GEOLOGIJA 48/1, 107–116, Ljubljana 2005
Identifikacija potencialno aktivnih struktur vzdol‘ reke Save na podlagi topografskih podatkov in podatkov nivelmanskega vlaka
Identification of potentially active structures along the Sava river using topographic, and leveling line data
Igor RI@NAR1, Bo‘o KOLER2 & Milo{ BAVEC3
1 Ulica bratov Martinec 40, Ljubljana, e-mail: igor.riznar@s5.net 2 Univerza v Ljubljani, Fakulteta za gradbeni{tvo in geodezijo, Jamova 2, Ljubljana, e-mail:
bozo.koler@fgg.uni-lj.si 3 Geolo{ki zavod Slovenije, Dimi~eva 14, 1000 Ljubljana, e-mail: milos.bavec@geo-zs.si
Klju~ne besede: nivelmanski vlak, geodinamika, aktivna tektonika, Ljubljanska kotlina Key words: leveling line, geodynamics, active tectonics, Ljubljana basin
Kratka vsebina
S primerjavo geodetskih podatkov nivelmanskega vlaka med Rate~ami in Ljubljano ter topografskega profila vzdol‘ reke Save smo ugotovili razlike v hitrosti vertikalnih premikov, ki jih pripisujemo recentni geodinamiki. Poleg splo{nega trenda relativnega dviganja v smeri od juga proti severu smo nakazali segmentacijo obmo~ja, ki ka‘e na obstoj aktivnih struktur v geolo{ki sestavi severnega dela Ljubljanske kotline in Zgornjesavske doline.
Abstract
Anomalies in vertical displacement rates related to recent geodynamics were determined between Rate~e and Ljubljana by comparing leveling line data with topography of the Sava river longitudinal profile. Beside the general trend showing increase of vertical displacement in the S-N direction, segmentation of the area is noted. The later suggests that active geological structures exist in the northern part of the Ljubljana basin and in the Upper Sava valley respectively.
Uvod
Kvartarna tektonska aktivnost v Ljubljanski kotlini je bila ‘e v preteklosti nakazana z razli~nimi geolo{kimi deli. Drobne in sodelavci (1960) so v glinokopu Lokarje pri Vodicah opisali nekaj deset metrov veliko gubo v plasteh gline in proda pleistocen-ske starosti; @lebnik (1971) omenja guba-nje sinklinale na Kranjskem in Sor{kem polju, ki naj bi se iz terciarja nadaljevalo v pleistocen; Ku{~er (1990) opisuje neenakomerne naklone starej{ih savskih zasipov, ki jih pripisuje stalnem dviganju obmo~ij
med Radovljico in Kranjem ter Medvodami in Mednim. Deformacij v würmskem zasipu ni opazil, pa~ pa v istem prispevku tudi kri-ti~no obravnava Premrujevo (1976) pojmovanje neotektonike. Omenjeni avtorji so na podlagi analize kvartarnih zasipov sklepali, da se je ta aktivnost po obdobju »rissa« (MIS 6, op.a.) kon~ala, ter da »würmski« (MIS 5d, op.a.) in mlaj{i zasipi niso deformirani. Vrabec (2001) je kasneje opozoril na znake, ki bi lahko kazali na subrecentno oziroma recentno aktivnost nekaterih struktur v Ljubljanski kotlini. V okviru projekta Karta aktivnih prelomov v Sloveniji je v zadnjih
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letih potekala identifikacija potencialno aktivnih geolo{kih struktur na obmo~ju Ljubljanske kotline. Na podlagi geolo{kih in geo-morfolo{kih kriterijev sta Ri‘nar (2003) in Poljak (2003, v: Bavec et. al., 2003) predstavila dva modela potencialno aktivne zgradbe osrednjega dela Ljubljanske kotline. Kasneje je Verbi~ (2004) na podlagi interpretacije geolo{kih podatkov in evidentiranih geomorfolo{kih oblik postavil strukturni stil kvartarnih deformacij med Kranjem in [marno goro. Zdi se, da je na {ir{em obmo~-ju Vodic in Medvod tak stil zelo verjeten (Bavec et al., 2004).
