**2. Relationship between the seismicity of the European Arctic and structural-tectonic elements of the lithosphere**

Instrumental observations of the seismicity in the European Arctic are carried out by a number of seismic services and networks, but the Norwegian seismological center NORSAR (http://www.norsardata.no), the Arkhangelsk seismic network of N. Laverov Federal Center for Integrated Arctic Research (http://www.fdsn. org/networks/detail/AH/), and the Kola Branch of the Geophysical service of RAS (http://www.krsc.ru) make the greatest contribution.

Each seismological service has its own high-priority zones and shadow zones where earthquakes are being recorded [18]. Combining efforts in seismological

**41**

**Figure 2.**

parts) and the Arctic shelf.

*Recent Geodynamics and Seismicity of the European Arctic DOI: http://dx.doi.org/10.5772/10.5772/intechopen.80800*

monitoring of the Arctic region can help to increase the accuracy in locating epicenters and estimating their energy. Obviously, an urgent problem is the expansion of seismic networks in the Russian sector of the Arctic region, where seismological observations are insufficient compared to foreign ones. The coverage density of seismic stations in the European Arctic is shown in **Figure 2**. The opening of several new seismic stations in the Russian Arctic recently allows to cover the European Arctic territory at large, but the number of stations is still small. The seismic stations installed on the Franz Josef Land (ZFI and OMEGA) and Severnaya Zemlya (SVZ) archipelagos make a special contribution to the European Arctic monitoring, allowing to investigate the seismicity of the Gakkel Ridge (central and eastern

*Results of the unified seismic catalog which makes use of stations in Fennoscandia, Spitsbergen, Franz Josef Land, Severnaya Zemlya archipelago, north of the Russian Platform, and the Kola Peninsula. The figure covers seismic events (red dots) for 1998–2017. For Novaya Zemlya we collected information from 1986. Some additional stations which provide minor contributions to this unified catalog are not shown on the map.*

Assessment of the seismic situation in the region is additionally complicated by the fact that the data in catalogs of different seismological services and networks are not unified, the quantity and quality of the initial data greatly vary, and different processing methods have been used for them. The parameters of the same earthquakes often vary in different information sources. The seismic data were generalized to increase the quality of earthquake location in the European Arctic [9]. For each network the zones of responsibility (priority) were determined where epicentral parameters are determined with minimal errors (**Figure 2**). For example, zones of responsibility of the NORSAR network are the Mona and Knipovich ridges and Svalbard, whereas those of the Arkhangelsk seismic network are the Gakkel

*Recent Geodynamics and Seismicity of the European Arctic DOI: http://dx.doi.org/10.5772/10.5772/intechopen.80800*

#### **Figure 2.**

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improvements of Arctic seismic networks suggests a need for revision. The contemporary seismicity and heat flow density are indicators of geodynamic processes [9]. Joint analysis of these fields will allow a better understanding of the regional

*Scheme showing locations of profiles A–B and C–D, geotraverses, and deep seismic profiles in water area (1-AR, 2-AR, 3-AR, 4-AR, DSS-82) and on land (Kvarts, Pechora, Rift, SW Vorkuta) in studied region.*

For this, a unified seismic catalog based on data from seismic networks that monitor the studied region was compiled; we generalized data of deep geological and geophysical cross sections of the crust and upper mantle along geotraverses [10–13] (**Figure 1**) and employed data on the spatial heat flow distribution [14–17]. Based on an analysis of the geological and geophysical data, we summarized the cross sections along the A–B and C–D profiles, which reflect the main structural features of the lithosphere in the region and make it possible to consider the rela-

geodynamics, and such analysis is the aim of this study.

tionship between the seismicity, heat flow density, and tectonics.

**structural-tectonic elements of the lithosphere**

(http://www.krsc.ru) make the greatest contribution.

