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Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
467
DOI: 10.4408/IJEGE.2013-06.B-45
GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES
(ATERNO RIVER, ABRUZZO, ITALY)
T
ommaso
PIACENTINI
(*)
, E
nrico
MICCADEI
(*)
, r
osamaria
DI MICHELE
(*)
,
n
icola
SCIARRA
(*)
& G
iovanni
MATALONI
(**)
(*)
Università degli Studi “G. d’Annunzio” di Chieti-Pescara - Dipartimento di Ingegneria e Geologia - Pescara, Italy
(**)
Università degli Studi “G. d’Annunzio” di Chieti-Pescara - Dipartimento di Architettura - Pescara, Italy
INTRODUCTION
Among the types of instability, which vary in
terms of typology, evolution and dimension, rock falls
represent a constant hazard for structures, buildings
and the population, because of their extreme speed
(K
EEfEr
, 2003; s
carascia
m
uGnozza
et alii, 2006).
Rock falls have been studied all over the world in
several geographical and morphostructural settings,
from huge mountain escarpments to small cliffs, with
different approaches (from standard geomorphologi-
cal analysis to multidisciplinary analyses including
geology, geomorphology, geomechanics, geophysics,
modeling/ software simulation, laser scanning, etc.)
(E
vans
& H
unGr
, 1993; D
E
G
rEGorio
et alii, 1994;
B
aillifarD
et alii, 2003; D
El
m
ascHio
et alii, 2003;
B
iancHi
f
asani
et alii, 2004, 2006; B
uDETTa
, 2004;
r
EicHEnBacH
et alii, 2005; B
iancHi
f
asani
et alii,
2006; D
i
c
rEscEnzo
& s
anTo
, 2007; l
EuraTTi
et alii,
2007; c
alisTa
et alii, 2008; P
iacEnTini
& s
olDaTi
,
2008; P
aronuzzi
, 2006; c
HiEssi
et alii, 2010).
Rock falls in central Italy (Abruzzo Region) oc-
cur within the chain area, at the junction between the
chain area and the piedmont and between piedmont
hills and coastal sectors with wide coastal cliffs. This
type of landslide occurs mostly in different main mor-
phostructural settings, such as: faulted homoclinal
ridges on marine Meso-Cenozoic carbonate rocks,
calcareous rock slopes of karst landforms, structural
scarps on marine Neogene arenaceous, gypsum and
conglomerate deposits, structural scarps on conglom-
ABSTRACT
Among the types of instability, which vary in
terms of typology, evolution and dimension, rock falls
represent a constant hazard for structures, buildings
and the population, because of their extreme speed.
Rock falls in central Italy (Abruzzo Region) oc-
cur within the chain area, at the junction between the
chain area and the piedmont and between piedmont
hills and coastal sectors with wide coastal cliffs.
This work focuses on the multidisciplinary analy-
sis of rock falls affecting fault homocline ridges and,
particularly, on the case of the San Venzanzio gorges
(Aterno river) well known for rock falls particularly af-
ter the 2009 L’Aquila eartquake. The gorges are located
along the Aterno river within the central Apennines, be-
tween L’Aquila and Sulmona, in a geological and geo-
morphological context typical of the Apennines chain.
The analysis is based on 1:5.000-1.10.000 field
geological and geomorphological mapping integrated
with reported events analysis, photogeological analy-
sis, laser scanning and geomechanical investigations.
This approach is considered vital for a correct inves-
tigation of rock fall hazard and susceptibility, particu-
larly on large slopes where topographical, geological,
tectonic, geomechanical and geomorphological vari-
ation control rock fall development. In these cases,
only a complete geological, morphostructural and
geomechanical data set allows to achieve effective
results when applying deterministic and probabilistic
methods for rock falls investigation.
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T. PIACENTINI, E. MICCADEI, R. DI MICHELE, N. SCIARRA & G. MATALONI,
468
International Conference Vajont 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide Padua, Italy - 8-10 October 2013
The area has been studied since the 1990s through
field surveys, focusing on the morphotectonic setting
and Neogene-Quaternary tectonic evolution, which
is difficult to understand due to high bedrock fractu-
ration and cover deposits (m
iccaDEi
et alii, 1999a,b).
Over the last few decades this area has been involved
in the new Geological Map of Italy, scale 1:50.000
(APAT, 2006; ISPRA, 2010).
This study stemmed from the consideration that
rock falls accounted for 67% of the mass movements
triggered by the 2009 L’Aquila earthquake in the
mountain area (some of them in the San Venanzio
gorges >40 km from the epicenter area) (m
iccaDEi
et
alii, 2010) and other episodes were recorded during
extreme weather events that caused floods in the pied-
mont and coastal areas. The analysis of rock falls is
mostly based on field data and has been carried out
through: a historical analysis of past events, a multi-
temporal and multiscale analysis of aerial photos, geo-
logical and geomorphological field mapping, a geo-
mechanical analysis of rock masses, and laser scanner
imaging (B
iancHi
f
asani
et alii, 2006; c
alisTa
et alii,
2008; m
iccaDEi
et alii, 2012b).
