Earthquake prediction


by I_am_learning
Tags: earthquake, prediction
I_am_learning
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#19
Apr29-12, 08:07 PM
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Another Question, "Is it possible to fully know about the intensity of the Earthquake, and how far and with what force it is going to travel, just by measuring the surface shakes by a sensor?".

I ask this because, when I am standing on the road-side and a heavy vehicle passes by, I feel shaking as much as or even more than a significant earthquake. But that quake isn't going to travel far.

I may have used Layman terms, but I hope you can get what I am trying to ask.
Thanks.
davenn
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#20
Apr29-12, 09:46 PM
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no not really

I suspect the intensity dissapates in the same or similar way to light, radio waves, sound waves .... the wavefront spreads out over a wider area and is controlled by the "inverse square law" every time you double the distance there is only 1/4 the amount of energy recorded at a given point.

now on top of that you also have the type of ground the seismic waves are travelling through and how that type of ground responds to the shaking. In general the softer the ground the more intense the shaking.
so for example ... take you and me we are the same distance from a M6 event, you were on soft alluvial gravels and soil (sediment) and I was on bedrock. You would feel stronger shaking than me.

There's just so many other variables too.....
the depth of the sedimentary layer and its distance from the epicentre of the event
this can determine if the sediments can respond in resonance to the frequency of the seismic waves. sediments 2km deep may respond very differently to a quake at 20 km distance then they do to a M6 quake at 50km. The quake at 50 km may cause more shaking which goes against assumptions.

Buildings and other structures such as bridges and overpasses respond differently in the same way as the ground does....

A M6 event at say 50km distance and 2 buildings, side by side in a street, one of 4 levels (stories) the other of 15 levels depending on the frequency of the seismic waves that reach the buildings, one is resonant to the freq of the waves and crumbles down the other isnt and only suffers minor damage.

I saw this effect when I visited Christchurch city last year after the M6.3 shook the city from only ~ 10 - 15 km distance. Buildings of similar building quality, but showing substantially different degrees of damage depending on their height. Christchurch is build on a very soft sediment basic, its basically a multiple river delta. The natural ground water level is only ~ 1 metre below the ground surface in many areas.
Neither the ground nor the buildings could handle the intense vertical and horizontal movements, that in several areas exceeded 1G of acceleration!!!

Another classic example of this was the 1985 M8.0 Mexico earthquake. The epicentre was 370 km west of Mexico City, yet the city was pretty much destroyed and a huge death toll. for some time seismologists didnt understand why a quake at such distance from the city did so much damage.
Studies revealed that Mexico City sat atop of a huge and deep sedimentary basin. These sediments amplified the shaking substantially and the ground motions in the city were stronger than those recorded closer to the epicentre of the quake.

well that was a huge write-up haha hopefully helpful in answering the questions

cheers
Dave
davenn
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Apr29-12, 10:03 PM
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And another variable.....

no two quakes are the same
depending on how the faultline ruptures will determine how the seismic waves radiate out from the epicentre. You may find people/structures in a particular location get more shaking than those in another. The seismic waves dont always radiate out evenly in all directions. In fact I would go as far to say that they probably never radiate out evenly in all directions.
radiation pattern would be controlled by things like...
1) rupture direction of the fault eg. bi-lateral or unilateral
2) type of rupture eg strike-slip, thrust or some variation in between
3) ground type on one side of the fault softer/harder than that on the other side of the fault

when I get time I will do some drawing of faults and rupture types and put in another post

Dave
Bobbywhy
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#22
Apr29-12, 10:16 PM
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Quote Quote by I_am_learning View Post
Another Question, "Is it possible to fully know about the intensity of the Earthquake, and how far and with what force it is going to travel, just by measuring the surface shakes by a sensor?".

I ask this because, when I am standing on the road-side and a heavy vehicle passes by, I feel shaking as much as or even more than a significant earthquake. But that quake isn't going to travel far.

