Precise Levelling Campaigns at Olkiluoto in 2010 and 2011

Transkriptio

1 Working Report Precise Levelling Campaigns at Olkiluoto in 2010 and 2011 Veikko Saaranen Paavo Rouhiainen Heli Suurmäki Finnish Geodetic Institute May 2013 Working Reports contain information on work in progress or pending completion. The conclusions and viewpoints presented in the report are those of author(s) and do not necessarily coincide with those of Posiva.

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3 PRECISE LEVELLING CAMPAIGNS AT OLKILUOTO IN 2010 AND 2011 ABSTRACT The Finnish Geodetic Institute established the Olkiluoto GPS network in 1994 and started precise levelling survey in autumn The first levelling survey included the GPS network and the line Lapijoki-Olkiluoto, which connects Olkiluoto to precise levelling network in Lapijoki and gives information about the movement of the Olkiluoto area relative to the continent. The line Lapijoki-Olkiluoto was decided to survey every fourth year and the GPS network every two years. New benchmarks have been added to the levelling network to give more precise information for the area with observed abnormal deformation. Height change of benchmarks GPS6 and GPS9 was more than one millimetre relative to other benchmarks between 2003 and New levelling loops were established and levelled onto the research facility ONKALO and the low and intermediate level waste (VLJ) repository in The levelling period of these micro loops was decided to be one year. In 2007 it was noticed that in the loop ONKALO benchmark was one millimetre higher than a year ago. Two new benchmarks were established in 2008 near Measurements in 2008 and 2009 supported earlier results and benchmark was still rising. The latest measurements in 2010 and 2011 show that this movement does not exist at the moment. Actually this benchmark is at a lower level relative to fixed benchmark than it was in In loop OLKIA benchmarks 03216, GPS6 and GPS7 have the same uplift rate between 2009 and GPS13 has uplifted 0.80 mm and other benchmarks mm relative to The problem area over the Olkiluoto strait was found out in A height difference of benchmark interval changed 1.9 mm between 2003 and Since 2007 the Olkiluoto strait line has been measured every year. In 2008 the difference was only 1.5 mm. The latest measurements show that this interval is not active at the moment. The height difference in 2011 was close to the result of The comparison between 2010 and 2011 measurements shows two new unstable benchmark intervals. Those are benchmark interval GPS in the VLJ loop and benchmark interval in the Olkiluoto strait line. The Lapijoki-Olkiluoto line measurements in 2003, 2007 and 2011 show insignificant elevation change between the mainland and Olkiluoto island since The new GPS stations GPS16, GPS17, GPS18 and GPS19 were established and connected to a levelling network in Keywords: Deformation of bedrock, precise levelling, vertical control