This methodological approach is vital for a
complete and effective analysis of rock fall hazard
erates and breccias of Quaternary continental deposits
(m
iccaDEi
et alii, 2013).
This work focuses on the multidisciplinary analy-
sis of rock falls affecting fault homocline ridges and
particularly, on the case of the San Venzanzio gorges.
The gorges are located along the Aterno river within
the central Apennines, between L’Aquila and Sul-
mona, in a geological and geomorphological context
typical of the Apennines chain.
Fig. 1 - Physiographic scheme of the Abruzzo region and
location map of the study area (red box)
Fig. 2 - Panoramic view of the San Venanzio gorges, along the Aterno river valley
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GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES (ATERNO RIVER, ABRUZZO, ITALY)
Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
469
STUDY AREA
The San Venanzio gorges are located along the At-
erno river valley, between the L’Aquila basin and the
Sulmona basin (Fig. 2). They are 9 km long, within an
asymmetric valley with NW-SE orientation, between
the Mt. Mentino ridge (1164 m a.s.l.) towards NE and
the Mt. Urano-Le Spugne ridge (1080-1046 m a.s.l.)
towards SW. The elevation of the Aterno river bed de-
creases from >400 m (at Molina Aterno) to <270 m
a.s.l. (at Raiano in the Sulmona basin). The transversal
profile is asymmetric, with a steep NE slope with >
200 m high rock scarps, and a moderately steep SW
slope with a transversal steps-like morphology.
MORPHOMETRY
Within the gorges elevation ranges from 1164
m a.s.l. on the NE side (Mt. Mentino) to 270-400 m
along the incision, to 1080-1046 m a.s.l. on the SW
side (Mt. Urano-Le Spugne) (Fig. 3a,b,d). The main
rock scarps are 20-50 m high on the SW slope and up
to >200 m high on the NE one.
The slope is very high on both sides (60-150%)
and susceptibility including kinematics, determinis-
tic and probabilistic methods. Moreover, this kind
of studies is required at various levels: on a regional
scale to prevent instability phenomena and reduce
the risk of rock fall; on a local scale for correct land
management as well as a tool for predicting the
scene of a disaster and its impact on the anthropized
landscape.
The relief features of the Central Apennines are
consist of N-S, NW-SE or E-W carbonate ridges
(2000-3000 m high), with intervening narrow valleys
parallel to the ridges and cut in either terrigenous or
carbonate rocks, or by wide intermontane tectonic
(and or karst) basins, in most cases, partially filled
with continental Quaternary deposits (Fig. 1). Ridges
have steep slopes and are incised, both longitudinally
and transversally, by deep cuts and gorges.
The development and deepening of the drainage
system in opposition to the tectonic activity and re-
gional uplift has meant that fluvial and slope-landslide
processes have dominated the evolution of the chain
landscape (D’a
lEssanDro
et alii, 2003).
Fig. 3 - San Venanzio gorge physiography: a) Elevation map; b) shaded relief image; c) slope map; d) aspect map
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T. PIACENTINI, E. MICCADEI, R. DI MICHELE, N. SCIARRA & G. MATALONI,
470
International Conference Vajont 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide Padua, Italy - 8-10 October 2013
GEOLOGY
The ridges surrounding the gorges consist of
slope-basin marine Meso-Cenozoic carbonate suc-
cessions, made up of interbedded micritic limestones,
calcarenites and calcirudites (m
iccaDEi
et alii, 1999b;
c
EnTamorE
et alii, 2006; m
iccaDEi
et alii, 2012 a and
references therein).
The structural setting results from a polyphasic
Neogene-Quaternary tectonics with strike slip tecton-
ics followed by an extensional one. Tectonic activity
developed since at least the Early Pleistocene and has
caused a vertical displacement of the bedrock in the
order of several hundreds of metres along the main
fault system. A series of secondary faults and transfer
elements is linked to the main ones.
The San Venanzio gorges are located between two
main NW-SE oriented and NE dipping calcareous ho-
moclines (Fig. 4). Mt. Urano is a ~35° NE dipping NW-
SE homocline made up of a slope-to-basin calcareous
succession. Mt. Mentino is a faulted NW-SE to N-S
homocline passing towards E to an overturned thrusted
anticline. Along the gorge, however, the calcareous
strata are mostly 30-40° ENE dipping. This structure is
cut also by E-W vertical strike slip and dip slip faults.
These homoclines are separated by a complex
tectonic fault zone along the Aterno river, which is
incorporated in the main fault system of the Aterno
(Fig. 3c). However the NE slope is step-like with steep
subvertical scarps and gentler intervening slopes (45-
110%), while the SW one is more regular (45-110%)
and is broken only by minor transversal scarps. The
overall features outline an asymmetric NW-SE valley.
The two main scarps analyzed in this work are
located on the NE slope. The highest one is in the SE
part of the gorge. It consists of at least three overlap-
ping 50-100 m scarps oblique to the slope, with an
overall elevation up to >200 m. The second scarp is
in the NW part of the slope. It is a single rectilinear or
slightly sinuous scarp, parallel to the valley, 30-100 m
high, with a secondary 30-60 m scarp at the base, in
the NW termination.
