ACTAGEOGRAPHICA GEOGRAFSKI ZBORNIK SLOVENICA 2019 59 1 ACTA GEOGRAPHICA SLOVENICA GEOGRAFSKI ZBORNIK 59-1 • 2019 Contents Maja KOCJANČIČ, Tomislav POPIT, Timotej VERBOVŠEK Gravitational sliding of the carbonate megablocks in the Vipava Valley, SW Slovenia 7 Małgorzata KIJOWSKA-STRUGAŁA, Anna BUCAŁA-HRABIA Flood types in a mountain catchment: the Ochotnica River, Poland 23 Irena MOCANU, Bianca MITRICĂ, Mihaela PERSU Socio-economicimpactofphotovoltaicpark:TheGiurgiucountyruralarea,Romania 37 Andrej GOSAR The size of the area affected by earthquake induced rockfalls: Comparison of the1998 Krn Mountains (NW Slovenia) earthquake (Mw 5.6) with worldwide data 51 Matej GABROVEC, Peter KUMER Land-use changes in Slovenia from the Franciscean Cadaster until today 63 Mojca FOŠKI Using the parcel shape index to determine arable land division types 83 Mateja FERK, Matej LIPAR, Andrej ŠMUC, Russell N. DRySDALE, Jian ZHAO Chronology of heterogeneous deposits in the side entrance of Postojna Cave, Slovenia 103 Special issue – Green creative environments Jani KOZINA, Saša POLJAK ISTENIČ, Blaž KOMAC Green creative environments: Contribution to sustainable urban and regional development 119 Saša POLJAK ISTENIČ Participatory urbanism: creative interventions for sustainable development 127 Jani KOZINA, Nick CLIFTON City-region or urban-rural framework: what matters more in understandingthe residential location of the creative class? 141 Matjaž URŠIČ, Kazushi TAMANO The importance of green amenities for small creative actors in Tokyo: Comparing natural and sociocultural spatial attraction characteristics 159 ISSN 1581-6613 9 771581 661010 ACTA GEOGRAPHICA SLOVENICA 2019 ISSN: 1581-6613 COBISS: 124775936 UDC/UDK: 91© 2019, ZRC SAZU, Geografski inštitut Antona Melika Internationaleditorialboard/mednarodniuredniškiodbor: DavidBole(Slovenia),MichaelBründl(Switzerland),RokCiglič(Slovenia), Matej Gabrovec (Slovenia), Matjaž Geršič (Slovenia), Peter Jordan (Austria), Drago Kladnik (Slovenia), BlažKomac (Slovenia), Andrej Kranjc (Slovenia), Dénes Lóczy (Hungary), Simon McCharty (United Kingdom), SlobodanMarković (Serbia), Janez Nared (Slovenia), Drago Perko (Slovenia), Marjan Ravbar (Slovenia), Nika Razpotnik Visković(Slovenia), Aleš Smrekar (Slovenia), Annett Steinführer (Germany), Mimi Urbanc (Slovenia), Matija Zorn (Slovenia) Editor-in-Chief/glavni urednik: Blaž Komac; blaz@zrc-sazu.si Executive editor/odgovorni urednik: Drago Perko; drago@zrc-sazu.si Chief editor for physical geography/glavni urednik za fizično geografijo: Matija Zorn; matija.zorn@zrc-sazu.siChief editor for human geography/glavna urednica za humano geografijo: Mimi Urbanc; mimi@zrc-sazu.si Chief editor for regional geography/glavni urednik za regionalno geografijo: Drago Kladnik; drago.kladnik@zrc-sazu.si Chief editor for spatial planning/glavni urednik za regionalno planiranje: Janez Nared; janez.nared@zrc-sazu.si Chiefeditorforruralgeography/glavnaurednicazageografijopodeželja:NikaRazpotnikVisković;nika.razpotnik@zrc-sazu.si Chief editor for urban geography/glavni urednik za urbano geografijo: David Bole; david.bole@zrc-sazu.si Chief editor for geographic information systems/glavni urednik za geografske informacijske sisteme: Rok Ciglič; rok.ciglic@zrc-sazu.siChief editor for environmental protection/glavni urednik za varstvo okolja: Aleš Smrekar; ales.smrekar@zrc-sazu.si Editorial assistant/uredniški pomočnik: Matjaž Geršič; matjaz.gersic@zrc-sazu.si Issued by/izdajatelj: Geografski inštitut Antona Melika ZRC SAZUPublished by/založnik: Založba ZRC Co-published by/sozaložnik: Slovenska akademija znanosti in umetnosti Address/Naslov: Geografski inštitut Antona Melika ZRC SAZU, Gosposka ulica 13, SI – 1000 Ljubljana, Slovenija The