Acoustic Seismic Survey in the Sea Area Close to Olkiluoto in 2015

Transkriptio

1 Working Report Acoustic Seismic Survey in the Sea Area Close to Olkiluoto in 2015 Kimmo Alvi, Joonas Virtasalo October 2016 POSIVA OY Olkiluoto FI EURAJOKI, FINLAND Phone (02) (nat.), ( ) (int.) Fax (02) (nat.), ( ) (int.)

2 Working Report Acoustic Seismic Survey in the Sea Area Close to Olkiluoto in 2015 Kimmo Alvi, Joonas Virtasalo Geological Survey of Finland October 2016 Working Reports contain information on work in progress or pending completion.

3 ABSTRACT Geological survey of Finland (GTK) conducted acoustic- seismic survey in the sea area close to Olkiluoto between The aim of the work was to study geological features of the area and post- glacial disturbance structures in particular. The survey area covered ~120 km 2 and the total length of survey lines was 257 km. Survey was done with R/V Geomari. The acoustic seismic methods provided highly detailed information of the geology of the work area. There was a pronounced NW-SE oriented trend in bedrock forms and sediment pattern throughout the survey area. Combination of GTK's lineament interpretation and bedrock bathymetry showed good correlation. Bathymetric depressions were interpreted as bedrock fracture zones. Several disturbance structures were identified from high frequency echo sounder profiles. They included faulting structures and funnel- like dewatering structures, caused by liquefication of silty layers within glacial clay unit. Their stratigraphic position was limited in an acoustic unit that represented varved glacial clays and their occurrence was concentrated near and along the bedrock fracture zones. Deposition of glacial clays took place after deglaciation between cal years BP and therefore the origin of disturbances is post-glacial. Most plausible explanation for their formation is one or several palaeoseismic events about 200 years after the deglaciation. Keywords: Acoustic-seismic survey, Olkiluoto, Disturbance structures.

4 Akustis- seismiset luotaukset Olkiluodon läheisellä merialueella, TIIVISTELMÄ Geologian tutkimuskeskus (GTK) suoritti akustis- seismisiä luotauksia Olkiluodon läheisellä merialueella Luotausten tarkoituksena oli selvittää alueen geologisia piirteitä, kallioperän topografiaa ja post- glasiaalisia häiriörakenteita. Luodatun alueen pinta-ala oli n. 120 km 2 ja luotauslinjojen yhteispituus 257 km. Luotaukset tehtiin T/A Geomarilla. Akustis- seismisillä menetelmillä saatiin yksityiskohtaista tietoa luotausalueen geologiasta. Alueella oli selvä Luode- Kaakko suuntautuneisuus, mikä kuvastui sekä kallioperän topografiaan, että pintasedimentin jakautumiseen. GTK:n lineamenttitulkinnan ja kallioperän muotojen välillä oli selkeä yhteneväisyys. Kallioperän painaumat tulkittiin murrosvyöhykkeiksi. Akustisesta aineistosta tulkittiin useita luotausprofiileja, joissa oli nähtävissä siirrosrakenteita, sekä silttisten välikerrosten nesteytymisen aikaansaamia vedenpurkausrakenteita. Häiriörakenteiden esiintyminen rajoittui akustiseen kerrokseen, joka vastaa peräytyvän mannerjäätikön edustalle kerrostuneita glasiaalislustosedimentejä ja niitä esiintyi lähinnä kallioperän murrosvyöhykkeiden läheisyydessä. Glasiaalisavien kerrostuminen voidaan ajoittaa tapahtuneeksi deglasiaation jälkeen n v. eaa., joten kerroksen sisäisiä rakenteita voidaan pitää post- glasiaalisina. Niiden todennäköisimpänä syntymekanismina voidaan pitää jäästä vapautuneen maankuoren liikuntojen aikaansaamia yhtä tai useampaa maanjäistystä. Avainsanat: Akustis seisminen luotaus, Olkiluoto, häiriörakenteet.

5 1 CONTENTS ABSTRACT TIIVISTELMÄ 1 INTRODUCTION RESEARCH AREA RESEARCH METHODS DATA PROCESSING AND INTERPRETATION RESULTS Geological features Bedrock features Sediment features Disturbance structures CONCLUSIONS APPENDICES APPENDIX Bathymetric map, 1: APPENDIX Bedrock elevation map, 1: APPENDIX Geologic surface map, 1: Zip... Report, geologic cross sections in table form, maps in PDF format.