Fig. 5 - Steps-like slopes with structural scarps and fault
scarps on the NE slope of the San Venanzio gorges
(for scarp legend see Fig. 6): a) SE part; b) cen-
tral part
Fig. 4 - Geological map of the San Venanzio gorges
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GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES (ATERNO RIVER, ABRUZZO, ITALY)
Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
471
1999b; D’a
lEssanDro
et alii, 2003).
The landform distribution is strongly controlled
by the morphotectonic setting of the area, which in-
duced variable slopes with scarps and step-like slopes
(Fig. 5). The step-like slopes are related to the strata
attitude (on the dip slope side) and to tectonic ele-
ments (on the fault slope).
The main landforms within the gorges include the
following (Fig. 6): structural landforms, slope land-
forms and mass movement, fluvial landforms (along
the main gorge). Karst landforms are widespread
along the calcareous slopes and on top of the ridges.
Structural scarps occur along the main banks and
strata on the SW side of the valley; these landforms
edge wide dip slopes, 30-40° NE-dipping; fault scarps
occur on the NE side of the valley along the main
faults, with an up–to-100m height, from vertical to
high angle SW-dipping; ridges are present on top of
the main homoclines, straight and NW-SE oriented.
Slope landforms and mass movements include the
following: talus slopes, which are mainly active in
the NE slope and mainly inactive or dormant in the
SW slope; locally talus cones occurring at the slope
base and rock falls at the base of the main scarps all
along the valley and within the gorge; several debris
channels incising the NE slope and feeding the talus
slopes and cones. Fluvial landforms are mainly gorges
valley (B
osi
& B
ErTini
, 1970; m
iccaDEi
et alii, 1999b;
APAT, 2006; f
alcucci
et alii, 2011). This is affected
by a polyphasic tectonic with strike slip and dip slip
movements displacing previous thrust faults with a
complex interference geometry.
On the gorges’ slopes cover Quaternary deposits are
poorly present. They are mainly made up of talus slope
deposits and rock fall deposits in the NE slope and of
talus slope and thin colluvial deposits in the SE slope.
Only at the outlet of the gorge into the Sulmona basin,
can a thick complex Middle Pleistocene to Holocene
succession of cover Quaternary deposits be found, most-
ly related to alluvial, lacustrine and slope environments,
forming active, inactive and relict landforms (B
aGnaia
et alii, 1989; m
iccaDEi
et alii, 1999a; APAT, 2006).
GEOMORPHOLOGY
The ongoing uplift of the area and the local tec-
tonic effects induced the valley and gorge incision
controlled by the high fracturation of the rock masses
along different directions (main faults NW-SE sec-
ondary ones NE-SW, N-S, E-W). The morphostruc-
tural features are well defined by faulted homocline
ridges separated by a deep tectonic asymmetric val-
ley with a dip slope on the SW side (Mt. Urano ho-
mocline) and a fault slope on the NE side (Mt. Men-
tino homocline) (D
EmanGEoT
, 1965; m
iccaDEi
et alii,
Fig. 6 - Geomorphological and rock fall map of the San Venanzio gorge from reported events and field survey
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T. PIACENTINI, E. MICCADEI, R. DI MICHELE, N. SCIARRA & G. MATALONI,
472
International Conference Vajont 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide Padua, Italy - 8-10 October 2013
incised in the bottom of the valley. Karst landforms
affect all the calcareous ridges; large landforms (i.e.
dolines) are present on the summit of the Mt. Mentino
ridge but mostly outside the study area; small land-
forms (i.e. karren, lapiez, underground channels and
fissures) affect all the rock scarps of the valley, open-
ing and enlarging tectonic joints and faults and induc-
ing a strong weathering of the rocks.
DATA AND RESULTS
Rock falls affect all the scarps within the gorges.
Some of them are inactive, outlined by rock fall de-
posits; most are active, affecting the main bare rock
scarps. Active rock falls have involved the road and
railroads running into the gorge several times, as doc-
umented by reported events and field mapping.
The San Venanzio gorge has been known for dec-
ades for rock fall damages, which required the installa-
tion of several protections (barriers, netting) along a road
(SS 5 Tiburtina) and a railroad (L’Aquila-Sulmona).
AVI Project data (CNR-GNDCI, 1998), tech-
nical reports, newspapers, and civic committees
allowed us 17 main reported events have been col-
lected based on AVI Project data (CNR, 1998), tech-
nical reports, newspapers, and the documents owned
by civic committees (Tab. 1). These events resulted
in moderate to severe damages. The largest event
occurred after the 2009 L’Aquila earthquake, which
triggered multiple rock falls on a >150 m long scarp,
requiring traffic blockage for several months. Minor
events not affecting infrastructures are frequent all
along the main scarps.
The reported event time distribution (Fig. 7) shows,
on average, one event every 1-10 years before 2009,
four multiple events on 6 April 2009 (L’Aquila earth-
quake main shock) and 2-4 events per year after 2009.
