ORIGINAL RESEARCH PAPER

Geomorphic setting and geohazard-related featuresalong the Ionian Calabrian margin between Capo Spartiventoand Capo Rizzuto (Italy)

Danilo Morelli • Angela Cuppari • Ester Colizza •

Francesco Fanucci

Received: 10 April 2010 / Accepted: 31 March 2011

� Springer Science+Business Media B.V. 2011

Abstract The aim of this work is to describe the morpho-

dynamic processes of coastal and submarine areas based on

morpho-bathymetric data and sub-bottom acoustic profiles

from the Calabrian Ionian margin (from Capo Spartivento

to Capo Rizzuto). We describe some of the most significant

geo-hazard features and show some examples of their

complex interactions and related potential risk. The rela-

tionship between these geo-hazard features and the active

tectonics and some severe historical earthquakes and tsu-

namis is also discussed. The studied area is characterized

by several well developed canyon systems. The retrogres-

sive erosion of the canyon heads affects the continental

shelf and interacts with the coastal morpho-sedimentary

processes, evidencing the intense geomorphic activity of

this sector of Ionian margin. The widespread evidence of

mass wasting processes and slope instability, together with

the historical seismicity, makes this area also an ideal case

study for investigating on the possible relationship between

earthquakes and landslide-triggered tsunamis and assessing

the potential risk.

Keywords Marine geo-hazard � Submarine landslide �Submarine canyon � Active tectonics �Marine morphology �Marine cartography � Ionian Calabrian margin

Introduction

During the last decade most research programs in marine

geology focused on the analysis of seafloor features and

shallow sediments packages, aiming at defining seafloor

instability and sediment mass wasting processes that may

represent hazard for coastal areas and infrastructures. In

this view, a number of national and international research

projects have involved the Italian continental margins

(COSTA Project, Canals et al. 2004; MALISAR Project,

Migeon et al. 2007, MAGIC Project, Chiocci and Ridente,

this volume), where the interests for geo-hazard investi-

gation and risk analysis are rooted in the well-known high

concentrations of historical and recent natural disasters

(Italian Catalogue of Tsunami, Tinti et al. 2004; Lorito

et al. 2008). These events are often connected to the intense

seismicity (e.g. Ligurian, Calabrian and Sicilian margins)

which may influence both the long- and short-term mor-

phodynamic evolution. Moreover, such catastrophic events

may be amplified by human activity (e.g. the 1977 Gioia

Tauro harbour landslide, Colantoni et al. 1992; the 1979

Nizza harbour landslides, Cochonat et al. 1993).

The geographical distribution and frequency of geo-

hazard features indicative of intense erosion and sediment

failure along the Italian margins, such as canyons and

widespread submarine landslides, have been better con-

strained with the recent increase of Multibeam swath

bathymetry acquisition combined with high resolution

seismic data.

Detailed 3D reconstructions of surficial and deep-seated

morpho-structural settings have improved the identification

of marine geo-hazard features, allowing a better compre-

hension of geomorphic processes resulting in the rapid

morpho-dynamic evolution of continental margins. This

rapid geomorphic shaping of the seafloor is often related to

D. Morelli (&) � A. Cuppari � E. Colizza � F. Fanucci

Department of Geosciences, University of Trieste,

Via Weiss 2, 34128 Trieste, Italy

e-mail: morelli@units.it

A. Cuppari

e-mail: cuppari@units.it

E. Colizza

e-mail: colizzae@units.it

F. Fanucci

e-mail: fanucci@units.ts

123

Mar Geophys Res

DOI 10.1007/s11001-011-9130-4

sediment erosion and mass wasting; where these processes

cluster and focus, they may lead to the development of

canyon systems deeply and diffusely incising the shelf and

slope region.