**2. Relationship between the seismicity of the European Arctic and** 

Instrumental observations of the seismicity in the European Arctic are carried out by a number of seismic services and networks, but the Norwegian seismological center NORSAR (http://www.norsardata.no), the Arkhangelsk seismic network of N. Laverov Federal Center for Integrated Arctic Research (http://www.fdsn. org/networks/detail/AH/), and the Kola Branch of the Geophysical service of RAS

Each seismological service has its own high-priority zones and shadow zones where earthquakes are being recorded [18]. Combining efforts in seismological

**40**

**Figure 1.**

*Results of the unified seismic catalog which makes use of stations in Fennoscandia, Spitsbergen, Franz Josef Land, Severnaya Zemlya archipelago, north of the Russian Platform, and the Kola Peninsula. The figure covers seismic events (red dots) for 1998–2017. For Novaya Zemlya we collected information from 1986. Some additional stations which provide minor contributions to this unified catalog are not shown on the map.*

monitoring of the Arctic region can help to increase the accuracy in locating epicenters and estimating their energy. Obviously, an urgent problem is the expansion of seismic networks in the Russian sector of the Arctic region, where seismological observations are insufficient compared to foreign ones. The coverage density of seismic stations in the European Arctic is shown in **Figure 2**. The opening of several new seismic stations in the Russian Arctic recently allows to cover the European Arctic territory at large, but the number of stations is still small. The seismic stations installed on the Franz Josef Land (ZFI and OMEGA) and Severnaya Zemlya (SVZ) archipelagos make a special contribution to the European Arctic monitoring, allowing to investigate the seismicity of the Gakkel Ridge (central and eastern parts) and the Arctic shelf.

Assessment of the seismic situation in the region is additionally complicated by the fact that the data in catalogs of different seismological services and networks are not unified, the quantity and quality of the initial data greatly vary, and different processing methods have been used for them. The parameters of the same earthquakes often vary in different information sources. The seismic data were generalized to increase the quality of earthquake location in the European Arctic [9]. For each network the zones of responsibility (priority) were determined where epicentral parameters are determined with minimal errors (**Figure 2**). For example, zones of responsibility of the NORSAR network are the Mona and Knipovich ridges and Svalbard, whereas those of the Arkhangelsk seismic network are the Gakkel


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**Table 1.**

*Example of the unified seismic catalog.*

**43**

magnitude is 2.9.

*Taimyr accretion belt.*

**Figure 3.**

*Recent Geodynamics and Seismicity of the European Arctic DOI: http://dx.doi.org/10.5772/10.5772/intechopen.80800*

Ridge, Franz Josef Land, Severnaya Zemlya, and Novaya Zemlya archipelagos. The unified seismic catalog for 1998–2017 contains data on earthquakes in the European sector of the Arctic region north of 70°N, recorded by at least three seismic stations.

*Spatial distribution of seismic events in the Severnaya Zemlya archipelago region on the map of main neotectonic and geomorphological elements of the Arctic by [21]. Lithospheric plates: (1) with late Precambrian basement, (2) with late Precambrian basement that was subjected to Hercynian tectonic deformations, (3) with Grenvillian basement, (4) Neoproterozoic Taimyr accretionary belt, (5) troughs with suboceanic type crust, (6) continental slope, and (7) oceanic crust. Neotectonic faults: (8) normal faults, (9) thrusts, (10) undetermined type, (11) structures boundaries, (12) earthquakes, and (13) seismic stations. I,* 

The unified seismic catalog consists of two parts: (a) primary epicentral parameters (basic data in **Table 1**) calculated for earthquakes according to priority zones and (b) alternative versions of the earthquake parameters (alternative data in **Table 1**). There are a number of earthquakes whose parameters were calculated only by the network. According to the catalog, earthquakes in the European Arctic range from 0.9 to 6.2 in magnitude, and the representative

The difficulty is that the predominant numbers of earthquakes are recorded by single station only and they cannot be included in the seismic catalog (about 20% of the total number) due to the poor quality of their processing. For example, the spatial distribution of earthquakes (red circles) recorded by the SVZ station during 2017 and processed using wave forms from other seismic stations installed in the Arctic region is shown in **Figure 3**, in which the earthquake processing results recorded by the SVZ station only are presented also. Location of earthquake epicenters is reliant on the hodograph type which is absent for the central part of the Arctic Ocean; as a result, we use the NOES [19] or BARENTS [20] regional hodographs. As a result, we can determine the most likely areas of their location roughly. However, even at the first approach, these epicenters are confined to the eastern part of Gakkel Ridge, the boundary of the

An excerpt from the unified catalog is presented in **Table 1**.