Za dolo~itev vertikalnih premikov na do-lo~enem obmo~ju lahko uporabimo rezultate izmer nivelmanske mre‘e vi{jih redov. Namen tega dela je bil oceniti uporabnost podatkov o vi{inski izmeri nivelmanskega poligona Rate~e – Ljubljana za ocenjevanje vertikalnih premikov, preveriti skladnost premikov z anomalijami v reliefu ter oceniti potencial za navezavo ugotovljenih premikov s potencialno aktivnimi geolo{kimi strukturami.
Nivelmanski poligon Rate~e – Ljubljana
Nivelmanske mre‘e vi{jih redov, ki so stabilizirane na obmo~ju R Slovenije, so bile vklju~ene v izmere I. in II. nivelmana visoke natan~nosti (NVN), ki so bile izvedene na obmo~ju SFRJ. Nivelmanska mre-‘a I. NVN je bila izmerjena po 2. svetovni vojni. Nivelmanski poligon od Rate~ do Ljubljane je bil tako izmerjen leta 1947. Omenjeni nivelmanski poligon je bil ponovno izmerjen leta 1971, ko je na ob-mo~ju R Slovenije potekala izmera II. NVN. V nivelmanskem poligonu od Rate~ do Ljubljane imamo stabiliziranih 47 reper-jev, ki so bili zajeti v obe izmeri NVN.
Vertikalni premiki reperjev in analiza na-tan~nosti dolo~itve vertikalnih premikov so bili dolo~eni za obdobje od I. do II. izmere NVN. Vertikalni premiki so bili dolo~eni na osnovi spremembe nadmorskih vi{in to~k, glede na izhodi{~ni reper B.V. 478, ki je stabiliziran v bli‘ini fundamentalnega reperja FR1014 (^rnu~e). Natan~nost dolo~itve vertikalnega premika posameznega reperja, je bila dolo~ena na osnovi natan~nosti dolo~it-ve nadmorskih vi{in to~k v I. in II. izmeri NVN.
Igor Ri`nar, Bo‘o Koler & Milo{ Bavec
Kategorizacija reperjev
Geodetski reperji obravnavanega nivel-manskega poligona so stabilizirani v razli~-ne objekte vzdol‘ ‘elezni{ke proge. Ker smo se ‘eleli izogniti uporabi nezanesljivih podatkov, smo reperje kategorizirali glede na geolo{ko podlago ter stanje objektov v katere so stabilizirani.
Opravili smo pregled vseh nivelmanskih reperjev vzdol‘ omenjene proge. Reperje smo kategorizirali po vzoru podobne naloge opravljene na obmo~ju Kr{ke kotline (P o -ljak, 1997). Polo‘aj geodetskega poligona je predstavljen na sliki 1.
Ker so vsi reperji stabilizirani v objekte in ne neposredno v mati~no kamnino, je bilo pri pregledu vsakega potrebno najprej oceniti stanje objekta. V glavnem gre za razmeroma stare objekte, saj je bila velika ve~ina reperjev vgrajena v za~etku 20. stoletja, nekateri pa so {e starej{i.
Reperje smo glede na pri~akovano stanje razdelili na pet kategorij.
A – Reper stabiliziran v mati~no kamnino.
A’ – Reper stabiliziran v nedeformiran objekt, ki je temeljen v mati~no kamnino.
B – Reper stabiliziran v nedeformiran objekt, ki je temeljen v »zemljino« oziroma nevezane sedimente (prod, pesek, te‘kognetna glina)
B’ – Reper stabiliziran v nedeformiran objekt, za katerega ne vemo zanesljivo v kaj je temeljen.
C – Reper stabiliziran v objekte, ki ka‘ejo znake strukturnih deformacij.
Reperje kategorij A smo privzeli kot uporabne za oceno geodinamike in reperje kategorij B kot pogojno uporabne. V kategoriji C so reperji, ki jih glede na dana{nje stanje objektov ne bi smeli upo{tevati, vendar do-pu{~amo mo‘nost, da so bili v ~asu, ko sta bili izmeri izvedeni {e v zadovoljivem stanju.