Mass wasting processes are often the effect of multiple

factors which can variably interplay, making sediment

instability one of the most difficult geo-hazard to be eval-

uated. In many cases the difficulty of predicting geo-hazard

related to the complex processes like sediment failure

depends also on the scarce availability of spatial and

temporal information relative to their occurrence. How-

ever, the likelihood of geo-hazards and their possible

effects can be inferred from specific geomorphic features

(e.g. horseshoe scar, migrating bedforms, accumulation or

dispersion of giant blocks) as well as from the stratigraphic

record (e.g. debris deposits, hummocky deposits), properly

evaluated within the context of known recent and historical

events (e.g. earthquakes, inundations, and tsunamis).

The Ionian Calabrian margin is one of the most inter-

esting areas for applying the above investigative criteria in

order to define the main geomorphic features, their rela-

tionship with stratigraphy and seismotectonic setting and,

finally, the resulting geo-hazard potential. The Ionian

Calabrian margin has been the object of the MESC-05

research Project (Morphology and Evolution of the Sub-

marine Canyons in the Ionian Margin of Calabria- Uni-

versity of Trieste, Italy). In the framework of the MESC-05

project, a survey has been performed on board of the R/V

OGS EXPLORA (summer 2005) during which Multi-beam

and CHIRP data were acquired, covering the Ionian shelf

area and slope up to 1,600 m depth from Capo Spartivento

to Capo Rizzuto (Figs. 1, 2).

The collected high resolution swath bathymetry data

allowed us to define in detail the main morphological

features of the area, confirming the prevalence of the ero-

sional and mass wasting processes, particularly along

canyon systems in the slope and within the shelf area. The

deeply incised canyon headscarps and channels suggest

that erosion and sediment mass wasting may have been

accompanied by landslides. These features have been

evaluated in terms of geo-hazard potential in the frame-

work of the MaGIC project (Marine Geohazard along the

Italian Coasts).

The regional seismotectonic setting (Fig. 1) is domi-

nated by the Calabrian arc subduction zone, and is

responsible for large historical earthquakes and tsunamis

events, as well as for the high uplift rates of 0.8–0.9 mm/

year during the Plio-Quaternary (Ghisetti 1979; Canu and

Trincardi 1989; Westaway 1990; Dai Pra et al. 1993;

Bordoni and Valensise 1998; Ferranti et al. 2007). Locally,

regional uplift was accompanied by extensional and strike-

slip tectonics, by which formed ridges and basins also

within the offshore, including the study area (e.g. Sparti-

vento and Catanzaro basins; Ambrosetti et al. 1987; Del

Ben et al. 2008). This process is one of the main causes for

the intense erosion and mass wasting processes in the study

area, where the margin is characterized by a very narrow

continental shelf and steep slope, frequently incised by

canyon systems that backstep landward very close to the

modern coast and affect coastal sediment dispersal (Fig. 2;

Cuppari et al. 2007; Morelli 2008; Colizza et al. 2008).

In particular, sediment is intercepted by canyon heads-

carps and channels and is directly conveyed into the slope,

determining, on one hand, coastal erosion and shoreline

Fig. 1 Structural setting and active tectonics of the Calabrian Arc

and surronding area (Ferranti et al. 2007, modified). In a solid blackline: Front of the contractional orogen in the Apennines and Sicily;

dotted black lines: Depth (km) of the Ionian slab; gray patchesbounded by thick dashed lines: Moho Depth (km) in the Tyrrhenian

Sea; thin, solid gray lines: Uplift and subsidence rates (mm/year) in

the Late Pleistocene. In b structural setting (Del Ben et al. 2008,

modified) seismicity and active tectonics of the Calabrian Arc and of

the Ionian margin. The double-arrowed line shows extension

direction (Monaco and Tortorici 2000). Focal mechanisms of

moderate to large earthquakes (M [ 4) are shown (Ferranti et al.

2007 and references therein)

Mar Geophys Res

123

retreat, and promoting on the other hand sediment mass

wasting (debris and turbidity flows). The regional geomor-

phic setting is characterized by areas of different concen-

trations and intensity of these processes, coinciding with

different seismo-tectonic activity within three distinct areas:

the Squillace Gulf, the Siderno-Bovalino Gulf and the Stilo

rise area.