FIELD SURVEY
Field survey allowed for the mapping of the fol-
lowing rock falls features (Fig. 6): a) recent rock fall
detachment scars, b) rock fall bodies or single blocks,
and c) unstable blocks, which in two sites were inves-
tigated with laser scanning, together with d) reported
events pre-, sin-, and post-2009 earthquake.
Rock falls affect steep to vertical to overhanging
scarps mostly on the NE side of the gorges. Detach-
ment areas are controlled by strata attitudes parallel to
the slope or inclined less than the scarps (SW side of
the gorges), inducing slide mechanisms, or by antidip
strata intersecting joints parallel to the scarps (NE side
of the gorges), inducing toppling mechanisms, or by
oblique joint intersection, inducing toppling or wedge
sliding (locally on the NE side). Fall mechanisms are
related to rock quality, jointing, discontinuity orien-
tations compared to slope orientation and roughness,
block size. Fall paths, followed by rebound and roll-
ing, run several hundreds metres along the slopes
and usually reach the gorge bottom or are stopped by
roads, railroads or other obstacles. The biggest blocks
usually get break during rebound.
Field survey outlined variable jointing along the
main scarps, isolating unstable blocks having a mod-
erate (<1 m
3
) to large size (>2-3 m
3
) (Fig. 8a,b,c,d).
The main unstable blocks are due to: 1) large rock
slices surrounded by edge joints from which large
blocks could slide or topple, 2) highly jointed rock
peaks and pinnacles, from which moderate size rock
volumes could fall, 3) multiple blocks along the main
joints, from which multiple falls could occur.
Rock fall deposits at the base of slopes and scarps
show an irregular (locally progressive) size distribution
along the slope profile due to rock jointing and slope an-
gle. The deposits are made up of small to moderate size
Fig. 7 - Rock falls reported events time distribution
Tab. 1 - Rock fall events reported from AVI Project, tech-
nical reports, newspapers and local inventories
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GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES (ATERNO RIVER, ABRUZZO, ITALY)
Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
473
Fig. 8 - Unstable blocks and rock falls occurred in the San Venanzio gorges (Aterno river): a) central sector NE slope, un-
stable blocks along a N-S vertical joint; b) SE sector NE slope, prismatic unstable blocks with possible sliding on
strata; c) outlet of the gorges NE side, unstable blocks and scars on conglomerates and breccias of the Quaternary
continental deposits; d) NW sector NE slope, unstable blocks with possible wedge sliding; e) SW sector SW slope,
multiple rock falls; f) San Venanzio hermitage, rock fall scar and deposit; g) NW sector NE slope, rock falls on N140
open joints; h) central sector NE slope, large rock fall blocks
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T. PIACENTINI, E. MICCADEI, R. DI MICHELE, N. SCIARRA & G. MATALONI,
474
International Conference Vajont 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide Padua, Italy - 8-10 October 2013
The second site (SS5 at km 164,500, NE slope
of the gorges, B in Fig. 4) is 200 m high and 300 m
wide, showing again a step-like morphology. In this
case vertical segments are up to 30 m high and over-
hanging segments are up to 15 m high and >5 m thick;
unstable rock volumes are up to 30-50 m
3
(Fig. 9b).
GEOMECHANICAL INVESTIGATIONS
Susceptibility of the slopes to rock falls was ana-
lyzed by investigating the geomechanical features
of the slopes (I.S.M.R., 1978) and outlining possible
movement mechanisms and block dimensions. Inves-
tigations were carried out on the main rock scarps af-
fected by rock falls along the SS 5 road. Litology, joint
density and weathering and discontinuity sets were
analyzed together with their relationship with the rock
scarp attitude and main fault planes, in order to define
blocks susceptible to fall. The five investigation sites
are located all along the gorges from SW to NE and
were selected according to their geological and geo-
morphological features and their position along the SS
5 road. In all the sites open or closed pervasive joints
are present, with a high to very low joint density and
variable attitude. The statistical analysis of discontinu-
ity orientation and spacing and their relationship with
slope orientation allowed to define the main discontinu-
ity sets and the fall mechanism (Tab. 2; Fig. 10).
Joint spacing is from high (joint spacing >100 cm)
to very low (6 cm); along the main faults cataclasite
belts are present. This allows to infer the size of pos-
sible unstable blocks from medium-sized to small (>1
m
3
to 0.01 m
3
). Bigger blocks are locally present (Fig.
7) and smaller ones fall with a high frequency and are
responsible for talus slopes and cone formation. Ac-
cording to these data the rock quality is from moderate
to very poor (along the main cataclasite belts).
calcareous blocks within a pebble to cobble matrix, with
size generally increasing down slope. The large blocks
(>1 m
3
) are scattered along the slope, mostly in the lower
part and occasionally in the intermediate part (stopped
by natural or anthropic obstacles) (Fig. 8e,f,g,h).