papers are available on-line/prispevki so dostopni na medmrežju: http://ags.zrc-sazu.si (ISSN: 1581–8314) Ordering/naročanje: Založba ZRC, Novi trg 2, p. p. 306, SI – 1001 Ljubljana, Slovenija; zalozba@zrc-sazu.si Annual subscription/letna naročnina: 20 € for individuals/za posameznike, 28 € for institutions/za ustanove. Single issue/cena posamezne številke: 12,50 € for individuals/za posameznike, 16 € for institutions/za ustanove. Cartography/kartografija: Geografski inštitut Antona Melika ZRC SAZU Translations/prevodi: DEKS, d. o. o. DTP/prelom: SYNCOMP, d. o. o. Printed by/tiskarna: Tiskarna Present, d. o. o. Print run/naklada: 350 copies/izvodov The journal is subsidized by the Slovenian Research Agency and is issued in the framework of the Geography of Slovenia coreresearchprogramme(P6-0101)/revijaizhajaspodporoJavneagencijezaraziskovalnodejavnostRepublikeSlovenijein nastajav okviru raziskovalnega programa Geografija Slovenije (P6-0101). The journal is indexed also in/revija je vključena tudi v: SCIE – Science Citation Index Expanded, Scopus, JCR – Journal Citation Report/Science Edition, ERIH PLUS, GEOBASE Journals, Current geographical publications, EBSCOhost,Geoscience e-Journals, Georef, FRANCIS, SJR (SCImago Journal & Country Rank), OCLC WorldCat, Google scholar,and CrossRef. Oblikovanje/Design by: Matjaž Vipotnik. Front cover photography: Stone bridge over the Rak River on the outskirts of the Rakov Škocjan polje, which is otherwiseknown for its beautiful natural bridges (photograph: Matej Lipar).Fotografija na naslovnici: Kamniti most čez reko Rak na obrobju kraškega polja Rakov Škocjan, ki je sicer bolj znano počudovitih naravnih mostovih (fotografija: Matej Lipar). THESIZEOFTHEAREAAFFECTED BYEARTHQUAKEINDUCEDROCKFALLS:COMPARISON OFTHE1998KRNMOUNTAINS (NWSLOVENIA)EARTHQUAKE(MW5.6) WITHWORLDWIDEDATA Andrej Gosar Very large rockfall on Osojnica Mountain in the Tolminka valley induced by the 1998 earthquake. DOI: https://doi.org/10.3986/AGS.4845 UDC: 550.348.435(497.4) COBISS: 1.01 The size of the area affected by earthquake induced rockfalls: Comparison of the 1998 Krn Mountains (NW Slovenia) earthquake (Mw 5.6) with worldwide data ABSTRACT:The1998KrnMountainsM w5.6earthquakehadwidespreadeffectsonthenaturalenvironment, amongwhichrockfallsprevail.Allrockfallswereevaluatedtoestimatethetotalaffectedarea.The180km2 area(r=7.6km)wasestablishedandcomparedwithtwoworldwidedatasets.Theaffectedareaisconsiderably below the upper bound limit established from both datasets. The same is valid for the nearby 1976 Friuli Mw 6.4 earthquake with a 2050km2 affected area. However, comparison with the ESI 2007 scale defini­tions has shown that the area affected by the 1998 IVII–VIII event is significantly larger than the one proposed by this scale, but smaller for the 1976 Imax max X event. This could not be explained by differences in hypocentral depth or focal mechanisms of both events. The results of the study have implications for seismichazardassessmentandforunderstandingenvironmentaleffectscausedbymoderateearthquakes in mountain regions. KEYWORDS:earthquakeeffects,intensity,rockfall,macroseismicinvestigations,EnvironmentalSeismic Intensity scale, Krn Mountains, Slovenia Velikost območja pojavljanja skalnih podorov zaradi potresa: primerjava potresa Mw 5,6 leta 1998 v Krnskem pogorju (SZ Slovenija) s svetovnimi podatki POVZETEK:Potresleta1998vKrnskempogorjuzMw5,6jeimelobsežneučinkevnaravnemokolju, med katerimi so prevladovali skalni podori. Vse podore smo raziskali z namenom ocene velikosti celotnega območjapojavljanja.Ugotovilismo80km2velikoobmočje(r=7.6km)ingaprimerjalizdvemasvetovnima zbirkama podatkov. Celotno prizadeto območje ob Krnskem potresu je znatno manjše od zgornje meje