Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: ukmicky on 27/02/2008 02:23:29
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Who felt the earth tremor. it was at about 1 am and i felt it in london . I thought i was just me going MAD but according to the news it was about 5.1 on the richter scale
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I have been hearing about it, and lots of people farther south and farther west than me felt it (and the epicentre was to the north east of me by quite a way), but I felt not a thing.
At first I though it was just me being inattentive, but looking around the house, nothing seems to have moved, so if it did pass through here, it could not have been that dramatic.
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I was in Hull at the time, It made my chair move from side to side for a few seconds. But nothing more. Yet others in Hull (according to sky news) had it so bad that they thought a jet plane had crashed through their home!
I think they just wanted their name read out on the news.
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(transferred from chat)
Well that was a good one, started at 00:58 and lasted around 10-15 seconds.
Anyone else experience it?
A few seconds of rumble beforehand, windows shook and some things fell of the bathroom shelf into the bath. Some minor damage to properties and people mainly from falling chimneys.
Where I live in Sheffield is on the edge of a fault line and I rocked in bed! (so that's what bedrock is) grin
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I'm sure people in parts of America and Japan would laugh at us Brits getting excited about a 5.1
I was in Japan for a large one and I remembered that you had to get under a table but the table in my house was a tatarmi one (You sit crosslegged around it so the legs are v.short.) I still managed to get under it, thought I was going to die. I leant some good Japanese swear words as the scaffolders on the building next door werent best pleased.
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No, m'dear, a 5 mag. earthquake is not a tame one. It can cause lives so it is quite luck no one died.
This was apparently caused by compressional forces due to the continued separation of the UK from mainland Europe. To the north, there are older rocks that have deeper "roots" and are less able to be deformed than the younger rocks to the east and south.
The tectonic stresses are indicated by the lines on the map below from
http://www-wsm.physik.uni-karlsruhe.de/index.html
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2Fuk_eireT.jpg&hash=9f840033e6985b2976db070df03bc67b)
The black arrows that point at each other are measured compressional forces and the green with a square are upward forces. The blue is forces whose main component is down warping and the red is from a well bore. The compass direction of the lines is the direction of the forces.
If you compare this with a geologic map of the UK the types of rocks are evident.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FukGEOmap8.jpg&hash=aa0fcc1e240e9dcd146e2e276521d0d8)
The olive and greens are Triassic and younger rocks, the pink, blue and gray are the Permian and older rocks that were originally part of the continent. The younger rocks were deposited after the island started separating from the main part of Europe.
It is (dun, dun, dun, daaaaahhhhh!)
GEOLOGY IN ACTION !
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I guess no one was killed because we have had our last two 5+ earthquakes in the early hours of the morning when people are in bed. I read in Japan that most people die in earthquakes because they panic, run outside and get hit by falling objects. That is why I hid, bravely, under the table. Info. very useful, I shall use it in the future.
Oh yes and our houses are made of bricks so they are harder to shake down. People should learn from the three little pigs.
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Oh yes and our houses are made of bricks so they are harder to shake down. People should learn from the three little pigs.
Actually it is more complex than that, and badly built brick houses are more dangerous (not least because when they do fall down, they hurt more; but also because they wont bend with the shocks).
I don't think it that common for serious injuries at anything below 6, but Japan can easily go to 7 and above (and don't forget we are talking about a logarithmic scale).
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I woke up because of the noise. I wondered what the loud low rumble was. Then the house started shaking so I thought "oh, so it's an earthquake". I went back to sleep. You are a lot more likely to be killed by a thunderbolt in the UK than by an earthquake.
For the record, it's less annoying than being woken up by a bomb.
BTW JimBob, Re. "It can cause lives so it is quite luck no one died."
Actually, it's a different sort of "the earth moved" event that's associated with causing lives.
Thanks for the maps.
The comment about the 3 little pigs is proably more apropriate when thinking about tornado damage.
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BTW JimBob, Re. "It can cause lives so it is quite luck no one died."
Actually, it's a different sort of "the earth moved" event that's associated with causing lives.
How so? A young man had his hips crushed when a chimney fell on him. It would have taken one brick to the head to have killed him.
The comment about the 3 little pigs is proably more apropriate when thinking about tornado damage.
I'll explain the problems with masonry construction in earthquakes when I get back from a doctor's appointment.
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Jimbob,
Read what you actually wrote.
"It can cause lives"
As I said, it's something else that does that.
Masonry does fall down in earthquakes, but it does a better job than timber when it comes to stopping flying debris so it's good to hide behind in a tornado. Of course, if it falls on you you are in big trouble but while it stands it's good stuff.
I seem to remember hearing somewhere that "earthquakes don't kill people- buildings do".
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Jimbob,
Read what you actually wrote.
"It can cause lives"
As I said, it's something else that does that.
