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markuster
03-03-2010, 02:49 AM
Hi,


Only to know about the best products to
measure of an earthquake or seism.

It seems that Parallax has different sensors but I don't know
if they are able to measure an earthquake or seism with
good accuracy.

Thanks Mark

Franklin
03-03-2010, 03:14 AM
Define "good accuracy" it all hinges on that. Most accelerometers measure in G's and depending on what the level of acceleration you want to measure will dictate the device you choose.

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- Stephen

markuster
03-03-2010, 04:10 AM
Hi ,

I understand you but ,
I don't know about the accuracy , just I was thinking about the
best Parallax solution. ( Just the best Parallax sensor for this purpose)

Any help is welcome.
Thanks, Mark.

Humanoido
03-05-2010, 01:57 AM
There is no "one" sensor to detect and measure an earthquake. Even the accelerometers do not have good enough accuracy to do this. Instead, you must design a very sensitive, and somewhat complicated, machine to detect the difference between an actual earthquake and someone walking across the floor. This will involve some mechanics. There are different earthquake waves that must be identified. I suggest you google seismometer and study and research the examples. If you want to make a more simple and cost effective school project, take a look at the vibra tab mass sensor from Parallax. If you put a mass on the top, such as a paper clip, it can be used as a demonstration. There is a writeup about the vibra tab mass in the issue of Penguin Tech which includes software. With a slight modification to the code, it can return a stream of numbers that can be conditioned. The sensor is $1.79 and a real bargain considering its applications. Remember to include the 5.1 volt zener diode voltage suppressor in the circuit.

Piezo Film Vibra Tab Mass
www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/89/Default.aspx?txtSearch=vibra+tab+mass (http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/89/Default.aspx?txtSearch=vibra+tab+mass)

Penguin Tech Magazine
Software for Piezo Film Vibra Tab Mass sensor
http://forums.parallax.com/showthread.php?p=747812

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humanoido
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Post Edited (humanoido) : 3/4/2010 6:11:12 PM GMT

JohnB
03-05-2010, 06:26 AM
The Lehman seismometer is a well documented 'homebrew' system that many amateur seismologists have built and used. Look at the following URL:

http://psn.quake.net/lehman.htm

John

kf4ixm
03-05-2010, 06:50 AM
You can use either of the accelorometers that parallax sells, the memsic 2125 is a 2 axis, with this one set up with the x axis parallel with north and south and y axis parallel with east and west, you can detect the s-waves of both axis. with the H48C or MMA7455 tri axis, in addition to detecting the s-waves in the n-s & e-w direction, you can detect the p-waves on the z axis, or up and down movements. as far as accuracy of detected motion, that is up to how you have the accelerometer mounted. All seismic detectors are mounted rigidly to solid bedrock by either large lag bolts or concreted into soild bedrock. you can look at the datasheets on the product pages of these accelerometers respectivly to determine what thier mechanical/electrical accuracies are. you would read such data as g-force on all 3 axis to determine siesmic movements.

http://en.wikipedia.org/wiki/Seismic_wave

Post Edited (kf4ixm) : 3/4/2010 11:01:09 PM GMT

hover1
03-05-2010, 08:37 AM
According to the spec sheet (http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/MXD2125G&M.pdf) on the Memsic 2125, the resolution better than 1 milli-g. I'm not a seismologist, but that sounds like it would pick up pretty small events.

Jim

Read about the Quake-Catcher Network:

http://qcn.stanford.edu/



Post Edited (hover1) : 3/5/2010 12:44:03 AM GMT

kf4ixm
03-05-2010, 09:16 AM
yes it is, and im not one either. but in my testing along the same lines with the 2125, i could definatly detect a train going down the tracks over 3/4 a mile away with the 2125 mounted to a steel pole concrete in the ground, although i couldn't physically 'feel' it, the readings from the 2125 were showing a couple of tenths of a g movement/vibration.

hover1 said...
According to the spec sheet (http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/MXD2125G&M.pdf) on the Memsic 2125, the resolution better than 1 milli-g. I'm not a seismologist, but that sounds like it would pick up pretty small events.

Jim

Read about the Quake-Catcher Network:

http://qcn.stanford.edu/

hover1
03-05-2010, 09:52 AM
Thanks kf4ixm

Good to know there is some·hard evidence.

I have a train track 1/4 mile away. I must try that out.