On two of the main scarps in the middle part of
the gorges (along the SS5 road; location in Fig. 4) la-
ser scanner imaging has been performed (acquisition
with Topcon GLS 1000, Long Range terrestrial Laser
Scanner; processing with ScanMaster) in order to ana-
lyze in detail the scarp morphology and geometry as
well as the size of unstable blocks. The first site (SS5
at km 163,400, NE slope of the gorges; A in Fig. 4) is
a 150 m high and 200 m wide scarp showing a clear
step-like morphology, directly overhanging the SS
5 road. The laser scanner allowed to outline vertical
segments up to 20 m high and overhanging segments
up to 5 m high and 2 m deep; unstable blocks are up
to >3-5 m
3
(Fig. 9a).
Fig. 9 - Detailed morphometric cross section from laser
scanner imaging: a) site A; b) site B (location in
Fig. 4)
Tab. 2 - Geomechanical investigations data. Orientation of slopes, strata (S0) and main joints (F1,2,3,4) analyzed along the
San Venanzio gorges; in brackets is the spacing of discontinuity (ISMR, 1978); estimated Jv for each site
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GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES (ATERNO RIVER, ABRUZZO, ITALY)
Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
475
In the NW part of the gorges on the NE slope (4 in
Fig. 10) the intersection of several high angle discon-
tinuity sets (N30-60/75-80 and N230/85) and strata
(S0-N330/15) enables wedge sliding along NW-SE
slopes SW dipping (N145/77) and locally toppling.
In the extreme NW part of the gorges, again on the
NE slope (5 in Fig. 10) the most critical discontinu-
ity set (N140-160/70-72) is parallel to the main slope
(N150/68) and enables toppling mechanisms.
CONCLUSIONS
The San Venanzio gorges are a peculiar site for
the analysis of rock falls. They are permanently un-
der study and monitoring due to the high frequency of
rock falls triggered by high present and past seismicity
of the area or by heavy rainfall events and controlled
by the deep incision of the gorges and the evolution of
fault slopes and dip slopes of the Aterno asymmetric
tectonic valley between Mt. Mentino and Mt. Urano
faulted homocline ridges.
The analysis of morphostructural control on rock
falls as presented in this work is based on 1:5.000-
1.10.000 field geological and geomorphological
mapping integrated with reported events analysis,
photogeological analysis, laser scanning and geome-
chanical investigations. This approach is considered
vital for a correct investigation of rock fall hazard and
susceptibility, particularly on large slopes where topo-
graphical, geological, tectonic, geomechanical and
geomorphological variation control rock fall develop-
ment. In these cases, only a complete geological, mor-
The stability analysis of the slopes is based on the
analysis of the discontinuity set orientations: Strata
(S0) are the first and most important discontinuity
sets: a) N200-230/20-30 on the SW side of the SE part
of the gorges; b) N280-290/30-40 on the SW side of
the central part of the gorges; c) highly variable on
the NE side of the gorge, from horizontal to N310-
330/15-20 in the NW part, to low angle and high angle
(10-20° to 85°) S dipping in the central part, to 160-
200/25-35 in the SE part of the gorges.
In the SE part of the gorges on the SW side of
the valley (1 in Fig. 10) the intersection of strata at-
titude (S0-N220/20) and scattered joint sets (N345/65,
N30/70, N180/75, N225/80) induces the instability of
small-medium size wedge blocks (<1 m
3
) with slide
and topple mechanisms.
On the SW side of the gorges, again in the SE
part (2 in Fig. 10), strata attitude (S0-N250/35) and
joints (N270-290/75-80 and N30-70/75-60) define ob-
lique wedge blocks susceptible to toppling and fall on
NW-SE, NE dipping slopes (N345/65). The physical
and karst weathering of rock and joints weaken the
rock masses and increase, together with shrub and tree
roots, rock fall susceptibility.
In the central sector (3 in Fig. 10) on the SW side
of the valley, parallel strata (S0-N280/30) and slope
orientation (N270/70), with strata dip angle less than
slope angle, enable the development of sliding. Slid-
ing and fall are also controlled by N140-160/70 joints
(several metres long, 5-20 cm open, low roughness,
20-30 cm spaced) that cut strata transversally.
Fig. 10 - Geomechanical investigations data. a) Plots of the main discontinuity sets (strata and joints; lower hemisphere
projection) along the San Venanzio gorges from SE to NW (for investigation sites’ location see Fig. 4); black line:
slope orientation; blue line: strata attitude (S0); red line: joints (F1,2,3,4). b) Markland test plot: quadrangle: strata;
triangle: joints
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T. PIACENTINI, E. MICCADEI, R. DI MICHELE, N. SCIARRA & G. MATALONI,
476
International Conference Vajont 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide Padua, Italy - 8-10 October 2013
phostructural and geomechanical data set allows to
achieve effective results when applying deterministic
and probabilistic methods for rock falls investigation.
