It's a case of bringing risk down to roughly the same tolerable level, in different circumstances. We have met the enemy, and he is us — Pogo
Previously, we've touched upon about earthquakes in Switzerland. Historically we also know about Italy, both in the south but also north (Friuli, Umbria) and even Portugal (which I don't really understand at first glance). The only European country which has to deal with major earthquakes at a fairly regular basis is Greece.
Anything above 7.0 Richter scale with an epicentre nearby a major city may well give abhorrent chaos in countries where modern architecture has not been previously tested by a big quake. I'd suspect some hazard evaluation should be available at the seismological services in each country, but I already have a PhD to finish...
How strong have the earthquakes been in Switzerland? Magnitude 4?
There are earthquakes in the Alps, but the major plate boundary (responsible for the Lisbon earthquake) is in the Southern Mediterranean (which explains Turkey, Greece, Southern Italy and Southern Spain).
Though there is this:
Plate tectonics - Wikipedia, the free encyclopedia
Not all plate boundaries are easily defined. Some are broad belts whose movements are unclear to scientists. One example would be the Mediterranean-Alpine boundary, which involves two major plates and several micro plates.
The Basel earthquake has been estimated with a intensity of IX, which can probably be correlated to a Richter scale (or the more accurate Seismic Moment). I found a hazard analysis on Basel here wherein they write:
Earthquake Scenarios for the City of Basel
The calculated scenarios are an intensity VII - VIII earthquake and one of intensity IX. These represent the expected value with return period of 475 years generally used in building codes, and the intensity of the earthquake in 1356.
Meaning, the building codes do no provide for earthquakes the magnitude of the 14th century Basel quake, and the estimated damage is considerable (Fig 1). How likely is it that we'll have another one? Don't know, but the very fact that one happened should bear caution - it's a known unknown. If stress can build up in that region to such levels, it can happen again.
The simplification of the plates in the picture works as a first approximation concept - there is no nicely defined 8 pixel line, especially when it concerns converging plates which is a very messy process. The idea one would get from the picture above when focussed on the African-EuroAsian plate margins is completely wrong. One would have to zoom in on the Mediterranean, start here.
Yes, most of the tectonic action is concentrated at a particular zone and you're correct that the majority of the major earthquakes will be centred around the Mediterranean countries. The uncertainty is: what's the extent of major seismic event towards the north? For now, we know at least Basel, and the north of Italy, can be affected. Although, for Basel, it's not clear to me if it's because of plate convergence to the south or by normal faulting as a response to crustal loading.
To address the original comment, Germany doesn't appear on Wikipedia's List of deadly earthquakes since 1900.
Portugal had a magnitude 7.8 in 1969 which killed 13 people (both the earliest and strongest on the list for Portugal, which suggests a gap in the data).
Spain has one in magnitude 5.3 in 1997 which killed one person.
The strongest on the list for France was a magnitude 4.2 which killed one person in 2001. The weakest and earliest is a 3.5 in 1983, also killing one.
Switzerland is not on the list, and neither is Austria.
Italy has 31 earthquakes on the list. The earliest is a magnitude 6.8 in 1905, killing about 1200 people. The weakest is a 4.2 in 1987, killing 2. The strongest is a 7.2 in 1908, killing 80 thousand.
Greece has 39. The earliest and strongest is a magnitude 8.2 in 1903, killing 2. The weakest is a 4.6 in 1978, killing 1. The deadliest is a 7.2 in 1953, killing 600.
Japan has 74 earthquakes on the list. The earliest is a 7.0 in 1900. The strongest is an 8.4 in 1933, killing 3,000. The deadliest is the 1923 Kanto Earthquake, magnitude 7.9 killing 140 thousand.
The US (excluding "minor outlying islands") has 29. The earliest, strongest and deadliest is the 1906 SF earthquake, 7.8 killing 1200 people. We have met the enemy, and he is us — Pogo
The most powerful recent quakes were
However, I recall reading an article by some geologists critical of the ruling assumption that the central part of the rift zone shifts in a 'lubricated' way -- that assumption is unproven, and that would imply the possibility of strong earthquakes with a low frequency. I.e., what the USA had at New Madrid in 1812 (incidentally the strongest for the contiguous states in recorded history), and China at Tangshan in 1976. Such low-frequency events are definitely missing from risk calculations, especially for high-rises, which haven't been around for long. *Traitor*, n. A benighted individual who perceives an illusory distinction between serving his nation and abetting the criminals who govern it.
We know that large magnitude events have occurred prior to the 20th century. Has modern architecture (eg. flats and office blocks) in these countries withstood a direct hit of major earthquakes? No - because they're untested. There were no major events in this time period. And Messina was bad enough.
Developments and architecture work on hindsight, retrospection and, worse, amnesia - not foresight. I've used the housing planning in England's river stormbeds during last year's floodings as example of that. I don't believe it's really that different for earthquakes.