6 2 1 INTRODUCTION This report presents results of acoustic-seismic survey in the sea area close to Olkiluoto in The work was conducted by the Geological Survey of Finland (GTK), commissioned by Posiva OY. The survey was done with the research vessel Geomari between The purpose of the work was to study geological features of the area and to find out if any indications of post glacial faulting or deformation can be detected in marine sediments. Similar acoustic seismic surveys have been done in the Olkiluoto area in 2000 and 2008, as part of GTK's on-going mapping program, as well as a joint mapping work with Posiva (Rantataro, 2000; Rantataro and Kaskela (2010). Post glacial disturbances in the Olkiluoto sea area have been studied in detail by Kotilainen and Hutri (2004) and Hutri and Kotilainen (2007). Their studies were based on GTK's acoustic seismic survey data. GTK's aero geophysical and morphological lineament interpretations (Kuivamäki, 2001) were available as a background data for 2015 survey to determine possible faultand fracture zones. All results are presented according ETRS89-TM35-FIN coordinate system.

7 3 2 RESEARCH AREA The survey area is located North and North-West of Olkiluoto, extending from Eurajoensalmi towards the open sea (Figure 1). Southern part of the area overlaps the 2000 and 2008 survey areas. Direction of survey lines was SW-NE, with a line spacing of 250m. This line configuration was chosen to cross the prevailing direction of interpreted lineaments at right angle. Total length of the survey lines was 257 km, covering an area of about 120 km 2. For navigational safety, the survey was limited in areas with water depth more than 5m. Figure 1. Survey lines at the sea area close to Olkiluoto. Red lines mark the area that was surveyed in 2015.Green and blue lines mark the areas surveyed in 2008 and 2000, respectively.

8 4 3 RESEARCH METHODS Acoustic profiling is accomplished by towing or mounting to the vessel, a sound source that emits acoustic energy in timed intervals behind a research vessel. The transmitted acoustic energy is reflected from boundaries between various layers with different acoustic impedances (i.e. the water-sediment interface or boundaries between geologic units). Acoustic impedance is defined by the bulk density of the medium times the velocity of the sound within that medium. The reflected acoustic signal is received either by a ship-towed hydrophone, or with a receiver system, by the same tuned transducer array that generates the outgoing source signal. The receiver converts the reflected signal to an analogue signal. The analogue signal is digitized, displayed, and logged with a computer. The data can then be processed and imported to computer software for interpretation. The higher frequencies of operation provide the highest resolution, but are limited in amount of penetration below the sea floor. The lower frequencies provide more penetration, but less resolution. Acoustic equipment used by GTK include high- and mid frequency sediment echo sounders (28 khz pinger and 3,5-8 khz chirp), a single channel, low frequency boomer (ELMA, Hz), a multibeam echo sounder (Atlas FS20) and a dual frequency side scan sonar (Klein 3000, 100/500 khz). The 28 khz pinger has a very good vertical resolution (±5-10 cm). It is used to determine the thickness of soft sediment layers and to visualize the internal structures and boundaries between different clay units. The low frequency boomer has a rather low resolution (±2 m) but instead a very good penetration into non-cohesive sediments (sand, gravel, till). In terms of penetration and resolution, the chirp falls somewhere between these two and therefore adds significantly to the information available for interpretation Side scan sonar creates an acoustic image (similar to an aerial photograph in appearance) of the sea floor on both sides of the vessel. It is used to identify objects (boulders, shipwrecks, cables, etc.) on the sea floor and to determine the quality and horizontal extent of surface sediments. Side scan coverage depends on the frequency but usually a coverage of m per transect can be achieved. Strong thermal layering can have a negative effect on both the quality of the image and/or the coverage. Multibeam echo sounder is used to collect highly accurate (theoretical resolution ± 5 cm) bathymetric data over a wide "swath" across the vessel track. The swath width is operator selectable and depends on the water depth. Usually swath width of 6-10 water depth is collected. Atlas FS 20 system also records backscatter information, which provides additional information of the bottom quality. All survey equipment record simultaneously, so that the data from the different sensors can be readily compared and combined. Survey speed is kept constant, usually at 4-5 kn. This is important, since the time interval of the outgoing acoustic signal is constant and thus all speed changes affect the data "density".

