, Hordaland. The earthquake

was located to 60.62°N and 4.40°E with a magnitude ML=2.9 and it was given a fixed

depth of 15 km. The earthquake is located at the Øygarden fault where the last larger

earthquake was reported 8 December 2000, with magnitude MW=3.6.


27

Figure 20. Macroseismic map of the March 24, 2012 earthquake southwest of Fedje, Hordaland.

The reported intensities have not been manually evaluated.

5.7 Voss earthquake

On 24 March 2012 at 11:06, a second earthquake was reported felt in Hordaland. The

earthquake was located to Voss at 60.64°N and 6.40°E with 15.3 km depth and

magnitude ML=3.0. People at Voss reported a strong sound and shaking, and many

feared an avalanche.

Having a reasonably good azimuthal coverage for this earthquake, it was possible to

determine a fault plane solution (Figure 22). The solution shows strike-slip faulting on

fault planes oriented either NW-SE or SE-NW. The maximum compression (P axis) is

nearly horizontal and oriented EW in agreement with the regional stress pattern.


28

Figure 21. Macroseismic map of the March 24, 2012 earthquake at Voss. The reported intensities

have not been manually evaluated.

Figure 22. Fault plane solutions determined thtough program HASH and FPFIR for the Voss

earthquake on 24 March 2012.


29

5.8 Earthquakes north of the Faroe isles

During last half of 2012 and beginning of 2013 earthquakes have been located north

of the Faroe islands. An earthquake occurred on 5 August 2012 at 21:19. The

earthquake was located to 64.406˚N 4.416˚W with magnitudes MLBER =2.7 and

MLBGS=3.6. The earthquake was registered both on Norwegian and British seismic

stations. On 5 December 2012, two slightly smaller earthquakes occurred in the same

area with magnitude MLBER =2.3 and MLBER =2.4 and 4 March 2013 an MLBER =2.8

and MLBGS=3.6 earthquake were located to the same area. In 2007, similar

magnitudes earthquakes were observed in this area. Figure 23 shows the location of

earthquakes from 2000 to March 2013.

Figure 23. All earthquakes located north of the Faroe Islands after January 2000. Earthquakes

recorded in 2012/2013 in blue and earthquakes recorded in 2007 in yellow.


30

6 Felt earthquakes

In total, 22 earthquakes were reported felt and located within the target area during

2012 (see Table 5 and Figure 24). Not all earthquakes were felt in Norway. For the

Jan Mayen island the number of felt earthquakes is expected to be larger then

reported.

Figure 24. Location of the 22 earthquakes reported felt during 2012. Not all earthquakes are felt

in Norway.

From 2006 it is possible to report felt earthquakes over the internet. When an

earthquake is reported felt by a sufficient number of people, questionnaires are

available for the public on the site www.skjelv.no.

http://www.skjelv.no/


31

Table 5. Earthquakes reported felt in the BER database in 2012. Abbreviations are: ML = local

magnitude and Mw = moment magnitude, W: questionnaires received on web (Y/N). Earthquakes

reported felt in Norway are marked in colour.

Nr

Date

Time

(UTC)

Max.

Intensity

(MMI)

Magnitude (BER)

Instrumental

epicentre

location

W

1 26.01.12 01:04 III ML=2.2(BGS),ML=1.9 55.16N / 07.61W 2 20.02.12 05:35 III ML=2.6(BGS),ML=2.3 55.78N / 06.35W 3 26.02.12 22:31 II ML=2.9(BGS),ML=2.7 54.65N / 00.84W 4 29.02.12 09:14 III ML=2.8(BGS), ML=2.5 55.78N / 06.34W 5 29.02.12 09:25 III ML=2.1(BGS),ML=1.8 55.78N / 06.35W 6 29.02.12 14:55 III ML=2.4(BGS),ML=2.3 56.23N / 04.84W 7 02.03.12 14:59 III ML=3.2(BGS),ML=2.7 59.54N / 01.67W 8 04.03.12 23:23 III ML=2.8(BGS),ML=2.7 56.25N / 04.76W 9 14.03.12 19:22 V ML=3.2,ML=3.6(BGS) 59.52N / 05.58E Y

10 24.03.12 06:05 V ML=2.9,ML=2.6(NAO),

ML=3.3(BGS)