Nekateri objekti, v katere so bili stabilizirani reperji, so poru{eni, tako da o njihovem stanju v ~asu izmer nimamo podatkov. Ne glede na to dejstvo lahko na posameznih mestih z gotovostjo sklepamo v kaj so bili ti objekti temeljeni. To velja predvsem za objekte na prodnih (ali konglomeratnih) zasipih, kjer je debelina preperine razmeroma majhna (manj kot 1 m). Reperji (predvsem starej{i) so stabilizirani v solidno grajene
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stavbe, ki so bile v tak{nih primerih zagotovo temeljene v mati~no kamnino oziroma prod. Premiki reperja zaradi pogrezanja objekta so v takih primerih, {e posebej ko gre za objekte grajene na ravnini, kaj malo ver-
jetni. ^e je bil objekt, v katerega je bil stabiliziran reper, poru{en na primer leta 1980, ni nujno, da so vse meritve (zadnja je bila izvedena leta 1971) neuporabne. Menimo, da je bilo rezultate meritev teh reperjev kljub
Sl. 1. Polo‘aj nivelmanskega vlaka in projekcija topografskega profila Save (na vertikalno ravnino s slemenitvijo 128°) z ozna~enimi lokacijami anomalij (A-G).
Fig. 1. Position of the leveling line and projection of the Sava river topographic profile (projected to the 128° vertical plane). Anomalies are marked (A-G).
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Igor Ri`nar, Bo‘o Koler & Milo{ Bavec
vsemu smiselno pregledati in oceniti njihovo uporabnost. Vsekakor pa tak{ni reperji spadajo v najni‘jo kategorijo zanesljivosti in jih je smiselno uporabiti le pogojno.
Na osnovi terenskega ogleda smo se odlo-~ili, da nekatere reperje ozna~imo z dvojno oznako, na primer B - C. To so objekti, kjer so reperji prekriti z novo fasado. Gre za primere, ko ni jasno ali je bil objekt pred adaptacijo strukturno deformiran, vendar ni ni-kakr{nih znakov, ki bi kazali, da je bilo tako. Tak{ni reperji so na~eloma nezanesljivi, lahko pa bi bili tudi uporabni.
Z oznako C – B smo ozna~ili reperje, ki so stabilizirani v objekte na katerih fasadi so vidne razpoke, ki so bodisi posledica nabrekanja fasade oziroma dotrajanosti le-te ali pa gre za objekte, ki so razpokali v zadnjih
letih, ko so tik ob njih obnovili cesto in je fasada razpokala zaradi tresljajev ali potre-
sa.
Topografski profil vzdol‘ Save
Topografski profil vzdol‘ reke Save med njenim izvirom in Ljubljano smo izdelali na podlagi digitalnega modela vi{in InSAR 25 (© Geodetska uprava RS). Sestavljen je iz 5771 to~k. Ob analizi smo morali upo{tevati tudi nekatere omejitve, ki nastanejo zaradi napak, povezanih z velikostjo osnovne celice (25 m) in na~inom zajema izvornega podatka. Profil je tako zaradi uporabe neobdelanih podatkov nazob~an, na obmo~ju najve~-jih napak pa podatkov nismo upo{tevali.
Sl. 2. Primerjava topografskega profila Save in podatkov nivelmanskega vlaka (projekcija na
vertikalno ravnino s slemenitvijo 128°). Nakazana je segmentacija profila na pet odsekov. Oznake A,
B in B’, B-C in C-B so kategorije reperjev glede na geolo{ko podlago in kvaliteto vgradnje.
Fig. 2 A comparison of the Sava river topographic profile with the leveling line data between Rate~e
and Ljubljana (both projected to the 128° vertical plane). Segmentation into five sections is
indicated. A, B in B’, B-C in C-B are categories of bench mark quality regarding the bedrock type
and condition of the structure into which the bench mark is stabilized.
Identifikacija potencialno aktivnih struktur vzdol‘
Poleg tega smo morali pri interpretaciji upo-{tevati tudi dejstvo, da uporabljamo podatek radarskega odboja od vodne povr{ine, ki na obmo~ju akumulacijskih jezer za elektrarne na Savi odstopa od naravnega stanja. Enako kot v primeru nivelmanskega poligona smo za analizo uporabili projekcijo profila na vertikalno ravnino z azimutom 128°, kar v geolo{kem smislu pribli‘no ustreza t.i. dinarski smeri.