Geological setting

The study area is located in the Ionian Sea margin of

southern Calabria, whose Neogene geological evolution is

connected to the growth and SE migration of the Calabrian

Arc orogen and accretionary prism (Fig. 1). The prominent

arc-shaped orocline connecting the NW–SE trending

southern Apennines with the WSW striking Maghrebian

trusts belt, is rimmed by the Tyrrhenian and Ionian basins

characterized by thinned continental and oceanic crust.

According to several Authors, these physiographic and

geological units are the result of the Neogene north-wes-

terly subduction and easterly roll-back of the Adriatic–

Ionian slab (Malinverno and Ryan 1986; Doglioni et al.

1994; Gueguen et al. 1998; Faccenna et al. 2001; Ferranti

et al. 2009 and references therein).

Since the Late Oligocene to Early Pleistocene the process

has led to the development of a complex contractional belt

(Casero et al. 1992; Patacca and Scandone 2001) including a

stack of basement nappe and the Meso-Cenozoic sedimen-

tary cover. The accretionary prism, during its SE migration,

has involved the Oligocene–Quaternary terrigenous suc-

cession deposited in migrating foreland and piggyback

basins (Monaco et al. 1996; Patacca et al. 1990; Van Dijk

et al. 2000).

Since the Late Miocene, the structural evolution and

sedimentary succession of the Ionian area are comparable

to the typical development and migration of thin-skinned

thrust front fore-arc basins, with alternation of compres-

sional and extensional process, often accompanied by

strike-slip deformation. The Quaternary extensional phase

affecting the Calabrian Arc and the Ionian margin is tes-

tified by regional NE–SW normal fault systems and E–W

to NW–SE strike-slip fault systems segmenting the Cala-

brian Arc; these fault systems extend through the Ionian

shelf and slope (Figs. 1, 2; Sibari, Squillace Bovalino and

Spartivento faults in Del Ben et al. 2008; Van Dijk et al.

2000; Cuppari et al. 2004; Tansi et al. 2007).

During the Middle and Upper Pleistocene, the Calabrian

coast underwent significant tectonic uplift (Fig. 1; West-

away 1990; Bordoni and Valensise 1998; Ferranti et al.

2007). The regional uplift determined topographic steep-

ness, in turn enhancing erosion and large volume sediment

discharge by which mass movements and geomorphic

shaping of the margin significantly accelerated.

The surficial effects of these processes include topo-

graphic steepness with seismogenic normal and strike-slip

Fig. 2 3D view of the surveyed Ionian Calabrian Margin showing the

main morphological features of the three sectors of Bovalino-

Sidenno, Squillace Gulf and Stilo Rise. The relationship between

the main erosional-gravitational features and the active tectonics of

the Cabrian Arc is shown. The red lines indicate the main faults (by

Ambrosetti et al. 1987; Cuppari et al. 2004; Del Ben et al. 2008,

modified). The red circles and blue dots show the seismicity (by

Italian Seismicity Catalogue, 1981–2002—CSI 1.1, Castello et al.

2007, modified)

Mar Geophys Res

123

faulting, high persistence of erosion, large volume of sed-

iment discharge and related mass movements. These are

the major factors responsible for the rapidly evolving

morpho-dynamic features and geo-hazard elements detec-

ted in the surveyed area.

Methods

Multibeam bathymetry and Chirp sonar seismic data were

acquired in the frame of MESC-05 Project, over an area of

approximately 6,000 km2, including the continental shelf

and slope between Capo Spartivento and Capo Rizzuto

(Fig. 2) to a depth of 1,500 m. In addition, multi-channel

seismic sections acquired for hydrocarbon exploration have

been used for investigating the deep-seated tectono-sedi-

mentary structures. Multi-beam data have been collected

using Reson 8110 and 8150 devices and then processed

with PDS2000; the DTM spatial resolution obtained was of

50 m (Fig. 2). When possible, the interpretation and map-

ping of geo-hazard features on the multi-beam dataset has

been supported by high-resolution (Benthos Chirp II)

seismic data. The most proximal reach of canyon heads,

which is very close to the coast, could not be covered by

multi-beam data; this coastal area, however, has been

mapped using side-scan sonar data (Italian Department of

the Environment and of the Territory Management.