9 Figure 2. Schematic illustration of GTK's acoustic seismic survey equipment. 5

10 6 4 DATA PROCESSING AND INTERPRETATION After quality control, the acoustic profiles were stored and post processed with MDPS software (MeriData Post-processing Software). Boundaries between geological units were interpreted from acoustic profiles; they were digitized and given sound velocity values, respectively. Time travel values were then converted into meters and thicknesses of different units could be established. Multibeam data was cleaned and visualized with Fledermaus software. Due to water depth at the survey area, no full bathymetric coverage could be achieved (App 1). Digitized boundaries were stored in table form with a positioning data and depth values (distance from water surface) at 5 m intervals. Tables also include the water depth (water-sediment interface from 28 khz pinger). A bedrock elevation map (App. 2) was prepared from tables, with 50-m cell size and interpolated values between survey lines. Geologic surface map (App. 3) was prepared by combining the interpreted profiles with side scan data. In this work, the 250 m line spacing allowed making of a side scan mosaic with full coverage. Map production was done with ArcGis software. Interpretation of different geological units is based on the visual recognition of certain boundaries in the survey data. The quality of the survey data is therefore critically important. Interpretation is usually verified by comparing acoustic profiles with sediment cores. Coring was not part of this work but results from earlier studies at Olkiluoto area (Rantataro, 2000) give a good basis for the identification of different geological units. In this work, the following layers are interpreted from the seismic acoustic profiles: bedrock, till, sand, glacioaquatic mixed sediment, glacial silt/clay, Ancylus clay, Litorina mud and recent mud. Bedrock includes both basement and sedimentary rock. The till, which is unsorted material detached from the base of an ice sheet and redeposited, exhibits all grain sizes from very fine-grained clay to large boulders. Glacioaquatic mixed sediment means material deposited near the glacier that cannot be classified with the acoustic seismic equipment used. Because of the good resolution of high frequency echo sounders, the boundaries between clay and mud units of different ages are normally very distinguishable. Also, any internal structure within the clay and mud units (faults, erosional surfaces, etc), can usually be identified. The glacial clays are distinguished most clearly from the echo sounder image as generally dark banded strata that follow bottom topography. The Ancylus clays are in general pale, banded layers that overlie the glacial clays. Like glacial clays, Ancylus clays tend to follow underlying topography. The Litorina mud is seen as a layer with poorly developed banding and a darker tone, probably due to organic material or gas formation. The Litorina mud is distributed as an asymmetric basin fills and thus differs from the older glacial and Ancylus clays which are layered in accordance with the underlying topography. There is much variation in the overall character of the recent mud from one area to another. The layer, which has a high water-content and only contains a moderate amount of organic material, is very pale and transparent, almost water-like. Elsewhere,

11 7 it can be nearly black and acoustically impenetrable if the layered sediment is rich in organic matter and its breakdown product, gas. Interpretation of non-cohesive sediments and identifying the sediment-bedrock interface can be a lot more challenging. Because of the low resolution of the boomer, small scale features in the bedrock surface are difficult to detect. Especially in areas with a shallow water depth, acoustic noise can quite often disturb the in-coming signal. The boomer signal does not penetrate intact bedrock surface but instead it is possible to identify broken and fractured bedrock areas and, to some extent, the internal reflectors in sedimentary rock.

12 8 5 RESULTS 5.1 Geological features Bedrock features Bedrock elevation map shows a clear NW-SE trend throughout the whole survey area (Figure 3). Topography is quite gentle at the southern part but gets steeper towards North. There is a continuous depression in the middle of the area, dipping gently to the NW, and another similar depression north from it. Several class II (morphologic) and class III (aero geophysical) lineaments coincide well with bedrock bathymetry. Apart from the obvious NW-SE trend there is also a marked correspondence between few more or less E-W oriented lineaments and bedrock forms. It is likely that the orientation of the bedrock features reflect larger scale fracturing and the depressions are indeed fracture zones. Seismic profiles across the bedrock depressions show the bedrock topography in detail (figures 4-7). Fractured bedrock surface was observed in several profiles across the bedrock depressions. The fragmentation can be estimated from the low frequency boomer data, as the signal is able to penetrate broken rock surface to some extent. The acoustic image of fractured rock therefore differs from that of an unbroken rock. This interpretation is by no means definite but rather subjective matter, based on comparison between all profiles from the survey area. The extent of sedimentary rock at Olkiluoto sea area was interpreted and presented by Rantataro and Kaskela (2008). Revised interpretation with current data set shows that the sedimentary rock area extends slightly north into 2015 survey area. The typical features of sedimentary rock (flat topography, internal reflectors) can be seen in seismic profiles. They can be distinguished from basement rock that clearly has more varying topography. The boundary between these two cannot be determined with current seismic methods, since the pulse penetration is too weak. The orientation of the bedrock features and the presence of an E-W trend along with the prevailing NW-SE direction are well pronounced in a bedrock aspect image (Figure 9). Slope directions are calculated for each 50 50m cell with ArcGis software with no relation to the slope angle. The absence of NE-SW oriented features can partly be explained by the fact that all values between survey lines are interpolated and therefore any continuous features in that direction would naturally be under-represented.

13 9 Figure 3. Bedrock elevation map at Olkiluoto survey area, Lineament interpretation is presented in blue and red lines. Seismic profiles a-d are presented in figures 4-7.

