Heat flow, seismic cutoff depth and thermal modeling of the Fennoscandian Shield

Being far from plate boundaries but covered with seismograph networks, the Fennoscandian Shield features an ideal test laboratory for studies of intraplate seismicity. For this purpose, this study applies 4190 earthquake events from years 2000–2015 with magnitudes ranging from 0.10 to 5.22 in Finnish and Swedish national catalogues. In addition, 223 heat flow determinations from both countries and their immediate vicinity were used to analyze the potential correlation of earthquake focal depths and the spatially interpolated heat flow field. Separate subset analyses were performed for five areas of notable seismic activity: the southern Gulf of Bothnia coast of Sweden (area 1), the northern Gulf of Bothnia coast of Sweden (area 2), the Swedish Norrbotten and western Finnish Lapland (area 3), the Kuusamo region of Finland (area 4) and the southernmost Sweden (area 5). In total, our subsets incorporated 3619 earthquake events. No obvious relation of heat flow and focal depth exists, implying that variations of heat flow are primarily caused by shallow lying heat producing units instead of deeper sources. This allows for construction of generic geotherms for the range of representative palaeoclimatically corrected (steady-state) surface heat flow values (40–60 mWm−2). The one-dimensional geotherms constructed for a three-layer crust and lithospheric upper mantle are based on mantle heat flow constrained with the aid of mantle xenolith thermobarometry (9–15 mWm−2), upper crustal heat production values (3.3–1.1 μWm−3), and the brittle-ductile transition temperature (350 °C) assigned to the cutoff depth of seismicity (28 ± 4 km). For the middle and lower crust heat production values of 0.6 and 0.2 μWm−3 were assigned, respectively. The models suggest a Moho temperature range of 460 to 500 °C.Being far from plate boundaries but covered with seismograph networks, the Fennoscandian Shield features an ideal test laboratory for studies of intraplate seismicity. For this purpose, this study applies 4190 earthquake events from years 2000–2015 with magnitudes ranging from 0.10 to 5.22 in Finnish and Swedish national catalogues. In addition, 223 heat flow determinations from both countries and their immediate vicinity were used to analyse the potential correlation of earthquake focal depths and the spatially interpolated heat flow field. Separate subset analyses were performed for five areas of notable seismic activity: the southern Gulf of Bothnia coast of Sweden (area 1), the northern Gulf of Bothnia coast of Sweden (area 2), the Swedish Norrbotten and western Finnish Lapland (area 3), the Kuusamo region of Finland (area 4) and the southernmost Sweden (area 5). In total, our subsets incorporated 3619 earthquake events. No obvious relation of heat flow and focal depth exists, implying that variations of heat flow are primarily caused by shallow lying heat producing units instead of deeper sources. This allows for construction of generic geotherms for the range of representative palaeoclimatically corrected (steady-state) surface heat flow values (40–60 mW m−2). The 1-D geotherms constructed for a three-layer crust and lithospheric upper mantle are based on mantle heat flow constrained with the aid of mantle xenolith thermobarometry (9–15 mW m−2), upper crustal heat production values (3.3–1.1 μWm−3) and the brittle-ductile transition temperature (350 °C) assigned to the cut-off depth of seismicity (28 ± 4 km). For the middle and lower crust heat production values of 0.6 and 0.2 μWm−3 were assigned, respectively. The models suggest a Moho temperature range of 460–500 °C.Peer reviewe

Automatic data processing and analysis system for monitoring region around a planned nuclear power plant

