application of squeesartm to the characterization of deep seated gravitational slope deformations-...

8/12/2019 Application of SqueeSARTM to the Characterization of Deep Seated Gravitational Slope Deformations- The Berceto Case Study (Parma, Italy).

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ProceedingsoftheSecondWorldLandslideForum37October2011,Rome

Andrea Tamburini(1), Sara Del Conte

(1), Gianfranco Larini

(2), Luigi

Lopardo(2),ClaudioMalaguti

(2),PaoloVescovi

(3)

Application of SqueeSARTM

to the characterization

of deep seated gravitational slope deformations:

theBerceto

case

study

(Parma,

Italy).

(1) TeleRilevamentoEuropa T.R.E.S.r.l.,RipadiPortaTicinese79,20149Milano,Italy,+39024343121

(2) RegioneEmiliaRomagna,Servizio TecnicoBacinidegliAffluentidelPo (STBPO),viaGaribaldi75,43121Parma,Italy

(3) Universit di Parma,Dipartimento Scienze della Terra, CampusUniversitario,VialeG.P.Usberti157/A,43124Parma,Italy

AbstractSqueeSAR

SAR

interferometry

is

today

one of the most advanced technologies for surfacedeformationmonitoring capable ofovercomingmost ofthe limitations of conventional differential radarinterferometry.Itexploitslongtemporalseriesofsatelliteradar data, acquired over the same area of interest atdifferent times, to identify natural radar targetswhereveryprecisedisplacementinformationcanberetrieved.

Thanks to its capability to detectmillimetre leveldisplacements over long periods and large areas,SqueeSARanalysiscanbeconsideredcomplementarytoconventionalgeologicalandgeomorphologicalstudiesinlandslide detection and monitoring, supporting theperformance of landslide inventories at regional scale.Theavailabilityofsurfacedisplacementtimeseriesforalltheradarbenchmarksidentifiedmakesitalsopossibletochange the scale of the analysis from regional to local,allowing an in depth study of the evolution of singleinstability phenomena, supporting the design oftraditionalmonitoringnetworks, and evenverifying theefficiencyofremedialworks.

The above approach was applied to study theBerceto deep seated gravitational slope deformation(DSGSD) (Parma, Italy)byprocessingsatelliteSARdatarelevanttothe19922000timespan.Bycombiningresults

obtainedin

both

ascending

and

descending

acquisition

geometries,itwaspossibletoretrievebothverticalandEWcomponentsofsurfacedisplacements.

A correlation with the results of the geophysicalinvestigations will be proposed, with a preliminaryinterpretationof the surfacedisplacement trends in theupperpartoftheslope.

Keywords:InSAR,permanentscatterers,DGSD,Berceto.

Introduction

The

Berceto

village

is

located

near

the

top

of

an

unstable

slope, characterized by periodical reactivations oftenfollowing intense meteorological events. Thesereactivations have been responsible for damages to

buildings

and

infrastructures

since

a

long

time.

The

BercetounstableslopeisreportedintheItalianLandslideInventory(IFFI)Project,partly fundedbyISPRA(ItalianInstituteforEnvironmentalProtectionandResearch).

Geophysical surveys and borehole investigationshave been recently carried out in order to obtainsubsurface data enabling a better understanding of theslopebehaviour.EightDCresistivitytomographyprofileswere recorded in the upper part of the slope andcontinuouscoreboreholesweredrilled.

Attheendoflastyear,satelliteradardatahavebeenprocessed with SqueeSAR technique, based on analgorithmdevelopedbyPolitecnicodiMilano (POLIMI)and licensed exclusively to TRE, which enables toovercometheerrors introduced intosignalphasevaluesby atmospheric artefacts, which typically affect thetraditional interferometric approach. By exploiting theESA (European SpaceAgency) ERS12 archives, surfacedisplacement data relevant to 19922000 period wereobtained.

An integrated approach based on the correlationamongtheabovedata,aimedatassessingtheriskrelatedto the landslide evolution, is still in progress; somepreliminaryresultswillbepresentedinthispaper.