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5 TARKKAVAAITUSKAMPANJAT OLKILUODOSSA VUOSINA 2010 JA 2011 TIIVISTELMÄ Geodeettinen laitos perusti Olkiluodon GPS-verkon vuonna 1994 ja suoritti ensimmäiset tarkkavaaitukset Olkiluodon alueella vuoden 2003 syksyllä. Tällöin vaaittiin GPS-verkko ja vaaituslinja Lapijoki-Olkiluoto. Linja liittää Olkiluodon alueen tarkkavaaitusverkkoon ja mahdollistaa Olkiluodon saaren ja mantereen välisen muutoksen seurannan. Mittaukset linjalla Lapijoki-Olkiluoto päätettiin suorittaa joka neljäs vuosi ja GPS-verkossa joka toinen vuosi. Tutkimusaluetta on laajennettu mittaustulosten perusteella. Vuonna 2005 havaittiin, että GPS6:n ja GPS9:n korkeusero muihin pisteisiin nähden oli kahdessa vuodessa muuttunut yhden millimetrin. Syksyllä 2006 ONKALOn ja VLJ-luolan yläpuolelle perustettiin seitsemän ja viiden pisteen mikrosilmukat. Nämä vaaitussilmukat on mitattu vuosittain. Vuonna 2007 havaittiin, että ONKALON yläpuolella sijaitseva kiintopiste oli vuodessa noussut lähes millimetrin ympäristöönsä verrattuna. Syksyllä 2008 sen lähistölle perustettiin kaksi uutta pistettä. Vuosien 2008 ja 2009 mittausten pohjalta todettiin, että oli edelleen hieman noussut ympäristöönsä nähden. Uudet mittaukset 2010 ja 2011 osoittavat, että kiintopisteen liike ei ole jatkunut, vaan uusissa mittauksissa pisteen korkeus on laskenut suhteessa kiinnitettyyn pisteeseen Vuonna 2011 Olkiluodon saaren silmukassa OLKIA ainoastaan GPS6 ja GPS7 olivat samalla korkeudella kiinnitettyyn pisteeseen nähden kuin vuonna Muut pisteet olivat korkeammalla tasolla. Eniten oli noussut GPS mm. Muiden pisteiden nousu oli mm. Vuoden 2007 mittaus Lapijoki-Olkiluoto linjalla toi esille uuden muutosalueen. Kiintopistevälin korkeusero oli muuttunut 1.9 mm neljässä vuodessa. Väli otettiin tarkemman tutkimuksen kohteeksi ja sen vuosittaiset mittaukset aloitettiin. Vuonna 2008 korkeusero oli osittain palautunut ja oli enää 1.5 mm. Uusimmat mittaukset eivät ole osoittaneet merkittävää muutosta. Vuoden 2011 tulos oli lähes sama kuin vuonna Vuosien 2010 ja 2011 mittauksien tuloksia vertailemalla löytyi VLJ-silmukasta merkittävä muutos kiintopistevälillä GPS Olkiluodon salmen vaaituslinjan väli on myös muuttunut merkittävästi. Lapijoki-Olkiluoto väli on mitattu 2003, 2007 ja Mittaustulosten mukaan muutokset Olkiluodon saaren ja mantereen välillä ovat pieniä. Vuoden 2011 aikana perustettiin ja liitettiin vaaitusverkkoon uudet GPS-asemat GPS16, GPS17, GPS18 ja GPS19. Avainsanat: Kallioperän deformaatio, tarkkavaaitus, korkeuskontrolli

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7 1 TABLE OF CONTENTS ABSTRACT TIIVISTELMÄ 1 INTRODUCTION LEVELLING IN 2010 AND RESULTS IN 2010 AND Height differences and adjustment result for Height differences and adjustment result for COMPARISON WITH PREVIOUS LEVELLINGS Standard deviations for the comparisons between levelling Lapijoki-Olkiluoto Olkiluoto strait OLKIA and OLKIB Micro loop ONKALO Micro Loop VLJ GPS antenna platform measurements FUTURE PLANS SUMMARY REFERENCES APPENDIX I, OBSERVATION IN 2010 AND APPENDIX II, POSIVA LINE PAPERS

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9 3 1 INTRODUCTION The Finnish Geodetic Institute started the precise levelling in order to monitor vertical movements at the Olkiluoto area in autumn The GPS network and the Lapijoki- Olkiluoto line between Olkiluoto island and continent were measured during the first observation year. The levelling interval of the Lapijoki-Olkiluoto line was decided to be four years and of the GPS network two years. The new levelling loops were established and levelled onto the research facility ONKALO and the low and intermediate level waste (VLJ) repository in The levelling period of these micro loops was decided to be one year. The Olkiluoto strait line has been measured every year since The new GPS stations GPS16, GPS17, GPS18 and GPS19 were established and connected to a levelling network in This report treats the levelling campaigns in the autumns 2010 and 2011 and the comparison with the previous campaigns (Lehmuskoski 2004, 2006, 2008 and 2010). The fieldwork and the calculations were carried out by the same method that was used in the Third Levelling of Finland (Lehmuskoski et al. 2010).