–SI.DI.MAR). Earthquake and tsunami events reported in

historical catalogues (Tinti et al. 2004) have been also

considered in order to better evaluate the geo-hazard

Fig. 3 Detailed 3D view of the

Bovalino-Siderno area which

shows the morphodynamic

characters of the canyons and of

the slope area (above). Side-

scan sonar records show the

proximity of the Bovalino

Canyon head to the shoreline

and to the urban areas (below)

Mar Geophys Res

123

potential of the geomorphic features investigated in the

study area.

Results

Based on seafloor morphology, three different areas can be

distinguished on the Ionian Calabrian margin: the Squillace

Gulf and the Siderno-Bovalino basin, separated by the Stilo

rise (Fig. 2). The former two are characterized by the

maximum concentration of erosional and mass wasting

features (Figs. 3, 4) and by a narrow shelf (1–5 km) rim-

med by a steep (5�–18�) slope, which is incised by can-

yons, gullies, and landslide scars. Gullies on the upper

slope alternate with canyon heads deeply incising the shelf;

the lower slope is dominated by fan-shaped deposits. The

canyon thalwegs are straight or meandering, locally with

sharp deviations, and are formed downslope by the con-

fluence of numerous tributary channels. The frequent

occurrence of landslide scars testifies recurrent sediment

mass transport and failure, particularly in the canyon heads

and along their steep flanks (up to 20�; Figs. 3, 4). Despite

the evidence of the frequency and high diffusion of these

processes, landslide accumulation bodies at the base of the

slope are scarce or absent.

In the Stilo rise area the shelf is wider (5–8 km) and the

slope is less steep (2�–5�) than in the two former areas.

Evidence of sediment erosion and instability is less

frequent and limited to the flanks of the Assi Channel and

the surrounding slope area (Fig. 2). The Assi Channel head

affects the outermost continental shelf and forms a small

valley on the slope with a meandering, locally sharply

deviating course (Fig. 4).

Based on a more detailed analysis, the narrow shelf

(1–2 km; Fig. 3) of the Bovalino-Siderno sector between

the canyon heads is characterized by a shelf-break area

completely carved by small channel heads responsible for

its progressive retreat. The entire slope area is very steep

and characterized by small channels and gullies that indi-

cate frequent erosion and large mass transport of sediment.

These are also responsible for the deep incisions of the

canyons and for occurrence of landslide scars along their

flanks. The thalwegs are mostly straight along the steep

upper slope and meandering at the base of the Bovalino

Canyon, continuing their course across the deep-sea fan

area. The Bovalino, Siderno and Caulonia canyon heads

are particularly developed and retreated within the shelf,

reaching a short distance from the shoreline (20–500 m).

Clusters of instrumental seismic epicentres with maximum

magnitude 3–4 (Tinti et al. 2007) appear located within the

areas of the canyons development, and might testify the

recent activity of NW–SE trending regional fault systems

(Figs. 2, 3; Ambrosetti et al. 1987; Cuppari et al. 2004; Del

Ben et al. 2008). Recent fault activity is confirmed by

historical large earthquakes whose devastating effects have

also led to major flooding events along the coast a short

Fig. 4 Seafloor morphology of the Squillace Gulf and Stilo rise sectors which shows the main erosional and gravitational processes and geo-

hazard sites of the area (red line) detected

Mar Geophys Res

123

distance from the canyon heads (e.g. 1784 Roccella event

and 1907 Bovalino event; Tinti et al. 2007).

In the Gulf of Squillace, one of the most significant geo-

hazard features is represented by the upper portion of the

Botricello Canyon (Fig. 4). The canyon head of the main

channel is close to the coast, while the secondary channel

head is intersecting a forward shelf edge sector. The wes-

tern flank of this canyon is affected by retrogressive

gravitational-erosive processes testified by well evident

landslide scars that are progressively reducing the slope

area which delimits the canyon from the Serre Channel.