60.82N / 04.88E Y

11 24.03.12 11:06 V ML=3.0,ML=3.2(NAO),

ML=3.3(BGS)

60.64N / 06.40E Y

12 15.04.12 15:53 III ML=1.9,

ML=2.0 (NAO)

54.46N / 02.97W

13 13.05.12 16:07 III ML=2.1,ML=2.8 (NAO) 66.53N / 13.35E N 14 02.07.12 07:03 V ML=2.9,ML=2.7 (NAO) 60.46N / 06.22E Y 15 02.07.12 22:36 II ML=2.4,ML=3.1 (NAO) 66.06N / 13.35E N 16 10.08.12 10:59 III ML=2.0,ML=2.3 (BGS) 56.56N / 05.69W 17 30.08.12 13:43 VI Mw=6.7,MB=6.9,

ML=6.2 (NAO)

71.44N / 10.05W N

18 30.10.12 07:24 V MW=2.9,ML=3.0,

ML=3.2 (NAO)

62.19N / 05.17E Y

19 31.10.12 15:59 II ML=2.7,ML=2.9 (BGS) 55.97N / 05.94W 20 22.11.12 19:46 III ML=2.0 (BGS) 55.77N / 06.26W 21 28.11.12 21:37 III ML=2.2, ML=2.1 (BGS) 54.51N / 02.98W 22 29.11.12 02:23 V ML=4.6,ML=4.7 (NAO) 70.97N / 07.09W N


32

7 Use of NNSN data during 2012

Data collected on Norwegian seismic stations are made available through the Internet

and is provided on request to interested parties. Therefore it is difficult to get a

comprehensive overview on the use and all publication based on Norwegian data.

Publications and reports

Gibbons, S. J., F. Ringdal and T. Kværna, 2012 Ratio-to-moving-average

seismograms: a strategy for improving correlation detector performance,

Geophysical Journal International, Vol. 190, No. 1. (July 2012), pp. 511-521,

doi:10.1111/j.1365-246x.2012.05492.x

Gibbons, S. J., 2012.The Applicability of Incoherent Array Processing to IMS

Seismic Arrays. Pure and Applied Geophysics In Pure and Applied

Geophysics (online only 17 October 2012), doi:10.1007/s00024-012-0613-2

Havskov, J, P. Bormann and J. Schweitzer, 2012. Seismic source location.

http://ebooks.gfz-potsdam.de/pubman/item/escidoc:43361:4;

doi:10.2312/GFZ.NMSOP-2_IS_11.1; 36 pp., escidoc:44031 P. Bormann (ed.)

(2012), New Manual of Seismological Observatory Practice 2 (NMSOP-2).

2nd (revised) edition, Potsdam: Deutsches GeoForschungsZentrum GFZ, doi:

10.2312/GFZ.NMSOP-2

Harris, D. B., S. J. Gibbons, A. J. Rodgers and M. E. Pasyanos, 2012. Nuclear Test

Ban Treaty Verification: Improving Test Ban Monitoring with Empirical and

Model-Based Signal Processing. IEEE Signal Processing Magazine, Vol. 29,

No. 3. (May 2012), pp. 57-70, doi:10.1109/msp.2012.2184869

Klinge, K., J. Schweitzer and P. Bormann, 2012. Record examples of underground

nuclear explosions http://ebooks.gfz-

potsdam.de/pubman/item/escidoc:43265:5; doi:10.2312/GFZ.NMSOP-

2_DS_11.4; 6 pp., escidoc:44029 P. Bormann (ed.) (2012), New Manual of

Seismological Observatory Practice (NMSOP-2). 2nd (revised) edition,

Potsdam: Deutsches GeoForschungsZentrum GFZ, doi:

10.2312/GFZ.NMSOP-2

Schweitzer, J., J. Fyen, S. Mykkeltveit, S. J. Gibbons, M. Pirli, D. Kühn and T.

Kværna, 2012. Seismic Arrays. http://ebooks.gfz-

potsdam.de/pubman/item/escidoc:43213:7; doi:10.2312/GFZ.NMSOP-2_ch9;

80 pp., escidoc:44028 P. Bormann (ed.) (2012), New Manual of Seismological

Observatory Practice (NMSOP-2). 2nd (revised) edition, Potsdam: Deutsches

GeoForschungsZentrum GFZ, doi: 10.2312/GFZ.NMSOP-2

NNSN related Talks & Posters 2012

Bondevik, S., Sørensen, M.B. and Gjevik, B. (2012). Norwegian fjords sang along –

observations of seiches following the 2011 Tohoku, Japan, earthquake, oral

presentation at ESC General Assembly, Moscow, August 2012.


