Earthquake

[JB]

Wonder if there's been much rock fall underground! I'm mildly annoyed with the timing actually. Was on a bit of a solo Carlswark excursion hours before and it would have been great/absolutely terrifying to have experienced a decent earthquake underground. Might not get the chance for another 20 years or so and much more interesting than an eclipse!

Jules.

 

[paul]

Yes, but I can think of several places I would NOT want to be underground if there was the chance of the SLIGHTEST tremor...

Have you heard of the story about JRat furtling in a surface dig in Assynt (I forget the name of the dig just now) in a shakehole of boulders? He and a second caver resurfaced for a fag break when there was a tremor and the whole lot ran in!

 

[cap n chris]

Not on the same scale but many caves round `yer are within tremor-ness of the local quarry so caving during blasting times often means you can feel/hear the shock wave.

 

[Skyrmy]

Wonder if there's been much rock fall underground!

Will be a case of wait and see most likely - bound to be plenty of info coming from this weekends trips I would imagine.

 

 

[Walrus]

Aren't you supposed to wait a week or so before venturing underground in case of aftershocks or to allow stuff to settle?

 

[gus horsley]

Blasting at a nearby quarry is more likely to cause instability than an earthquake due to a different kind of shock wave.  In the case of an earthquake it would theoretically only affect caves which are very close to the surface.  Apparently there were miners underground during the 1906 San Francisco earthquake who heard a noise but didn't realise it was an earthquake till they got to the surface. 

 

[Dave H]

My missus jabbed me in the ribs and shouted "What' that?" at the oncoming rumble.
I grunted "earthquake", farted, rolled over, and went straight back to sleep (apparently).
She on the other hand was quite scared, and let me know all about it this morning 

 

[nickwilliams]

In the case of an earthquake it would theoretically only affect caves which are very close to the surface.

That's an interesting theory, Gus. Can you explain it a bit further? (I'm not saying you are wrong: I'm intrigued and would like to know more.)

Nick

 

[Peter Burgess]

Actually, I've heard much the same thing - that mines are often not affected by earthquakes, depending on the depth etc. I've also heard that a large part of Wrysgan slate quarry collapsed in the 1980s because of an earthquake. Having seen the collapse, I sometimes wonder if it was the mine collapsing that caused the earthquake rather than the other way around!

 

[CaverA]

There is a good wiki article relating to Gus's statement. I remember covering this at GCSE, and being told that the S waves were far more destructive.

http://en.wikipedia.org/wiki/Seismic_wave

Sam

 

[Cave_Troll]

since most caves in the uk are less than 200m deep, i'd say that that was practically on the surface!

 

[Slug]

There is a good wiki article relating to Gus's statement. I remember covering this at GCSE, and being told that the S waves were far more destructive.

http://en.wikipedia.org/wiki/Seismic_wave

Sam

Well I've looked at this link, and I think I understand it. So What did we get this morning ?, a "P", an "S" a "Rayliegh" or a "Love". My chair seemed to go back and forth , rather than up and down...........Next doors Dog went potty for about an hour.

 

[Peter Burgess]

Earthquakes are good for encouraging the formation of new caves. If we get more joints and cracks in the limestone for water to flow into, we'll end up with more cave passages!

 

[Hatstand]

we'll end up with more cave passages!

We is a little optopistic don't ya think???  :

 

[Brains]

we'll end up with more cave passages!

We is a little optopistic don't ya think???  :

Well, I suppose we might get some slip rift systems, but it would be our descendents that get the water worn passage I reckon...

 

[Skyrmy]

Earthquakes are good for encouraging the formation of new caves. If we get more joints and cracks in the limestone for water to flow into, we'll end up with more cave passages!

  Here's to reincarnation then 

 

[Slug]

Its a long shot considering the timing , but, Was anyone actually underground when it happened ?.

 

[martinr]

...the 1968 Meckering earthquake.. Magnitude RM 6.9 (or) It may have been the Cadoux in 1979 (RM6.2) These are 350 and 430 km NNE of Jewel Cave. Anyway an earthquake shook the Jewel Cave kiosk ? cracking the brick walls,
refrigerator doors opened and items tumbled off shelves. Clearly this created some concerns amongst those in the kiosk ? but some dozens of visitors in the cave had no idea an earthquake had occurred until they emerged to the shaken icecream purveyors.

source: http://www.ackma.org/journal/58/ANDYSEZ%2051.pdf

 

[graham]

You frequently see fallen stal, especially broken columns, and have some expert tell you that they fell during an earthquake. While there can be little doubt that some did, I suspect that the vast majority of breaks are down to much smaller and more localised effects, such as the sediment on which they are rooted being undermined by washout.

 

[Limestone_Cowboy]

In reply to the earlier comments about the type of seismic waves felt during this earthquake I would like to point out that earthquakes generate both 'P' or compressional waves and 'S' or shear waves. The other types mentioned, rayleigh and love waves, are surface waves and are caused by the constructive interferance of the S waves and their reflected counterparts from deeper layers. P waves have the smallest amplitude then S waves then surface waves. They also have differing frequencies and you can get phenomenom where they change from one wave to another. The P waves arrive first followed by the S waves and then the surface waves, however the surface waves will not be felt in the immediate viscinity of an earthquake as it takes time and hence distance to set them up from the interferance. You can see the seismograms fro the earthquake on the British geological survey website at http://www.bgs.ac.uk/news/Market_Rasen_Feb_27_2008_web.pdf. The initial blip is the P waves arriving at the station then the S waves are the next biggest bit, it doesn't look like any surface waves were present at this locality or at least only very weak ones.