Analiza topografskega profila je pokazala ve~ nezveznosti v obi~ajnem konkavnem re~-nem profilu. Od severozahoda proti jugovzhodu si sledijo naslednje anomalije (sl. 2, 3):
– Jesenice (B),
– Moste (C),
– Radovljica (D),
– Naklo (E),
– Kranj (F),
– Medvode (G).
Anomalije v o‘ini pod Mostami (C) in med Tr‘i{ko Bistrico ter Soro je kot »tektonsko pogojene« ocenil ‘e Ile{i~ (1953), ki je za svojo analizo uporabil bistveno manj kvaliteten vhodni podatek. Anomalija pri Mostah je na topografskem profilu vsekakor najbolj izrazita, vendar pa lahko na podlagi kvali-tetnej{ih vhodnih podatkov, ki smo jih uporabili tu, v profilu opazujemo vsaj {est zgoraj navedenih anomalij, ki razdelijo potek pri~akovanega normalnega profila Save na sedem odsekov.
Dinamika reperjev nivelmanskega poligona
Podatke o izmeri nivelmanskega poligona smo za primerjavo s topografijo Save projicirali na vertikalno ravnino z azimutom 128° (sl. 2, 3). @e hiter pogled v podatke poka‘e na ve~ kot o~itno recentno geodinamiko. Od letnega dviganja velikostnega reda 2.55 ± 0.40 mm/leto na obmo~ju Zgornjesavske doline, ki je dolo~eno glede na izhodi{~ni reper B.V. 478, se dviganje bolj ali manj zvezno zmanj{uje do obmo~ja med Kranjem in Medvodami, kjer se merske to~ke pribli‘ajo stabilnemu stanju. ^e poskusimo vertikalne premike, dobljene na osnovi izmere nivel-manskega poligona, bolj detajlno analizirati, lahko na prvi stopnji prepoznamo {tiri obmo~ja nezveznosti (sl. 2), na drugi stopnji, ki pa je ‘e zelo obremenjena s subjektivnimi ocenami, pa celo na sedem obmo~ij, ki se
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ujemajo z anomalijami v topografskem profilu Save (sl. 3).
Obmo~ja nezveznosti v nivelmanskem poligonu
Prva nezveznost je opazna na za~etku poligona med to~kami pri Rate~ah in Zelencih
(A) (sl. 2). Od tod je jasno razpoznaven enakomeren trend pojemanja vertikalnih premikov vse do Jesenic (B). Med Jesenicami
(B) in Mostami (C) vertikalni premiki skokovito narastejo. Od Most se pojemanje vertikalnih premikov s primerljivim trendom nadaljuje pribli‘no do Kranja, kjer je spet zaznavna anomalija (F). Ju‘no od Kranja se trend hitrosti vertikalnih premikov nekoliko zmanj{a. Ju‘no od Medvod bele‘imo celo minimalne negativne vrednosti vertikalnih premikov, ki pa so statisti~no nepomembne .
Kot smo omenili, je podrobnej{a raz~leni-tev rezultatov izmere nivelmanskega poligona (sedem obmo~ij nezveznosti) mo~no subjektivna, zato je predstavljena le kot ena izmed mo‘nosti in kot usmeritev nadaljnjega dela (sl. 3). Razlike med nekaterimi odseki so sorazmerno dobro vidne, nekatere nezveznosti v rezultatih nivelmanskega poligona pa so bile definirane s pomo~jo primerjave in ujemanja z anomalijami topografskega profila Save. Skupno smo tako prepoznali sedem anomalij. Povpre~ni stati-sti~no pomembni vertikalni premiki na ob-mo~jih, ki smo jih izdvojili na sliki 3 so:
– Rate~e - Zelenci (A): 2.551 ± 0.402 mm/ leto,
– Zelenci (A) - Jesenice (B): 2.35 ± 0.25 mm/leto,
– Jesenice (B) - Moste (C): 1.80 ± 0.30 mm/ leto,
– Moste (C) - Radovljica (D): 1.60 ± 0.30 mm/leto,
– Radovljica (D) - Naklo (E): 0.80 ± 0.30 mm/leto,
Povpre~ni statisti~no nepomembni vertikalni premiki na obmo~jih, ki smo jih izdvojili na sliki 3 so:
