Review of the 1755 Lisbon Earthquake Based on Recent Analyses of Historical Observations - Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes - page 273

Fig. 11 The dispersion of the results is well referred in the data of the seism of 1950 in India (Mw
8.6; distance in miles)

9.0 events have been generated.
However, even though occurring in a collision zone, the 1755 earthquake presents
many characteristics that suggest a magnitude of that value. Certainly, due to the
non existence of a single geological structure large enough to release such amount
of energy, a multiple event involving more than one structure (for instance, parallel
structures, rupturing in cascade) might be a possibility. Figure 8 shows alignments
and gaps in the seismicity of last 50 years that fit this hypothesis.

Up to now only in subduction zones large Mw >

4 Description of the City of Lisbon and Quantification
of Damage

The city of Lisbon, around re-occupation (1147) fulfilled essentially the interior of
the Mourish Wall with a population of about 15,000 inhabitants, organized in only
seven parishes, with its main hills, roman monuments and the arm of the Tagus river
spread to Rossio (Castilho 1893).
The city develops differently along the times with its own rhythms. For instance
the evolution during the second half of the XIIIth century and the first half of the
XIVth century was rather quick.
The urban network (Fig. 12) was composed by the open squares near the river and
Rossio and the hills that surrounded downtown. More than 140 important buildings
were identified in the XIIth century, and by the time of the earthquake several new
buildings, some of great grandeur like the Opera House were present.
In 1755, Lisbon was organized in 43 parishes, from which the first 39 were the
city itself and the other 4 correspond to the parishes of the farms that, today, belong
to the City Council of Lisbon.