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11 5 2 LEVELLING IN 2010 AND 2011 The precise levelling campaign in 2010 includes the loops above ONKALO and VLJ repository and the Olkiluoto strait line. All the levelling lines were measured in Their levelling dates are shown in Table 1. Table 1. Levelling lines and observation dates. Loop, GPS pillar or line Date ONKALO and VLJ and Olkiluoto strait and Lapijoki-Olkiluoto OLKI B and OLKIA and GPS Stations Posiva Oy employed the assisting personnel for the levelling campaigns. The crew and the used instruments are given in Table 2. Table 2. Field crew and instruments. Surveyors Paavo Rouhiainen (2010 and 2011), Veikko Saaranen (2011) Levelling expedition 2010 Simo Muttilainen, Jari-Pekka Mäntylä, Teppo Levelling expedition 2011 Peltola and Jarno Reijonsaari Margus Erstu, Jevgeni Frid, Sami Lehtonen, Samu Maijala and Simo Muttilainen Levelling instrument Zeiss DiNi12, number Rod pair (3 metres) Zeiss Nedo LD13, numbers and Rod (1 metre) Zeiss Nedo LD11, number Thermometer Rod bases Tripods Distance meter Umbrella Car Personal Navigator Fluke 54 II Turtles and spikes Wild GST 20 normal, Zeiss extendable Rollfix Alexo Toyota Hiace, UXY-346 Garmin etrex The description of the levelling is presented in Lehmuskoski 2006, Chapter 3. In Appendix I there is in the chronological order information about every benchmark interval measured in One page represents one benchmark interval and one levelling direction. The upper part of the page shows time, crew, instrumentation, road type and weather. The lower part gives observations and environmental data for every step. At the end of the observation file there are an uncorrected height difference, distance between benchmarks and possible remarks.

12 Figure 1. Levelling network in the 2011 adjustment. The Lapijoki-Olkiluoto line (red line) was measured in Benchmark was used as a fixed benchmark. In the 2010 adjustment three separate networks had fixed values from the 2011 adjustment. 6

13 7 3 RESULTS IN 2010 AND 2011 An adjustment program is Local X- Positioning system. An adjustment method is a constrained net. The weight of each observation is inversely proportional to the distance of the benchmark interval. A priori accuracy in the adjustment has been 1.0 mm/ km and in a statistical testing reference variance 1.0 (unitless) was used. Observations in the adjustments are from line papers which are presented in Appendix 2. In line papers, the height difference is mean of forward and back measurements. Some intervals belonged to more than one line. In this case, all height differences were in the adjustment. The height differences were corrected for rod meter, tidal deformation and refraction before adjustment. We used the Zeiss Nedo LD13 bar code invar rods with an aluminum frame for the ordinary precise levelling. Zeiss Nedo LD11 invar rod with an aluminum frame was used when the elevations of the GPS antenna platforms were levelled. The rod calibrations were carried out before and after the field season using the FGI vertical rod comparator (Takalo 1999, Takalo and Rouhiainen 2002). The corrected value for the levelling epoch was obtained by linear interpolation. During the levelling an air temperature and its difference between 2.5 m and 0.5 m above the ground were registered with a Fluke 54 II thermometer at one minute intervals. Refraction correction was computed with the Kukkamäki formula (Hytönen 1967) and tidal correction with the formulas of Heikkinen (1978). 3.1 Height differences and adjustment result for 2010 There are 21 height differences and 22 benchmarks in the adjustment of the 2010 measurements (Tables 3 and 4). The observations were performed in three lines which are ONKALO (on10), VLJ (vl10) and Olkiluoto strait (st10). For every line one fixed benchmark was used. Benchmark was fixed for the adjustment of the ONKALO loop at its N60 elevation m derived from the 2003 campaign. Starting values for VLJ and Olkiluoto Strait are from the 2011 adjustment. In Loop VLJ starting value is m at benchmark GPS9A and in Olkiluoto Strait it is m at benchmark The accuracy for the 2010 measurements of the adjustment is 0.27 mm/ km. The average precision of the adjusted heights is 0.16 mm. The precisions presented in Tables 4 and 6 are dependent on the location of the fixed benchmark in the network.

14 8 Table 3. Observations in the 2010 adjustment. Columns are benchmarks (from, to), line, distance (km), observation, adjustment correction and adjusted height difference on on on on on on on on on on st st st st st GPS9A GPS9B vl GPS9B vl vl vl vl GPS9A vl

15 9 Table 4. Benchmarks in the 2010 adjustment and their KKJ coordinates in zone 27 and geographical coordinates longitude ( ) and latitude ( ), height (m) and precision (mm) Fixed Fixed GPS9A Fixed GPS9B Height differences and adjustment result for 2011 There are 122 height differences and 87 benchmarks in the adjustment of the 2011 measurements (Tables 5 and 6). The N60 elevation m derived in from the 2003 campaign was fixed in the adjustment. The observation data include lines Lapijoki-Olkiluoto (LAPI), ONKALO (on11), VLJ (vl11) and Olkiluoto strait (st11). Loop OLKIA and levellings for GPS stations were included in lines 11gp, GP17, GP18, GP19, GP6A, GP6S, GP9S, GPS2, GPS4, GPS7 and GPS8. The accuracy for the 2011 measurements of the adjustment is 0.23 mm/ km. The average precision of the adjusted heights is 0.37 mm. The levelling was focused on a bolt A on the GPS antenna platform. To compute height observation to an antenna platform level, height of the bolt mm has to correct from an observation.