Geologicalsetting

The Berceto area is located along a regional SWNEtectonicdiscontinuity,separatingtwodifferentsectorsoftheApenninechain:theLigurianEmiliantotheNWandthe TuscanEmilian to the SE. In the NW Apenninesegment thickExternalLigurianUnits arepreserved; intheSEsegment,moreexhumatedby tectonicuplift, theunderlying foredeep units are exposed (Bernini et al,1997).This tectonicuplift tookplaceduringPleistocene(Argnanietal,2003),accompaniedbyextensionalNWSEfaultson theTyrrhenian sideof theApennines (BerniniandPapani,2002).

IntheBercetoarea,closetothedividebetweentheManubiola and Baganza rivers (fig. 1), the transversaldeformation band produced SWNE sinistral strikeslip


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A.Tamburini,S.DelConte,G.Larini,L.Lopardo,C.Malaguti&P.Vescovi ApplicationofSqueeSARTMtothecharacterizationofdeepseatedgravitationalslopedeformations:theBercetocasestudy(Parma,Italy).

faults, NNESSW extensional faults, and superimposedNWSEnormalfaults(Bertoldietal,2004).ThestackofLigurian Units largely outcrops (Vescovi, 2002). TheoverturnedM.CaioFlysch,affectedbySWNEhighangletranspressive faults is tectonically overlain by ShalyChaoticComplex,consistingofblackandgreyshale,with

pervasivedevelopment

of

scaly

fabric

(Pini,

1999),

often

associated with ophiolitic bodies. The Shaly ChaoticComplexisoverthrustbytheScabiazzaSandstone,about100m thick, stratigraphicallyoverlying theMt.Rizzone

ShaleandLimestone,outcroppinginexcavationslocatednear the village (Bertoldi et al, 2004). The ScabiazzaSandstoneconsistsofaturbiditesequenceshowingthinbedded shaly and marly lithofacies, alternated bymediumbedded sandstone lithofacies. This unit wasaffectedbySvergingrecumbentfoldsandgentlydipping

detachmentfaults,

crossed

by

high

angle

fault

systems:

theNEtrending sinistral transpressive faults, theNNESSWnormalfaultsandtheNWSElatenormalfaults.

.

Figure1Location

map

of

the

study

area,

with

the

average

yearly

surface

displacement

velocity

measured

along

the

satellite

LOS.

This structural framework and the lithologicalcharacteristicsoftheScabiazzaSandstoneareconsideredresponsibleforthedevelopmentofatrenchatthetopoftheBercetoslope.

A50mboreholedrilledinthevillagein2001foundUpperPleistocene laminated lacustrinesedimentsabout25m thick (radiocarbondating 29,620290 14CyrB.P.)deposited in the trench (Unit5 inBertoldietal.,2004).The lacustrine sediments overlay a sedimentary brecciacontaining very weathered clasts of sandstone in silty

matrix(Unit

6in

Bertoldi

et,

al.,

2004)

and

passing

up

intopeat (radiocarbondating 11,15070 14CyrB.P.).Thelacustrinesequencewasaffectedby foldingandexhibits

shear surfaces, testifying both compressive and, likely,extensive deformation occurred during the LatePleistocene gravityinduced deformation of the Bercetoslope; these deformative phases may have producedeither a rotational rockslide (Bertoldi et al, 2004) orslidingovera shear surfacegentlydipping towardsNW(Corsinietal.,2006).

Surfacedisplacements

In

the

early

90s

the

first

data

on

Earths

surface

provided

bySyntheticApertureRadar(SAR)mountedonsatellites,have imparteda significantbreakthrough in the fieldofEarth Observation. Since then new unthinkable

2


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perspectives have been gained on surface deformationphenomena analysis and monitoring. The advanced

survey techniques of Earth's superficial displacementsfromsatelliteareknownasSARInterferometry(InSAR).

Figure2Geologicalcrosssections1and2.Keytosymbols:1,Mt.CaioFlysch(thickbeddedmarlstones);2,ShalyChaoticComplex(withophiolitebreccias);3,Mt.RizzoneShaleandLimestone;4,ScabiazzaSandstone(4a,Thinbeddedshaleandsandstonelithofacies;4b,Mediumbeddedsandstonelithofacies;4c,Thinbeddedmarlsandsandstonelithofacies);5,LatePleistocene

Lacustrinedeposits;6,stratigraphicboundary;7,overthrustandlowangledetachmentfaults;8,highanglefaults(shiftedbygravitywherehatched);9,gravitationalfaults(inferredwherehatched).

