On the record.

Lest we forget. …

I was looking for the latest tremors in the UK from the BSGS and found the FAQs.

I thought I had better record this before they change it to suit me:

Originally posted by British Geological Survey:

Can earthquakes be predicted?

Although it is known that most global earthquakes will concentrate at the plate boundaries, there is no reliable method of accurately predicting the time, place and magnitude of an earthquake.

Most current research is concerned with minimising the risk associated with earthquakes, by assessing the combination of seismic hazard and the vulnerability of a given area. Many seismic countries, however, have research programs based on identifying possible precursors to major earthquakes.

This includes the study of dilatancy, how rocks crack and expand under the increased stress associated with the earthquake.

Some major earthquakes, but not all, are heralded by the occurrence of foreshocks, which can be detected by dense local monitoring networks. Other instruments can measure changes in the levels of radon gas, electrical and magnetic properties, velocity changes of seismic waves and changes in topography.

Long term monitoring and examination by these sensors is required as some or all of these factors may change due to the opening of cracks prior to the earthquake.

All attempts to predict earthquakes have, however, been generally considered as failures and it is unlikely that accurate prediction will occur in the near future.

Efforts will, instead, be channelled into hazard mitigation.

Earthquakes are difficult or impossible to predict because of their inherent random element and their near-chaotic behaviour.

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3 thoughts on “On the record.

  1. This is good:

    What is earthquake magnitude?It is a measure of earthquake size and is determined from the logarithm of the maximum displacement or amplitude of the earthquake signal as seen on the seismogram, with a correction for the distance between the focus and the seismometer.This is necessary as the closer the seismometer is to the earthquake, the larger the amplitude on the seismogram, irrespective of the size or magnitude of the event.Since the measurement can be made from P, S or surface waves, several different scales exist, all of which are logarithmic because of the large range of earthquake energies (for example a magnitude 6 ML is 30 times larger, in terms of energy than a magnitude 5 ML).The Richter local magnitude (ML) is defined to be used for 'local' earthquakes up to 600 km away, and is the magnitude scale used by BGS when locating UK earthquakes.Surface wave magnitude (Ms) is based on the maximum amplitude of the surface wave having a period of 20 + 2 s. It is used for observations near the earthquake epicentre where the surface wave is larger than the body wave. This scale applies to any epicentral distance or type of seismograph.Body wave magnitude (mb) is calculated from the body waves (P,PP,S) and are usually used at larger distance from the earthquake epicentre (P-wave attenuation is less than surface waves, with distance).It can be used for any earthquake of any depth.Moment magnitude (Mw) is considered the best scale to use for larger earthquakes as the Ms saturates at about magnitude 8.Moment magnitude is measured over the broad range of frequencies present in the earthquake wave spectrum rather than the single frequency sample that the other magnitude scales use.For comparison purposes, a magnitude 5 ML earthquake is equivalent to the explosion of 1,000 tons of TNT whereas a magnitude 6 ML earthquake is the energy equivalent of 30,000 tons of TNT or a 30 kilotonne nuclear explosion.

    Kilotonne; I ask you. Bloody Harold Wilson. I'd like to kick his arris.It is a magnitude explanation that is employed earthwide.It helps most people understad what powers are involved.I mean, you are quite familiar with the explosive forces of nuclear bombs aren't you?And you often handle TNT right?How about a more familiar chemical?A ton of high explosives is about the same energy value as a ton of petrol (burned in oxygen presumably, weight of O2 gas not included.)Can you picture a tonne (metric ton) of petrol?The average tank of petrol in a medium to large car is 40 to 50 litres. A litre of petrol is slightly less than a litre of water = 1 kilo. So a little more than a tonne of petrol is 1000 litres.So you are looking at 20 or so large cars running…Oops:Originally posted by wiki.answers.com:

    The conversion factor for Petrol is .711 so 1 litre weighs .711kg.Density at 60 degree F 737.22 kg per cubic meter (http://www.simetric.co.uk/si_liquids.htm)One cubic meter equals 1000 liters (http://www.metric-conversions.org/volume/liters-to-cubic-meters.htm)Petrol weight 1Litre = 0.711kg (at 60 deg F)NOTE:The density varies between refineries, between lots and with temperature.Read more: http://wiki.answers.com

    OK I have to up…. ahhh… forget ithttp://en.wikipedia.org/wiki/Fuel_economy_in_automobiles

  2. What's the big deal?What is all the fuss about?Peopl generally think of earthquakes in terms of the damage they do. They tend to understand about the stuff you can just feel and the resutls that you can see: Cracks in walls, broken chimney and destroyed housing.They probably think the Magnitude value means Richter Scale.Actually he did design a scale to go with the seismometers of his day. But the one most people think of in terms of structural damage is the Mercalli scale.Now there are all sorts of scales depending on the wave types measures, distances to the epicentres and the recording instruments at the stations.The preliminary value given by the recent NEIC lists is a very general value and is later corrected in the case of those quakes large enough to warrant research.More here:http://en.wikipedia.org/wiki/Richter_magnitude_scale

  3. Let's try this another weigh.What is the calorific values of loaves and fishes?Say you had 5 loaves and 3 not very large fish.The first to calibrate the energy value of an atom bomb did it on site. He threw some paper scraps in the air and timed it so the last caught them. He guestimated that how far from him they fell compared to how far other scraps fell before and after then worked out the work done in moving them.I have no idea if there was any computation for what synergy might have been involved, supposing the power adsorption of limitless infinities of scraps of paper encircling the blast.Late metered readings of the powers involved reckoned the first comparison of nuclear bombs with anything.And from there the devastating impacts have been in use ever since.We don't really need to be any the wiser. But it does limit the enquiring mind to the scope of present beliefs.The first cause for instance. The earth's heat budget is known to meteorologists everywhere. And it doesn't allow for any messing around with fault-lines.Who but a Weatherlawyer would put a cat in with them pigeons?

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