16 10 Table 5. Observations in the 2011 adjustment. Columns are benchmarks, line, observation, adjustment correction and adjusted height difference. * = Measured from or to the bolt A on an antenna platform level. GPS13A gp GPS8A 11gp GPS8A GPS8 * 11gp GPS8 * GPS8B 11gp GPS8B gp AP41 11gp AP41 GPS4B 11gp GPS4B GPS4C 11gp GPS4C AP41 11gp AP41 GPS1A 11gp GPS1A GPS1B 11gp GPS1B gp AP6 11gp AP6 GPS2B 11gp GPS2B GPS2 * 11gp GPS2 * GPS2A 11gp GPS2A AP6 11gp AP gp GPS17A GP GPS17A GPS17B GP GPS17B GPS17C GP GPS17C GPS17N GP GPS17N GPS17 * GP GPS17 * GPS17N GP GPS17N GPS17A GP GPS17A AP17 GP AP GP GPS18A GPS18B GP GPS18B GPS18C GP GPS18C GPS18N GP GPS18N GPS18 * GP GPS18 * GPS18N GP GPS18N GPS18A GP GPS18A AP18 GP AP18 GPS16C GP GPS16C GPS16A GP GPS16A GPS16B GP GPS16B GPS16N GP GPS16N GPS16 * GP

17 11 GPS16 * GPS16N GP GPS16N GPS16C GP GPS16C AP5 GP AP20 GP AP20 AP19 GP AP19 GPS19A GP GPS19A GPS19B GP GPS19B GPS19C GP GPS19C GPS19N GP GPS19N GPS19 * GP GPS19 * GPS19N GP GPS19N GPS19A GP GPS19A AP19 GP AP19 AP20 GP AP GP GPS6A GP6A GPS6A GPS6B GP6A GPS6B GPS7A GP6A GPS7A GPS7B GP6A GPS7B GPS13B GP6A GPS13B GPS13A GP6A GPS13A GPS13 * GP6A GPS13 * GPS13B GP6A GPS6A GPS6 * GP6S GPS6 * GPS6B GP6S GPS9B GPS9 * GP9S GPS9 * GPS9A GP9S GPS2A GPS2B GPS GPS4C GPS4 * GPS GPS4 * GPS4B GPS GPS7A GPS7 * GPS GPS7 * GPS7B GPS GPS8A GPS8B GPS LAPI LAPI LAPI LAPI LAPI LAPI LAPI LAPI LAPI AP4 LAPI

18 12 AP LAPI AP20 LAPI AP LAPI LAPI LAPI LAPI LAPI LAPI AP5 LAPI AP LAPI LAPI GPS3B GPS3 * OLKB GPS3 * GPS3A OLKB GPS3A GPS3B OLKB GPS3B OLKB GPS3A OLKB on on on on on on on on on on on on st st st st st GPS9A GPS9B vl GPS9B vl vl vl vl vl GPS9A vl

19 13 Table 6. Benchmarks in the 2011 adjustment and their KKJ coordinates in zone 27 and geographical coordinates longitude ( ) and latitude ( ), height (m), precision (mm). * = Measured to the bolt A on an antenna platform level. Adjusted height includes the height of the bolt A mm. AP AP AP AP AP AP AP AP GPS2 * GPS3 * GPS4 * GPS6 * GPS7 * GPS8 * GPS9 * Fixed

20 GPS13 * GPS16 * GPS17 * GPS18 * GPS19 * GPS1A GPS1B GPS2A GPS2B GPS3A GPS3B GPS4B GPS4C GPS6A GPS6B GPS7A GPS7B GPS8A GPS8B GPS9A GPS9B GPS13A GPS13B GPS16A GPS16B GPS16C GPS16N GPS17A GPS17B GPS17C GPS17N GPS18A GPS18B

