CELEBRATION 2000 seismic experiment

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An overview of recent seismic refraction experiments in Central Europe.

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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

Domains of Archean mantle lithosphere deciphered by seismic anisotropy- initial results from the LAPNET array in northern Fennoscandia

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Structure of the Suasselka postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

Understanding the inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating the continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in the northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the presentday seismicity of the Suasselka postglacial fault (SPGF), which was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised an area of about 20 to 100 km and consisted of eight short-period and four broadband three-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September 2011-May 2013. Recordings of the array have being analysed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittila gold mine. As a result, we found a number of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single-station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1-1 Hz and to calculate corresponding surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curve inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low-velocity region as a non-healed mechanically weak fault damage zone (FDZ) formed due to the last major earthquake that occurred after the last glaciation.Peer reviewe

Underground Vertical Seismic Profiling with Conventional and Fiber-Optic Systems for Exploration in the Kylylahti Polymetallic Mine, Eastern Finland

Seismic reflection methods have been used for the exploration of mineral resources for several decades. However, despite their unmatched spatial resolution and depth penetration, they only have played a minor role in mineral discoveries so far. Instead, mining and exploration companies have traditionally focused more on the use of potential field, electric and electromagnetic methods. In this context, we present a case study of an underground Vertical Seismic Profiling (VSP) experiment, which was designed to image a (semi-)massive sulfide deposit located in the Kylylahti polymetallic mine in eastern Finland. For the measurement, we used a conventional VSP with three-component geophones and a novel fiber-optic Distributed Acoustic Sensing (DAS) system. Both systems were deployed in boreholes located nearby the target sulfide deposit, and used in combination with an active seismic source that was fired from within the underground tunnels. With this setup, we successfully recorded seismic reflections from the deposit and its nearby geological contrasts. The recording systems provided data with a good signal-to-noise ratio and high spatial resolution. In addition to the measurements, we generated a realistic synthetic dataset based on a detailed geological model derived from extensive drilling data and petrophysical laboratory analysis. Specific processing and imaging of the acquired and synthetic datasets yielded high-resolution reflectivity images. Joint analysis of these images and cross-validation with lithological logging data from 135 nearby boreholes led to successful interpretation of key geological contacts including the target sulfide mineralization. In conclusion, our experiment demonstrates the value of in-mine VSP measurements for detailed resource delineation in a complex geological setting. In particular, we emphasize the potential benefit of using fiber-optic DAS systems, which provide reflection data at sufficient quality with less logistical effort and a higher acquisition rate. This amounts to a lower total acquisition cost, which makes DAS a valuable tool for future mineral exploration activities.Peer reviewe

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

Full-Scale Crustal Interpretation of Kokkola–Kymi (KOKKY) Seismic Profile, Fennoscandian Shield

The Kokkola–Kymi Deep Seismic Sounding profile crosses the Fennoscandian Shield in northwest-southeast (NW–SE) direction from Bothnian belt to Wiborg rapakivi batholith through Central Finland granitoid complex (CFGC). The 490-km refraction seismic line is perpendicular to the orogenic strike in Central Finland and entirely based on data from quarry blasts and road construction sites in years 2012 and 2013. The campaign resulted in 63 usable seismic record sections. The average perpendicular distance between these and the profile was 14 km. Tomographic velocity models were computed with JIVE3D program. The velocity fields of the tomographic models were used as starting points in the ray tracing modelling. Based on collected seismic sections a layer-cake model was prepared with the ray tracing package SEIS83. Along the profile, upper crust has an average thickness of 22 km average, and P-wave velocities (Vp) of 5.9–6.2 km/s near the surface, increasing downward to 6.25–6.40 km/s. The thickness of middle crust is 14 km below CFGC, 20 km in SE and 25 km in NW, but Vp ranges from 6.6 to 6.9 km/s in all parts. Lower crust has Vp values of 7.35–7.4 km/s and lithospheric mantle 8.2–8.25 km/s. Moho depth is 54 km in NW part, 63 km in the middle and 43 km in SW, yet a 55-km long section in the middle does not reveal an obvious Moho reflection. S-wave velocities vary from 3.4 km/s near the surface to 4.85 km/s in upper mantle, consistently with P-wave velocity variations. Results confirm the previously assumed high-velocity lower crust and depression of Moho in central Finland.Peer reviewe

Crustal Architecture of the Inverted Central Lapland Rift Along the HUKKA 2007 Profile

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