The rapidly evolving mass-wasting processes are supported

by multi-channel seismic profiles which show deep-seated

landslide slip planes and their correspondence with a deep

compressive structure (Fig. 5). This finding is consistent

with the regional tectonic evolution, which is characterized

by the presence of a blind Plio-Quaternary and still active

arc-shape compressive front (Fig. 2; Ambrosetti et al.

1987; Del Ben et al. 2008).

The historical data of this area show a tsunami event on

8th March 1832 which struck the coastal area from Ca-

tanzaro Lido to Steccato village with maximum flooding at

Magliacane village for about 900 m, corresponding to the

canyon head. The tsunami wave of 20 m height 2 km

offshore was triggered by an earthquake with epicentre on

land, about 20 km from the coast (Tinti et al. 2007).

The Serre Channel presents a fan-shaped head charac-

terized by minor channel with shell-shaped erosion scars

which flow in the Catanzaro Canyon (Fig. 4). Chirp and

multi-channel seismic profiles suggest a channel head

development linked to surficial and deep-seated mass

movement which may be favoured by the presence of gas

charged sediments (Fig. 5). In the area where the gravita-

tional processes are concentrated, a deep compressive

structure, as described for the Botricello Canyon, is present

(Fig. 5) and its recent activity is confirmed by a cluster of

instrumental seismic epicentres with maximum magnitude

3.4 (Tinti et al. 2007). Moreover the fault planes have

likely controlled the upward migration of gas into the

younger sedimentary covers (Fig. 5).

The Sellia Canyon head is located at depth of 40 m at

a distance of 1 km from the shoreline (Fig. 6). The con-

cave-shaped axial profile and the meandering morphology

of the thalweg suggest a smaller persistence of the ero-

sional and mass wasting processes than on the other

canyons of this area. However, at the confluence with the

Squillace Canyon, the canyon thalweg is more straight

and carved with very steep flanks (Fig. 4). In this sector

the Chirp profiles show evidence of incipient destabili-

zation of significant thickness of sedimentary cover. The

Catanzaro Canyon head is subject to evident retrogressive

erosion (Fig. 6). The canyon is narrow, straight, directly

connected to the mouth of the Corace River, and drains

coastal deposits and flood supply (Fig. 7). Its northern

flank is marked by many landslide scars and an incipient

secondary channel. In this area, where small earthquake

epicentres cluster, high resolution seismic profiles show

how slope instability may be related to active faults and

gas leakage (Fig. 6).

Near the coast, the fan-shaped canyon head is at a dis-

tance of 50 m from the shoreline along a frontal area of

about 3.5 km. The coastal area affected by the head canyon

is strongly urbanized, with the presence of the Catanzaro

Lido tourist harbour (Fig. 7).

The head of Copanello and Soverato Canyons can be

described as a single zone of landslide and erosional geo-

hazard (Fig. 4). The head of the canyons reaches the

shoreline near Soverato at a distance of 100–200 m, where

coastal indentations are conditioned by a master fault

outcropping on land. In this area the morpho-dynamic

Fig. 5 3D view of the Serre Channel b and its surficial (Chirp profile;

in a) and deep seated structural setting (multichannel seismic section;

in c)

Mar Geophys Res

123

processes are amplified and the area is characterized by

both potential submarine landslides and destabilization of

the coastal zone. In this situation gravitational processes

can simultaneously affect the coast and the seabed.

The Assi Channel head is strongly conditioned by scars

that characterize the southern side of the Stilo Rise. This

situation can be classified as a slow gravity mass flow

(Fig. 8). The channel head interests only the outermost

shelf edge at a distance of 4–5 km from the Assi river

mouth. In the shelf area the seabed morphology shows

scarce morpho-dynamic evidence of direct and recent

interaction between the Fiumara Assi river sediment dis-

charge events and the channel head erosional processes.

Nevertheless the two areas are linked by a gentle seabed

scarp coinciding with a WNW–ESE trending and NNE

dipping normal fault which displaces the Holocene

deposits (Fig. 8).

