In a message dated 2006/11/02, sophie@.................. writes:

> Hello,
> My name is Sophie, I am 11 years old and I want to build a seismometer 
> system to investigate earthquakes. I live in England so most big 
> earthquakes I would like to detect are a long way away but I would also 
> like to detect the blasting in the quarry about a mile away if I can.
> I have read lots of interesting things on the web page but am not sure 
> what sort of sensor would be best for me and dad to make. Can you help 
> me decide which sort to build

Hi Sophie + Dad,

       You will likely only be picking up quite distant earthquakes. The UK 
gets maybe 40 very small local quakes each year. See 
http://www.earthquakes.bgs.ac.uk/ You will only pick one of these up if they are within about 100 miles 
of you. Earthquakes often start with a P wave at about 1 to 2 cycles per 
second, later an S wave at about 0.5 to 1 cycle per second and these are followed 
by much larger surface waves which take 10 to 30 seconds each. For quakes from 
the other side of the world, you may only pick up the surface waves. We get a 
fair number of regional quakes from the Mediterranean area. 
       A "garden gate" type of pendulum sensor will pick these up. It is not 
too difficult to make one of these. See 
http://jclahr.com/science/psn/chapman/lehman/index.html
       You can buy 'long period' geophones of about 1 second, but they are 
quite expensive. See www.geophone.com type LF-24.
       An alternative is to buy 4.5Hz used geophones from psn.quake.net and 
use an extra SEQUA10 extension amplifier from Sara, but neither of these will 
pick up the slow surface waves.
       You will also need a seismic type amplifier, an analogue to digital 
converter and a 'spare' computer to record and display the traces. Your dad 
could likely make an amplifier, but you will probably need to buy an ADC. Have a 
look at www.sara.pg.it for electronics and Mauro's website at 
http://mariottim.interfree.it/index_e.htm Mauro also provides a free seismic recording and 
analysis program called Seismowin which you can download onto your computer.
       The software timing clocks on computers are not accurate enough for 
recording seismic signals and may drift by 30 seconds a day. However Sara sell 
an inexpensive DCF77 radio clock module which connects to their ADC. This is a 
lot cheaper than GPS clock modules and it covers all of the UK.
       A complete long period system from Sara would be a SPOW10 power 
supply, a SAMP20 amplifier, a SADC10 a to d converter and a DCF77 clock module. 
These are the electronics boards. You can buy an Al box from Maplin to house them. 
I suggest that you buy the connecting cables from Sara. There is carriage and 
VAT at 20% to add to the Sara prices. 
       All this is likely to make quite a large hole in your pocket money. 
Ask your dad to EMail me if he wants any further help or advice? There are other 
choices possible.

       Best Wishes,

       Chris Chapman
       
       
In a me=
ssage dated 2006/11/02, sophie@.................. writes:



Hello,

My name is Sophie, I am 11 years old and I want to build a seismometer 

system to investigate earthquakes. I live in England so most big 

earthquakes I would like to detect are a long way away but I would also 

like to detect the blasting in the quarry about a mile away if I can.

I have read lots of interesting things on the web page but am not sure 

what sort of sensor would be best for me and dad to make. Can you help 

me decide which sort to build




Hi Sophie + Dad,



       You will likely only be picking up quit=
e distant earthquakes. The UK gets maybe 40 very small local quakes each yea=
r. See http://www.earthquakes.bgs.ac.uk/ You will only pick one of these up=20=
if they are within about 100 miles of you. Earthquakes often start with a P=20=
wave at about 1 to 2 cycles per second, later an S wave at about 0.5 to 1 cy=
cle per second and these are followed by much larger surface waves which tak=
e 10 to 30 seconds each. For quakes from the other side of the world, you ma=
y only pick up the surface waves. We get a fair number of regional quakes fr=
om the Mediterranean area. 

       A "garden gate" type of pendulum sensor=
 will pick these up. It is not too difficult to make one of these. See http:=
//jclahr.com/science/psn/chapman/lehman/index.html

       You can buy 'long period' geophones of=20=
about 1 second, but they are quite expensive. See www.geophone.com type LF-2=
4.

       An alternative is to buy 4.5Hz used geo=
phones from psn.quake.net and use an extra SEQUA10 extension amplifier from=20=
Sara, but neither of these will pick up the slow surface waves.

       You will also need a seismic type ampli=
fier, an analogue to digital converter and a 'spare' computer to record and=20=
display the traces. Your dad could likely make an amplifier, but you will pr=
obably need to buy an ADC. Have a look at www.sara.pg.it for electronics and=
 Mauro's website at http://mariottim.interfree.it/index_e.htm Mauro also pro=
vides a free seismic recording and analysis program called Seismowin which y=
ou can download onto your computer.

       The software timing clocks on computers=
 are not accurate enough for recording seismic signals and may drift by 30 s=
econds a day. However Sara sell an inexpensive DCF77 radio clock module whic=
h connects to their ADC. This is a lot cheaper than GPS clock modules and it=
 covers all of the UK.

       A complete long period system from Sara=
 would be a SPOW10 power supply, a SAMP20 amplifier, a SADC10 a to d convert=
er and a DCF77 clock module. These are the electronics boards. You can buy a=
n Al box from Maplin to house them. I suggest that you buy the connecting ca=
bles from Sara. There is carriage and VAT at 20% to add to the Sara prices.=20=


       All this is likely to make quite a larg=
e hole in your pocket money. Ask your dad to EMail me if he wants any furthe=
r help or advice? There are other choices possible.



       Best Wishes,



       Chris Chapman