pojavljanjaugotovljenezaobezbirki.Enakoveljazabližnjipotresleta1976vFurlanijizMw6,4,prikaterem jebila velikost prizadetega območja2050km2.Po drugistranipa jeprimerjava z ESI2007pokazala, da je celotno prizadeto območje ob potresu leta 1998 z Imax VII–VIII izrazito večje od opredelitve v tej letvici in manjše za potres leta 1976 z Imax X. Te razlike ni mogoče pojasniti z razliko v globini žarišča ali razliko v žariščnemmehanizmuobehpotresov. Rezultatiteštudijesopomembni zaocenjevanjepotresnenevar­nosti in za razumevanje učinkov na okolje pri srednje močnih potresih v goratih območjih. KLJUČNEBESEDE:učinkipotresa,intenziteta,skalnipodor,makroseizmičneraziskave,lestvicaEnvironmental Seismic Intensity, Krnsko pogorje, Slovenija Andrej Gosar Slovenian Environment Agency, Seismology and Geology Office and University of Ljubljana, Faculty of Natural Sciences and Engineering andrej.gosar@gov.si The article was submitted for publication on January 4th, 2017. Uredništvo je prejelo prispevek 4. januarja 2017. 1 Introduction Earthquakes have long been recognized as an important trigger of slope movements in areas with pro-nouncedtopography.Forsomeearthquakes,especiallyinAsiaandLatinAmerica,theyhavemoredramatic consequences than ground shaking itself, through damming narrow valleys (e.g. Komac and Zorn 2016) orburyingcompletesettlements(GuerrieriandVittori2007).Inareaswithunfavourablegeomorphicand geologicsettingslandslidesorrockfallscanbecomeaprimarysourceofdamageanddeathtoll.Forexam­ple,inthePeruvianearthquakein1970,almosthalfofthe54,000fatalitieswereduetoanimmenselandslide that descended from Nevado Huascaran, burying two villages (Reiter 1990). Inspiteoftheirgeomorphicandeconomicsignificance,earthquake-inducedslopemovementsarestill poorlyunderstood,especially how dothe number, size and distribution of landslides orrockfalls depend on the magnitude and intensity. For hazard assessment, it is necessary to establish correlations between seismicgroundshakingandlandslidesorrockfallsindifferentgeological,topographical,andclimaticcon­ditions. One of the first systematic studies was done by Keefer (1984) who analysed 40 strong historical earthquakesdistributedworldwideintheperiod1811–1980withthemagnituderangeof5.2–9.5inorder to determine the characteristics, geological environments, and hazards of slope movements. He identi­fied 14 types of slope movements and found out that rockfalls, disrupted soil slides, and rock slides were themostcommon. Correlationsbetweenearthquakemagnitudeandslopemovementsdistributionshow thatthemaximumaffectedareaincreasesfromapproximately0km2atM=4.0to500.000km2atM=9.2. Keefer also discovered that each type of earthquake-induced slope movement occurs in a particular geo­logicalenvironment.TheworkofKeefer(1984)wasextendedbyRodriguez,Boomer,andChandler(1999) who studied additional 36 earthquakes in the magnitude range of 5.4–7.8 which occurred between 1980 and1997andcomparedtheresultsofbothstudies.Theircorrelationbetweenearthquakemagnitudeand the total area affected by slope movements differs somewhat from Keefer’s. For the intermediate magni­tude range of 5.4–7.0, a modified relation was suggested. However, the scatter of data from which the correlation was derived was greater than that found by Keefer. Both studies analysed the world’s largest earthquakes with relatively few examples of weaker events inthemagnituderangeof5.2–6.0orintensitiessmallerthanVII.However,recentstudiesinSpainhaveshown thatlandslidesalsoresultedfromlowermagnitude(Mw<5.0)earthquakes(Delgadoet al.2011).Theywere observedatgreaterdistances(>10km)incomparisontopreviousstudies.AnotherstudyofaMw4.7earth­quake with the Imax V EMS-98 in central Spain (Delgado et al. 2015) has shown that this event