– Naklo (E) - Kranj (F): 0.25 ± 0.25 mm/ leto,
1  Povpre~ni vertikalni premik
2 Povpre~na natan~nost dolo~itve vertikalnega premika (1 ?)
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Igor Ri`nar, Bo‘o Koler & Milo{ Bavec
Sl. 3. Primerjava topografskega profila Save in podatkov nivelmanskega vlaka (projekcija na
vertikalno ravnino s slemenitvijo 128°). Nakazana je segmentacija profila na osem odsekov. Oznake
A, B in B’, B-C in C-B so kategorije reperjev glede na geolo{ko podlago in kvaliteto vgradnje.
Fig. 2 A comparison of the Sava river topographic profile with the leveling line data between Rate~e
and Ljubljana (both projected to the 128° vertical plane). Segmentation into eight sections is
indicated. A, B in B’, B-C in C-B are categories of bench mark quality regarding the bedrock type
and condition of the structure into which the bench mark is stabilized.
– Kranj (F) - Medvode (G): 0.00 ± 0.20 mm/leto.
Na obmo~ju od Medvod do Ljubljane zna-{ajo povpre~ni vertikalni premiki 0.10 ± 0.15 mm/leto in so statisti~no nepomembni.
Diskusija
Anomalije v topografskem profilu Save in rezultati izmere nivelmanskega poligona med Rate~ami in Ljubljano se prostorsko razmeroma dobro ujemajo. Na podlagi njihove primerjave smo dobili indice o re-centni geodinamiki Zgornjesavske doline in Ljubljanske kotline. Nesporno lahko ugotovimo, da se velikost vertikalnih premikov
ozemlja pove~uje v smeri od juga proti severu. Z manj zanesljivosti lahko profil med Rate~ami in Ljubljano razdelimo na segmente, vendar je jasno da so v dinamiki premikov prepoznavne nezveznosti, ki so po na{em mnenju posledica aktivnih struktur.
Vertikalno ravnino z azimutom 128° smo za projekcijo obravnavanih podatkov izbrali iz dveh razlogov. Najprej zato, ker v grobem sledi toku Save in poteku nivelmanske-ga vlaka, drugi~ pa, ker poteka pre~no na smer struktur, ki sta jih v svojih modelih predvidela tako Poljak (2003, v: Bavec et. al., 2003) kot R i ‘ n a r (2003) ter jih je v Verbi~ (2004) med Kranjem in [marno goro ocenil kot potencialno aktivne. Gre torej
Identifikacija potencialno aktivnih struktur vzdol‘
za strukture, ki v grobem potekajo pre~no na dalj{o os Ljubljanske kotline in so bile v omenjenih poro~ilih ocenjene kot kompre-sijske (gube, reverzni prelomi). Zbrani podatki bodo uporabljeni za nadaljnje delo. Izkazalo se je tudi, da so vertikalni premiki, ki jih dobimo na osnovi ve~krat izmerjenih nivelmanskih poligonov, koristen pripomo-~ek za popolnej{e razumevanje geodinami-ke. Tako bomo posku{ali ponoviti geodetsko izmero, ki bo pove~ala natan~nost vhodnih podatkov in tako omogo~ila popolnej{o identifikacijo aktivnih struktur.
Zahvala
Delo je nastalo v okviru projekta Karta aktivnih prelomov v Sloveniji, ki ga finan~-no podpira Agencija za okolje RS pri Ministrstvu za okolje in prostor.
Identification of potentially active
structures along the Sava river using
topographic, and leveling line data
Preface
Quaternary tectonic activity in the Ljubljana basin has been proven in the past (e.g. Drobne et al., 1960; discussed [ifrer, 1961; @lebnik, 1971; Ku{~er , 1990). The authors however concluded that according to the properties of the Quaternary infill, the activity ceased after the “Rissian” (MIS 6) period, suggesting that “Würmian” (MIS 5d) and younger infill is not deformed. Vra-b e c (2001) noted certain phenomena that could possibly be a consequence of sub-recent or recent tectonic activity. Through the course of the project “Map of active faults in Slovenia” attempts were made to identify active structures in the Ljubljana basin. Two conceptual models of central basin’s potentially active structural build-up were introduced (Ri`nar, 2003; Poljak , 2003, in: Bavec et al., 2003) followed by a concept (Verbi~, 2004), describing the Quaternary deformation structural style in the area between Kranj and [marna gora. The concept proved plausible in the broader surroundings of Vodice and Medvode (Bavec et al., 2004).