SAR data processing techniques have beendeveloped and improvedbyRadarGroupofElectronicsDepartmentof thePolitecnicoofMilano (POLIMI) andafterbyTeleRilevamentoEuropa (TRE), firstspinoffofPOLIMI. TRE was granted exclusive license calledPermanent Scatterers (PS) technique, or PSInSAR(Ferrettietal.,2001).TheSqueeSARtechnique(Ferrettietal.,2011)isasecondgenerationalgorithm,anevolutionofPSInSARtechnology,thatsearchesfortargetsonthegroundthatreturnstableradarreflectionsovertimebacktothesatellite.

Aswellknown,aSARimageisacollectionofsignalscoming from different types of radar targets, eithernatural (forests, rocks, etc) or manmade (buildings,bridges,poles,etc).Thesignalrecordedbythesensorcanvaryabruptlyeven inneighborpixels,dependingonthedifferent radarsignaturesof the illuminatedobjectsandtheacquisitiongeometry.Ingeneral, imagepixelswhereInSAR data can be extracted belong to two families oftargets: pointwise targets (Permanent Scatterers, PS),wherethereflectedenergycomes fromasingleorafewconnected pixels, and Distributed Targets (DS). ADistributed Scatterer (DS) corresponds to ahomogeneous area spread over a group of pixels in aradar

image,

like

for

example

an

agricultural

field,

a

forest, a debris covered area. The characteristics of theradarreturnscomingfromallpixelscorrespondingtothe

same DS, are statistically homogeneous, i.e. theinteractionbetween the radar targetongroundand theelectromagnetic wave is almost identical and can bemodeledbythesameprobabilitydensityfunction.

While PS typically correspond to pointwisescatterers exhibiting a very high Radar Cross Section(RCS), the amplitude of the radar return of a pixelbelongingtoaDSisusuallymuchweaker,duetothelackof a dominant scatterer in the resolution cell, and ischaracterizedby lowerSNR. Indeed, iftheestimationofdisplacementrateandelevationvaluesisperformedonapixelbypixel basis across aDS, results arevery noisy.However, by averaging the signal of all the pixelsbelonging to the sameDS, it ispossible to significantlyimprove the estimation quality, obtaining SNR valuessimilartothePS,atthecostofalossofspatialresolutiondue to the averaging process.Thanks to typical remotesensing characteristic and in particular, the ability ofcoveringvastremoteareasofEarth'ssurface(fromafewto thousandsof squarekilometres)and to theabilityofestimating displacement with millimetre accuracy,SqueesAR is a very effective tool for highprecisionmonitoringofsurfacedisplacements,andcanbeappliedatdifferentscales,fromregionaltosinglebuilding.

TheSqueeSARTM

analysis

provides

for

each

measurement point the average yearly displacementvelocity value and a displacement time history.

3


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Displacements are measured along the line of sight(LOS)oftheradarbeam.ThesatellitesflyovertheEarthalong polar orbits, and therefore pass over the area ofinterest in two possible geometries: ascending, flyingfrom south to north, and descending, from north tosouth. The availability of displacement data in both

ascendingand

descending

geometries

over

the

same

area

enhancesthecoverageofthestudyareaandenablestheestimation ofvertical andEWhorizontaldisplacementfields.

Figure 3verticalaverageyearlydisplacement rateprovidedbySqueeSARTManalysis

Twodata

sets

of

77

descending

and

27

ascending

SAR scenesacquiredbyERS1andERS2 satelliteswereprocessed, covering the periodJuly 1992 January 2001.Morethan6000measurementpointsinbothacquisitiongeometrieswereidentifiedwithinthestudyarea.

Figure 4 EW horizontal average yearly displacement rateprovidedbySqueeSARTManalysis

Themainresultsoftheanalysisaresummarized inthefollowingpoints:

the average yearly displacement rate (LOSdisplacements, descending geometry) is 1015mm/yr inthe urbanized area, 2030mm/yr near the foot of theslope,withmaximumvaluesupto50mm/yrmeasuredinthemidpartoftheslope

the yearly displacement rate distribution

evidencesthe

upper

limit

of

the

sliding

area,

correspondingtotheeasternlimitoftheurbanizedarea within the urbanized area and the upper right

part of theBerceto slope, seasonaldisplacement cycles,sometimes superimposed on the average displacementtrend,seemtobepresent;theamplitudeoftheseasonalcyclesreachesmaximumvaluesofabout10mm;

in the lower left part of the Berceto slope, thedisplacement timehistory seems to showan increaseofdisplacementrateduringspring;

the estimation ofvertical from EW horizontalcomponents obtained by geometrically combining data

acquiredin

ascending

and

descending

geometries

indicates that the vertical component prevails in theupper part of the slope, while the EW horizontalcomponent inhigher than theverticalone in the lowerpartoftheslope.