triggered many small rockfalls at distances of 20–30km from the epicentre. Weak ground-motion attenuation was identifiedasthemostprobablereasonforoccurrenceofslopeinstabilityatlargedistances.Maximumepi-central distance of landslide occurrence and the total affected area were both far above the upper bound curvesderived byKeefer (1984) or Rodriguez, Boomer, andChandler (1999). Identificationof variations in ground-motion attenuation or areas which are especially prone to slope movements due to geological setting is important for realistic seismic hazard assessment in problematic areas (Papanikolaou 2011). Various macroseismic scales developed during the 20th century(MCS, MSK, MM, EMS-98) only partly included the effects of earthquakes on the natural environment. But recent studies offered new evidence that coseismic environmental effects (e.g. Komac 2015) provide precious information on the earthquake intensityfield,complementingthedamage-basedmacroseismicscales.Therefore,thedefinitionofthehigh­er intensity degrees can effectively take advantage of the diagnostic characteristics of the environmental effects (Guerrieri and Vittori 2007). TheEMS-98scale,whichispredominantlyusedinEurope,considersfourcategories(Grünthal1998): theeffectonhumansandobjects,aswellasthedamagetobuildingsandthenaturalenvironment.However, environmentaleffectsareonlybrieflydescribed.Themainproblemisthatthesamephenomenonisattrib­uted to a very wide range of intensity degrees, which prevents its practical application. In 2007, the ESI 2007 was introduced as a scale based only on the effects on the natural environment (GuerrieriandVittori2007).Accordingtothisscale,secondaryeffectsinducedbythegroundshakinginclude groundcracks,slopemovements,liquefaction,anomalouswaves,andhydrogeologicalanomalies.TheESI 2007 describes each type’s characteristics and size (volume) as a diagnostic feature in a range of intensity degrees. One of the diagnostic characteristics for intensities higher than VI is also the total affected area (Table 1). Table1:Extraction from the ESI2007 scale with a description ofslope movements characteristicfor each intensity degree(after Guerrieri andVittori 2007). Intensity Slope movements Total affected area IV Largely Exceptionally, rocks may fall and small landslide may be (re)activated, along slopes where the – observed equilibrium is already near the limit state, e.g. steep slopes and cuts, with loose and generally saturated soil. V Strong Rare small rockfalls, rotational landslides and slump earth flows may take place, along often but – not necessarily steep slopes where equilibrium is near the limit state, mainly loose deposits and saturated soil. VI Slightly Rockfallsandlandslideswithvolumereachingca.103m3cantakeplace,especiallywhere – damaging equilibrium is near the limit state, e.g. steep slopes and cuts, with loose saturated soil, or highly weathered/ fractured rocks. VII Damaging Scattered landslides occur in prone areas, where equilibrium is unstable (steep slopes of 10 km2 loose/saturated soils), while modest rockfalls are common on steep gorges, cliffs). Their size is sometimes significant (103–105m3); in dry sand, sand-clay, and clay soil, the volumes are usually up to 100m3. VIII Heavily Smalltomoderate(103–105m3)landslidesarewidespread inproneareas;rarelytheycanoccur 100km2 damaging also on gentle slopes; where equilibrium is unstable (steep slopes of loose/saturated soils; rockfalls on steep gorges, coastal cliffs) their size is sometimes large (105–106m3). IX Destructive Landsliding iswidespread inproneareas,alsoongentleslopes;whereequilibrium isunstable 1,000km2 (steep slopes of loose/saturated soils; rockfalls on steep gorges, coastal cliffs) their size is frequently large (105m3), sometimes very large (106m3). X Very Largelandslidesandrockfalls(>105–106m3)arefrequent,practicallyregardlessofequilibrium 5,000km2 destructive state of slopes, causing temporary or permanent barrier lakes. River banks, artificial embankments, and sides of excavations typically collapse. XI Devastating Largelandslidesandrockfalls(>105–106m3)arefrequent,practicallyregardlessofequilibrium 10,000km2 state of slopes, causing many temporary or permanent barrier lakes. River banks, artificial embankments, and sides of excavations typically collapse. Significant landslides can occur even at 200–300km distance from the epicenter. XII Completely Largelandslidesandrockfalls(>105–106m3)arefrequent,practicallyregardlesstoequilibrium 50,000km2 devastating state of the slopes, causing many temporary or permanent barrier lakes. River banks, artificial embankments, and sides of excavations typically collapse. Significant landslides can occur at more than 200–300km distance from the epicenter. The 12 April 1998 earthquake in Krn Mountains (Figures 1 and 2) had prominent effects on the nat-uralenvironment,mainlyexpressedasmassiverockfalls.Theearthquakemagnitude(Mw)was5.6andits Imax wasVII–VIIIEMS-98(Zupančičet al. 2001). ItcausedseveredamagetobuildingsintheUpperSoča valley but no casualties. Some of its effects have already been discussed in this journal (e.g. Zorn 2002). Theaffectedareaispredominantlyasparselyinhabitedmountainousenvironment.Theapplicationofthe EMS-98scaleforintensityassessmentwasthereforelimitedtoonlyafewsettlementsintheepicentralarea. TherewasanearlyattempttoalsouseenvironmentaleffectstoassesstheintensitiesusingtheEMS-98scale (Vidrih, Ribičič, and Suhadolc 2001), but it was determined that this scale is not sufficiently detailed in descriptionsofeffectscharacteristicforparticularintensitydegrees.AftertheESI2007waspresented,Gosar (2012) performed a study aimed to evaluate its applicability to this event. It was proved that the ESI 2007 canbesuccessfullyappliedintheepicentralareatosupplementtheEMS-98scaleforintensityassessment, although the ESI 2007 is mainly aimed to evaluate much stronger earthquakes. The1998earthquake,aneventwitharelativelymoderatemagnitude,wasnotexpectedtocausesuchalarge numberofrockfalls,includingsomelargeandverylargeones.Sincethedamagewasconcentratedmainlyto buildingswithpoorseismicdesign(Komac,Zorn,andKušar2012)ortoareaswithpronouncedsiteeffects (Gosar 2007), rockfalls were the most prominent characteristic of this event (Vidrih and Ribičič 1998). It isthereforeachallengetocomparetheextentofenvironmentaleffectswithotherearthquakesworldwide and especially with the nearby 1976 Friuli Mw 6.4 earthquake. The latter occurred 35km to the West in NEItaly(Aoudiaet al.2000;CarulliandSlejko2005)inmountainswithasimilargeologicalsetting(Govi and Sorzana 1977). Since the type of environmental effects depends largely on the geological setting (for Figure 1: Location map of the study area with the epicentre of the 12th April 1998 earthquake in Krn Mountains. example landslidesprevail in looser rocks and rockfalls in harder rocks), oneof the possibilities forcom­parisonincludedintheESI2007scaleisthesizeofthetotalaffectedarea.Theaimofthisstudywastherefore tocomparethetotalaffectedareaofthe1998earthquakewithavailabledatafromworldwidestudiestosee if this earthquake deviates from established relationships between the magnitude or maximum intensity of the event and the total area affected by slope movements. 