*Recent Geodynamics and Seismicity of the European Arctic DOI: http://dx.doi.org/10.5772/10.5772/intechopen.80800*

#### **Figure 3.**

*Arctic Studies - A Proxy for Climate Change*

**42**

**Basic data**

**Date** 08.10.2013 08.10.2013 09.10.2013 09.10.2013 16.10.2013 18.10.2013 20.10.2013 21.10.2013 22.10.2013 23.10.2013 23.10.2013 24.10.2013 24.10.2013 25.10.2013 25.10.2013

**Table 1.**

*Example of the unified seismic catalog.*

01:25:56.0 *Note: ASN, Arkhangelsk seismic network; Ml, local magnitude.*

80.33

40.06

1.9

Franz-Victoria Graben

ASN






22.48.21.7

76.60

9.08

2.6

Knipovich region

NORSAR

22:48:21.0

76.77

7.79


ASN

23:46:07.0

85.01

12.02

3.4

Gakkel Ridge

09.51.00.8

77.92

8.50

2.2

Knipovich region

NORSAR

ASN






09:51:01.0

77.88

8.58

3.2

ASN

14:17:00.0

85.25

26.91

3.0

Gakkel Ridge

10.31.04.8

77.76

8.56

3.7

Knipovich region

22.45.10.9

73.53

8.47

3.4

Mohns Ridge

19:04:49.8

86.28

49.91

3.3

Gakkel Ridge

16.49.53.8

72.33

2.73

3.4

Mohns Ridge

02:05:18.5

84.56

12.47


Gakkel Ridge

16:33:09.0

79.14

4.19

3.5

Knipovich region

ASN ASN NORSAR

ASN NORSAR NORSAR

ASN






10:31:08.9

77.78

8.99

3.9

ASN


























06:13:55.0

81.42

−1.63

3.6

Knipovich region

ASN






03.32.57.0

73.17

7.31

3.0

Mohns Ridge

09:10:26.0

84.06

4.51

3.3

Gakkel Ridge

01.39.58.9

74.29

15.23

4.3

Mohns Ridge

**Origin time**

**Lat**

**Lon**

**Ml**

**Region**

**Data source**

NORSAR

ASN NORSAR











01:40:00.0

74.44

15.30


ASN

**Origin time**

**Lat**

**Lon**

**Ml**

**Data source**

**Alternative data**

*Spatial distribution of seismic events in the Severnaya Zemlya archipelago region on the map of main neotectonic and geomorphological elements of the Arctic by [21]. Lithospheric plates: (1) with late Precambrian basement, (2) with late Precambrian basement that was subjected to Hercynian tectonic deformations, (3) with Grenvillian basement, (4) Neoproterozoic Taimyr accretionary belt, (5) troughs with suboceanic type crust, (6) continental slope, and (7) oceanic crust. Neotectonic faults: (8) normal faults, (9) thrusts, (10) undetermined type, (11) structures boundaries, (12) earthquakes, and (13) seismic stations. I, Taimyr accretion belt.*

Ridge, Franz Josef Land, Severnaya Zemlya, and Novaya Zemlya archipelagos. The unified seismic catalog for 1998–2017 contains data on earthquakes in the European sector of the Arctic region north of 70°N, recorded by at least three seismic stations. An excerpt from the unified catalog is presented in **Table 1**.

The unified seismic catalog consists of two parts: (a) primary epicentral parameters (basic data in **Table 1**) calculated for earthquakes according to priority zones and (b) alternative versions of the earthquake parameters (alternative data in **Table 1**). There are a number of earthquakes whose parameters were calculated only by the network. According to the catalog, earthquakes in the European Arctic range from 0.9 to 6.2 in magnitude, and the representative magnitude is 2.9.