21 15 GPS18C GPS18N GPS19A GPS19B GPS19C GPS19N

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23 17 4 COMPARISON WITH PREVIOUS LEVELLINGS The heights and height differences for 2010 and 2011 are from Tables 3-6. The results of Lehmuskoski (2008 and 2010) were adopted for the previous levellings. Land uplift corrections were not used for computing the results for the loops on the Olkiluoto island or the line Olkiluoto strait where the theoretical changes of land uplift are very small. The N60 elevation derived in from the campaign in 2003 was fixed for the later campaigns. When the N60 elevations of GPS points were compared, we used the mean of their reserve mark pair with the exceptions of GPS2 and GPS4, whose other pair had been damaged. 4.1 Standard deviations for the comparisons between levelling The accuracies of the levelling in 2010 and 2011 from the adjustments are τ = ± 0.27 mm/ km in 2010 and τ = ± 0.23 mm/ km in This accuracy includes small GPS loops. Without these small loops accuracy would be τ = ± 0.25 mm/ km. For the previous levelling accuracies were estimated in Lehmuskoski (2010) by the Formula 1. (Kääriäinen 1966). 2 n i e, (1) n 1 i 1 Fi Fe where n = number of the loops, φ i = closing error of the loop, F i = circumference of the loop, φ e = closing error of the circumference of the network and F e = length of the circumference of the network. Accuracy estimates for all levelling campaigns are given in Table 7. Table 7. Accuracy estimates for levelling campaigns ( / ) ±0.10 ±0.14 ±0.17 ±0.23 ±0.12 ±0.14 ±0.27 ±0.23 When we compare the results of two campaigns, the standard deviation of their difference is estimated by the formula τ Δ 2 = τ τ 2 2, where τ 1 and τ 2 are the accuracies of the comparable campaigns. The standard deviations for the comparisons are presented in Table 8. Table 8. Standard deviations τ Δ 2 for the comparisons mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km mm/ km

24 18 The critical value can be considered significant, when the change of the elevation is more than threefold of the standard deviation of the discrepancy: T D 3 For instance, if the elevation difference of one kilometre long interval has changed from 2005 to 2010 more than 0.90 mm, the change can be considered to be significant. 4.2 Lapijoki-Olkiluoto Levelling line Lapijoki-Olkiluoto has been measured every fourth year. This 14 kilometres long line connects the GPS network on the Olkiluoto island to the precise levelling network of Finland at Lapijoki. Levelling results measured in 2003 and 2011 indicate that Olkiluoto island is not uplifting or going down relative to Lapijoki. Land uplift corrected height difference from 2003 to 2011 is mm (Fig. 2). Without land uplift correction difference is only 0.27 mm. From NKG2005 land uplift model (Ågren and Svensson, 2007) we get that during one year land uplift at Olkiluoto is 0.17 mm more than at Lapijoki (Table 9). Benchmark interval has a significant difference in comparison with 2007 levelling (Table 9). In Olkiluoto strait has significant deformation (Table 10). When we compare the latest levelling to 2003 the situation is different. There seem to be eight benchmark intervals which have changed significantly since It is interesting to see that Olkiluoto strait interval has changed only 0.44 mm since 2007 (Fig. 3). 2,00 1,38 1,20 1,00 0,00 0,30 0,14 0,05 0,52 1,36 0,40 0,04 1,14 1,09 0, ,00 0,00 0,09 0,55 0,22 0,28 0,69 0,51 2,00 3,00 4,00 5,00 2,07 2,28 2,75 3,77 3,70 Land uplift corrected Land uplift corrected Figure 2. Line Lapijoki-Olkiluoto. Land uplift corrected height differences in Lapijoki- Olkiluoto line between previous levellings in 2003 and 2007 and the new levelling in 2011 (in millimetres).

25 19 Table 9. Significance of the elevation differences in Lapijoki-Olkiluoto line. Change of the elevation difference (mm). Corrected for land uplift. Significance of the standard deviation Distance (km) NKG2005 land uplift (mm/y) Lehmuskoski(2008) Olkiluoto strait The 2007 observations indicated that between 2003 and 2007 the benchmark on the Olkiluoto island had lifted 1.91 mm up compared to the benchmark on the continent. This was the motivation to start yearly measurements over the Olkiluoto strait. The elevation change of this interval has returned since 2007 (Fig. 3). At the moment the most interesting deformation happens in a short, only 39 metres long, the interval between benchmarks and It has been measured twice in 2011 and both measurements gave same height difference of mm. This value is about a half millimetre more than in the previous measurements and is significant (Fig. 4, Fig. 5 and Table 10).