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Leveling line from Rate~e to Ljubljana
During the 1st and 2nd Yugoslav Leveling precise leveling network in Slovenia was established. The 1st Yugoslav Leveling was performed after the World War II and the leveling line from Rate~e to Ljubljana was measured in 1947. This leveling line was measured again in 1971 during the 2nd Yugoslav leveling. There are 47 benchmarks included into 1st and 2nd Yugoslav Leveling between Rate~e and Ljubljana.
Vertical movements and the precision of definition of vertical movement were determined for the period between 1st and 2nd Yugoslav Leveling. The vertical movement rate of benchmark is obtained as the ratio between the difference in height and the time interval between the respective measurements. The vertical movement rates of individual benchmarks are calculated with regard to the benchmark B.V. 478 which is stabilized near fundamental benchmark FR1014 (^rnu~e). The accuracy of vertical movement rate is determined on the basis of the accuracy of the height above see level in the 1st and 2nd Yugoslav Leveling.
Categorization of the benchmarks
The leveling line benchmarks were stabilized in various buildings along the railway. An inspection and categorization of the benchmarks was performed in order to asses the quality as well as to eliminate uncertain data. Both, the bedrock type as well as the condition of the structures were taken into account for the categorization, similarly to a comparable study performed in the Kr{ko basin area (Poljak, 1997). The position of the leveling line is shown in figure 1.
Since all the benchmarks were stabilized in structures and not in the bedrock itself, the condition of the structures had to be assessed. Most of them are rather old, originating from begining of the 20th century, some of them are even older.
The benchmarks were accordingly divided into five categories.
A – The benchs marks stabilized in bedrock
A’ – The benchmarks stabilized in undamaged structures founded in bedrock
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B – The benchmarks stabilized in undamaged structures founded in sediments
B’ – The benchmarks stabilized in unde-formed structures founded under unknown conditions
C – The benchmarks stabilized in damaged structures
For the assessment of the geodynamics, benchmarks of A category were accepted as relevant and those of B category as conditionally relevant. C category represents benchmarks that should not be accepted considering the present state of the structures in which they are stabilized. There is, however, a possibility that at the time of the measurements (30 or more years ago) those structures were still in good condition and therefore those measurements are still relevant.
Some structures bearing benchmarks are now in ruins and we don have the data about their condition at the time of the measurements. Regardless to that, we can deduce with a high confidence from geologic data and observations, in what media these buildings were founded. Benchmarks (especially the older ones) were stabilized into well built structures definitely founded in bedrock or gravel. Vertical displacements of the benchmarks due to the consolidation of the ground after they were stabilized, are very unlikely. If the structure bearing the benchmark was ruined after the last measurement that does not imply that all the measurements are not relevant, since the last ones were taken from 1970 to 1971. Such measurements were taken as conditionaly relevant and marked as C category.
Some benchmarks are marked with a double sign e.g. B – C. This type of category was applied to benchmarks which were covered with a new façade and no data was available about the eventual structural deformations of the building prior to adaptation. On the other hand we have no data suggesting the opposite. In principle, these data are unreliable but could also be relevant.
Benchmarks designated as C – B were stabilized into buildings where the cracking of the façade was observed as a consequence of recent (after last measurement) degradation of the façade or where cracking is a consequence of proven recent anthropogenic activity in the vicinity (e.g. reconstructi-
Igor Ri`nar, Bo‘o Koler & Milo{ Bavec
on of the road) or as consequence of recent earthquake shocks.