SubsurfacestructureoftheupperBercetoslope

EightDC resistivity tomographyprofiles,with 126smartelectrodes spaced 11.5m for a total length of 1437.5meach, crossing the upper part of the Berceto slopeincluding the village were recorded. The investigationdepthwasabout250m.Accordingtothelithologyofthegeological

units

recognized

in

the

study

area,

three

geoelectric units were recognized: resistive (coherentlithologies), conductive (shaly lithologies) andintermediate (heterogeneous lithologies and/or highwatercontent).

Two resistivity profiles, together with theirgeological interpretation (Figure 5 and 2 respectively),havebeenselectedasrepresentativeofthegeologicalandstructuralframeworkoftheBercetoslope.Fromageneralpoint of view, the following sequence was recognized,from top to bottom: an upper intermediate resistivityunit (IRU), a central conductive unit (CU) and a lower

resistiveunit

(RU).

A

more

detailed

description

of

the

selectedcrosssectionfollows.The resistivityprofile 1exhibits the IRU (Scabiazza

Sandstone) characterized by thinbedded shales andsandstones, including more resistive mediumbeddedsandstonesupto100mthickintheNWpart.TheupperIRU isdislocated bydiscontinuities interpreted both astectonicfaultsand/orgravitationalslidingsurfaces.Suchdiscontinuities are SEdipping near the Baganzavalley,NWdippingontheBercetoslope.ThecentralCU(ShalyChaotic Complex) even if more continuous than theupper one,with an average thickness of about 100m,

appearsstretched

in

at

least

three

points,

one

of

which

corresponding to thedeepeningof the lowerRU in theNW part of the cross section. This lower RU was

4


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5

interpreted as the Mt. Caio Flysch, which exhibits anantiformalgeometry faulted in theNWpart,where theunitisabout150mdeeper.

The resistivity profile 2 crosses the Bercetovillageand the trenchwith the lacustrine sedimentspreviouslydescribed, evidenced by high conductivity values. The

upperIRU

shows

higher

conductivity

values

compared

to

crosssection1,probablyrelatedtoahigherwatercontentinmore fracturedandpermeable levels.ThecentralCU(Shaly Chaotic Complex) has an average thickness ofabout 100m,and isclearlystretched in theNWpartofthe section.Compared to cross section 1, the lowerRU(Mt.CaioFlysch) is lessevidentbutvisibleat the same

depth.

Figure5DCresistivitytomographyprofiles1(byGEOINVESTs.r.l. Piacenza,up)and2(bySGGs.r.l.Siena,down).

Geoelectrical data were integrated with borehole

data

and

structural

data

collected

on

the

outcrops

close

to the village and along Baganza valley, in order toprovide a geological interpretation of the subsurfacestructureoftheBercetoslope.

The geological cross section 1 (corresponding toresistivityprofile1)showsintherightpartSWNEhighangle faults affecting the Mt. Caio Flysch; under theBercetovillagethisunitexhibitsanantiformalstructure,visible inoutcropalongtheBaganzariver.TheMt.CaioFlysch is overthrusted by the Shaly Chaotic Complex,which is overthrustedby the Scabiazza Sandstone.ThislastwasdeformedbyapreApennine Sverging folding,detached byNdipping low angle surfaces and by highangle

faults

related

to

Apennine

tectonics.