The head morpho-dynamic characters and the location

suggest that its main development is attributable to the Last

Glacial Maximum (*25–16 ka). The recent erosional and

mass-wasting features are likely induced by the flank

channel steepness.

Fig. 6 Chirp profile (b) of the

northern side of the Catanzaro

Canyon (a). The area is

characterized by mass wasting

conditioned by active faults and

fluid escape (disruption of the

layering). The Chirp profile and

3D view (in c) show an inferred

mud volcano feature

Mar Geophys Res

123

Discussion

The different morphological character of the three sectors

described above reflect, to some extent, the effect of the

regional uplift and active tectonics on the morphodynamic

evolution of the Ionian Sea margin of Calabria. Distribu-

tion of mass wasting and erosional features, as well as the

main canyon heads, coincide with fault systems and tec-

tonic lineaments dissecting the Calabrian Arc (Fig. 2), and

are located near the coastal infrastructures.

In terms of potential geo-hazard, these coastal areas are

exposed to retrogressive erosion of the canyon headscarps

yielding sediment mass-wasting and failure, both on the

shelf edge, where sediment loading is significant, and on

the steep slope and canyon flanks; slope failure is also

associated with gas-charged sediment and shallow faults

dissecting Pleistocene and Holocene deposits.

The absence of significant landslide accumulations at

the base of the slopes suggests that the sediment failure

mainly occurred as small-scale processes in form of fre-

quent and diffused debris flows (grain/mud flows) evolving

downslope into turbidity flows, rather than as large-scale

landslides (debris avalanches). Nevertheless, it is also

possible that larger landslide deposits may have been

reworked and/or transported at greater distance (McAdoo

et al. 2000; De Blasio et al. 2006).

An example of very large slope failure is recorded in the

area between the two canyons of Bovalino and Siderno,

where the widespread retrogressive erosional and gravita-

tional processes have reduced the shelf to a narrow sub-

littoral zone (Fig. 3). Relative to such events, it is still a

matter of debate whether seismicity may have contributed

to slope instability and whether instability progressed

Fig. 7 Side-scan sonar records of the head of Catanzaro Canyon

which show its proximity to the coastal area and to the tourist harbour

Fig. 8 3D view of the head of Assi Channel which affects the shelf edge. In the shelf area Chirp profiles show the presence of active faults that

displace the base of the Holocene section

Mar Geophys Res

123

through frequent and small events or less frequent but

larger submarine landslides.

The hypothesis that large landslides are responsible for

the collapse of a shelf area portion must be better evalu-

ated. In particular, further investigation is required in order

to constrain the cause-and-effect relationship between

historical earthquakes, large submarine landslides, and

historical tsunamis which affected the coastal areas (e.g.

1784 Roccella event and 1907 Bovalino event; Fig. 9).

Defining such relationships would significantly increase the

evaluation of the potential geo-hazard and related risk

along the studied margin.

Nonetheless, the most critical geo-hazard situation is

represented by the active retrogressive development of the

Bovalino, Siderno and Caulonia canyon heads. Their

proximity to the coastline (20–500 m) causes the instability

and capture of coastal sediments (Fig. 3).

Analogous situations have been recognized in other

areas of the Gulf of Squillace at the heads of the canyons of

Botricello, Serre, Sellia, Copanello, Soverato and in the

most extreme conditions, near the Catanzaro Lido Harbour

(Catanzaro Canyon; Figs. 4, 5, 6, 7).

In the same areas, based on the available data, the

presence of active faults may allow us to hypothesize a

possible relationship between recent fault activity and the

focussing of erosional and gravitational processes respon-

sible for the channels and canyons’ development. Despite

this evident correlation only further investigations, specif-

ically regarding the individual most critical geo-hazard

situations, will verify the consistency of this hypothesis.