26 20 2,50 Change of elevation difference in ,00 1,50 1,91 1,48 1,58 1,47 1,00 1,09 0,50 0, Figure 3. Elevation change of interval relative to 2003 observation. Figure 4. Line Olkiluoto strait has six benchmarks. At the moment most active part of the line is

27 21 0,70 0,60 0,50 0,40 0,30 0, ,10 0, ,10 0,20 Figure 5. Elevation differences in the line Olkiluoto strait between previous levelling in 2009 and the new levellings in 2010 and 2011 (in millimetres). Table 10. Elevation differences in the Olkiluoto strait in and significance of an elevation difference between the latest measurements. The elevation differences (mm). Not corrected for land uplift Distance mean(km) Significance of height change According to Lehmuskoski (2010) the 2004 measurement of interval was levelled 31 st of March and other measurements have been done in late autumn and the reason for the elevation difference is thus the different temperature of bedrock in March and September, estimated to be about 15 C in the vicinity of the surface of the bedrock (Lehmuskoski et al. 2006). 4.4 OLKIA and OLKIB The loop OLKIA has been measured in 2003, 2005, 2007, 2009 (Lehmuskoski 2004, 2006, 2008 and 2010) and Like in earlier levelling reports the elevation differences were computed in millimetres and land uplift correction was not applied. In order to compare the N60 elevations to earlier campaigns the height of the nodal

28 22 benchmark derived in 2003 ( mm) was kept fixed. In Fig. 8 deformation history of ONKALO can be seen. According to Lehmuskoski (2010) the most remarkable deformation in loop OLKIA has been at GPS6 in and at GPS13 in The reason for the changes were large construction works near these stations, parking area around GPS6 and nuclear power station of Olkiluoto 3 near GPS13. Lehmuskoski (2010) has analyzed that the northern part of the Olkiluoto island rises compared to the middle and southern parts (Fig. 6). Using 2011 observations we can see that the movement of GPS6 is minimal relative previous measured in The most significant movement has been from GPS7 to GPS13 (Fig. 9 and Table 11). When we compare uplift relative to we can see that only GPS6 and GPS7 are stable. GPS13 has uplifted 0.8 mm and other benchmarks mm (Fig. 9). Loop OLKIB connects GPS3 to This interval has been stable during the years, and no significant deformation has happened since previous measurements (Table 12 and Fig. 7). Figure 6. Deformation in Loop OLKIA Change of N60 elevation compared to benchmark in Red bar gives the change to 2005, blue bar to 2007 and black bar to 2009 (Lehmuskoski 2010).

29 23 Figure 7. Loops OLKI A and OLKI B. 1,80 1,60 1,40 1,20 1,00 0,80 0,60 0, > > > >2011 0,20 0,00 0, GPS6 GPS7 GPS9 GPS GPS4 GPS GPS Figure 8. Deformation in Loop OLKIA relative to benchmark Since 2003 has GPS6 raised 1.6 mm, GPS9 1.3 mm and GPS4 almost 1.6 mm. In this picture GPS station deformation is focused on the mean movement of the reserve marks.

30 ,00 0,82 0,82 0,80 0,65 0,64 0,60 0,50 0,40 0,52 0,41 0,41 0,20 0,06 0,00 0,08 0,04 0,35 0,11 0,00 0,20 0,44 0,40 0,40 0,41 0,00 Figure 9. Height differences in Loop OLKIA between previous levelling in 2009 and the new levelling in 2011 (in millimetres).

31 Table 11. Significance of elevation difference changes between 2011 and previous levellings in loop OLKIA. N Observation 2011 Distance km Elev. difference and significance Elev. difference and significance Elev. difference and significance Elev. difference and significance GPS6A GPS6B GPS7A GPS7B GPS13B GPS13A GPS9A GPS9B GPS8A GPS8B GPS4B GPS1A GPS1B GPS2B GPS2A

32 26 Table 12. Observations in loop OLKIB in 2011 and comparison with the previous measurements. In this loop there is no any significant change between measurements. N Obs 2011 Distance Elev. difference and significance Elev. difference and significance Elev. difference and significance Elev. difference and significance GPS3B GPS3A Micro loop ONKALO According to Lehmuskoski (2010) the most interesting benchmark in ONKALO is (Fig. 10 and Fig. 11). Other benchmarks show rather small vertical movements. Benchmark over ONKALO compared to the nodal benchmark was lifted almost one millimetre between the levelling in In 2009 it was almost on the same level as in 2008 but the direction of the movement was still upwards. In Lehmuskoski (2010) other interesting question was if benchmark could belong to the same rising area. New observations in 2010 and 2011 give negative answer to that question. Both benchmarks and were at a lower level relative to in 2010 and 2011 than in Figure 10. Loop ONKALO.