The Institute of Seismology of University of Helsinki is building a new local seismic network, called OBF network, around planned nuclear power plant in Northern Ostrobothnia, Finland. The network will consist of nine new stations and one existing station. The network should be dense enough to provide azimuthal coverage better than 180° and automatic detection capability down to ML −0.1 within a radius of 25 km from the site.The network construction work began in 2012 and the first four stations started operation at the end of May 2013. We applied an automatic seismic signal detection and event location system to a network of 13 stations consisting of the four new stations and the nearest stations of Finnish and Swedish national seismic networks. Between the end of May and December 2013 the network detected 214 events inside the predefined area of 50 km radius surrounding the planned nuclear power plant site. Of those detections, 120 were identified as spurious events. A total of 74 events were associated with known quarries and mining areas. The average location error, calculated as a difference between the announced location from environment authorities and companies and the automatic location, was 2.9 km. During the same time period eight earthquakes between magnitude range 0.1–1.0 occurred within the area. Of these seven could be automatically detected. The results from the phase 1 stations of the OBF network indicates that the planned network can achieve its goals.Abstract. The Institute of Seismology of University of Helsinki is building a new local seismic network, called OBF network, around planned nuclear power plant in Northern Ostrobothnia, Finland. The network will consist of nine new stations and one existing station. The network should be dense enough to provide azimuthal coverage better than 180° and automatic detection capability down to ML −0.1 within a radius of 25 km from the site. The network construction work began in 2012 and the first four stations started operation at the end of May 2013. We applied an automatic seismic signal detection and event location system to a network of 13 stations consisting of the four new stations and the nearest stations of Finnish and Swedish national seismic networks. Between the end of May and December 2013 the network detected 214 events inside the predefined area of 50 km radius surrounding the planned nuclear power plant site. Of those detections, 120 were identified as spurious events. A total of 74 events were associated with known quarries and mining areas. The average location error, calculated as a difference between the announced location from environment authorities and companies and the automatic location, was 2.9 km. During the same time period eight earthquakes between magnitude range 0.1–1.0 occurred within the area. Of these seven could be automatically detected. The results from the phase 1 stations of the OBF network indicates that the planned network can achieve its goals.Peer reviewe

A benchmark case study for seismic event relative location

'Precision seismology' encompasses a set of methods which use differential measurements of time-delays to estimate the relative locations of earthquakes and explosions. Delay-times estimated from signal correlations often allow far more accurate estimates of one event location relative to another than is possible using classical hypocentre determination techniques. Many different algorithms and software implementations have been developed and different assumptions and procedures can often result in significant variability between different relative event location estimates. We present a Ground Truth (GT) dataset of 55 military surface explosions in northern Finland in 2007 that all took place within 300 m of each other. The explosions were recorded with a high signal-to-noise ratio to distances of about 2 degrees, and the exceptional waveform similarity between the signals from the different explosions allows for accurate correlation-based time-delay measurements. With exact coordinates for the explosions, we are able to assess the fidelity of relative location estimates made using any location algorithm or implementation. Applying double-difference calculations using two different 1-D velocity models for the region results in hypocentre-to-hypocentre distances which are too short and it is clear that the wavefield leaving the source region is more complicated than predicted by the models. Using the GT event coordinates, we are able to measure the slowness vectors associated with each outgoing ray from the source region. We demonstrate that, had such corrections been available, a significant improvement in the relative location estimates would have resulted. In practice we would of course need to solve for event hypocentres and slowness corrections simultaneously, and significant work will be needed to upgrade relative location algorithms to accommodate uncertainty in the form of the outgoing wavefield. We present this data set, together with GT coordinates, raw waveforms for all events on six regional stations, and tables of time-delay measurements, as a reference benchmark by which relative location algorithms and software can be evaluated.Peer reviewe

BABEL3&3a : Crustal-Scale Structures of the Precambrian Svecofennian Accretionary Orogen in the Fennoscandian Shield

obs typo in the title: The title will be changed to FIRE3&3A: Crustal-Scale Structures of the Precambrian Svecofennian Accretionary Orogen in the Fennoscandian Shield. in the second printed version.Peer reviewe

Seismic velocity models based on wide-angle refraction and reflection profiles in Finland

