[QUOTE=michaf;117704]But still, it's a very major chance anyway you look at it. I'm glad to live in Holland, albeit much of that is below sealevel. (Flooding is the only major disaster that can strike Holland afaik)[/QUOTE]I'm just across the sea from Holland and although above sea level, not a long way above sea level. Luckily, I'm well in-land.

Neither of us is in a particularly seismically acitive zone, so only small earthquakes (though over the last thousand years or so they have just about reached Richter 5 in the fault that lies in the English channel near Dover) and no volcanoes.

However, in terms of tornados per square meter per second, southern England is the most likely place in the world to encounter them (I've seen two myself, and have been within 50km of several more) and The Netherlands is the second most likely.

We occasionally get massive tsunamis. One around 10k years ago caused massive damage all over the North Sea. There are places in Scotland where beach material was carried many kilometers inland. That tsunami was caused by a landslip off the Norwegian coast. If the south western quarter of La Palma falls into the sea, as it's very likely to do in the fairly near future, we should be ok as we're protected by England and northern France, but I certainly wouldn't want to be anywhere near Bristol, South Wales or southern Eire. (Or in Florida, for that matter, as the waves would stand a good chance of washing over the entire peninsular from east to west.)

Although, by definition, we don't get hurricanes over here, storms with hurricane-strength winds are not that uncommon. I've experienced two since 1987.

Asteroid strikes can hit essentially anywhere...


Paul

[quote=davieddy;117703]
If so perhaps bigger quakes have lower frequency.
[/quote]

Yes. I expect energy is proportional to the volume of stressed rock,
and volume is proportional to wavelength^3.
In fact one could argue that the maximum strain in a wave
(~amplitude/wavelength) was determined by the maximum strain
in the ground prior to the quake, which suggests wave intensity
might be independent of energy of quake at an appropriate distance
away (likely to be proportional to wavelength).

This is truly "seat of the pants" physics:smile:

[QUOTE=xilman;117713]However, in terms of tornados per square meter per second, southern England is the most likely place in the world to encounter them (I've seen two myself, and have been within 50km of several more) and The Netherlands is the second most likely.[/QUOTE]Incidentally, my parents live in the Derbyshire village of Breaston. (As did I, until I left for Oxford.)

Breaston was struck by a tornado on my mother's birthday (24th September) this year. It missed my parents' house by well under a kilometre.

Paul

[quote=ATH;117532]The richter scale is ~ log[sub]10[/sub](amplitude) but the energy rises a factor of 1000 when richter scale rises 2 values, so the Richter scale is ~ log[sub]sqrt(1000)[/sub](energy) ~ log[sub]32[/sub](energy).

[/quote]

This is saying energy^2 proportional to amplitude^3, other things being
equal.

My deliberations are trying to explain this qualitatively.

David

[QUOTE=xilman;117713]
However, in terms of tornados per square meter per second, southern England is the most likely place in the world to encounter them (I've seen two myself, and have been within 50km of several more) and The Netherlands is the second most likely.
[/QUOTE]

Eeks :)
First time I hear that...
Is there a difference in strength between hurricanes and tornados, or is it the same words for the same phenomenon?

[quote=michaf;117752]Eeks :)
First time I hear that...
Is there a difference in strength between hurricanes and tornados, or is it the same words for the same phenomenon?[/quote]

They are different phenomena. Search for each and you will find a wealth of information.

I did some searching after xilman's post, because I had always thought that "tornado alley" in the central US had the most frequent occurance of tornados in the world. He may be right on the per unit area per sec qualification, but everything I've read indicates that most of these are not particularly dangerous tornados. The really destructive ones are generally found in tornado alley, with the strongest (class F5) having wind speeds of greater than 260mph. I've lived in "tornado alley" all my life, but have never actually seen a tornado (but have seen the effects of several).

[QUOTE=bsquared;117753]He may be right on the per unit area per sec qualification, but everything I've read indicates that most of these are not particularly dangerous tornados. The really destructive ones are generally found in tornado alley, with the strongest (class F5) having wind speeds of greater than 260mph.[/QUOTE]Quite true. We get a few F3 per annum but (AFAIK) never F5 strength.

However, we really do get 30 to 40 tornados each year, and in an area which is much smaller than tornado alley.

Paul

[quote=xilman;117762]

However, we really do get 30 to 40 tornados each year, and in an area which is much smaller than tornado alley.

Paul[/quote]

I don't doubt you ;) I just didn't know your area gets so many. Here is a nice site I found which talks about frequency and magnitude of tornados globally, focusing on the US: [URL]http://www.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html[/URL]

I would rather be in your situation: more likely to see the awesome and mysterious phenomena of a tornado without all the fuss and bother of potential mayhem and destruction...

[quote=ewmayer;117574]Decimal fascist. :mad:[/quote]
Especially when 32~SQR(1000):lol:

[quote=xilman;117762]Quite true. We get a few F3 per annum but (AFAIK) never F5 strength.

However, we really do get 30 to 40 tornados each year, and in an area which is much smaller than tornado alley.

Paul[/quote]

Calling Cambridge and its environs the UK's "Silicon Valley" is one thing.
Trying to compete with "Tornado Alley" is quite another. And as for
earthquakes, I don't think the English Channel is much competition
for San Andreas.

David:smile:

(St. Catz 1972)

Huygen's principle and earthquakes
 

Picture an earthquake size L just before it happens.

The typical wavelength is L, as is the diameter of
the "fault", so diffraction effects scale similarly.

Huygens would compute the amplitude as proportional to
area(L^2). And the energy is proportional to the volume (L^3).

So amplitude proportional to energy^(2/3).

Ernst/Paul/any other physicist out there like to
agree/disagree with this?

David