33 27 The new measurements did not indicate any active crustal deformation over ONKALO. All the elevation differences between 2009, 2010 and 2011 were below statistically significant level. Comparison between previous levelling in 2009 and the new levelling in 2010 are in Table 13 and for 2011 in Table 14. Figure 11. Change of N60 elevation compared to benchmark in 2006 in Loop ONKALO. Red bar gives the change to 2007, blue bar to 2008 and black bar to Black numbers (-0.1) give the change of N60 elevation (Fig. 6., Lehmuskoski 2010). 0,10 0,00 0,02 0,08 0,08 0,02 0,06 0,10 0,16 0,00 0, ,10 0,20 0,25 0, ,30 0,37 0,40 0,50 0,39 0,39 0,44 0,44 Figure 11. Differences in N60 heights relative to in Loop ONKALO.

34 28 Table 13. Elevation difference and significance of the difference between 2010 observations and previous measurements in Loop ONKALO. N Obs Distance 2010, km Elevation difference and significance in Elevation difference and significance in Elevation difference and significance in Elevation difference and significance in

35 Table 14. Elevation difference and significance of the difference between 2011 observations and previous measurements in Loop ONKALO. N Obs Distance 2011.km Elevation difference and significance in Elevation difference and significance in Elevation difference and significance in Elevation difference and significance in Elevation difference and significance in

36 Micro Loop VLJ According to Lehmuskoski (2010) there are some movements in loop VLJ (Fig. 13), which exceed a significance limit but are not systematic, and can be related to the temperature differences of the bedrock during different years. Another remark in Lehmuskoski (2010) is about the intervals and where the elevation difference increase systematically but does not yet exceed the significance limit (Fig. 12 and Table 15). The difference between 2010 and 2011 measurements in interval GPS9A is 0.67 mm. It is a significant deformation in this 88 metres long interval (Fig. 14 and Table 17). Deformation in the intervals and were well below significant level. Figure 12. Deformation analysis picture based on levellings (Lehmuskoski 2010, Fig. 7). Change of N60 elevation compared to reserve mark GPS9B in 2006 in Loop VLJ. Red bar gives the change to 2007, blue bar to 2008 and green bar to 2009 ).

37 31 Table 15. Significance of N60 elevation changes of intervals (Lehmuskoski 2010, Table 16). Interval Distance Change of N60 elevation Significance of standard (km) (mm) deviation GPS9A GPS9B GPS9B GPS9A Figure 13. Loop VLJ.

38 32 0,30 0,20 0,10 0,00 0,10 GPS9B GPS9A GPS9B ,20 0,30 0,40 Figure 14. Differences in N60 heights in Loop VLJ between previous levelling and the new levellings in 2010 and 2011 (in millimetres).

39 Table 16. Elevation difference and significance of the difference between 2010 observations and previous measurements in Loop VLJ. N Observation 2010 GPS9B Distance 2011 km Elev. difference and significance Elev. difference and significance Elev. difference and significance Elev. difference and significance GPS9A GPS9B Table 17. Elevation difference and significance of the difference between 2011 observations and previous measurements in Loop VLJ. N Observation 2011 GPS9B Distance 2011 km Elev. difference and significance Elev. difference and significance Elev. difference and significance Elev. difference and significance Elev. difference and significance GPS9A GPS9B