The difficulty is that the predominant numbers of earthquakes are recorded by single station only and they cannot be included in the seismic catalog (about 20% of the total number) due to the poor quality of their processing. For example, the spatial distribution of earthquakes (red circles) recorded by the SVZ station during 2017 and processed using wave forms from other seismic stations installed in the Arctic region is shown in **Figure 3**, in which the earthquake processing results recorded by the SVZ station only are presented also. Location of earthquake epicenters is reliant on the hodograph type which is absent for the central part of the Arctic Ocean; as a result, we use the NOES [19] or BARENTS [20] regional hodographs. As a result, we can determine the most likely areas of their location roughly. However, even at the first approach, these epicenters are confined to the eastern part of Gakkel Ridge, the boundary of the

Kara plate, and fall into the zone of the North Taimyr deformation associated with tectonic fault. Seismicity around Severnaya Zemlya to all appearance is consequence of rifting processes emerging in the central seismically active zone of the Laptev Sea.

#### **Figure 4.**

*Contemporary seismicity in map showing main structural-tectonic elements in Barents Sea region (with data from [13, 22]). The figure covers seismic events (red dots) for 1998–2017, and for Novaya Zemlya we collected information from 1986. Notation: SA, St. Anna trough; HO, Hipopen-Olga trench; FV, Franz-Victoria trough; O, Orly trough. (1) basins: (a) central Barents and (b) north Barents. (2) Cratonic massifs: (a) Svalbard anteclise, (b) Pechora plate, and (c) north Siberian threshold. (3) marginal troughs: (a) Sedov trough, (b) Korotaikha Basin, and (c) Kos'yu-Rogovskaya Basin. (4) slopes of deep basins: (a) east Barents step zone, (b) south Barents step zone, (c) kola monocline, (d) East Novaya Zemlya monocline, (e) East Novaya Zemlya step zone, and (f) north Siberian step zone. (5) Baikalian folding: Pai-Khoy range. (6) North Kara syneclise. (7) Caledonian folding structures of Scandinavian peninsula. (8) Luninskaya saddle. (9) early Cimmerian folding of Novaya Zemlya. (10) deep basins (SB, south Barents; NB, north Barents; SK, South Kara). (11) boundaries of near-shelf and unclassified faults. (12) largest faults, strike-slips, and thrusts. (13) active spreading center. (14) superorder structures.*

**45**

*Recent Geodynamics and Seismicity of the European Arctic DOI: http://dx.doi.org/10.5772/10.5772/intechopen.80800*

cal peculiarities of this region (**Figure 4**):

ing morphostructures form [2, 6].

fold zone of the Scandinavian Peninsula.

Let us compare the spatial distribution of earthquakes from the unified seismic catalog and the positions of the main structural-tectonic elements in the Barents Sea region [13, 22]. By all data generalizing, we can reveal the following geodynami-

1.Seismic activation of the arch-block ascent of Svalbard, Franz Josef Land, and the Belyi Rise was caused by tectonic stresses for which tensional and shorten-

3.Particular weak earthquakes were revealed in the boundaries of tectonic structures in the Central Barents Basin (Norwegian shelf) and in the Caledonian

4.Singular seismic event was recorded on the slopes of deep basins, namely, in

5.Seismic activity was recorded in the marginal eastern part of the Barents Sea plate, in the Novaya Zemlya fold zone, and in the Sedov Trough [23, 24]. As an

example, here are two seismic events that occurred on Novaya Zemlya:

We also note the event recorded in the South Barents Basin in November 11, 2009 (t0 = 04:18:20.2, lat 71.52, lon 47.06, ML = 3.2) [24]. The geological feature of the event epicenter is the big thickness of the sedimentary cover (15–20 km), which

Thus, the earthquake distribution reflects the impact of the spreading processes and transforms movements and the result of tectonic stress fields generated directly in the marginal parts of the Barents Sea plate, with singular events being recorded in its central part. The maximum cluster of earthquakes is located along the central

years) makes it possible

i.October 11, 2010, t0 = 22:48:29, lat 76.18, lon 63.94, ML = 4.49.

ii.March 4, 2014, t0 = 04:42:36, lat 74.72, lon 56.72, ML = 3.3.

makes it unique and requires additional geophysical studies of the area.

