[Johnny Brown]

From the BBC site titled 'How earthquakes happen'



So now you know...

or fault propogation (Isn't the bedrock all boulder clay in that area?)

The main 10-second quake, which struck at 0056 GMT at a depth of 15.4km (9.6 miles),

I don't think the tertiary deposits are more than a few hundred feet thick, if that. Proper bedrock scene youth.

[SA Chris]

it was only an hour at castleford, don't get too excited.

I wouldn't. Thought you had done cham trip already.

[jern]

http://www.bgs.ac.uk/news/Market_Rasen_Feb_27_2008_web.pdf

BGS reckon a depth of 5km. Should be in something fairly solid at that depth. Bedrock is Kimmeridge clay in the area -soft as ...

From the BBC site titled 'How earthquakes happen'

Yeah that cleared it up nicely for me as well

[andy_e]

andi - there are a bunch of seismographs on the pdf press release on the BGS site. Unfortunately they don't say where each were recorded but the ones at the bottom show something on a timescale similar to what I felt.

HPK is Haverah Park, Leeds uni's seismometer across the road from little almscliff. And according to google WOL is Wolverton, CWF is charnwood forest, leicester, and MCH is Michaelchurch, gloucestershire (probably)
(http://www.earthquakes.bgs.ac.uk/monitoring/bgs_stations_map.html)

15km focus depth suggests it probably wasn't mine collapse... That's about half of the crust thickness - god knows what's down there.

EDIT- 5km is about the depth of the oil field groups isn't it?


Yeah, Market Rasen, that well-known mountainous region

[dave]

I bet the Sun and Daily Star have a simplified version of this graphic in todays editions.

[GCW]

The Sun had this:






EDIT:  Interestingly, if you google image "simple earthquake diagram" you also get:



Quite helpful really.

[Johnny Brown]

HPK is Haverah Park, Leeds uni's seismometer across the road from little almscliff. And according to google WOL is Wolverton, CWF is charnwood forest, leicester, and MCH is Michaelchurch, gloucestershire

Nice one, makes more sense now.

Would a mine collapse really cause a quake of this magnitude anyway?
According to Barnsley's answer to Billy Elliot, the coal seams close up pretty much as soon as they get the coal out - the seams are thin in the first place and can only keep them open for a short time.

Yeah, Market Rasen, that well-known mountainous region

and subduction zone. 

[andy_e]

Most of the UK's quakes are caused by mine collapse of some sort- very rarely are they big enough to feel though. I think the Manchester swarm a few years ago had something to do with mines...

[SA Chris]

Most of the UK's quakes are caused by mine collapse of some sort- very rarely are they big enough to feel though.

quakes = earth tremors surely? An earthquake can't be caused by a mine collapse?

In Johnannesburg you feel tremors from mine collapses on a fairly regular basis. Most of the seams there are held open by wooden stacks which are left to collapse of their own accord in time, once the seam has been mined.

[andy_e]

Is there a difference between a tremor and a quake? Is it like calling a car an automobile or is there actually a technical difference?

[jern]

Would a mine collapse really cause a quake of this magnitude anyway?
According to Barnsley's answer to Billy Elliot, the coal seams close up pretty much as soon as they get the coal out - the seams are thin in the first place and can only keep them open for a short time.

Depends how they're mined..longwall closes up quick. Room and pillar (old skool) can stay open for decades - a lot of Sheffield has these underneath (definitly around the Poly). I could go on...  (but I wont)

[SA Chris]

I'm no seismologist, but I was pretty sure earthquakes were caused by naturally occurring geological activity, whereas a tremor is manmade?

[Bonjoy]

Is a tremor not just a small quake?

[Jaspersharpe]

Earthquakes are natural events wheras tremors are caused by giant worms from space. FACT.

[lagerstarfish]

Earthquakes are natural events wheras tremors are caused by Kevin Bacon. FACT.

[Paul B]

woke both of us up here and showed up the shoddy build quality of our building all off the cladding was making a hell of a racket.

[Norton Sharley]

what they done, pinned loads of illegal immigrants to the outside of your building? 

[AndyR]

I'm no seismologist, but I was pretty sure earthquakes were caused by naturally occurring geological activity, whereas a tremor is manmade?

Dunno about the terminology, but in general, man-made events only propagate compressive waves (this is why it's so easy for seismometers to detect 'secret' underground nuclear tests), whereas natural events propagate compressive and shear waves - in general, it's the shear waves that cause the most damage.
Depth of 5-10 km in most parts of the UK would put you close to the boundary with pre-cambrian basement rock.

[Johnny Brown]

showed up the shoddy build quality of our building all off the cladding was making a hell of a racket.

Hmm... I've cladded a few high rises and would be mighty nervous about them in an earthquake. Most of the panel systems just slot together with basic hooks and keyholes.

whereas natural events propagate compressive and shear waves - in general, it's the shear waves that cause the most damage

They 'felt' like compressive waves last night, very much back and forth. Can any one drop some SCIENCE and confirm?

Depth of 5-10 km in most parts of the UK would put you close to the boundary with pre-cambrian basement rock

Aye, that's what I was thinking. All my ole textbooks are in my folks attic, anyone any idea how thick the continental crust is hereabouts?

[andy_e]

Probably about 15-20km I think, I presume we're on continental crust?

[AndyR]

whereas natural events propagate compressive and shear waves - in general, it's the shear waves that cause the most damage

They 'felt' like compressive waves last night, very much back and forth. Can any one drop some SCIENCE and confirm?

Depth of 5-10 km in most parts of the UK would put you close to the boundary with pre-cambrian basement rock

Aye, that's what I was thinking. All my ole textbooks are in my folks attic, anyone any idea how thick the continental crust is hereabouts?

You'd need to look at the seismographs to work out how the ground was moving - remember the shallow drift geology and house structure will probably modify the movement significantly so that it would make it difficult to differentiate.
AndiE is on the money with cont crust thickness below UK (generally reckoned to be 15 km IIRC).
BBC site reckons it's related to the midlands craton - this is the big chunk of pre-camb basement that is closer to the surface than usual in the softer padded parts of the UK  - gives rise to charnwood forest and some stuff around nuneaton, plus, I think, long mynd, pontesford etc

[Fiend]

EDIT:  Interestingly, if you google image "simple earthquake diagram" you also get:



Quite helpful really.

Right. Now this is catching my interest. (Sorry you geologists keep going, I'm sure it will all make sense). But anyway. What I want to know is, is there a possibility of combining both milk foam AND whipped cream onto an espresso shot, to get the ultimate foamy, creamy, coffee indulgence??

[Houdini]

Ach, Du Britishers . . .

[andy_e]

It is possible, but the milk foam and and whipped cream need to be subducted 'til the pressure's great enough but the temperature is lowered (due to rocks heating very slowly) resulting in the famous  foamy cream/blueschist/eclogite facies often studied.

What do they reckon happened in the craton? Faulting around the edge?

[Fiend]

Damn you.

Okay, a non-coffee question:

Has Eastern  England's finest sport climbing crucible, Filey Brigg, fallen down?