Topographic line along the Sava River
A topographic line was constructed along the course of the Sava river between its source and Ljubljana. The line was composed of 5771 points obtained from InSAR 25 DEM (© Geodetska uprava RS). Restrictions of the DEM were taken into account. Namely, due to the size of the grid cell (25 m), the line may be irregular to a level that required us to omit the data at two locations (Figs. 2, 3). The reflection of the radar signal due to ant-hropogenicaly elevated water surfaces (power-plant accumulations) was also considered. In order to compare the topografic line with the geodetic data both were projected onto a vertical plane oriented at 128° approximately corresponding to the so called “di-naric direction” in geological sense.
Several anomalies of the normal concave river longitudinal profile were recognized. In the NW-SE direction these anomalies were denominated as follows (Figs. 2, 3):
– Jesenice (B),
– Moste (C),
– Radovljica (D),
– Naklo (E),
– Kranj (F),
– Medvode (G).
Ile{i~ (1953) recognized anomalies at Moste (C) and between Tr`i{ka Bistrica and Sora respectively, even though he had to rely on elevation data of rather poor quality. Using the higher quality elevation data, we were able to define at least six anomalies (listed above) dividing the normal river profile into seven sections of presumably normal concave river profile.
The dynamics of the leveling-line measuring points
Leveling line data was projected onto a vertical plane oriented in the direction 128° and compared with topography of the Sava river (Figs. 2, 3). A mere glance into the leveling line graph reveals an obvious sign of recent geodynamics in the area. In the Upper Sava valley (NW of Jesenice) the uplift reaches 2.5 ± 0.40 mm/year. Towards the
Identifikacija potencialno aktivnih struktur vzdol‘ reke Save na podlagi topografskih ...                  115
SE the vertical displacement diminishes more or less continuously to reach a stable state between Kranj and Medvode A closer look, however, reveals certain anomalies within the leveling line. Four areas of discontinuity are rather obvious (Fig. 2) while further division that results in distinguishing seven areas of discontinuity corresponding to the anomalies in the Sava longitudinal profile (Fig. 3) is highly subjective.
Areas of discontinuity within the leveling line
From the NW towards the SE, the first discontinuity was recognized in the vicinity of Rate~e and Zelenci (A, Fig.2). Further towards the SE, the uplift rate continuously decreases until Jesenice (B). Between Jesenice and Moste (C) there is an abrupt increase in the uplift rate which is followed by another section of continuous decrease until Kranj, where another anomaly (F) appears. Further southwards the trend slightly decreases yet south of Medvode first negative values of vertical displacements were noted that are, however, statistically not significant.
As mentioned above, a more detailed subdivision of the leveling line (seven areas of discontinuity) is highly subjective, and is therefore presented only as an alternative option and as a guideline for further investigations (Fig. 3). Several discontinuities are well defined whereas others were determined by comparison with the topographic line. Statistically significant average vertical displacements were obtained at following localities (Fig. 3):
– Rate~e - Zelenci (A): 2.553 ± 0.404 mm/ leto,
– Zelenci (A) - Jesenice (B): 2.35 ± 0.25 mm/leto,
– Jesenice (B) - Moste (C): 1.80 ± 0.30 mm/ leto,
– Moste (C) - Radovljica (D): 1.60 ± 0.30 mm/leto,
– Radovljica (D) - Naklo (E): 0.80 ± 0.30 mm/leto,
3  Average vertical displacement
4  Average accuracy of the vertical displacement measurement (1 ?)
Not significant vertical rate of displacement was measured at:
– Naklo (E) - Kranj (F): 0.25 ± 0.25 mm/ leto,
– Kranj (F) - Medvode (G): 0.00 ± 0.20 mm/leto.
Not significant vertical displacement rate were also observed between Medvode and Ljubljana. The average vertical displacement rate for this segment of the leveling line is -0.10 ± 0.15 mm/yr.
Discussion
Topographic anomalies of the Sava river longitudinal profile correspond relatively well to anomalies within the leveling line between Rate~e and Ljubljana. We interpret the anomalies as indices for active geodyna-mics in the Ljubljana basin. It is rather clear that the amount of vertical uplift decreases in the direction form NW to SE. Although more ambiguity arises while trying to divide the dynamics into sections, it is not ambiguous that certain irregularities do exist within the general trend.