2 Methods The extensive effects of the 1998 earthquake on the natural environment were spread over a large area and thereforerequiredasystematicapproachindatacollectionandanalysis.Soonaftertheearthquakeoccurred itbecameapparentthatrockfallswerethemostfrequentphenomenonandtheonlyonespreadoverthetotal affectedarea(VidrihandRibičič1998).Asystematicapproachwasparticularlyimportantbecausethewider epicentral area is situated in high mountains, where access roads are only available in certain valleys. Data collectionandanalysiswerethereforebasedonacombinationoffieldsurveysandanalysesofaerialphotographs. Rockfallsandlandslidesweresurveyedinthefieldinthemonthsfollowingtheearthquakeandadata­baseofrockfallswasprepared.AregularaerialphotographysurveyoftheNWpartofSloveniawascarried outinJuly1998,justthreemonthsaftertheearthquake,whichwasveryusefulforthisstudy.Rockfallswere clearlyvisibleontheseimagesbecausethenewlyexposedsurfacesorrockdebrisandblockswerestillfresh, before lichens and vegetation started to change their surfaces. Stereo pairsof aerial images were analysed using stereo glasses while Digital Ortho Photos were analysed with GIS software. Quantitativeassessmentoftherockfallandlandslidesize(volume)isimportantfortheapplicationof various criteria in the ESI 2007 scale, but not so much for the assessment of the total affected area. For landslidesthisisnormallyeasier,becauseitispossibletomeasuretheareaandestimatetheaveragethick­ness of thelandslide body. Rockfallsare much more irregular than landslides,whichiswhyestimation of theirvolumeisusuallymoredifficultandrequiresmoreexperience.KrnMountainsarebuiltofMesozoic carbonates, predominantly of Upper Triassic limestones and dolomites (Zupančič et al. 2001). The area is cut by several faults which extend mainly in the NW-SE direction. In general the rocks are highly frac­tured, loose, and prone to slope movements. 3 Rockfalls induced by the 12th April 1998 earthquake Detailedinvestigationsshowedthattheearthquakecausedatleast78rockfalls(Figure2).Thesewereclas­sifiedintofivegroupsaccordingtotheirestimatedvolume(Table2).Thedistributionofverysmallrockfalls, which predominate in number (53), is quite uneven. On the other hand, medium to very large rockfalls areclearlydistributedinazoneapproximately5kmwideand9kmlong,whichextendsinaNW-SEdirec­tion, along the seismogenic Ravne fault (Figure 2). The termination of rockfalls occurrence is very sharp totheSEoftheepicentre,intheTolminkavalley,butmoregradualtotheNW,W,andN.Thestrongmotion data inversion revealed that the Ravne fault ruptured in a length of 12km between the Bovec basin and theTolminkavalley(Bajcet al.2001).Themajorityofthemedium,large,andverylargerockfallsoccurred along the same segment. Table 2: Distribution of rockfalls caused by 12 April 1998 earthquake according to their size. Size of rockfall Estimated volume (m3) Number Very small Small Medium Large Very large 102 103 104 105 >106 53 13 6 4 2 Figure 2: Locations of rockfalls in the Upper Soča valley caused by the 12 April 1998 earthquake with a contour of the total affected area (blue dashed line) and the trace of the seismogenic fault (red dashed line). Figure 3: Larger rockfalls in Krn Mountains: a) Osojnica in Tolminka valley, b) Krn and Krnčica, c) Veliki Šmohor, d) Škril in Lepena valley. p ThelargestrockfalloccurredonVelikiLemežintheLepenavalley.Itsvolumewasestimatedas15×106m3 bycomparingtwodigitalelevationmodelswhichshowthetopographyoftheareabeforeandaftertheearth­quake.Thesecondlargestrockfallwiththeestimatedvolumeof3×106m3occurredonOsojnicaMountain above the Tolminka valley (Figure 3a). Four rockfalls were classified as large. On the slopes of Krn and KrnčicaMountainsseveralmassiveplanarrockslidesoccurred(Figure3b),developedalongcracksorbed-ding planes within limestone dipping downslope. The Škril rockfall (Figure 3d) is a typical example of awedge-shapedrockslide(Vidrih2008).Thereweresixrockfallsofmediumsize.AnexampleistheVelikiŠmohorrockfall(Figure3c),wherethetopofthemountaincollapsedeventhoughtheslopeisnotverysteep. 