The complex and variable features of the San Ve-
nanzio gorges are outlined by geological and geomor-
phological mapping. The faulted homocline ridges of
Mt. Mentino and Mt. Urano have been affected by a
strong polyphasyc tectonics that developed since the
Neogene time and throughout the Quaternary (m
icca
-
DEi
et alii, 1999 b; APAT, 2006; m
iccaDEi
et alii, 2012
a), in relation to: a) N-S thrusting (Upper Messinian -
Lower Pliocene); b) strike slip tectonics along NW-SE
high angle faults (including the San Venanzio gorges
faults) (possibly Middle Pliocene); c) dip slip faulting
again along NW-SE high angle faults (in some cases
reactivation of previous faults, i.e. San Venanzio gorg-
es faults) (Pleistocene-Holocene). The intersection
and interference of these features, activated on differ-
ent times and with different movements, are responsi-
ble for the complex geological and morphostructural
setting and for the high jointing of rocks. The San
Venanzio gorges were incised after the Pleistocene
uplift along an asymmetric tectonic valley between
Mt. Mentino and Mt. Urano faulted homocline ridges.
Within the valley several high angle faults affect
the calcareous bedrock (N120-150; N40-60; N70-
110) intersecting previous thrust faults (N180/10-30)
and are characterized by fault breccias and cataclasite
belts. Rock falls within the San Venanzio gorges occur
on vertical, step-like or overhanging slopes (structural
scarps or fault scarps) due to sudden detachments from
rock scarps. They occur more in the NE side of the
valley than in the SW one due to the morphostructural
setting of the slopes and vegetation (SW: heavy tree
canopy on dip slope, NE: bare, shrubby or sparse trees,
step-like fault slope). The rock falls frequency seems to
have strongly increased after the 2009 L’Aquila earth-
quake (during which two multiple events occurred)
from 1 event every 1-5 years before 2009, to 2-4 events
per year after 2009. This could be due to increased care
Fig. 11 - A) Plots summarizing the stability conditions: 1) on the SW slope (a: main discontinuity sets; b: Markland test for me-
dium angle slopes; c: Markland test for high angle scarps); 2) on the NE slope (a: main discontinuity sets; b: Mark-
land test for medium angle slopes; c: Markland test for high angle scarps). B) Rock scarps summarizing the main
discontinuity set affecting the San Venanzio gorges area: S0-N330/15; F1-N120/80; F2= N220/65; F3-N120/90;
F4-N270/80. At the intersection of the main joints and strata a rock fall occurred on 13 October 2011 involving the
block outlined in the image
background image
GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES (ATERNO RIVER, ABRUZZO, ITALY)
Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
477
Abruzzo Region and analyzed at the light of the rela-
tionship between landslide distribution and morpho-
structural setting, resulting from the regional landslide
inventory. In the San Venanzio gorges rock falls occur
on: a) calcareous faulted homocline ridges; b) struc-
tural scarps on faulted breccias and conglomerates of
Quaternary continental deposits (Fig. 12).
ACKNOWLEDGEMENTS
This work is supported by E. Miccadei Faculty
funds, University of Chieti Pescara.
The authors wish to thank the Corpo Forestale
dello Stato (COA-Pescara) for allowing us for an heli-
copter survey of the San Venanzio gorges, Dr. Daniela
Piacentini for the fruitful discussion about rock falls’
geomorphology and Berardino Musti and Pro Valle
Subequana commettee for providing data and reports
of rock fall events. The authors wish also to thank the
Struttura Speciale di Supporto Sistema Informativo
Regionale of the Abruzzo Region for providing the
topographic data and aerial photos for the geomor-
phological investigations.
by people and governmental and local public bodies
to rock falls in this area after the 2009 L’Aquila earth-
quake, but also to increased rock fall susceptibility of
the rock scarps induced by the seismic shaking and the
related mechanical weathering.
Geomechanical investigations allowed to outline
the main discontinuity sets, strata and joints (mostly
parallel or controlled by the main tectonic elements)
and to infer the size of possible unstable blocks (from
~1 m
3
to 0,01 m
3
). The rock quality is from moderate
to very poor. The poorest rocks are those along strike
slip faults and related cataclasite belts, and at the in-
tersection with thrust faults; the scarps of these areas
are affected by high frequency falls of small blocks
(usually <0,01 m
3
) that feed talus slopes and cones.
Moreover karst weathering affect the rock scarps with
a double effects: a) small karst landforms induce a
heavy weathering of the rock masses worsening the
rock quality conditions, while b) locally karst precipi-
tation and carbonate concretion formation induce the
sealing of joints and the strengthening of rock masses.
The geomechanical investigation and the compari-
son with main tectonic features outline that instability
mostly affects N300-350 NE dipping strata (S0), inter-
sected by N175 vertical and N130/70 discontinuities,
on the SW side of the valley on high angle slopes, in-
ducing slide mechanisms. On the NE side of the valley
instability mostly affects N330-350 NE dipping strata
(S0), intersected by N175 vertical and N130/70 discon-
tinuities a) with a slide mechanism when the dip angle
is less than the slope, b) with a topple mechanism when
the dip angle is more than the slope, c) with wedge slid-
ing when intersecting N060/90 and N090/90 disconti-
nuities transversal to the slopes (Fig. 11).