The data was projected onto a vertical plane oriented in direction 128e for two reasons. As first, this plane follows the general direction of the leveling line and the Sava river flow, and secondly it is perpendicular to structures predicted in models by P o -ljak (2003, in: Bavec et. al., 2003) and Ri‘nar (2003) and that were in places assessed as potentially active by Verbi~ (2004). These structures cross the Ljubljana basin roughly perpendicular to its longitudinal axis, and they were assessed as com-pressional in the reports mentioned. The results will be used as grounds for further investigations. This work has proved that consecutive levelings can be of use at estimating active geodynamics. Future work will be aimed towards new geodetic measurements and further identification of active structures.
Acknowledgements
The project Active Faults of Slovenia is financially supported by Environmental Agency of the Republic of Slovenia.
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Igor Ri`nar, Bo‘o Koler & Milo{ Bavec
Literatura-References
B a v e c , M., P o l j a k , M., D e m { a r , M., Raj-ver, D., Komac, M., Toman , M., Stojanova , S., Mu{i~ , B., V r a b e c , M., V e r b i ~ , T. & R i ‘ -n a r , I. 2003: Izdelava geolo{kih kart – karta aktivnih prelomov v Sloveniji. Raziskave na obmo~-ju Ljubljansko – kranjske kotline. Letno poro~ilo za leto 2003. – Tipkano poro~ilo, 33 str., 4 priloge, 4 dodatki, Geolo{ki zavod Slovenije.
B a v e c , M., C e l a r c , B., P o l j a k , M., Dem-{ a r , M., R a j v e r , D., S k a b e r n e , D., V e r b i ~ , T., R i ‘ n a r , I., P r e u s s e r , F. & C u l i b e r g , M. 2004: Izdelava geolo{kih kart – karta aktivnih prelomov v Sloveniji. Letno poro~ilo za leto 2004. 1. del: Raziskave na obmo~ju Ljubljanske kotline in Ra{kega preloma. – Tipkano poro~ilo, 110 str., 4 priloge, Geolo{ki zavod Slovenije.
D r o b n e , F., P a v l o v e c , R. & [ e r c e l j , A. 1960: Nekaj analiz ter problematika pleistocen-skih sedimentov v Lokarjih pri Vodicah. – Kamni-{ki zbornik, 6, 163-194, Ljubljana.
I l e { i ~ , S. 1953: Podol‘ni profil zgornje Save. – Geografski vestnik, 25, 27-44, Ljubljana.
P o l j a k , M. 1997: Geolo{ka interpretacija geodetskih meritev v okviru projekta stalnega dolo-
~anja tektonskih premikov v okolici JE Kr{ko. – Tipkano poro~ilo, 13 str., 12 dodatkov, Geolo{ki zavod Slovenije.
Premru, U., 1976: Neotektonika vzhodne Slovenije. - Geologija 19, 211-241,Ljubljana.
R i ‘ n a r , I. 2003: Izdelava geolo{kih kart – karta aktivnih prelomov v Sloveniji. Raziskave na obmo~ju Ljubljansko – kranjske kotline. Letno poro~ilo za leto 2003. Dodatek 1. – V: Bavec et al., 2003: Izdelava geolo{kih kart – karta aktivnih prelomov v Sloveniji. Raziskave na obmo~ju Ljubljansko – kranjske kotline. Letno poro~ilo za leto 2003. – Tipkano poro~ilo, 33 str., 4 priloge, 4 dodatki, Geolo{ki zavod Slovenije.
[ i f r e r , M., 1961: Pore~je Kamni{ke Bistrice v pleistocenu. – SAZU, 211 pp., Ljubljana.
V e r b i ~ , T. 2004: Strukturni stil tektonskih deformacij med Kranjem in [marno goro. – Tipkano poro~ilo, 17 str., 1 priloga, Toma‘ Verbi~, zasebni raziskovalec.
V r a b e c , M. 2001: Strukturna analiza cone Savskega preloma med Trstenikom in Stahovico. - Neobjavljeno doktorsko delo, 94 str., Univerza v Ljubljani.
@ l e b n i k , L. 1971: Pleistocen Kranjskega, Sor{kega in Ljubljanskega polja. – Geologija, 14, 5 -51, Ljubljana.