Based on the small development of the head and its

great distance from the coast, the Assi channel area can be

classified as a low geo-hazard feature. However, the area

must be better analyzed by further investigation focused on

the recent fault activity (Holocene; Fig. 8). A detailed

evaluation should be carried out to estimate the faults

capability of producing significant earthquakes or trigger-

ing tsunami events like those reported to be present in the

local historical record (Fig. 9; Sea rise at Stilo in 1783;

Tinti et al. 2007).

Conclusions

The interpretation of detailed swath bathymetry, Chirp

sonar and side-scan sonar data shows that the Calabrian

Ionian margin between Capo Spartivento and Capo Rizzuto

can be divided into the following three sectors undergoing

rapid though different geomorphic evolution: the Bovalino-

Siderno, the Stilo rise and the Gulf of Squillace sectors.

These sectors are characterized by a different morpho-

structural setting, but all evidence several geo-hazard fea-

tures. In particular, several canyon systems characterized

by well developed heads provide evidence of retrogressive

erosion and sediment failure. The vicinity of the canyon

heads to the shoreline causes the coastal transport to be

intercepted and sediment supplied by rivers is in greater

part conveyed directly to the slope, with the consequence

of enhancing shoreline erosion in areas settled by infra-

structures. Mass-wasting processes also affect the steep

flanks of canyons and of their tributary channels.

The absence of landslide deposits along the canyon

thalwegs and at the base of the slope indicates the persis-

tence of erosional processes strongly controlled by frequent

Fig. 9 3D view diagram of the Ionian Calabrian Margin showing the relationship between its seismotectonic setting, the main erosional-

gravitational features (canyon heads), historical tsunami (red star) and related earthquake epicentres (Tinti et al. 2004)

Mar Geophys Res

123

turbidity flows, or dynamic processes as disintegrative

mass failure associated with large submarine landslides.

The focusing and development of these processes could be

mostly conditioned by the margin structural setting and

influenced by the activity of the offshore extent of fault

systems known on land. The offshore extent of these sys-

tems frequently coincides with the main canyon heads and

small channels (Assi Channel) on the margin.

In many cases, mass-wasting processes may be favoured

by the presence of gas charged sediment, along the flanks

of canyons, as evidenced by seismic data.

An interesting aspect put in evidence by the correlation

between the known historical tsunami events and the

described marine geo-hazard features, is the reduced dis-

tance of the latter from the coastal zones that were dam-

aged (Fig. 9). This distance in many cases turns out to be

less than the distance of the related earthquake epicentre.

Based on this evidence one can surmise that the tsunamis

have been generated by large submarine landslides trig-

gered by repeated earthquake loading. This hypothesis is

only partially supported by the frequency of landslide scars

and widespread mass movements described, and requires

further investigation aimed at defining the volume and

velocity of the failed deposit, as well as their age in order to

verify the consistency with the occurrence of known his-

torical earthquakes. A similar, more complete analysis

would allow to better address geo-hazard evaluation and

risk assessment relative to earthquake triggering of land-

slides and landslide-generated tsunamis in the studied area.

Acknowledgments This work was supported by University of

Trieste (Department of GeoSciences; Resp. F. Fanucci and E. Coli-

zza). We are grateful to the support of Project MaGIC (Marine

Geohazard along the Italian Coasts; Resp. F.L. Chiocci) funded by the

Italian Civil Protection Department and coordinated by the Institute of

Environmental Geology and Geoengineering of the Italian National

Research Council (IGAG-CNR). The marine geophysical data were

acquired in the framework of the MESC-05 project (Morphology and

Evolution of the Submarine Canyons in the Ionian Margin of Cala-

bria; Resp. E. Colizza), on board of the R/V OGS-EXPLORA and

supported by the Department for the Development of Marine Tech-

nology and Research of the Osservatorio Geofisico Sperimentale

(Trieste; Resp. R. Ramella). The Side-Scan Sonar data were collected

by the Italian Department of the Environment and of the Territory

Management. (SI.DI.MAR). L. Ferranti (University of Naples—

FedericoII) is thanked for his helpful suggestions. We are also

grateful to D. Ridente (IGAG-CNR) and of an anonymous reviewer

for their careful review and to F.L. Chiocci for editorial guidance.

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