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As a matter of fact the studies on the vertical movements in the 
Pisa plain ground and in the city centre have been so far carried 
out through a broad network of precision levelling performed 
from the 70s up to now (which reaches out northwards as far as 
Torre del Lago Puccini, southwards as far as Leghorn and 
eastwards up to the Pisa hills). These studies have supplied 
interesting results, essential also for the comprehension of the 
causes of the possible movements occurring in the future. 
We could not therefore ignore, in the plan of a new network 
monitoring the ground deformations, the alterations in the 
enviromental conditions which have had beyond doubt an 
influence on the steadiness of the area of the plain and of the 
town complex concerned by the present examination, such as. 
- the reconstructions made in the city centre, even though 
within restricted areas; 
- the continuous expansion of the inhabited area beyond the 
ancient walls, considered both as an increase in the used 
surface and as an augmentation in the number of buildings 
on the same surface; 
- the growing water needs following the increase in the 
population and the deep changes of habits ever since the 
economic development: an undoubted consequence is the 
enhanced exploitation of the waterbeds lying on the base of 
the hills bounding the plain. 
boreholes, partially utilised for water supply, within the 
radius of about 0.5 km from the two geothermal wells. 
4 A microseismic network consisting of 5 triaxial stations 
will be set up in the area within a few kilometres from the 
geothermal wells. 
2. LAYOUT OF LEVELLING NETWORK 
2.1 Outlines 
The network, covering an area of around 60 km 2 , develops for 
some 70 km on the whole and it consists of 12 polygons located 
along ways which can usually be run over by motorcars (fig. 1). 
Seven of these twelve polygons develop in the ancient centre of 
Pisa and in the surrounding residential areas, while five of them 
reach out northwards in the plain of Pisa in the territory far from 
the city centre. 
The criterion under lying the network project was its ability to 
monitor the ground vertical movements at best and to include 
the highest possible number of benchmarks already existing; 
this will be dramatically important both to create the "zero" 
measure for the future and to determine or "write" the history of 
the local subsidence in order to interprete the events ahead in 
the light of the past ones. 
Fig. 1 - Show's the site of the twelve benchmark meshes forming the monitoring network