Laajakulmaiseen taittumis- ja heijastusluotaukseen perustuvat seismiset tutkimukset (WARR) ovat olleet keskeisessä roolissa Fennoskandian kilven rakenteellisessa tutkimuksessa. 1980-luvulta lähtien niissä on kerätty tieteellisesti arvokasta dataa sekä tuotettu seismisiä kuoren nopeusmalleja, jotka eivät ole aiemmin olleet julkisesti saatavilla. Tämän raportin kuvailemassa työssä vanhat nopeusmallit ja laajakulmasektiot muokattiin helpommin käytettäviin formaatteihin ja tallennettiin turvallisesti tutkimusdatan säilytyspalvelu IDAan. IDAssa tutkimusdata on avoimesti saatavilla ja tietokokonaisuuksille on IDAssa pysyvät DOI-tunnisteet. Säilötyn datan käyttö on määritelty Creative Commons By Attribution version 4.0 -lisenssillä. Sama data tulee myös saataville Geologian tutkimuskeskuksen Hakku-palveluun. Saatavilla olevat kaksiulotteiset nopeusmallit on tallennettu muotoon, jossa seisminen nopeus on määritetty koordinaattien pisteissä eri syvyyksillä tekstitiedostoissa. Laajakulmasektiot on tallennettu standard IBM SEG-Y -muotoisina. Tässä raportissa kuvaillaan taittumis- ja heijastusluotaustutkimuksia, saatavilla olevaa dataa sekä sen käyttöä.Seismic wide-angle refraction and reflection (WARR) surveys have been crucial in the study of the structure of the Fennoscandian shield. The valuable data and crustal seismic velocity models of major WARR studies from the 1980s to the present day have not been previously available to the public. In the work described in this report, the velocity models and wide-angle data were re-formatted to more accessible data formats and safely stored in the IDA Research Data Storage service for open access and data identification through Digital Object Identifiers. Data use is allowed under the Creative Commons By Attribution version 4.0 license. The data is also made available through the Hakku service of the Geological Survey of Finland. The velocity models are stored in a universal velocity point format in text files and wide-angle sections are stored in standard IBM SEG-Y format. A general description of WARR studies, available data and data use is given in this report

Seismic velocity models based on wide-angle refraction and reflection profiles in Finland

Laajakulmaiseen taittumis- ja heijastusluotaukseen perustuvat seismiset tutkimukset (WARR) ovat olleet keskeisessä roolissa Fennoskandian kilven rakenteellisessa tutkimuksessa. 1980-luvulta lähtien niissä on kerätty tieteellisesti arvokasta dataa sekä tuotettu seismisiä kuoren nopeusmalleja, jotka eivät ole aiemmin olleet julkisesti saatavilla. Tämän raportin kuvailemassa työssä vanhat nopeusmallit ja laajakulmasektiot muokattiin helpommin käytettäviin formaatteihin ja tallennettiin turvallisesti tutkimusdatan säilytyspalvelu IDAan. IDAssa tutkimusdata on avoimesti saatavilla ja tietokokonaisuuksille on IDAssa pysyvät DOI-tunnisteet. Säilötyn datan käyttö on määritelty Creative Commons By Attribution version 4.0 -lisenssillä. Sama data tulee myös saataville Geologian tutkimuskeskuksen Hakku-palveluun. Saatavilla olevat kaksiulotteiset nopeusmallit on tallennettu muotoon, jossa seisminen nopeus on määritetty koordinaattien pisteissä eri syvyyksillä tekstitiedostoissa. Laajakulmasektiot on tallennettu standard IBM SEG-Y -muotoisina. Tässä raportissa kuvaillaan taittumis- ja heijastusluotaustutkimuksia, saatavilla olevaa dataa sekä sen käyttöä.Seismic wide-angle refraction and reflection (WARR) surveys have been crucial in the study of the structure of the Fennoscandian shield. The valuable data and crustal seismic velocity models of major WARR studies from the 1980s to the present day have not been previously available to the public. In the work described in this report, the velocity models and wide-angle data were re-formatted to more accessible data formats and safely stored in the IDA Research Data Storage service for open access and data identification through Digital Object Identifiers. Data use is allowed under the Creative Commons By Attribution version 4.0 license. The data is also made available through the Hakku service of the Geological Survey of Finland. The velocity models are stored in a universal velocity point format in text files and wide-angle sections are stored in standard IBM SEG-Y format. A general description of WARR studies, available data and data use is given in this report

