NEOTEKTONIKK

This report constitutes the itinerary for a two-day field excursion to postglacial faults and rock avalanches in northern Troms and western Finnmark. Day 1 has three stops along the route from Tromsø to Nordmannvikdalen in Kåfjord, Troms. Day 2 has two localities along the Stuoragurra fault in Masi. The Nordmannvikdalen and Stuoragurra faults are part of the Lapland province of postglacial faults which consists of nine reverse faults and two normal faults in northern Fennoscandia. The faulting was most likely associated with major earthquakes with magnitudes of 7-8 on Richters scale.
The reverse Stuoragurra fault has a length of 80 km and a scarp height of maximum 7 metres. The fault is located within the regional Mierujavri Sværholt Fault Zone which is of Proterozoic age. The fault cross-cuts glaciofluvial deposits and is consequently younger than 9600 C14 yars. During 1998, two trenches were made across the Stuoragurra Fault, between Kautokeino and Masi. For the first time, the fault was directly observed in the bedrock. The fault did not penetrate the overlying glacial materials, but rather folded them, forming a blind thrust. Large liquefaction and other deformation structures were found in the glaciofluvial sediments in both trenches. Veins of angular and subangular pebbles from the local bedrock (Masi Quartzite) penetrate more than 10 metres laterally from the thrust plane and into the sediments in the footwall. It is thought that these veins were possibly injected during the fault activity. Deformational structures seen in the trench can be explained as a result of one major fault event.
The normal Nordmannvikdalen fault has a length of 1.5-2 km and a scarp height of one metre. The fault is most likely due to a deep-seated deformation, but a gravitational origin can not be ruled out. Two rock avalanches in Nordnesfjellan and Manndalen in Lyngenfjorden, northern Troms are described. The avalanches in the area were most likely triggered by the large earthquakes which were formed during the postglacial faulting.

The NEONOR project represents a national effort by several national research
and mapping institutions to study neotectonic phenomena through a
multidisciplinary approach. Information on present land uplift, seismiticiy,
rock stress and postglacial faults is compiled in a 1:3 million map of Norway
and adjacent areas. There is a good evidence for conjugate set of normal
faults perpendicular to the extensive system of NE-SW trending reverse faults
in northern Fennoscandia. (Forkortet)

Geodynamic modelling of the present crustal uplift indicates that the uplift of western Norway and northern Norway is partly due to other mechanisms that the glacioisostatic rebound. We have also deduced a new model based on the 'seismic pumping' mechanism to explain the observed correlation between land uplift and groundwater yield in Norway. Rock avalanches and landslides represent the most hazardous effects of earthquakes in Norway with its mountainous terrain, deep fjords and relatively large areas with unstable quick-clay. New seismic mini-arrays in the Ranafjorden area and the northern North Sea have sharply defined zones of increased seismicity. A total of 350 earthquakes have been detected in the outer Ranafjord area during the project period (2 1/2 years) with magnitudes up to 2.8. This is very high onshore Baltic Shield areas. The return perios of magnitude 6 and 5 earthquakes have been estimated to 1500 and 130 years respectively. The M6 earthquake in 1819 in Mo i Rana triggered several rockfalls and a landslide.

The NEONOR project represents a national effort by several national research and mapping institutions to study neotectonic phenomena through a multi-diciplinary approach. Information on present land uplift, seismicity, rock stress and postglacial faults is compiled in a 1:3 million map of Norway and adjacent areas.

The present report aims on graviational slope failures in Møre & Romsdal andSogn & Fjordane counties. It presents selected examples and an overview of theregional occurrence of rock avalanches and other bedrock failures. The datadiscussed here have been collected through several NGU projects since 1995, thepresent one being: "Regional landslide occurrences and possible post-glacialearthquake activity in northwestern Norway" (phase D); a project funded byNorsk Hydro ASA and NGU. Geological studies show that several areas in westernNorway have been affected by a significant number of large rock avalanchesthroughout the postglacial period. The geographic distribution of rockavalanches and gravitational bedrock fractures clearly shows a clustering inspecific zones, with the highest frequency in the inner fjord areas of westernNorway. The highest number of such features are also found in two smaller areasof Møre & Romsdal, in a more coastal position around Oterøya and Syvdsfjorden.A group of gravitational failures also occur in the phyllite areas in Aurland,Sogn og Fjordane.The age of the features is still poorly constrained, but a review of existingdatashed som light on the time-frame. The bedrock fractures and rock avalanchesaround Oterøya probably occurred shortly after the deglaciation. The timeconstraint is weak for the coastal area further southwest, but the data pointto several events of different ages. Several dated events in the inner fjordareas of Møre & Romsdal suggests high rock-avalanche activity during the secondhalf of the Holocene. This can be seen in context with a neotectonic fault(Berill fault) in Innfjorden, west of Romsdalen. The Berill fault is at leastyounger than the Younger Dryas period (11500 cal. BP). Some dates of rockavalanches around 3000 cal. BP in Innfjorden and Tafjorden indicate arelationship with the faulting event. The data from Aurland in Sogn & Fjordanesuggest that the gravitational failures in the phyllite area are related to twostages, one shortly after the deglaciation and a smaller event at about 3000cal. BP.Review of historical earthquakes indicate that the triggering of large rockavalanches and deep-seated bedrock failures requires a minimum earthquakemagnitude of about 6.0-6.5 on the Richter scale. The distinct clustering offeatures in specific zones indicates that large earthquake played a role. Therecently detected neotectonic fault (Berill fault) further help to explain somerock avalanches in the fjords of Møre og Romsdal. The fault is situated in thearea of the highest land-uplift gradient in western Norway, which could be thecause for crustal instability. Earthquakes related to this fault were probablyof the order of M 6.5. The spatial distribution of the clustering in Møfre &Romsdal seems to fit a relationship between aerial extent of landslides andearthquake magnitudes of M 6.5 In conclusion, future work should especiallyaim on further investigations of possible neotectonic faults, in order to get abetter understanding of the palaeoseismic activity.