**3. Correlation between heat flow, seismicity, and deep structure**

to consider the Earth's thermal component as constant [25]. There are two main heat sources: that supplied from the mantle (~60%) and that formed by radioactive

The time of thermal relaxation of the Earth (~1.5 × 109

axis of mid-ocean ridges (MOR).

i.January 23, 2012, t0 = 09:52:55.0, lat 80.11, lon 72.71, ML = 2.7. ii.November 10, 2002, t0 = 11:04:41.7, lat 70.47, lon 49.62, ML = 2.0. In addition, two earthquakes were recorded in the Kola monocline: i.November 5, 2002, t0 = 07:31:16.22, lat 70.17, lon 34.25, ML = 1.6. ii.November 2, 2000, t0 = 08:14:24.61, lat 70.12, lon 36.56, ML = 1.1.

2.Extension of the continental shelf margin and its elongation in the Franz Victoria, St. Anna, and Orly toughs [2, 6], and probably isostatic compensation of rapid sedimentation at the offshore boundary, is reflected as weak

seismicity within the ML magnitude range of 0.6–4.9.

the eastern Barents and southern Barents step zones:

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of the Laptev Sea.

Kara plate, and fall into the zone of the North Taimyr deformation associated with tectonic fault. Seismicity around Severnaya Zemlya to all appearance is consequence of rifting processes emerging in the central seismically active zone

*Contemporary seismicity in map showing main structural-tectonic elements in Barents Sea region (with data from [13, 22]). The figure covers seismic events (red dots) for 1998–2017, and for Novaya Zemlya we collected information from 1986. Notation: SA, St. Anna trough; HO, Hipopen-Olga trench; FV, Franz-Victoria trough; O, Orly trough. (1) basins: (a) central Barents and (b) north Barents. (2) Cratonic massifs: (a) Svalbard anteclise, (b) Pechora plate, and (c) north Siberian threshold. (3) marginal troughs: (a) Sedov trough, (b) Korotaikha Basin, and (c) Kos'yu-Rogovskaya Basin. (4) slopes of deep basins: (a) east Barents step zone, (b) south Barents step zone, (c) kola monocline, (d) East Novaya Zemlya monocline, (e) East Novaya Zemlya step zone, and (f) north Siberian step zone. (5) Baikalian folding: Pai-Khoy range. (6) North Kara syneclise. (7) Caledonian folding structures of Scandinavian peninsula. (8) Luninskaya saddle. (9) early Cimmerian folding of Novaya Zemlya. (10) deep basins (SB, south Barents; NB, north Barents; SK, South Kara). (11) boundaries of near-shelf and unclassified faults. (12) largest faults, strike-slips, and* 

*thrusts. (13) active spreading center. (14) superorder structures.*

**44**

**Figure 4.**

Let us compare the spatial distribution of earthquakes from the unified seismic catalog and the positions of the main structural-tectonic elements in the Barents Sea region [13, 22]. By all data generalizing, we can reveal the following geodynamical peculiarities of this region (**Figure 4**):


i.January 23, 2012, t0 = 09:52:55.0, lat 80.11, lon 72.71, ML = 2.7.

ii.November 10, 2002, t0 = 11:04:41.7, lat 70.47, lon 49.62, ML = 2.0.

In addition, two earthquakes were recorded in the Kola monocline:

i.November 5, 2002, t0 = 07:31:16.22, lat 70.17, lon 34.25, ML = 1.6.

ii.November 2, 2000, t0 = 08:14:24.61, lat 70.12, lon 36.56, ML = 1.1.

	- i.October 11, 2010, t0 = 22:48:29, lat 76.18, lon 63.94, ML = 4.49.

ii.March 4, 2014, t0 = 04:42:36, lat 74.72, lon 56.72, ML = 3.3.

We also note the event recorded in the South Barents Basin in November 11, 2009 (t0 = 04:18:20.2, lat 71.52, lon 47.06, ML = 3.2) [24]. The geological feature of the event epicenter is the big thickness of the sedimentary cover (15–20 km), which makes it unique and requires additional geophysical studies of the area.

Thus, the earthquake distribution reflects the impact of the spreading processes and transforms movements and the result of tectonic stress fields generated directly in the marginal parts of the Barents Sea plate, with singular events being recorded in its central part. The maximum cluster of earthquakes is located along the central axis of mid-ocean ridges (MOR).