The geomorphologic surveys carried out in the
gorges area before and after the April 2009 earthquake
were compared to previous studies on landslides in the
REFERENCES
APAT (2006) - Carta Geologica d’Italia (scala 1:50.000), Foglio 369 “Sulmona”. Servizio Geologico d’Italia, APAT.
B
aGnaia
r., D’
EPifanio
a. & s
ylos
l
aBini
s. (1989) - Aquila and Subaequan Basins: an example of Quaternary evolution in
Central Apennines, Italy. Quaternaria Nova, 2: 187-209.
B
aillifarD
f., J
aBoyEDoff
m. & s
arTori
m. (2003) - Rock fall hazard mapping along a mountainous road in Switzerland using
a GIS-based parameter rating approach. Nat. Hazards Earth Syst. Sci., 3: 431-438.
B
iancHi
f
asani
G., c
HiEssi
v., D
i
l
uDovico
a., E
sPosiTo
c. & s
carascia
m
uGnozza
G. (2006) - Analisi della caduta blocchi
nell’area di Pizzone (IS) in relazione all’assetto geologico-strutturale. Rend. Soc. Geol. It., 2: 49-61.
B
iancHi
f
asani
G., E
sPosiTo
c., m
affEi
a. & s
carascia
m
uGnozza
G. (2004) - Geological controls on slope failure style of
rock avalanches in Central Apennines (Italy). In: l
acErDa
, E
HrlicH
, f
onToura
& s
ayao
(
EDs
). Landslides: evaluation and
Fig. 12 - Morphostructural scheme of rock falls: a) on cal-
careous faulted homocline ridges forming talus
slopes and cones (NE slope of the San Venanzio
gorges, asterisk indicates the discontinuity inter-
section and the related scarps as in Fig. 5b and
11b); b) on structural scarps on faulted breccias
and conglomerates of Quaternary continental de-
posits (NE slope of the San Venanzio gorges at the
outlet into the Sulmona basin, see also Fig. 8c)
background image
T. PIACENTINI, E. MICCADEI, R. DI MICHELE, N. SCIARRA & G. MATALONI,
478
International Conference Vajont 1963-2013. Thoughts and analyses after 50 years since the catastrophic landslide Padua, Italy - 8-10 October 2013
stabilization. International Symposium on Landslide. Rio de Janeiro 2004: 501-507.
B
osi
c. & B
ErTini
T. (1970) - Geologia della media valle dell’Aterno. Mem. Soc. Geol. It., 9: 719-777.
B
uDETTa
P. (2004) - Assessment of rock fall risk along roads. Nat. Hazards Earth Syst. Sci., 4: 71-81.
C.N.R. - G.N.D.C.I. (1998) - Progetto AVI: censimento delle aree italiane vulnerate da calamità idrogeologiche. Rapporto di
sintesi Abruzzo. Presidenza del consiglio dei Ministri, Dipartimento della Protezione Civile.
c
alisTa
m., s
ciarra
n., D
i
G
ianDomEnico
B. & D
E
G
irolamo
c. (2008) - Analisi dei fenomeni di crollo in condizioni statiche e
dinamiche delle coste garganiche: il caso di Peschici (FG). Giornale di Geologia Applicata, 8 (2): 263-275.
c
EnTamorE
E., c
rEscEnTi
u. & D
ramis
f. (Eds.) (2006) - Note illustrative della Carta Geologica d’Italia (scala 1:50.000),
Foglio 369 "Sulmona". Servizio Geologico d’Italia, APAT.
c
HiEssi
v., D’
orEficE
m., s
carascia
m
uGnozza
G., v
iTalE
v. & c
annEsE
c. (2010) - Geological, geomechanical and geostatistical
assessment of rockfall hazard in San Quirico Village (Abruzzo, Italy). Geomorphology, 119: 147-161.
D'a
lEssanDro
l., m
iccaDEi
E. & P
iacEnTini
T. (2003) - Morphostructural elements of central-eastern Abruzzi: contributions to
the study of the role of tectonics on the morphogenesis of the Apennine chain. Quat. Int., 101-102C: 115-124.
D
E
G
rEGorio
E., G
uaDaGno
f.m., n
aPoliTano
P. & r
Ea
G. (1994) - Caratterizzazione geomeccanica e fenomeni di instabilità dei
versanti calcarei di Krupp (Isola di Capri). Geol. Romana, 30: 553-562.
D
El
m
ascHio
l., P
izziolo
m., G
ozza
G. & P
iacEnTini
D. (2004) - Una metodologia integrata in ambiente GIS per l’analisi dei
fenomeni di crollo: il caso di studio di Monte delle Formiche (BO). Il Geologo dell’Emilia Romagna, Anno IV, 19: 43-51.
D
EmanGEoT
J. (1965) - Geomorphologie des Abruzzes Adriatiques. C. Rech. et Doc. Cart. Mem. Doc., 1-403, Paris.
D
i
c
rEscEnzo
G. & s
anTo
a. (2007) - High-resolution mapping of rock fall instability through the integration of photogrammetric,
geomorphological and engineering-geological surveys. Quat. Int., 171-172: 118-130.