33

Fyen, J., S. J. Gibbons, T. Kværna, S. Mykkeltveit, F. Ringdal, M. Roth and J.

Schweitzer, NORSAR’s automatic processing. Joint Scientific Commission

meeting AFTAC, Florida 6-8- November 2012

Fyen, J. and M. Roth, 2012. NORSAR history and field installation in text and

pictures. Joint Scientific Commission meeting AFTAC, Florida 6-8-

November 2012

Gibbons, S. J., 2012. The Applicability of Incoherent Array Processing to IMS

Seismic Array Stations. Geophysical Research Abstracts Vol. 14, EGU2012-

1366, 2012 EGU General Assembly 2012

http://meetingorganizer.copernicus.org/EGU2012/EGU2012-1366.pdf EGU

2012 oral presentation, Vienna International Center, 25 April 2012

Knapmeyer-Endrun, B., M. Ohrnberger and J. Schweitzer, 2012. Temporal variability

of the noise wavefield at different scales: Influence on H/V and FK results.

Noise and Diffuse Wavefields, Extended Abstracts of the Neustadt Workshop,

11 – 14 November 2012, Deutsche Geophysikalische Gesellschaft

Mitteilungen, Sonderband IV/2012, 29-30, 2012

Knapmeyer-Endrun, B., M. Ohrnberger and J. Schweitzer, 2012. Temporal variability

of the noise wavefield at different scales: Influence on H/V and FK results,

Neustadt Workshop “Noise and Diffuse Wavefields“, 11. – 14. November

2012

Kværna, T., 2012. Verification-related research at NORSAR. Joint Scientific

Commission meeting AFTAC, Florida 6-8- November 2012

Kværna, T., M. Pirli and J. Schweitzer, 2012. Overview of the seismological activities

in the Arctic region, including plans for a seismic array on Bear Island. Joint

Scientific Commission meeting AFTAC, Florida 6-8- November 2012

Kværna, T. and F. Ringdal, 2012. Analysis of the IDC reviewed event bulletin for

detection capability estimation of the IMS seismic stations. Joint Scientific


Kværna, T, S. J. Gibbons, D. B. Harris and D. A. Dodge, 2012. Adapting Pipeline

architecture to track developing aftershock sequences and recurrent

explosions. Joint Scientific Commission meeting AFTAC, Florida 6-8-

November 2012

Ottemöller, Lars, 2012. Observations from the Ongoing Storfjorden, Svalbard,

Earthquake Sequence. ESC2012.

Pirli, M., J. Schweitzer and B. Paulsen, 2012. A long earthquake series in the

European Arctic: challenges and limitations to seismotectonic interpretation,

33rd General Assembly of the European Seismological Commission, Moscow,

August 2012

Pirli, M. and J. Schweitzer, 2012. Seismic activity at the region of convergence of the

Mohns and Knipovich Ridge, as seen within the International Polar Year 33rd

General Assembly of the European Seismological Commission, Moscow,

August 2012


34

Roth, M and J. Fyen, 2012. Seismic sensors with hybrid response at the IMS array

PS27, Norway. Joint Scientific Commission meeting AFTAC, Florida 6-8-

November 2012

Schøyen, N. K., 2012 NORSAR – infrastrucure and network. Joint Scientific


Sørensen, M.B., Ottemöller, Raeesi, M. and Storheim, B.M. (2012). The 30. August,

2012 M6.6 Jan Mayen earthquake, oral presentation at Nordic Seismology

Seminar, Tallinn, October 2012.

Sørensen, M.B., Bondevik, S. and Gjevik, B. (2012). Norwegian fjords sang along –

observations of seiches following the 2011 Tohoku, Japan, earthquake, oral

presentation at Nordic Seismology Seminar, Tallinn, October 2012.

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Documents

Seismicity of Norway and surrounding areas for 2012nnsn.geo.uib.no/reports/2012/seismicity_2012_final.pdfstations (red) and in addition the data are transferred from Ekofisk (EKO1),