14 10 Figure 4. Seismic profile a. Gentle topography of the sedimentary rock on the left side of the profile is clearly different from the basement rock area in the middle of the profile. Figure 5. Seismic profile b. Steep bedrock topography in the northern part of the survey area.

15 11 Figure 6. Seismic profile c. Inclined internal reflectors within sedimentary rock. Figure 7. Seismic profile d. Relatively low bedrock relief at the SE part of the main bedrock depression zone.

16 12 Figure 8. Extent of sedimentary rock area at the sea area outside Olkiluoto. The interpretation is combination between 2008 and 2015 seismic survey data.

17 13 Figure 9. Bedrock aspect image showing calculated slope directions in 50 50m cell size Sediment features Bedrock is covered by Quaternary sediments throughout the whole survey area, but for few outcrops. Till is by far the most abundant surface sediment. It was probably deposited by the late Weichselian ice sheet, which, according Kotilainen& Hutri (2004), retreated from the Olkiluoto area at ~ cal. years BP. In the Olkiluoto sea area, till typically forms a conforming layer, 1-3 m in thickness, over the bedrock but at places makes up formations up to 10 m in thickness. Narrow troughs and grooves on the exposed till surface have been filled with softer sediments. Bedrock depressions have been filled with glacial- and post glacial clays, up to 15 m in thickness. Figure 10 shows a typical stratigraphic sequence of glacial- and post glacial clays in the Olkiluoto area.

18 14 Figure 10. A high frequency echo sounder profile (28 khz Pinger) showing a typical stratigraphic sequence of glacial and post glacial marine sediments in the Olkiluoto area. The clay/till and till/bedrock interfaces are not visible in high frequency profile. The oldest glacial silts/clays were deposited during the deglaciation at end of the Yoldia stage and at the beginning of the Ancylus Lake stage of the Baltic Sea. The glacial clay is fine grained, layered or varved clay, deposited in the vicinity of a glacier. It is distinguishable in echo sounding profiles by its banded appearance and its conformity with the underlying topography. In their work, Kotilainen and Hutri made a varve count from two sediment cores and were able to determine the time frame for the formation of the glacial clay unit in Olkiluoto area to be somewhere between years after the deglaciation. Thin, whitish layer of homogenous clay separates varved clays from overlying sulphide banded Ancylus clays. The Litorina clays have been deposited in a marine environment c years ago, when environmental conditions in the sea were favourable for a moderately abundant fauna. The most recent clayey gyttja sediments are recognizable in echo sounding profiles as a weak, transparent, light layer. In sheltered areas at Eurajoensalmi the fluffy upper layer can be up to 2m in thickness. Submarine extension of "Särkänhuivi" esker, consisting of glaci-fluvial sand, is running in the middle of the survey area. It is largely covered by younger sediments and in places removed completely by erosion. Bedrock topography is reflected in both sediment pattern as well as surface forms of exposed till cover as a clear NW-SE orientation. There are erosional grooves on the clay surface caused by currents, and typically a thin layer of erosional sand is found throughout the survey area on clayey bottoms. The erosional sand was present in most cores taken from Olkiluoto area in 2000 and it is also recognizable in side scan images. Geological surface map is presented in Figure 11.

19 15 Figure 11. Geological surface map of the Olkiluoto 2015 Survey area. 5.2 Disturbance structures Several features were observed in echo sounding profiles that can be classified as disturbance structures. These are structures that cut or distort the continuous acoustic banding or boundaries of the identified geologic units and that can be, with any amount of certainty, said to have been formed after the sediment deposition. Horizontal distribution of disturbance structures shows a clear lineation along the bedrock fracture zones. They are especially abundant along the long continuous depression in the middle of the survey area (figure 12). There are a number of series of closely-spaced small parallel faults, larger faulting structures and funnel-like dewatering structures to be seen in acoustic profiles (figures 13-14). In connection with these, gravitational debris flow structures can be seen at places. In some cases, the same feature can be traced through several parallel survey lines, as can be seen in figure 15. Here, funnel-like dewatering structures form a longitudinal discharge channel that cuts through the same geological unit in four parallel profiles in NW-SE direction. All observed disturbance structures are concentrated near and along the interpreted bedrock fracture zones. Stratigraphically, their occurrence is limited in the geological unit that represents varved glacial deposits, with alternating clay and silt layers. Due to the lower resolution of the deep-penetrating survey equipment, such disturbance structures in non-cohesive sediments (till, sand) or bedrock cannot be readily observed.

20 16 Figure 12. Distribution of interpreted disturbance structures in the Olkiluoto survey area.

