Can we predict the arrival of an earthquake?

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Can we predict the arrival of an earthquake?
« on: 18/05/2008 15:33:28 »
L:-)VE;-)LY  asked the Naked Scientists:

Hello sir,

i saw earthquakes in china. Can people be warned before it strikes to prevent deaths? If not why? If yes, how?

Also, what causes cyclones? it seems da Westens& Eastens are more vulnerable 2 them.

What do you think?


Offline Bass

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Can we predict the arrival of an earthquake?
« Reply #1 on: 18/05/2008 16:38:58 »
Geoscientists can predict probabilities that a large magnitude earthquake may strike an area during a given period of time (usually at least 10 years), but have not yet been able to predict the precise time and location of individual earthquakes.  These probability predictions are based on measuring the stress build-up in rocks in tectonically active areas.

For instance, seismologists may predict that southern California has a 95% probability of a 7.0+ earthquake occurring in the next 15 years- but can't predict exactly where, when and how large that earthquake will be.  When rocks are finally strained beyond their capacity to hold together, they break- and an earthquake is the result.  There are too many variables to predict exactly when and where that last incremental strain will occur that causes the earthquake.

As to your cyclone question, one of the forum's meteorological experts could better provide you with a answer.
« Last Edit: 19/05/2008 00:28:22 by Bass »
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Can we predict the arrival of an earthquake?
« Reply #2 on: 18/05/2008 23:37:40 »
As to your cyclone question, one of the forum's meteorological experts could better provide you with a answer.

until then...

What causes a cyclone?
well firstly it helps if we know what a cyclone is. To start with this will depend on where you live, in the atlantic/eastern pacific oceans they are called hurricanes, typhoons in the western pacific, the willy willies (don't ask me why) in australia and cyclones in the indian ocean - tropical cyclones, that is. This does not change what one is, but what you know it as.
For a tropical cyclone to form there must be a favourable 'environment' in place, such as warm ocean waters throughout a depth of around 150 feet and relatively moist air near the midlevel of the troposphere.
Another factor is that the mean wind speed has to be 64 knots or greater and their location needs to be 5 degrees lat. or more away from the equator, this is because they need the coriolis force to make the cyclone spin, any closer then the force is too weak. Having said that, and like all things, there are exceptions, although in this case, only two.
This also explains why the 'hurricane' of october 1987 in the uk, was not actually a hurricane. Whilst the winds may have been of hurricane force the blew in an almost straight lines, there was no spin or rotation, so there was no hurricane. Michael Fish was correct.
Once the environment is favourable, there also needs to be a seeding mechanism, this can be easterly waves, west african disturbance line, tutt or an old front boundary.
Once the cyclone has been seeded, or more acurately once a disturbance has formed and convection developes, if it remains over warm water (stationary or moving) and the upper winds are weak it will become organised and a depression is formed.
The warm water is the power source of the cyclone, as this water rises in the atmosphere it cools and condenses in to liquid form (cloud). The condensation releases (latent) heat, this makes the air lighter still and it continues to rise more air moves in at the surface of the storm to replace that air, which in turn causes the wind to get stronger.
This also explains why cyclones are short lived once they reach and travel over land, their energy source (the warm water) is removed. So the cyclone is powered by convection, and it is this convection that shows us the purpose of the cyclone, "they take heat that is stored in the ocean and transfer it to the upper atmosphere where the upper level winds carry that heat to the poles. This keeps the polar regions from being as cold as they could be and helps keep the tropics from overheating"
or something like that....

Easterly Waves: Also called tropical waves, this is an inverted trough of low pressure moving generally westward in the tropical easterlies. A trough is defined as a region of relative low pressure. The majority of tropical cyclones form from easterly waves.

West African Disturbance Line (WADL): This is a line of convection (similar to a squall line) which forms over West Africa and moves into the Atlantic Ocean. WADL's usually move faster than tropical waves.

TUTT: A TUTT (Tropical Upper Tropospheric Trough) is a trough, or cold core low in the upper atmosphere, which produces convection. On occasion, one of these develops into a warm-core tropical cyclone.

Old Frontal Boundary: Remnants of a polar front can become lines of convection and occasionally generate a tropical cyclone. In the Atlantic Ocean storms, this will occur early or late in the hurricane season in the Gulf of Mexico or Caribbean Sea.


Offline JimBob

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Can we predict the arrival of an earthquake?
« Reply #3 on: 19/05/2008 05:44:08 »
Thank you, Paul, for the Cyclone answer.

As for earthquakes - there is some research in China that is focusing on animal behavior to predict earthquakes but obviously it has not been perfected to any great extent - the massive earthquake of this last week has shown that to be the case.
The mind is like a parachute. It works best when open.  -- A. Einstein


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Can we predict the arrival of an earthquake?
« Reply #4 on: 19/05/2008 06:33:39 »
animals can also predict weather events, one theory is that they can hear the low frequency noise of distant storms.