Lithospheric studies along seismic profile KOKKY, between Gulf of Bothnia and Gulf of Finland, Baltic Shield

Volume: 19 Host publication title: Geophysical Research AbstractsNon peer reviewe

The Finnish National Seismic Network : Toward Fully Automated Analysis of Low‐Magnitude Seismic Events

We present an overview of the seismic networks, products, and services in Finland, northern Europe, and the challenges and opportunities associated with the unique combination of prevailing crystalline bedrock, low natural intraplate seismic background activity, and a high level of anthropogenic seismicity. We introduce national and local seismic networks, explain the databases, analysis tools, and data management concepts, outline the Finnish macroseismic service, and showcase data from the 2017 M 3.3 Liminka earthquake in Ostrobothnia, Finland.Peer reviewe

Retrievals of Riming and Snow Density From Vertically Pointing Doppler Radars

Retrievals of ice and snow are made from Ka- and W-band zenith-pointing Doppler radars at Hyytiala, Finland, during the snow experiment component of the Biogenic Aerosols: Effects on Clouds and Climate (2014) field campaign. In a novel optimal estimation retrieval, mean Doppler velocity is exploited to retrieve a density factor parameter, which modulates the mass, shape, terminal velocity, and backscatter cross sections of ice particles. In a case study including aggregate snow and graupel we find that snow rate and ensemble mean ice density can be retrieved to within 50% of in situ measurements at the surface using dual-frequency Doppler radar retrievals. While Doppler measurements are essential to the retrieval of particle density, the dual-frequency ratio provides a strong constraint on particle size. The retrieved density factor is strongly correlated with liquid water path, indicating that riming is the primary process by which the density factor is modulated. Using liquid water path as a proxy for riming, profiles classified as unrimed snow, rimed snow, and graupel exhibit distinct features characteristic of aggregation and riming processes, suggesting the potential to make estimates of process rates from these retrievals. We discuss the potential application of the technique to future satellite missions. Plain Language Summary Ground-based radar measurements of ice clouds and snow are used to estimate the size, number, and density of snowflakes. Doppler velocity measurements of particle fall speeds are used to estimate the mass and shape of the snow particles. The properties of snow estimated using radar compare well against measurements of particles at the surface and estimates of the amount of liquid water in the atmosphere; the presence of liquid water relates to the potential for riming, in which snowflakes increase in density and fall speed by collecting and freezing liquid droplets. More accurate estimates of snow density from ground-based and satellite radars help to improve global estimates of precipitation and snow accumulation and the representation of clouds and snow in weather and climate models.Peer reviewe

Linking vgll3 genotype and aggressive behaviour in juvenile Atlantic salmon (Salmo salar)

We tested the possibility that vgll3, a gene linked with maturation age in Atlantic salmon (Salmo salar), may be associated with behaviour by measuring aggressiveness and feeding activity in 380 juveniles with different vgll3 genotypes. Contrary to our prediction, individuals with the genotype associated with later maturation (vgll3*LL) were significantly more aggressive than individuals with the genotype associated with earlier maturation (vgll3*EE). Individuals with higher aggression were also significantly lighter in colour and had higher feeding activity. Although higher aggression was associated with higher feeding activity, there was no association between feeding activity and vgll3 genotype. Increased aggression of vgll3*LL individuals was independent of their sex and size, and genotypes did not differ in their condition factor. These results imply that aggressive behaviour may have an energetic cost impairing growth and condition, especially when food cannot be monopolized. This may have implications for individual fitness and aquaculture practices.Peer reviewe