21 17 Figure 13. Faulting structures (red lines) in the Olkiluoto acoustic profiles (28 khz pinger). Faulting structures are limited in the glacial varved clays (dark banded layer). Overlying Ancylus clays are undisturbed.

22 18 Figure 14. Dewatering structures (arrows) in the Olkiluoto acoustic profiles (28 khz pinger). Upper layers of glacial varved clays have been completely removed, while the continuous pale layer of homogenous clay conforms to underlying topography.

23 19 Figure 15. Four dewatering structures in a perfect NW-SE oriented lineation. The circled structures in high frequency acoustic profiles a-d are marked on the bedrock elevation map with respective letters. Distance between profiles is 250m. Following findings emerge from the survey data. Firstly; there are a number of disturbance structures to be seen in the glacial clay unit throughout the survey area. Secondly; no such structures can be seen in sediments overlying that unit. Thirdly; by their stratigraphic position, their age can be determined with fairly good accuracy. The time of the formation of these structures can be determined, as described above, to be about years after the ice sheet retreat. At that time, the Olkiluoto area was submerged more than 150 m of water and it is therefore highly unlikely that any of the structures could have been caused by wind or wave induced erosion. Such features are also known to be caused by glaciotectonic deformation (Hart and Boulton, 1991) and/or glacial surges (Elverhøi, 1984). However, since the disturbance structures occur in the upper part of the glacial varved clay unit, it is likely that the ice margin had already retreated from the area and such mechanisms seem less plausible. The most likely scenario is that the disturbances were caused by palaeoseismicity, i.e. one or several earthquakes in short time at about years BP. Their location near and along the interpreted lineaments strongly suggest that old fracture zones were reactivated due to released stress during and after the ice retreat. Faults are likely to be caused by bedrock movements with a strong vertical component. The direction of the

24 20 initial movement cannot be determined from acoustic data. The same palaeoseismic event(s) is likely to have caused liquefication of silt layers and lateral movement in the glacial varved clays. Increased pore water pressures in the silt layers, confined by finer grained clay layers, may have resulted in build-up and sudden release of pore water and the consequent formation of above mentioned dewatering structures. Comparable fault series, debris flow deposits and dewatering structures, confined to the glacial varved clays and associated with palaeoseismicity that took place shortly after deglaciation are reported by Kotilainen & Hutri (2004) and Hutri & Kotilainen (2007) in acoustic profiles from 2000 Olkiluoto survey data and by Virtasalo et al. (2007) from the nearby Archipelago Sea.

25 21 6 CONCLUSIONS 257 km of survey lines were studied with acoustic seismic methods at Olkiluoto sea area between The seismic acoustic data provided detailed information about bedrock topography and sediment features in the survey area. NW- SE oriented lineation in bedrock topography can be seen to reflect large scale fracturing. Several disturbance structures were identified from acoustic profiles. They included faulting structures and funnel- like dewatering structures, sometimes together with gravitational debris flow. The occurrence of disturbance structures is limited in an acoustic unit that represents varved glacial clays and the timing of their formation is fairly accurate. The deposition of glacial clay unit took place during and after the deglaciation of Olkiluoto area and that can be dated between ~ cal years BP. It is therefore safe to say that all observed disturbance structures are of post glacial origin. The most plausible mechanism for their formation is one or several palaeoseismic events at about cal years BP. The release in stress after deglaciation is likely to have caused one or several earthquakes. The location of disturbance structures along the bedrock depressions suggests that there has been reactivation of old fracture zones and subsequent faulting and liquefication of silty layers within varved glacial clay unit.

26 22 REFERENCES: Elverhøi, A., Glacigenic and associated marine sediments in the Weddell Sea, fjords of Spitsbergen and the Barents Sea: a review. Marine Geology 57, Hart, J.K., Boulton, G.S., The interrelation of glaciotectonic and glaciodepositional processes within the glacial environment. Quaternary Science Reviews 10, Hutri. K, Kotilainen. A, 2007: An acoustic view into Holocene palaeoseismicity offshore southwestern Finland, Baltic Sea. Marine Geology 238, Kotilainen, A., Hutri, K., Submarine Holocene sedimentary disturbances in the Olkiluoto area of the Gulf of Bothnia, Baltic Sea: a case of postglacial palaeoseismicity. Quat. Sci. Rev. 23, Kuivamäki A., 2001: Olkiluodon alueellisen ruhjetulkinnan tarkistus. Posiva Oy, Työraportti , 37 s. Rantataro, J., 2001: Akustis seismiset tutkimukset Olkiluodon läheisellä merialueella vuonna Working report , Posiva Oy, 8p, 51 app. Rantataro, J., Kaskela, A., 2010: Acoustic seismic studies in the sea area close to Olkiluoto in Working report , Posiva Oy, 21p, 11 app. Virtasalo, J.J., Kotilainen, A.T., Räsänen, M.E. & Ojala, A.E.K. 2007: Late-glacial and post-glacial deposition in a large, low relief, epicontinental basin: the northern Baltic Sea. Sedimentology 54,