D
oGlioni
n. & s
alTi
l. (2009) - Studio del versante roccioso sovrastante la S.S.5 “Tiburtina” tra le progressive 163+250 -
168+000 e 161+000 - 162+000 per il pericolo indotto dalla caduta massi. Relazione geologica tecnica. Committente
ANAS S.p.A. - Compartimento dell’Aquila.
E
vanss
G. & H
unGr
o. (1993) - The assessment of rockfall hazard at the base of talus slopes. Canadian Geotecnical Journal,
30: 620-636.
f
alcucci
E., G
ori
s., m
oro
m., P
isani
a.r., m
Elini
D. G
alaDini
f. & f
rEDi
P. (2011) - The 2009 L'Aquila earthquake (Italy):
What's next in the region? Hints from stress diffusion analysis and normal fault activity. Earth and Planetary Science Letters,
305 (3-4): 350-358.
K
EEfEr
D.K. (2003) - Investigating landslides caused by earthquakes. 359 a historical review. Surv. Geophy., 23 (6): 473-510.
ISPRA (2010) - Carta Geologica d’Italia (scala 1:50.000), Foglio 378 "Scanno". Servizio Geologico d’Italia, ISPRA.
I.S.R.M. (1978) - Suggested methods for the quantitative description of discontinuities in rock masses. Int. Journ. Rock Mech.
Min. Sci. & Geomech. Abstracts, 15.
l
EuraTTi
E., c
orraDo
l
ucEnTE
c., m
EDDa
E., c
orsini
a., B
orGHi
a. & B
orGaTTi
l. (2007) - Studio, mitigazione e monitoraggio
della frana di crollo coinvolgente la strada comunale “Tagliole-Lago Santo(Comune di Pievepelago, Appennino
modenese).
Giornale di Geologia Applicata, 7: 85-89.
m
iccaDEi
E., B
arBEri
r. & c
avinaTo
G.P. (1999a) - La geologia quaternaria della Conca di Sulmona (Abruzzo, Italia centrale).
Geol. Romana, 34: 58-86.
m
iccaDEi
E., D’a
lEssanDro
l., P
aroTTo
m., P
iacEnTini
T. & P
raTurlon
a. (Eds.) (2012 a) - Note illustrative della Carta
Geologica d’Italia (scala 1:50.000), Foglio 378 "Scanno". Servizio Geologico d’Italia, ISPRA.
m
iccaDEi
E., P
aroTTo
m. & P
iacEnTini
T. (1999b) - Assetto geologico-strutturale dei Monti della Conca Subequana (Appennino
abruzzese). Geol. Romana, 34: 31-50.
m
iccaDEi
E, P
iacEnTini
T. & s
ciarra
n. (2010) - Seismically induced landslides caused by the earthquake of 6 April 2009 in
Abruzzo Region (Central Italy). In: W
illiams
et alii (E
Ds
.). Geologically active. Proceedings of 11
th
IAEG congress: 127-
141. Taylor & Francis, London.
m
iccaDEi
E., P
iacEnTini
T., G
ErBasi
f. & D
avErio
f. (2012 b) - Morphotectonic map of the Osento River basin (Abruzzo, Italy),
scale 1:30,000. Journal of Maps, 8 (1): 62-73.
m
iccaDEi
E., P
iacEnTini
T., s
ciarra
n. & D
i
m
icHElE
r. (2013) - Seismically induced landslides in Abruzzo (Central Italy):
morphostructural control. In: m
arGoTTini
C. et alii (
EDs
.). Landslide science and practice, 5: 315-320. Springer-Verlag
background image
GEOMORPHOLOGICAL ANALYSIS APPLIED TO ROCK FALLS IN ITALY:
THE CASE OF THE SAN VENANZIO GORGES (ATERNO RIVER, ABRUZZO, ITALY)
Italian Journal of Engineering Geology and Environment - Book Series (6) www.ijege.uniroma1.it © 2013 Sapienza Università
Editrice
479
Berlin Heidelberg.
P
aronuzzi
P. (2006) - Processi caratteristici e classificazione delle frane da crollo. Geologia Tecnica e Ambientale, 2006 (1-2): 5-25.
P
iacEnTini
D. & s
olDaTi
m. (2008) - Application of empiric models for the analysis of rock-fall runout at regional scale in
mountain areas: examples from the Dolomites and the northern Apennines (Italy). Geogr. Fis. Dinam. Quat., 31: 215-223.
r
EicHEnBacH
P., T
aGliavini
f., G
uzzETTi
f., P
asuTo
a. & f
uJizaWa
K. (2005) - Valutazione preliminare della pericolosità da
frana del M. Salta (prealpi friulane), con particolare riguardo alle frane da crollo. Giornale di Geologia Applicata, 2: 2-6.
s
carascia
m
uGnozza
G., B
iancHi
f
asani
G. & E
sPosiTo
c. (2006) - Le frane catastrofiche in roccia: un fattore di rischio in
Appennino? S.L.M., Riv. dell’IMONT, 27: 14-21.
background image
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