COMMENTS

Prior to 1994 most of the investigators considered the Gioia Tauro Plain as a Graben 
structure, bordered at its eastern margin by the Aspromonte Fault and at its western 
margin by the horst-like structure of Mount S. Elia. This hypothesis is supported by 
field reports contemporary to the 1783 earthquake, indicating the formation of a 20 km-
long crack running at the base of the presumed Aspromonte Fault and characterised by 
strong and fresh geomorphic evidence.

Valensise and D'Addezio (1994) first proposed that the Aspromonte Fault is no longer 
active because no clear evidence of offset deposits can be found and because of 
inconsistency of the landscape evolution in the Gioia Tauro Plain, that lies in the 
hangingwall of the fault. Based on the analogy with the nearby source of the 1908 
earthquake in the Messina Straits, they proposed that the causative source of the 5 
February 1783 earthquake is a relatively young, E-dipping blind normal fault (termed 
Gioia Tauro Fault) that is progressively generating a syncline having the axis about 5 
km inland and parallel to the coast. The same investigators contend that the present 
shape and elevation of the marine terraces encircling the Plain is best explained by the 
interplay between regional uplift and more localised bowl-shaped subsidence induced 
by the activity of the Gioia Tauro Fault.

Later on there have been several attempts to investigate the shape of the filling of the 
Plain in order to decide whether it is compatible with the action of a steeply-W-dipping 
or of a gently E-dipping fault. The basin fill turned out to be essentially bowl-shaped, 
with a maximum thickness of 300-500 m halfway between the Aspromonte piedmont 
and the present shoreline. This configuration is not compatible with sustained activity 
of the Aspromonte Fault, which should have induced an half-Graben pattern of 
sedimentation that is not observed.

The seismicity of the region is very limited and concentrates mostly at the edges of the 
proposed source. Important geochemical anomalies are also recorded at the 
northwestern end of the source and have been interpreted as evidence of the interplay 
between the Gioia Tauro Fault and the transverse structure known as Nicotera-Gioiosa 
Ionica Line.

Finally, Bosi and Galli (2000) opened a trench across the Aspromonte Fault near 
Cittanova. They found evidence for recent breaks that they interpret as evidence for 
primary surface faulting. The quality of the trenched materials (mostly unconsolidated 
scree at the contact between the crystalline Aspromonte rocks and the basin filling), 
however, suggests that any surface fractures could be also interpreted in terms of local 
readjustments due to the ground shaking. 

OPEN QUESTIONS

1) Is there a conclusive test that would settle the dispute between the E-dipping Gioia 
Tauro Fault and the W-dipping Aspromonte Fault?

2) Could the v-shaped river valleys and the three sets of triangular facets that are used 
to support the activity of the Aspromonte fault be the result of regional uplift instead of 
footwall uplift?

3) Could the 20 km-long crack observed by contemporary workers be due to differential 
behaviour of soft deposits under the seismic action, as suggested by De Dolomieu 
(1784)?