Jim


kf4ixm said...
yes it is, and im not one either. but in my testing along the same lines with the 2125, i could definatly detect a train going down the tracks over 3/4 a mile away with the 2125 mounted to a steel pole concrete in the ground, although i couldn't physically 'feel' it, the readings from the 2125 were showing a couple of tenths of a g movement/vibration.

hover1 said...
According to the spec sheet (http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/MXD2125G&M.pdf) on the Memsic 2125, the resolution better than 1 milli-g. I'm not a seismologist, but that sounds like it would pick up pretty small events.

Jim

Read about the Quake-Catcher Network:

http://qcn.stanford.edu/




Post Edited (hover1) : 3/5/2010 1:57:10 AM GMT

Humanoido
03-05-2010, 05:09 PM
kf4ixm said...
with the 2125, i could definatly detect a train going down the tracks over 3/4 a mile away with the 2125 mounted to a steel pole concrete in the ground, although i couldn't physically 'feel' it,
Very interesting! How can you tell the difference between actual earth quake and a vibration like a train or construction event, or maybe even your own walking?


kf4ixm said...
...the readings from the 2125 were showing a couple of tenths of a g movement/vibration
Which calibration program was used to output numbers in tenths of a g?

humanoido

kf4ixm
03-05-2010, 09:45 PM
Thats just it, with it mounted to something in the earths crust instead of solid bedrock, you will detect all sorts of vibrations that are not actual plate movements, like trains, traffic and such. most all usgs seismic sensors are placed out in the middle of nowhere, sometimes miles from roads and urban areas and these are usually in a hole in the ground, dug down to solid bedrock then mounted by lag bolts or set in concrete. the program i used was the demo program on the 2125 product page.

And let me just say, these claims that the memsic2125 can be used to detect siesmic events are from my own testing and research, not from Parallax product descriptions. i believe with the proper mounting and programming, these CAN be used for such.


humanoido said...

kf4ixm said...
with the 2125, i could definatly detect a train going down the tracks over 3/4 a mile away with the 2125 mounted to a steel pole concrete in the ground, although i couldn't physically 'feel' it,
Very interesting! How can you tell the difference between actual earth quake and a vibration like a train or construction event, or maybe even your own walking?


kf4ixm said...
...the readings from the 2125 were showing a couple of tenths of a g movement/vibration
Which calibration program was used to output numbers in tenths of a g?

humanoido

Mikerocontroller
03-05-2010, 10:40 PM
I suppose if you were in Chile a GPS would have worked. I know they use lasers to determine if any earth movement caused shearing across fault lines.

kf4ixm
03-06-2010, 01:49 AM
Yep, thats true, in fact, most usgs siesmic sensor arrays have gps and (in some cases) compass sensors onboard. although the compass sensors are not of much use because of constant magnetic declination over time, but in the short time span of a siesmic event, it will show if theres been any plate rotation during that time span before and after the siesmic event.

Mikerocontroller said...
I suppose if you were in Chile a GPS would have worked. I know they use lasers to determine if any earth movement caused shearing across fault lines.

Larry~
03-06-2010, 02:32 AM
Google geophone


http://www.geophone.com/Category.asp?CatID=1&SubCatID=3

Larry~
03-06-2010, 02:35 AM
Read this paper





http://micromachine.stanford.edu/smssl/projects/Geophones/DefenseBarzilaiFinalCopyWeb/DefenseBarzilaiFinalCopy.pdf

Humanoido
03-06-2010, 09:51 AM
There are different data sheets posted for the same sensor.
Unfortunately the data sheet I initially read did not have the
same sensitivity listed. I also see the range is extended
significantly in some of the data sheets for the same sensor.
Maybe it has an upgrade, but still the same part number.
So I will update the post in saying the milli-g sensitivity is indeed
sensitive enough. Now if we can just drill down deep in the earth
and access bedrock to mount the sensor for some accurate
earthquake detection...

kf4ixm: are you on the seismology team? Thanks for sharing
the detailed information.

humanoido

kf4ixm
03-06-2010, 10:09 AM
@humanoido
no im not on the seismology team, i didn't know there was one. i do geodetic and meterological sensor arrays and studies·purely as a hobby, maybe one day turn it into a lucrative hobby. :) in some places, solid bedrock can be found within a few inches to a few feet from the surface, especially around mountainous areas.

Post Edited (kf4ixm) : 3/6/2010 2:16:25 AM GMT