27 Haurkari Kruupkari Kinnaskeri Hoppostenkloppi Hopponen Hoppostenriutta Klepsunkari Hyviluoto Satamaa Iso Matiskari Hyviluoto Nuottakari Haminasalmi Orskeri Hopposten Ulkokari Aalskeri Vähä Matiskari Pirskeri Moukarkari Napulkari Kalaskrunni Ryöväskeri Haminakari Sinkari Ahterpeilpäri Truuthella Rahakari Rahakarinhella Rysinkari Takskeri Ylifäärtti Saukonkari Appelkrunninhella Tussut Miinakari Välikari Vähä Huilkrunni Kuornoorinkloppa Leppäsenkari Pitkä Enonkari Ylifäärtti Kuornoori Kränskrunni Tonkrunti Pöllä Iso Huilkrunni Kalliokari Saaristo Truutkrunti Praakkarit Haapaniemi Etelän Pirskeri Matinkivi Iso Kallokari Niitunloukko Flaara Fransinkari Vähä Kallokari Pirskerinfäärtti Haminakari Meri-Rounoori Reikrunti Koponloukko Kopo Pihlavakari Hakkurkallio Huhtmaa Kallioluoto Iso Katavakari Preiskeri Vähä Katavakari Kuuskari Pootreivi Iso-Pietari Ruusluoma Pässinkari Pietarmeri Merisalo Loukeentolppa Tylly Saattimenloukko Isomaa Vestareivi Säikkari Säikkä Portinmaankari Vähä-Pietari Suukari Munakari Loukeenkari Kriskilkari Haukkarit Vähä-Haavanen Pirtti-Maskali Pukkari Keski-Maskali Puu-Maskali Iso-Haavanen Leppä-Maskali Sandströminkari Pullinkari Haavasten Pitkäkari Santakari Mustakari Vähä Loukkeenmaa Loukkeenmaa Korppi Friskinkari Loukkeenkirkko Kiviranta Saukonkari Pääkarta Majaluoto Kotiranta Kolo Pohjanranta Uskalinmaa Kaksoskarit Isomatala Paskkarta Isosaari Mustakarta Vahemaansalmi Hulituskari Kopo Ulko Santakari Pohimatala Pihlukari Santakari Kuivalahdensalmi Särkänhuivi Pujonnokka Läiskyvätkivet Ulkosäikkä Kouklastunkivet Kallio-Hyörtti Maa-Hyörtti Lännenkivet Majaluomansalmi Pujo Pujonkulma Vuorela Niemenmaa Iso Pyrekari Levokari Maasäikkä Kalla Iso Savikarta Vähä-Siiliö Vähä Pyrekari Vähä Savikarta Finmatala Kallikari Iso Frouvankari Vähä Frouvankari Presidentinmatala Iso-Siiliö Iso Susikari Vähä Susikari Vähänniemenjärvi Tahkoluoto Keskivedenkivi Ulko-Prinkka Kalliopöllä Olli-faarin karta 2.5 km Vahonkari Tyrniemenkari Inonkarrat Puolivesikarta Aikonkivet Puskakari Puskakarta Munakari Keskikallio Selkänummenharju Ulkopää Mäntykari Kiskari Marikarinnokka Tankarit Appendix 1 Bathymetric map 1 : POMARKKU EURAJOKI Olkiluoto Water depth (m) PORI ULVILA LUVIA Pippurikarit Eurajoensalmi Tyrniemi Ruskikarta Truutkallio Ahtola Valkiakari Ruokkarta Eteläriutta Vähäniemi Maa-Prinkka Pöllä 0.5 Vähäkari Lohikallio Rääpinkivet 0 Kölviö Tuulikari Ulkoröyskä Hakoniemi Särkänmatala High : Acoustic seismic survey in the sea area close to Olkiluoto NAKKILA EURAJOKI RAUMA EURA Low : SÄKYLÄ PYHÄRANTA 10 km GEOLOGIAN TUTKIMUSKESKUS GEOLOGICAL SURVEY OF FINLAND GEOLOGISKA FORSKNINGSCENTRALEN Betonimiehenkuja Espoo PL/PB/P.O.Box 96 FI Espoo, Finland Tel / Sisältää Maanmittauslaitoksen Maastotietokannan 3/2013 aineistoa MML ja HALTIK Innehåller data från Landmäteriverkets Terrängdabas 03/2013 MML ja HALTIK Contains 03/2013 data from the Topographic Database of the National Land Survey of Finland NLS and HALTIK EUREF - FIN -TM35FIN