40 GPS antenna platform measurements Old GPS pillars in the Olkiluoto levelling network are GPS2, GPS3, GPS4, GPS6, GPS7, GPS8, GPS9 and GPS13. In 2011 measurements for the new GPS pillars GPS16, GPS17, GPS18 and GPS19 were performed. Old stations have two reserve marks. A new reserve mark GPS4C was established in New stations have four reserve marks: A, B, C and N. Measurements were performed so that the difference of the zero point of the rod scale from the bottom plate was eliminated during measurements. The levelling was focused on a bolt A on the antenna platform (Lehmuskoski 2006, Figures 5-6). To obtain the N60 elevation of the antenna platform, the height of the bolt, mm have to reduce from the levelling results. The reserve mark GPS2B was measured in It was found to be damaged by a working machine in 2009 so it was not used in the comparison with the previous measurements. Explanation of the columns of Table 18: 1. Reserve mark 2. Corrected elevation difference from reserve mark to GPS antenna platform level ("A" bolt height 19,912 mm removed from the adjusted height difference) 3. From adjustment N60 elevation of the bolt on the antenna platform in N60 elevation of the antenna platform in Mean height difference from the reserve marks to antenna platform In GPS2 only GPS2A was used and with GPS4 only GPS4B. 6. Mean height difference from the reserve marks to antenna platform In GPS2 only GPS2A was used and with GPS4 only GPS4B. 7. Change of the GPS antenna platform height difference from the reserve marks between (mm). 8. Change in the GPS antenna platform N60 height relative to the benchmark N60 elevation difference (mm).

41 35 Table 18. Height difference from reserve marks to GPS pillars in GPS2A GPS2 GPS2 GPS2B GPS3A GPS3 GPS3 GPS3B GPS4B GPS4 GPS4 GPS4C GPS6A GPS6 GPS6 GPS6B GPS7A GPS7 GPS7 GPS7B GPS8A GPS8 GPS8 GPS8B GPS9A GPS9 GPS9 GPS9B GPS13A GPS13 GPS13 GPS13B

42 36 Table 19. Observations from the reserve benchmarks to GPS antenna platform level for the GPS pillars established 2011 and the N60 heights of the GPS platform levels. At these values height of the bolt A mm on the GPS platform level has been removed. Observation from reserve mark to GPS platform level (mm). N60 height of the GPS platform level in 2011 (mm). GPS16A (GPS16) GPS16B GPS16C GPS16N GPS17A (GPS17) GPS17B GPS17C GPS17N GPS18A (GPS18) GPS18B GPS18C GPS18N GPS19A (GPS19) GPS19B GPS19C GPS19N

43 37 5 FUTURE PLANS The levelling in the loops and the lines will be continued according to the original plan: Autumn 2012: the micro loops ONKALO and VLJ and the line Olkiluoto strait. Autumn 2013: the micro loops ONKALO and VLJ and the loops OLKI A and OLKI B and the line Olkiluoto strait.

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45 39 6 SUMMARY The precise levellings at Olkiluoto were started in autumn First measurements included GPS network and Lapijoki-Olkiluoto line which connects the Olkiluoto island to the precise levelling network of Finland. In 2006 micro networks over the underground facilities ONKALO and VLJ repository were established. Since 2007 the Olkiluoto strait line and loops over ONKALO and VLJ repository have been measured every year. In autumn 2007 the northern part of Olkiluoto island was found to rise compared to the middle and southern parts. The movements of GPS6 and GPS9 from 2003 to 2005 were significant. In 2007 this movement seemed to stop. In autumn 2009 GPS6 had uplifted again and GPS13 was found to sink. Between GPS6 and GPS7 were stable but GPS13 was lifted 0.8 mm and other benchmarks in loop OLKIA were lifted mm relative benchmark In 2007 the benchmark over ONKALO was discovered to rise unexpectedly. This movement continued in 2009 but in 2010 and 2011 the benchmark was at a lower level than in The ONKALO loop measurements done in 2009, 2010 and 2011 do not show any significants movements. In the VLJ loop the difference between 2010 and 2011 measurements in the benchmark interval GPS9A was 0.67 mm which is a significant height difference change when distance between the points is only 88 m. The Lapijoki-Olkiluoto line has been measured in 2003, 2007 and These measurements show that movement between Lapijoki and Olkiluoto island is small. There are some unstable intervals inside Lapijoki-Olkiluoto line. In comparison with 2003 observation in 2007 a remarkable movement was found in a benchmark interval over the Olkiluoto strait. Later the movement over the Olkiluoto strait was found to be a little smaller and the measurement in 2011 gives the same result than 2007 measurement. The latest measurements show that the interval between benchmarks and had an elevation change between 2010 and 2011 measurements.