The

high

angle faultsappear shiftedbyNWdipping gravitationalfaults,thatcouldexplainthepresenceofplasticclayrichbreccia with arenaceous blocks levels identified inboreholesBH2atadepthof40and90mrespectively(fig.2).Thepresenceofgravitationalfaultscouldexplainthestretching observedwithin the Shaly Chaotic Complexandthehighersurfacedisplacementratepointedoutbysatelliteinterferometry.TheBercetolacustrinesequence,recognized in both boreholesBH3 andBH4 couldhaveprobablybeendislocatedbygravitationalfaults.About10m of lacustrine deposits, corresponding to the Unit 6

(Bertoldiet

al.,

2004),

were

encountered

in

Borehole

BH3;

thesameunit,overlainby4mthicklaminatedlacustrinesediments (Unit 5, Bertoldi et al., 2004), deformed by

extensionalshearing,were found inboreholeBH4.Such

laminated

deposits

appear

13

dipping,

meaning

the

occurenceofrotationalmovements.From a general point ofview the geological cross

section 2 (corresponding to resistivity profile 2) showsthesamegeologicalandstructural frameworkofsection1. About 25 m of laminated lacustrine deposits wereencountered in borehole BH1, within the trenchdelimited by gravitational faults corresponding to theBercetohollow.A2mthickplasticintervalwasfoundata depth of 58m, and interpreted as the evidence of agravitationalfault.

Discussionandconclusions

HypothesesabouttheevolutionoftheBercetoslopewereadvanced after integrating surface and subsurface dataandobservationswithliteraturedata.

The structural framework of the Berceto areaindicates that the upper Berceto slopewas affected bygravitational faults (Persaud and Pfiffner, 2004;UstaszewskiandPfiffner,2008).Onepossiblemechanismfor these gravitational slope processes are the deepseated gravitational slope deformations (DGSD) byDramis and SorrisoValvo (1994), recognised in severalparts of theNorthernApennines (DAmatoAvanzi and

Puccinelli,1996;

Coltorti

et

al,

2009).

The uppermost portion of the Berceto slope ischaracterized by the tectonic uplift related totranspressive tectonics; this structuremaybea relevant


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factor for the development of the DGSD (Dramis andSorrisoValvo(1994).

Several gravitational faults developed close to thenorthwestern side of the antiformal stacking of theburiedMt.CaioFlysch.WithintheScabiazzaSandstonegravitational faults using preexisting discontinuities

suchas

tectonic

faults

and

foliation

planes

and

the

kinematics seems a rotational sliding (Cruden andVarnes, 1996). Through the Shaly Chaotic Complex,characterized by lithologies affected by pronouncedfoliation, the gravitational deformations may developwith more ductile mechanical behaviour, resulting infailure surfaces flattening towards thevalley floor or adeepseated creep with very slow movement rates(Hutchinson,1988).

TheevolutionoftheDGSDwasprobalyresponsiblefortheformationofadepressionlargerthanthepresentBercetohollow,intheupperpartoftheslope,wherethe

lacustrinesequence

was

deposited.

According

to

radiocarbondata,thislacustrinesequencewasdislocatedduringtheHolocene.Thedifferenceinelevationbetweenthe bottom of the lacustrine basin encountered inboreholes BH1 and BH4 is about 50 m, which couldcorrespond toanhorizontaldisplacementofmore than100m, according to thepresentdaymorphology of theslope. Under this hypothesis the average yearlydisplacement rate is consistent with the presentdaysurface displacement ratemeasured from 1992 to 2000withsatelliteinterferometry.

Surfacedisplacementdata are also consistentwith

thehypothesis

of

gravitational

faults

reaching

the

Shaly

Chaotic Complex. The distribution of vertical vshorizontal component ratio indicates the presence ofrotational sliding surfaces; moreover the highestdisplacementratesoccurrinthecentralpartoftheslope,corresponding to the top of the deep antiformalstructure,where thedeformation of the slope seems toaffectathickersequence.

Finally, the interferometric data analysis providedsomeevidencesofcorrelationbetween landslideactivityandprecipitation.Seasonaldisplacementcyclesobservedinthetheurbanizedareaandtheupperrightpartofthe

Berceto

slope

can

be

explained

as

the

result

of

swelling

shrinkage deformation cycles, typical of the clayeydeposits, i.e. the lacustrine sequence. Moreoverdisplacementrateincreaseduringspringinthelowerleftpartof theBerceto slopecouldbean evidenceof creepphenomena superimposed on the deep deformationtrend,relatedtowatercirculation.

This first attempt of integration between surfacedisplacements provided by SqueeSARTM analysis andsubsurface data provided by geophysical and boreholeinvestigations suggested that the evolutional modelproposed for the Berceto DGSD is nevertheless morecomplex than expected. Further investigations areneeded in order to gathermore surface and subsurfacedata.Moreoveranewgroundbasedmonitoringsystemisbeinginstalled,inordertointegratetheresultsobtained

by satellite radar interferometry and improve theknowledgeoftheslopedynamics.