4 Comparisonofthetotalareaaffectedbyrockfallsinducedbythe1998 earthquake with worldwide data and the ESI 2007 intensity scale Figure2showsthedistributionofall78rockfallsclassifiedaccordingtotheirvolume.Thedensityofrock­fallsovertheaffectedareaisquiteuneven,dependingonthespatialdistributionofslopefailureproneareas. Onaveragetherewerethreerockfallsperkm2,butthenumberrangesfromonerockfallatlargerdistances fromtheepicentretomorethanfiverockfallsperkm2intheclosestepicentralarea.Adetailedanalysishas 1.000.000 100.000 10.000 1000 100 10 1 Totalaffectedarea(km2) Friuli 1976 Krn Mts. M6.4 w 1998 M5w .6 4 5 6 7 Moment magnitude (M )w 8 9 10 Keefer (1984) Keefer (1984)– data Rodriguez , Boomer and Chandler (1999) Rodriguez , Boomer and Chandler (1999) – data Figure 4: The area affected by rockfalls or landslides as a function of earthquake magnitude for 40 events which occurred worldwide in 1811–1980 (Keefer1984)and36events in1980–1997(Rodriguez,BoomerandChandler1999),andthedataforthe1976Friuliand1998KrnMountainsearthquakes. Thesolidline is the upper bounddeterminedbyKeefer(1984) andthe dashedline is the onedeterminedbyRodriguez,Boomer, andChandler (1999). shownthatallverysmallrockfalls(102m3)cannotreliablydeterminethetotalaffectedareabecausesome ofthemoccurredquitefarfromotherobservedphenomena. Suchexamplesaretheverysmallrockslides that occurred in the westernmost part of the investigated area (Figure 2). Therefore, we decided to draw a contour which delimits the total affected area as a limit of continuous (nearly spaced) observations of rockfalls which includes all small (103m3) and large (105m3) rockfalls (Figure2), missingonly a few very smallones.Theareaisnearlycircularwitharadiusofapproximately7.6kmandasizeof180km2.Asalready mentioned, the distribution of medium, large, and very large rockfalls clearly shows an elongated shape along the strike of the seismogenic Ravne fault (NW–SE) terminating sharply in the SE. The distribution ofsmallandverysmallrockfallsismoreuniform,withfewerobservedoccurrencesonlyintheeasternpart, characterized by karstified surfaces and less prominent topography and thus less prone to slope failures. Theobtainedresultswerefirstcomparedwiththe1976FriuliMw6.4earthquakeforwhichGoviand Sorzana (1977) made a detailed evaluation of slope movements based on aerial photo interpretation and field mapping. They discovered that photo interpretation is a very effective method, that rockfalls occurred mainly in places where they had already occurred in the past, and that the weakening of rocks bytectonicfracturingisanimportantfactorforrockfalldistribution.However,thisstudydoesnotinclude a map of rockfall distribution. The total affected area was estimated by Keefer (1984), based on studies of Ambraseys(1976)andGovi(1977),tobe2050km2large. Thiscorrespondstoacirclewithr=25.5km. AsignificantlystrongerearthquakeinageologicallysimilarareawhereMesozoiccarbonatesprevailresult­ed in the considerably larger affected area, as expected (Govi and Sorzana 1977). The results of the 1998 earthquake were then compared with the results for worldwide datasets, and established relations for the upper bound limit in the relation between the total affected area and earth-quakemagnitudeaccordingtoKeefer(1984)andRodriguez,Boomer,andChandler(1999).Eventhough rockfallswerethemostprominentandwidespreadphenomenonofthisearthquake,thetotalaffectedarea (180km2) is still much smaller than the established upper bound limits (Figure 4). For the Mw 5.6 earth­quaketheupperboundlimitoftheaffectedareais430km2accordingtoKeefer(1984)and880km2according to Rodriguez, Boomer, and Chandler (1999). Comparison of the relation between the total affected area and