Masonry does fall down in earthquakes, but it does a better job than timber when it comes to stopping flying debris so it's good to hide behind in a tornado. Of course, if it falls on you you are in big trouble but while it stands it's good stuff.
I seem to remember hearing somewhere that "earthquakes don't kill people- buildings do".
You are correct - it is buildings that kill, not the quake itself. Somehow the long post on masonry construction was deleted - there is a problem with the forum software. I am unable to redo it at the moment. Just suffice it to say that the magnitude of the earthquake is what knocks down buildings. Masonry will not stand up in a magnitude 6 quake and is in grave danger at a 5.5 magnitude. That is unless it is retrofitted or built with reinforcements to new standard earthquake codes. So the 5.0 magnitude (depending on which earthquake center's figure you use) is borderline.
The mag. 5 quake is equivalent in the amount of energy released to the nuclear bomb that destroyed Nagasaki at the end of WW II - 32 kilotons or 134.4 Trillion Joules. The depth to the epicenter dampened the effects somewhat but it is still very luck it wasn't near a large urban area.
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Side to side seem to cause most damage.. was this an up and down quake or did it move side to side!
I think it was around '92 or so we had a 7.2 followed by 7.1 or 7.0 with a couple five aftershocks.. It was a rolling motion and the hole street outside of my house was rolling like a wave coming from the south and rolling kind of northerly.. the cement was waving with two and three foot rolls past my front door.. It was scary telephone poles were laying way down then returning to upright position on the roll back!!!
The fives can be terrible also depending on how the hit and where they hit and the type of motion.. I have been in fives that seem mild and then 5's that were scary because of the type..
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Both types of quakes produce the same amount of side-to-side and vertical waves surface waves. They are know as S-waves and P-waves. There is no rational explanation for the subjective experience. It just is.
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"There is no rational explanation for the subjective experience. "
Surely distance from the epicentre would explain why some seem bigger than others?
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My fiance and I live approximately 45 miles from the epicentre, in Nottingham, UK and we experienced a lot of movement. Our old precast concrete garage attached the house made the most tremendous amount of rattling during the tremor. Only of course to reinforce my plans to demolish it and build a new blockwork one! ha ha! I was quite amazed at how much movement we experienced. However, you folks in the states are obviously accustom to such events and I can only assume that you're are having a little chuckle at our mere tremor! ha ha ha! My first experience I may add though.
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"There is no rational explanation for the subjective experience. "
Surely distance from the epicenter would explain why some seem bigger than others?
I was observing that different observers at the same place alway say somewhat different things about their experience. Such a phenom. is also seen at crime scenes where different witnesses have different recollections.
You are correct about the distance from the epicenter.
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Both types of quakes produce the same amount of side-to-side and vertical waves surface waves. They are know as S-waves and P-waves. There is no rational explanation for the subjective experience. It just is.
Do you think it is just where you are that makes it worse as I said it seems here at least that side to side do the most damage.. I have three huge splits in my houses foundation where it split the cement foundation under the back of the house?
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"There is no rational explanation for the subjective experience. "
Surely distance from the epicentre would explain why some seem bigger than others?
That makes some since.. we live on the San Andreas fault line ..Humboldt County kinda right on top of it!
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My fiance and I live approximately 45 miles from the epicentre, in Nottingham, UK and we experienced a lot of movement. Our old precast concrete garage attached the house made the most tremendous amount of rattling during the tremor. Only of course to reinforce my plans to demolish it and build a new blockwork one! ha ha! I was quite amazed at how much movement we experienced. However, you folks in the states are obviously accustom to such events and I can only assume that you're are having a little chuckle at our mere tremor! ha ha ha! My first experience I may add though.
You Know you may get used to having them but you never have a chuckle.. they are scary... no fun.. and they scare the soup out of little children and big children and their Mamas and Papas too!!!
No I feel for you all.. they are frightening!
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Both types of quakes produce the same amount of side-to-side and vertical waves surface waves. They are know as S-waves and P-waves. There is no rational explanation for the subjective experience. It just is.
There are two main types of seismic waves- body waves and surface waves. JimBob is correct that the two types of body waves are (1) primary or P waves and (2) secondary or S waves (also known as shear waves). P waves travel fastest and are often heard as a "snap" or "pop" whe the earthquake first starts. Neither P waves or S waves cause much damage.
The damaging seismic waves are surface waves, and can be imagined as ripples in a pond- they are transmitted along the surface of the earth. Two types here too: (1)Love waves and (2) Rayleigh waves. Love waves cause side to side movements and Rayleigh waves cause up and down (rippling) movements. Rayleigh waves are the most destructive. Virtually all damage from earthquakes is from these surface waves, which travel slower than the body waves.
Shaking is intensified in buildings built on unconsolidated sediments (gravel, sand, mud) and is minimized in buildings built on bedrock. We have occaisoinal quakes here- my house is on bedrock and barely moves, while my business partner's house is built on gravels/mud and gets shaken vigorously.