References

ArgnaniA.,BarbaciniG.,BerniniM.,CamuriF.,GhielmiM.,Papani

G.,RizziniF.,RoglediS.,TorelliL.,(2003)Gravitytectonicsdriven

byQuaternaryupliftintheNorthernApennines:insghtsfromthe

La SpeziaReggio Emilia geotransect.Quaternary International,

101102,pp.1326.

BerniniM., PapaniG., (2002) Ladistensionedella fossa tettonica

dellaLunigiananordoccidentale (conCartaGeologicaalla scala

1:50.000).Boll.Soc.Geol.It.,121,pp.313341.

BerniniM., Vescovi P.& ZanzucchiG., (1997) Schema strutturale

dellAppennino NordOccidentale. LAteneo Parmense Acta

Naturalia,33,pp.4354.

Bertoldi R., Chelli A., Roma R., Tellini C., Vescovi P, (2004) First

remarkson Late Pleistocene lacustrine deposits in theBerceto

area(NorthernApennines,Italy).IlQuaternario,17,pp.133143.

ColtortiM.,RavaniS.,CornamusiniG.,IelpiA.,VerrazzaniF.,(2009)

Asagging

along

the

eastern

Chianti

Mts.,

Italy.

Geomorphology,

112,pp.1526.

CorsiniA.,FarinaP.,AntonelloG.,BarbieriM.,CasagliN.,CorenF.,

GuerriL.,RonchettiF.,SterzaiP.,TarchiD., (2006)Spaceborne

and groundbased SAR interferometry as tools for landslide

hazardmanagement incivilprotection. International Journalof

RemoteSensing,27,pp.23512367.

CrudenD.M.&VarnesD.J.,(1996)Landslidestypesandprocesses.

In:A.K. Turner and R.L. Shuster (Eds.), Landslides investigation

andmitigation,T.R.B.Spec.Rep.247,NationalResearchCouncil,

pp.3675.

DAmatoAvanziG.&PuccinelliA.,(1996)Deepseatedgravitational

slopedeformationsinNorthWesternTuscany(Italy):remarkson

typology, distribution and tectonic connections. Geogr. Fis.

Dinam.Quat.,19,pp.325334.

Dramis F. & SorrisoValvo M., (1994) Deepseated gravitational

slopedeformations,relatedlandslidesandtectonics.Engineering

Geology,38,pp.231243.

FerrettiA.,PratiC.,Rocca F., (2001)Permanent Scatterers in SAR

Interferometry. IEEETrans.onGeoscienceandRemoteSensing,

Vol.39,no.1,pp.820

FerrettiA.,FumagalliA.,NovaliF.,PratiC.,RoccaF.,RucciA.,(2011)

A new algorithm for processing interferometric datastacks:

SqueeSAR. To be published on IEEE Trans. Geosciences and

RemoteSensing.

Hutchinson J.N., (1988) General Report: Morphological and

geotechnicalparametersoflandslides inrelationtogeologyand

hydrogeology.In

C.

Bonnard

(Editor),

Landslides.

Balkema,

Rotterdam,Vol.1,pp.336.

Persaud M. & Pfiffener O.A., (2004) Active deformation in the

eastern Swiss Alps: postglacial faults, seismicity and surface

uplift.Tectonophysics,385,pp.5984.

Pini, G.A., (1999) Tectonosomes and olistostromes in the argille

scaglioseoftheNorthernApennines, Italy.GeologicalSocietyof

AmericaSpecialPaper335,pp.170.

UstaszewskiM.&PfiffenerO.A., (2008)Neotectonicfaulting,uplift

and seismicity in the central and western Swiss Alps. In S.

Siegesmund, B. Fugenschuh and N. Froitzheim (Eds) Tectonic

Aspects of the AlpineDinarideCarpathian System. Geological

SocietyLondon,SpecialPublications,298,pp.231249.

VescoviP.,2002,Foglio216BorgoValdiTarodellaNuovaCarta

GeologicadItalia

alla

scala

1:

50.000

eNote

Illustrative.

Servizio

GeologicodItalia.

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application of squeesartm to the characterization of deep seated gravitational slope deformations-...

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