I may have used Layman terms, but I hope you can get what I am trying to ask.
Thanks.
I_am_learning, Here are two articles that may help you in getting a handle on the earthquake detection/warning process:

CREWS will establish, in the one of nationís highest at-risk earthquake regions, a comprehensive earthquake early warning system capable of rapid detection of regional earthquakes and the transmission of warnings to Coachella Valley users to initiate actions that will protect people and property.
http://www.crewsnet.org/

"Countries like Japan and Mexico, even Romania, have warning systems in place. But because of California's size, topography and other factors, it's actually harder to create one here.

"Because we live on top of the faults, it's a much more complicated endeavor than say in Mexico or Japan that have these early warning systems; the earthquakes tend to happen offshore," said Prof. Michael Oskin, Ph.D., a UC Davis geologist.

And living on top of faults means any early warning will be just a few seconds, if any.
For instance, on the state's beta system mimicking the Northridge earthquake, the early detection would have been able to give Downtown Los Angeles 11 seconds warning -- enough to shut down critical infrastructure like public transportation or a nearby nuclear power plant.

"It could even potentially give the public a few secondsí heads up so they can drop, cover and hold on," said Huston."
http://abclocal.go.com/kgo/story?sec...ics&id=8591701
I_am_learning
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May4-12, 12:05 PM
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Although I am late to reply, I just wanted to thank you people for providing various information and links. I really appreciate the helps.
davenn
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#24
May7-12, 05:42 PM
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Quote Quote by I_am_learning View Post
Although I am late to reply, I just wanted to thank you people for providing various information and links. I really appreciate the helps.
no probs :)
we are all learning. its always an ongoing process. I did geology at university knowing I would probably never be employed in that field ( I was quite happy with my electronics type work) I really went to uni to put some decent theory behind my years of practical experience.
As a result I was under no huge pressure to perform well at uni, and hence really enjoyed my studies ... BUT ohhhh dear my maths abilities really suck haha, I didnt get to do differential equations, calculus etc at high school and got thrown in at the deep end at university but managed to survive

Dont stop asking questions, If i cant answer, or find an answer for you, I'm sure some one else will

cheers
Dave
Tectonica
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#25
Jun18-12, 10:09 AM
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https://sites.google.com/site/earthquakepredict/e1
Please forgive me my bad English.
I read the topic about which you speak.
Predicting earthquakes for 1 to 2 minutes before the shock - it's a dead end.
I found the wave.
That wave create the earthquake.
It moves from the periphery to the site of the future epicenter.
There It creates an earthquake.
But you can see the path of the wave and determine where it goes.
I made a report to the Knesset of Israel in 2005.
I have received a positive decision of the expert commission in 2006.
There is no problem to make the system of earthquake prediction.
She tells strength, location, start and end of the earthquake in an hour or more before the quake.
The other day I received a second endorsement of the experts of international standing.
Ms Music
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#26
Jun18-12, 01:04 PM
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Quote Quote by davenn View Post
Radon is one useful predictor, but like a lot of predictors, it is not reliable. that is, there isnt always an increase of radon emission in the days or weeks prior to a quake.
Hi Dave,

Are there ever times where radon emissions increase but never followed by an earthquake?
Tectonica
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#27
Jun18-12, 01:13 PM
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According to my research, the earthquake has several stages of development.
The anomaly of radon can be on the first stage and on the latter.
The anomaly of radon in the first stage can be even if the earthquake will be force magnitude 3.
daveb
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#28
Jun18-12, 02:16 PM
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Quote Quote by Bobbywhy View Post
I had the misfortune to be asleep in my bed in Sherman Oaks (San Fernando Valley) of Los Angeles in January, 1994 during the "Northridge Earthquake".[/url]
Yeah, that was a "fun" one (I lived at Burbank and Canoga at the time). I had two sets of drawers that faced each other in the spare bedroom. They got shuffled like a deck of cards.


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