Karen, I agree- you never get used to them.
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So glad your back,
Skippy Bass, I am overwhelmed. The mob is turning against me!
I didn't mention Rayleigh waves as they can be consider to be due to an interferance pattern produced by the interaction of P & S waves, like waves intersecting on a pond. They are not propagated as far from the epicenter as P & S waves. They are slower than body waves (P & S), roughly 70% of the velocity of S waves, and have been asserted to be visible during an earthquake in an open space like a parking lot where the cars move up and down with the waves.
Analysis of the witness accounts of Rayleigh waves I have seen suggest that the apparent motion may be due to distortion of the human sensory system during the earthquake. On TV shows I have seen, placing people on "shake tables" causes the room to appear to ripple to them. In any case, waves of the reported amplitude, wavelength, and velocity of the "visible waves" have never been recorded instrumentally.
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In todays Guardian it says for each whole number increase on the Richter scale represents a tremor 31 more times powerful than the last. My husband thought it would be 10 times more powerful. Could anyone put him right.
Also when I was in the quake in Japan the noise of things vibrating was the most frightening part but it did seem to interfere with my senses generally. I felt off balance as well.
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In todays Guardian it says for each whole number increase on the Richter scale represents a tremor 31 more times powerful than the last. My husband thought it would be 10 times more powerful. Could anyone put him right.
Your husband is right - no need to be put there.
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Are you sure? I can't cope with the gloating.
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OK looking at wiki, it seems both sides are right.
http://en.wikipedia.org/wiki/Richter_magnitude_scale
The Richter magnitude scale, or more correctly local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a Wood-Anderson torsion seismometer output. The effective limit of measurement for local magnitude is about ML=6.8. The energy release of an earthquake scales with the 3/2 power of the shaking amplitude, and thus a difference in magnitude of 1.0 is equivalent to a factor of 31.6 in the energy released; a difference of magnitude of 2.0 is equivalent to a factor of 1000 in the energy released.
The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released.
So a whole number increase is a factor of 10 increase in wave amplitude, but a factor of 31.6 increase in energy.
I should have read that first - sorry.
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Then don't tell him! Jees, I can't believe a woman can't be even have a little smidgen of deviousness.
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Husband still smug but not gloating anymore. It is nice when we are both right. Anyone got anything to add on this?
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Basically as is said in geography... a hazard only becomes a hazard when people locate themselves in its area... And whoever said that a 5 is not a big quake is wrong... If you look at the Richter scale graphically it is a base 10 logarithmic scale which means that each quake number is 10 times more powerful than the last... these means that a magnitude 5 is 100000 more powerful than a 1!
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"these means that a magnitude 5 is 100000 more powerful than a 1"
Er, no it doesn't. Each quake number has 10 times the amplitude of the one below not 10 time the power. I'm guessing the the velocity of the wave is prety much independdent of the released energy. That means that a change of 1 unit gives 10 times the apmlitude and so takes roughly 10 times as long. But it dissipates 31.6 times as much energy in that time so it has about 3.16 times more power. A magnitude 5 quake would be about 316 times the power but I don't know how that relates to how much damage is done.
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"these means that a magnitude 5 is 100000 more powerful than a 1"
Er, no it doesn't. Each quake number has 10 times the amplitude of the one below not 10 time the power. I'm guessing the the velocity of the wave is prety much independdent of the released energy. That means that a change of 1 unit gives 10 times the apmlitude and so takes roughly 10 times as long. But it dissipates 31.6 times as much energy in that time so it has about 3.16 times more power. A magnitude 5 quake would be about 316 times the power but I don't know how that relates to how much damage is done.
Indeed you are correct :-) gold star for you, detention for me. Walks away in shame.
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I like your answer Bored C but I hope you don't gloat as much as hubby. Be humble in your glory.
Exodus, I just heard they have invented Sat Navs for zimmer frames so when senility takes over completely at least you can find your way home.
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I like your answer Bored C but I hope you don't gloat as much as hubby. Be humble in your glory.
Exodus, I just heard they have invented Sat Navs for zimmer frames so when senility takes over completely at least you can find your way home.
Its not senility today, its a hangover. lol
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I like your answer Bored C but I hope you don't gloat as much as hubby. Be humble in your glory.
Exodus, I just heard they have invented Sat Navs for zimmer frames so when senility takes over completely at least you can find your way home.
Why didn't you just say "walker" instead of zimmer frame? We Americans do not know what a bonnet is, a turtle or that both relate to a auto. That is all but I don't know.
Talk about the degradation of the English language.
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Which bit of a car is a turtle? I know you Americans drive slowly but turtles! Oh yes and on Docs behalf shouldn't it be an Auto. Anyway we are supposed to be talking about Earthquakes so lets take this outside.