NEOTEKTONIKK

The Stuoragurra Fault Complex (SFC) constitutes the Norwegian part of the larger Lapland Province of postglacial faults in northern Fennoscandia. The 90 km long SFC consists of two separate fault systems: the Máze Fault (revised) System in the southwestern area and the Iešjávri Fault System to the northeast. The distance between the fault systems is 12 km. The faults dip at an angle of 30–75° to the SE. Here we present data from trenching of different fault sections. The trenching reveals deformed overburden in all 11 sites and inclusions of peat and organic bearing soil in the deformed and partly overrun loose deposits on the footwall in most of the sites. Radiocarbon dating of macro remains of plants located in buried and severely deformed sediment horizons indicates late Holocene ages for the (final) formation of the different fault segments, more specifically that the faulting at Fitnajohka and Máze in the Máze Fault System formed during earthquakes younger than c. 470-500 years ago.

Neotektonikk er studiet av bevegelser og deformasjon av jordskorpen, som er nåværende eller nyere i geologisk tid. Kartet viser jordskjelv, fokalmekanismer, spenningsmålinger, postglasiale forkastninger, landhevning, submarine skred, vulkaner, oppløft/erosjon og sedimentavleiring i det norske område. (Neotectonics is the study of motion and deformation of Earth's crust that are current or recent in geological time. The map displays earthquakes, focal mechanisms, stress observations, postglacial faults, glacial isostatic adjustment, submarine slides, volcanoes, uplift/erosion and sediment deposition in Norway and adjacent areas.) Kartet også vedlagt i NGU-rapport 2018.010

Berggrunnen i den nordøstre del av Skagerrak består av prekambriske grunn- fjellsbergarter, paleozoiske overflatebergarter, senpaleozoiske dypbergarter og mesozoiske sedimentære bergarter. De paleozoiske overflatebergartene i Skagerrak kan knyttes sammen med de kambro-siluriske sedimentære bergartene i Langesundområdet. Utbredelsen av Mesozoiske sedimentære bergarter er større enn det tidligere undersøkelser har vist. Senpaleozoiske og posttriassiske normalforkastninger (NØ-SV til N-S orientering) med sprang opptil 200 ms to- veis gangtid er registrert. I tillegg opptrer mulige neotektoniske forkast- ninger.

The postglacial Stuoragurra Fault (SF) lies within the regional Mierujav'ri- Sværholt Fault Zone which is located in the extensive Proterozoic terrain of inner Finnmark. To explore the SF at depth, 135 m of core-drilling was located between two previous percussion drillholes. More detailed information has been acquired from the coredrilling as compared with the previous drilling. The location of the main fault zones from the core-drilling is consistent with the results from the geophysical measurements. The two uppermost zones are coinci- ding with 2-3 m wide zones of brecciation. The postglacial fault coincides with the lowermost of these zones and is composed of several thin (a few cm wide) zones of fault gouge within a 1.5 metre wide zone at a depth of 37 metres. We can conclude that the postulated listric shape of the fault is most likely to be the corrrected model. The annual average changes in elevation of benchmarks based on precision levelling in 1954 and later in 1975 along the old road from Alta to Kautokeino have shown a significant deviation from the general postglacial upheaval of Fennoscandia. Instead of an increasing uplift from 2 mm/year in Alta to 5 mm/year in Kautokeino as is generally indicated on land upheaval maps of Fennoscandia, a subsidence of the inland area was observed. During Quaternary geological mapping in the Iesjav'ri area one submerged shoreline has been observed at the southern margin of this lake. The shoreline is located roughly a few dm below the present water-level, and we think that this indicates that a vertical crustal movement with a N-S gradient opposite to that of the general postglacial rebound has occured during the last few hundred years. Relevelling of the profile of 1954 and 1975, however, did not reproduce this pattern. We therefore recommend that a system- atic mapping of the shorelines around Iesjav'ri should be carrie

Grunnseismiske undersøkelser med luftkanon (Sleeve gun) er utført i området Arendal - Kristiansand, fra kysten ut til midtlinjen mot Danmark. Undersøk- elsene viser at berggrunnen i området består av prekambriske grunnfjells- bergarter, overleiret av antatt tidligpaleozoiske (kambro-siluriske) og meso- zoiske (triassiske til krittassiske) sedimentære bergarter. De tidligpaleo- zoiske bergartene ligger stort sett med vinkeldiskordans på grunnfjellet, men stedvis er grensen normalforkastninger. De mesozoiske bergartene overleirer med vinkeldiskordans forkastede og skråstilte tidligpaleozoiske bergarter. Også de mesozoiske bergartene er påvirket av normalforkastninger. En av disse forkast- ningene ser ut til å ha vært aktiv i kvartær tid, men studier av jordskjelvdata fra 1964 - 1992 viser ingen klar sammenheng mellom slike neotektoniske struk- turer og registrerte jordskjelv.

Bleikvassli Gruber ble den 25.september 1997 utsatt for setninger og vanninn- trenging. Dette resulterte i at gruva ble fylt med vann i løpet av en uke og at en 10 meter høy vannkraftsdam tilhørende Statkraft ble ødelagt. NTNU, NORSAR og NGU har fått i oppgave av Gjensidige Forsikring å vurdere årsakene til setningen i gruva, og spesielt muligheten for at et jordskjelv som er registrert i området kan ha utløst setningen. Denne rapporten utgjør NGU's bidrag til vurderingene. Det vil bli utarbeidet en felles konklusjon fra de tre institusjonene.

GPR measurements have been carried out across presumed postglacial faults at Kåfjord, Troms and Fidnajohka,Finnmark,Norway. The purpose of the measurements was to map the subsurface extension of the faults, and to clarify whether the Nordmannsvik fault (Kåfjord) is a gravitational fault or a true tectonic, postglacial fault.

Neotectonic crustal deformations have been reported at a large number of locations in Norway (both on local and regional scales). The NEONOR Project represents a national effort by several national research and mapping institutions to investigate these phenomena through a multidiciplinary approach. Both the industry and the Norwegian Research Council contribute with major financial support. The main objectives of the NEONOR. Project are to systematically collect data, and to provide answers to the questions: 1) How can recent crustal deformation be characterised in time and space? 2) What processes cause the neotectonic crustal deformations? 3) What are the implications for migration and occurrence of fluids (especi- ally hydrocarbons and groundwater) in bedrock? 4) What are the implications for geohazard related to constructing sensitive installations like pipelines, gas-terminals and hydropower-plants. The initial phase of the project includes a systematic collection and charac- terisation of known deformations. New geological, geodetic and seismological data are, however, also acquired.