Usually, quakes have to be over 5 on the Richter scale to really be noticeable. I was in Estoril in 1969 when the last big earthquake hit Portugal and that was very noticeable at 7,9 on the Richter scale. Our poor new little Portuguese Podengo puppy, (fox terrier size), got the blame from my father, who woke up thinking the puppy was shaking the bed.
Luckily, the epicenter was deep down in the earth's mantle, so although there was a lot of superficial damage and unfortunately, a few deaths, it was nothing like the 1755 quake.
The following page from the Portuguese Met. Institute shows how frequent small tremors are, particularly in the Southern half of Portugal. However, most are of low impact so we don't feel them.
http://www.meteo.pt/pt/sismologia/actividade/
Seismic activity is high in this region because the southern part of Portugal lies just to the North of the boundary between the Eurasian Tectonic Plate and the African Tectonic Plate.
As regards according blame for last week's cliff face collapses near Albufeira, I don't think anyone can be blamed except people who ignore warnings. Apparently, according to press reports, Albufeira Camara had sealed the area with red "Police Type" tape and warning signs making it clear the area was dangerous. Unfortunately, if that was the case, and people ignored the warnings, you can't blame anyone except themselves.
The coastline worldwide is a dynamic feature and needs to be treated with respect. Cliffs collapse with or without earthquakes, tides rise quickly in areas such as the Bristol Channel and off Newfoundland and people get cut off.