28 Haurkari Kruupkari Kinnaskeri Hoppostenkloppi Hopponen Hoppostenriutta Klepsunkari Hyviluoto Satamaa Iso Matiskari Hyviluoto Nuottakari Haminasalmi Orskeri Hopposten Ulkokari Aalskeri Vähä Matiskari Pirskeri Moukarkari Napulkari Kalaskrunni Ryöväskeri Haminakari Sinkari Ahterpeilpäri Truuthella Rahakari Rahakarinhella Rysinkari Takskeri Ylifäärtti Saukonkari Appelkrunninhella Tussut Miinakari Välikari Vähä Huilkrunni Kuornoorinkloppa Leppäsenkari Pitkä Enonkari Ylifäärtti Kuornoori Kränskrunni Tonkrunti Pöllä Iso Huilkrunni Kalliokari Saaristo Truutkrunti Praakkarit Haapaniemi Etelän Pirskeri Matinkivi Iso Kallokari Niitunloukko Flaara Fransinkari Vähä Kallokari Pirskerinfäärtti Haminakari Meri-Rounoori Reikrunti Koponloukko Kopo Pihlavakari Hakkurkallio Huhtmaa Kallioluoto Iso Katavakari Preiskeri Vähä Katavakari Kuuskari Pootreivi Iso-Pietari Ruusluoma Pässinkari Pietarmeri Merisalo Loukeentolppa Tylly Saattimenloukko Isomaa Vestareivi Säikkari Säikkä Portinmaankari Vähä-Pietari Suukari Munakari Loukeenkari Kriskilkari Haukkarit Vähä-Haavanen Pirtti-Maskali Pukkari Keski-Maskali Puu-Maskali Iso-Haavanen Leppä-Maskali Sandströminkari Pullinkari Haavasten Pitkäkari Santakari Mustakari Vähä Loukkeenmaa Loukkeenmaa Korppi Friskinkari Loukkeenkirkko Kiviranta Saukonkari Pääkarta Majaluoto Kotiranta Kolo Pohjanranta Uskalinmaa Kaksoskarit Isomatala Paskkarta Isosaari Mustakarta Vahemaansalmi Hulituskari Kopo Ulko Santakari Pohimatala Pihlukari Santakari Kuivalahdensalmi Särkänhuivi Pujonnokka Läiskyvätkivet Ulkosäikkä Kouklastunkivet Kallio-Hyörtti Maa-Hyörtti Lännenkivet Majaluomansalmi Pujo Pujonkulma Vuorela Niemenmaa Iso Pyrekari Levokari Maasäikkä Kalla Iso Savikarta Vähä-Siiliö Vähä Pyrekari Vähä Savikarta Finmatala Kallikari Iso Frouvankari Vähä Frouvankari Presidentinmatala Iso-Siiliö Iso Susikari Vähä Susikari Vähänniemenjärvi Tahkoluoto Keskivedenkivi Ulko-Prinkka Kalliopöllä Olli-faarin karta 2.5 km Vahonkari Tyrniemenkari Inonkarrat Puolivesikarta Aikonkivet Puskakari Puskakarta LUVIA Keskikallio Mäntykari Kiskari Marikarinnokka Tankarit Appendix 2 Bedrock elevation map 1 : POMARKKU EURAJOKI Olkiluoto Meters below sea level PORI ULVILA Munakari Selkänummenharju Ulkopää Pippurikarit Eurajoensalmi Tyrniemi Ruskikarta Truutkallio Ahtola Valkiakari Ruokkarta Eteläriutta Vähäniemi Maa-Prinkka Pöllä 0.5 Vähäkari Lohikallio Rääpinkivet 0 Kölviö Tuulikari Ulkoröyskä Hakoniemi Särkänmatala High : -9 Acoustic seismic survey in the sea area close to Olkiluoto NAKKILA EURAJOKI RAUMA EURA Low : -47 SÄKYLÄ PYHÄRANTA 10 km GEOLOGIAN TUTKIMUSKESKUS GEOLOGICAL SURVEY OF FINLAND GEOLOGISKA FORSKNINGSCENTRALEN Betonimiehenkuja Espoo PL/PB/P.O.Box 96 FI Espoo, Finland Tel / Sisältää Maanmittauslaitoksen Maastotietokannan 3/2013 aineistoa MML ja HALTIK Innehåller data från Landmäteriverkets Terrängdabas 03/2013 MML ja HALTIK Contains 03/2013 data from the Topographic Database of the National Land Survey of Finland NLS and HALTIK EUREF - FIN -TM35FIN

