Can't resist.
Quiz show ("The Weakest Link* which I am watching ATM)
Q: The best point on a tennis racket with which to
hit the ball is called the what "spot"?
A: The G spot.

PS The guy just won:)

LOL - yes, few people know about *real* tennis sweet spot, probably due to its recent discovery, or perhaps because it sounds so similar to the sex-related one, or perhaps we're just such a sex-fixated culture composed of wannabe porn stars and the people who download them. But in any event, the tennis version was discovered by ATG female tennis player Steffi Graf, and retired men's great Stefan Edberg, in honor of which it is known [in unabbreviated form] as the "Graf-Edberg Spot."

[i]p.s.: Thanks for the glad-you-survived-the-quake sentiments, but seeing as this one was really quite modest AFA this area goes, if you have only a finite supply of remotely transmittable good karma, I beg you, save it for the next Big One.[/i]

[i]p.p.s.: I was momentarily tempted there to add a parting quip along the lines of "shake on it?", but I suppose that would be crass - real scary-earthquake survivors might well find fault with me.[/i]

[i]p.p.p.s.: I have on at least 2 occasions suggested to my buddies Larry Flax and Rick Rosenfield, co-CEOs of the California Pizza Kitchen chain of restaurants, to offer pizza with a choice of thin, thick and subducted crust, but for some reason they've never taken me up on it - I didn't even ask for trademark royalties. Stodgy old farts, no wonder [url=http://chart.finance.yahoo.com/c/my/c/cpki]their stock[/url] has been stuck in "random oscillation around a mean of $15" mode for the past decade. Time to shake up the business model, gentlemen![/i]

[quote=ewmayer;117915]LOL - yes, few people know about *real* tennis sweet spot, probably due to its recent discovery, or perhaps because it sounds so similar to the sex-related one, or perhaps we're just such a sex-fixated culture composed of wannabe porn stars and the people who download them. But in any event, the tennis version was discovered by ATG female tennis player Steffi Graf, and retired men's great Stefan Edberg, in honor of which it is known [in unabbreviated form] as the "Graf-Edberg Spot."

[/quote]

:lol:
Having googled "G spot" and been reminded that it was short
for "Grafenberg" I now appreciate the full humour of your post.

As Paul will testify, "real tennis" in England is a whole different
and ancient ball game.
I don't know when the term "sweet spot" was first applied to the
"centre of percussion", but the concept was understood long
before Graf and Edberg used their big rackets. Perhaps with
smaller rackets, the spot lay too near the rim or even outside it.
OTOH Cricket/baseball bats have been around a long time.

Huygens revisited
 

On reflection it is not obvious that increasing the
size of a given shape of earthquake is like increasing
the aperture of a hole in a diffraction experiment.
Back to square one re explaining
amplitude^3 proportional to energy^2:sad:

New Zealand's East Coast shaken by 6.8 Quake
 

[url=http://www.nytimes.com/reuters/world/international-newzealand-quake.html]New Zealand's East Coast shaken by 6.8 Quake[/url]
I see the famous "swimming pool magnitude gauge" was used successfully here as well:
[quote]Murray McPhail, who lives about 10 km from Gisborne, said he could see waves in his swimming pool as the quake shook.

"You could just about surf on it," McPhail told the NZ Press Association. "Stuff came out of cupboards, bottles fell off walls, ornaments fell."

A seismologist said the depth of the quake had limited damage and minimized any chance of a tsunami.[/quote]
...except in Mr. McPhail's swimming pool, apparently.

The quote about the quake depth raises an interesting issue for us backyard seismologists: We have rule-of-thumb methods for estimating quake distance [time between onset of initial rumbling and subsequent rolling, times 5 miles per second], magnitude [swimming pool water sloshing amplitude - we just need the right amplitude-vs-distance normalization] and direction [the ancient Chinese marbles-on-the-rim-of-a-a-bowl method], but none for estimating quake *depth*. Any ideas?

Rob G, were you shaken by the NZ quake?

[QUOTE=ewmayer;121128]Rob G, were you shaken by the NZ quake?[/QUOTE]

It was 8:55pm and my son woke up and came into the lounge announcing that his bed was shaking and that he had jumped under the doorway. My wife and I didn't notice a thing, and we were only 10ft away from him! May have had something do do with the drinks we had been having :whistle:

We thought he had just woken up from a dream until the 'breaking news' came on 10 minutes later.

We live half a mile from a huge rock quarry. While we are certain it is nothing like an earthquake, some of the explosive work there has been real surprising because there is no warning. At worst, however, the pictures on the wall rattle a little and that is about it.

We can't imagine a real earthquake. That would certainly be very freaky.

:unsure:

If one is native to an eq zone, it is fun to watch the non-natives freak when a small (or distant) quake happens.

True natives will return a seat-of-the-pants (or sole-of-the-foot) estimate, based upon the S and P waves. A handy thing if one is in bed (do I get out or stay put?)

One time I was walking along and saw non-natives stop stalk still in the open when one struck. I laid down a guess and had it within 0.5 magnitude and ~25km. (It was an aftershock occuring about 2-3 weeks later.)

[QUOTE=Uncwilly;121237]If one is native to an eq zone, it is fun to watch the non-natives freak when a small (or distant) quake happens.[/QUOTE]We get an analogous sort of reaction when visitors visit Oxford (and Cambridge) for the first time. Especially when they learn that New College, so called becauase it was the first one created after a gap of 65 years, was founded in 1379, so t's about 3 times as old as the US. My college, Exeter, was the one formed immediately before New College and dates from 1314.

I've visited a number significantly older places in the UK. Nottingham, for instance, has two thirteenth century pubs.


Paul

This is not really related to earthquakes, but imagine how much sway there is up on top of tall buildings.

[QUOTE=Xyzzy;121483]imagine how much sway there is up on top of tall buildings.[/QUOTE]

I was in a 12 story building during a fairly close 5.2 quake. It was the first building in Wellington built on the flexible rubber feet and stretching walls technology. The quake lasted for about 15 seconds but on the 10th floor it kept swinging on a couple of metres radius for about 5 minutes minutes before it stopped completely (extremely freaky!).

Can't imagine how much sway there would be on some of the skyscrapers.