This report describes a one-day field trip to observe relationships between brittle normal faults and landscape evolution on a post-glacial passive margin. The hypothesis that the great escarpment of western Norway was shaped after the main rift phases, through reactivation of inherited faults inboard of sharply tapering crystalline crust was based on combinations of apatite fission-track dating, structural geology, topographic analysis and interpretation of offshore deep seismic and potential field data. Comprised by nine stops, the trip begins in Molde and ends in Trondheim. The total driving time is a little over five hours.

The project is aimed to achieve a better understanding of shallow geological/seabed conditions and processes to support technical and environmental aspects of exploration and production along the western margin of the Hammerfest Basin and Loppa High, and in the Tromsø Basin/Ingøydjupet area.
The project has had the following subgoals:
- Detection of water column gas anomalies at selected pockmark locations
- Identification of neotectonic features
The project has the following results:
- A total of 16 gas flares were identified using the water column data collected using the multibeam echosounder system during cruises in 2008 and 2009. The gas flares are observed to occur mainly outside the pockmark areas along regional faults where the seabed is incised by iceberg ploughmarks. No correlation is found between flare occurrence and tidal cycles but a full tidal cycle monitoring has not been carried out to substantiate it.
- Pockmarks are interpreted to be formed after deglaciation due to melting of gas hydrates. They are probably not active at present.
- Multiple fault/lineament locations were identified. They are observed to be of reverse faults with thrusted part along the western side and deeper basin with larger sediment thickness along the eastern side. The faults are observed to be covered by undisturbed glaciomarine/marine sediments deposited after the last deglaciation, indicating little neotectonic activity.

This project aims to achieve a better understanding of shallow geological/seabed conditions and processes to support technical and environmental aspects of exploration and production in the Alvheim and Utsira High areas in the North Sea and the Harstad Basin in the SW Barents Sea.

The individual papers and reports from the NEONOR2 project (Neotectonics in Nordland - implications for petroleum exploration) are compiled in the present report. The results are also summarized and compared to the results from previous research projects (e.g. NEONOR project 1997-2000). The NEONOR2 project was a collaboration project between NGU, Kartverket, NORSAR, Norut, NPD and the universities of Bergen and Luleå. The project was in addition sponsored by the Norwegian Research Council and eleven petroleum companies. NEONOR2 investigated neotectonic phenomena onshore and offshore through a multidisciplinary approach including geological, seismological and geodetic studies combined with rock mechanics, applied geophysics and numerical modeling.

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 three separate fault systems; the Fitnajohka Fault
System in the southwest, the Máze Fault System in the central area and the Iešjávri Fault System to the northeast.
The distance between the fault systems is 7–12 km. The faults dip at an angle of 30–75° to the SE and can be traced
on reflection seismic data to a depth of c. 500 m. Here we present data from trenching of different sections of the
fault complex. The trenching reveals deformed overburden in all 8 sites, and inclusions of peat and organic bearing
soil in the deformed and partly overrun loose deposits on the footwall in all but one site.
Radiocarbon dating of organic matter 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 Máze, Fitnajohka
and Iešjávri (Guovziljohka) Faults formed during earthquakes younger than 600 years, younger than 1,300 years and
younger than 4,000 years BP, respectively. The youngest age is at the Masi (Mazé) site, where plant macrofossil data
from the buried sediments suggest an early to late Holocene vegetation cover. The reverse displacement of c. 9 m
and fault system lengths of 14 and 21 km of the two southernmost fault systems indicate a moment magnitude of c. 7
on Richter’s scale if just one rupture event is associated with each of these systems. The fault rupture with length and
height of fault scarps, and injections and throw-out of angular boulders and wedges of fault breccia reaching up to
15–20 m away from the fault scarp give the most distinct expressions of the associated earthquake magnitude with
the SFC. A total of c. 60 landslides, some of these possibly earthquake-induced, has been recorded along the SF.
Initial breakage or fracturing of bedrock with a potential to lead to larger rock avalanches are also recorded at a few
places in or close to the fault zone.