29 Haurkari Saukonkari Appelkrunninhella Kruupkari Välikari Napulkari Tonkrunti Kuornoori Kinnaskeri Ylifäärtti Hoppostenriutta Klepsunkari Rahakari Tussut Rupikari Ryöväskeri Sinkari Haminakari Hoppostenkloppi Hopponen Ahterpeilpäri Rahakarinhella Tyrmkari Pohjanfäärtti Takskeri Kalaskrunni Hyviluoto Iso Matiskari Satamaa Nuottakari Hyviluoto Orskeri Hopposten Ulkokari Aalskeri Vähä Matiskari Pirskeri Moukarkari Kuornoorinkloppa Vähä Huilkrunni Leppäsenkari Pitkä Enonkari Pöllä Ylifäärtti Kränskrunni Truutkrunti Iso Huilkrunni Kalliokari Saaristo Praakkarit Haapaniemi Etelän Pirskeri Matinkivi Iso Kallokari Niitunloukko Reikrunti Koponloukko Pihlavakari Flaara Kopo Hakkurkallio Huhtmaa Kallioluoto Iso Katavakari Vähä Katavakari Saattimenloukko Kuuskari Pootreivi Iso-Pietari Ruusluoma Pässinkari Pietarmeri Vestareivi Säikkari Vähä-Pietari Säikkä Portinmaankari Kriskilkari Haukkarit Vähä-Haavanen Pirtti-Maskali Pukkari Keski-Maskali Iso-Haavanen Leppä-Maskali Puu-Maskali Isomaa Suukari Munakari Loukeenkari Merisalo Tylly Pullinkari Loukeentolppa Preiskeri Fransinkari Vähä Kallokari Pirskerinfäärtti Meri-Rounoori Haminakari Haavasten Pitkäkari Santakari Mustakari Vähä Loukkeenmaa Korppi Friskinkari Loukkeenkirkko Pääkarta Loukkeenmaa Kiviranta Saukonkari Majaluoto Kotiranta Kolo Pohjanranta Vahemaansalmi Kaksoskarit Isomatala Paskkarta Isosaari Kopo Ulko Santakari Pohimatala Uskalinmaa Hulituskari Pihlukari Särkänmatala Ulkosäikkä Maa-Hyörtti Kallio-Hyörtti Maasäikkä Vähä Pyrekari Vähä Savikarta Lohikallio Finmatala Vähä Susikari Iso Frouvankari Iso Susikari Vähänniemenjärvi Tahkoluoto Keskivedenkivi Ulko-Prinkka Eteläriutta Olli-faarin karta 2.5 km Rääpinkivet Ruokkarta Kalliopöllä Puolivesikarta Ruskikarta Valkiakari Vahonkari Inonkarrat Tyrniemenkari Tyrniemi Eurajoensalmi Keskikallio Mäntykari Litorina mud Glacial silt/clay Erosional sand RAUMA EURA Sand Till SÄKYLÄ PYHÄRANTA Tankarit Acoustic seismic survey in the sea area close to Olkiluoto Glacioaquatic mixed sediment EURAJOKI Marikarinnokka EURAJOKI Olkiluoto Ancylus sulphide clay NAKKILA Pippurikarit Appendix 3 Geologic surface map 1 : Recent mud LUVIA Kiskari Erosion areas with sandy surface PORI ULVILA Ahtola Munakari Selkänummenharju Ulkopää Vähäniemi Maa-Prinkka Surface substrate POMARKKU 10 km Bedrock GEOLOGIAN TUTKIMUSKESKUS GEOLOGICAL SURVEY OF FINLAND GEOLOGISKA FORSKNINGSCENTRALEN Betonimiehenkuja Espoo PL/PB/P.O.Box 96 FI Espoo, Finland Tel / Sisältää Maanmittauslaitoksen Maastotietokannan 3/2013 aineistoa MML ja HALTIK Innehåller data från Landmäteriverkets Terrängdabas 03/2013 MML ja HALTIK Contains 03/2013 data from the Topographic Database of the National Land Survey of Finland NLS and HALTIK EUREF - FIN -TM35FIN Vähä Frouvankari Pöllä 0.5 Kölviö Tuulikari Vähäkari Kallikari Presidentinmatala Iso-Siiliö Levokari Vuorela Niemenmaa Iso Savikarta Vähä-Siiliö Majaluomansalmi Kouklastunkivet Pujo Iso Pyrekari Kalla Ulkoröyskä Lännenkivet Särkänhuivi Pujonnokka Läiskyvätkivet Kuivalahdensalmi Santakari