the macroseismic intensity using the ESI 2007 scale has shown that the area affected by the 1998 earthquake with Imax VII–VIII significantly exceedsthevalueexpectedfromtheESI2007scale(Figure5). AccordingtotheESI2007anareaofabout 30km2 is expected at this intensity, interpolated between 10km2 at intensity VII and 100km2 at intensi­ty VIII (Table 1, Figure 5). On the other hand, the area of 2050km2 affected by the 1976 earthquake with Imax X (Giorgetti 1976) is lower than the value expected from the ESI 2007, which assigns a total affected area of 5000km2 to intensity X (Table 1, Figure 5). The affected area depends not only on the magnitude of the earthquake but also on its hypocentral depth. When comparing the 1998 and the 1976 earthquakes, the difference in hypocentral depth is min­imal, namely 7.6km for the former and 6km for the latter. For the Friuli event the focal depth was first estimated at25km(Console1976)duetothelargedistancefromtheepicentretothenearestseismicsta­tioninTrieste.However,therelocationstudyofAoudiaetal.(2000)estimatesitat6km.Thesecondparameter which can affectthe shape andsize of the affected area is the focalmechanism whichinfluences theradi­ation of seismic energy from the source. It was a reverse one (a W–E trending fault) for the Friuli event (Console1976)andalmostapuredextralstrike-slip(aNW–SEtrendingfault)fortheKrnMountainsevent (Zupančič et al. 2001). The elongated shape of the area affected by medium to very large rockfalls in Krn Mountains is related to the direction of the strike-slip fault, but the total affected area seems to be more or less circular (Figure 2). 5 Conclusion Althoughthe1998KrnMountainsearthquakewasaneventwitharelativelymoderatemagnitude(Mw5.6), it had prominent and widespread environmental effects expressed mainly as rockfalls of different sizes. Nevertheless,comparisonofthetotalaffectedareaof180km2withestablishedrelationsforworldwidedatasets ofmainlystrongerearthquakes has shownthatthis area is still considerably below the upperboundlimit determinedbyKeefer(1984)andRodriguez,Boomer,andChandler(1999).Thesameistrueforthe1976 FriuliMw6.4earthquakewhichhadatotalaffectedareaof2050km2.However,comparisonwiththeESI2007 100.000 ESI 2007 scale Friuli 1976 Krn Mts. 1998 M5.6 w M6.4 w Totalaffectedarea(km2) 10.000 1.000 100 10 1 VII VIII IX X Macroseismic intensity (EMS–98) XI XII Figure5:TheareaaffectedbyearthquakeenvironmentaleffectsasafunctionofmaximumintensityaccordingtotheESI2007scale(GuerrieriandVittori2007) and the data for the 1976 Friuli and 1998 Krn Mountains earthquakes. scalehasshownthatthetotalaffectedareaintheKrnMountainsearthquakeissignificantlylargerthanwhat this scale proposes for an IVII–VIII event. For the Friuli IX earthquake, the affected area is much max max lowerthanexpectedfromtheESI2007scale.Thisdifferencecouldnotbeexplainedbydiffeencesinhypocen­traldepthorfocalmechanismsofthetwoearthquakes.Theresultsofthisstudyhaveimplicationsforrealistic seismic hazard assessment – identification of slower ground-motion attenuation or areas prone to slope movementsduetogeologicalsetting.Theyalsoprovideinsightintoenvironmentalseismiceffectscaused bymoderatemagnitudeearthquakesinmountainregions,builtofcarbonaterockspronetoslopefailures. ACKNOWLEDGEMENTS: The study was realized with the support of the research program P1-0011 financedbytheSlovenianResearchAgency. TheauthorisgratefultoMihaelRibičič,MarkoKočevar,and Tomaž Beguš for their contribution in field documentation of rockfalls. 6 References Ambraseys, N. N. 1976: The Gemona di Friuli earthquake of 6 May 1976 UNESCO Technical Report RP 1975-76. Paris. ARSO 2017: Database of earthquake induced rockfalls in Krn Mountains. 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