Instructables
Picture of This Seismometer is no toy!
This is an image of the computer recording "drum" that shows four events recorded on the same day at my station in Denver, CO; two in Mexico and two on the opposite side of the world in Sumatra. The vertical short-period instrument that recorded these events can be made in a home shop.

Smart phone "earthquake" apps that use the built-in screen-tilt accelerometers can only detect gross movements that can be felt. The seismometer in this Instructable can detect ground motion of less than 50 microns/sec. (a human hair is about 100 microns), way below what can be felt or seen. This makes it sensitive enough to detect earthquakes from anywhere in the world greater than magnitude 6.5 and much smaller for closer events. Yet, mechanical and electronic filtering limits local signal noise.
 
Remove these adsRemove these ads by Signing Up

Step 1: Comparison With Professional Instrument

Picture of Comparison With Professional Instrument
This instrument rivals those of the USGS Mobile Seismic Array if placed in a suitably quiet and environmentally stable location like a basement and you will be able to gather data in the background through a USB port using free software that requires very few cpu resources while performing other tasks on your computer.

Note that like the professional instrument it nicely differentiates between Primary and Secondary body waves as well as the larger surface (L) waves allowing distance to an event and even magnitude to be accurately measured.

Step 2: Seismometer (seismograph) System Components

Picture of Seismometer (seismograph) System Components
The seismometer consists of four basic components each of which I will describe in detail. The total cost will be between $300 and $350 U.S.. Free software to display and manipulate data is available online.
Alderin2 months ago

Very cool stuff. I'm also of the opinion that an Arduino could make
some improvements on the electronics side of the project. Capable of
low-power long-term logging to an SD card, and A/D up to 10 bits without much expensive hardware (other than the amplifier). A/D converter modules aren't too expensive to increase the resolution, I found a 24bit dual-channel A/D module on ebay for $6 US.

The Arduino software for datalogging to an SD card is already everywhere. I might even add a "run-length-encoding" compression to allow the log to cover longer periods. Could be done, might lower cost a lot. I'll have to do more digging.

And just for clarification, your pickup coil is 1 3/4" thick from outer edge to spool core? How much magnet wire is that?

barkergk (author)  Alderin2 months ago

Thanks Alderin. I don't really have experience with arduino, but there is no reason why it won't work. I would avoid 10 bit resolution and keep in mind that any design needs to have a low pass filter and should have a comutating auto zero (CAZ) function (see step 13). There is a link to magnet wire in step 7. Item 9 on that list should do the job (30 gauge, 1606 ft.)

auschwitz4 months ago

will the a/d converter work on windows 8 or 8.1?

barkergk (author)  auschwitz4 months ago

I don't know but I don't see why not. It is read through a USB port. Go to DataQ's website and see what you can find out.

http://www.dataq.com/

jab19518 months ago
(removed by author or community request)
barkergk (author)  jab19518 months ago

Jab, glad to see you making this seismometer. Since it was posted there may be some part changes you want to address. I think the Maxim commutating auto-zero (CAZ) op amp (Maxim MAX420CPA) is no longer made so you will want to look for an equivalent chip. Also, you will want to see what the latest updates are on the Dataq A/D converters while being sure to follow the resolution guidelines in the Instructable. Finally, the Amaseis software has been replaced by jAmaseis written by IRIS. It is also free and it is JAVA-based, but I don't know if they have written it to read Dataq A/D signals. You can still use the free original software which is what I still run. If you have any specific questions during your construction journey, I would be glad to answer them. Good luck and keep us posted on your progress.

barkergk (author) 1 year ago
Here is a "Great" Earthquake I just recorded on 2013-05-23 using the seismometer described in this Instructable
Mag. 8.3 Sea of Okhotsk SW of Esso Russia.
54.874°N 153.280°E depth = 608.9km (378.4mi)
EQ 8.2.JPG
Shreddi1 year ago
That is so cool. Thanks for sharing. Man, you have some patience. Great Job. thanks again.
JTomM1291 year ago
Nice 'ible. Looks a lot like a Scientific American project from about 1957 but of course back then no A/D converters or USB interface. It would be nice to use Aduino with a TCP/IP net sheild and get remote data downloads so you coul put this way away from man made activity. My $0.02 worth.
barkergk (author)  JTomM1291 year ago
Re: Scientific American Article, see my exchange with joen below. I would love to see someone (you?) give the Aduino idea a try.
panic mode1 year ago
this is one amazing instructable, an example how project should be documented. don't hink i will build one soon but still must thank you...
barkergk (author) 1 year ago
Below is an extra Instructable 3 month Pro membership.
First come, first serve.
redeem it here: http://www.instructables.com/go/pro?code=involved11rocky
Your gift code: involved11rocky
baudeagle1 year ago
Do you record any false readings from large trucks, mowing the lawn or just walking about the house?
barkergk (author)  baudeagle1 year ago
The raw data can be filtered on three levels.
The mechanical unit itself is tuned to relatively low frequency waves, the electronics have built-in filtering and the software can further filter the digital data. Having said that, it is best to have the unit in a quiet, thermally stable location at least six feet away from any foot traffic. Road traffic does not seem to be a significant issue. You are always going to get some "microseisms", but these are usually caused by the normal moans and groans of the earth, strong winds and even ocean storms causing large wave crashes on the coastline believe it or not.
joen1 year ago
Is the magnet holder for the magnetic damper attached to the base in any way or is it just sitting there the base unattached? This instructable reminds me of a column that appeared many years ago in Scientific American magazine called "The Amateur Scientist" where Martin Gardner presented many science projects like this in various fields of science.
Well done!
barkergk (author)  joen1 year ago
Yep! Good memory. The Scientific America Article featured Jim Lehman's horizontal long-period design in 1981 which I made and it is still running.
The magnetic damper just sits on the base so that it can be moved in and out of the blade easily for damping adjustment.
joen barkergk1 year ago
Well... maybe my memory isn't so good after all. Martin Gardner wrote the column "Mathematical Games" for Scientific American. "The Amateur Scientist" was written by several writers including C. L. Stong, Jearl Walker and others. I remember the article you mentioned which prompted my comment. Wow! Your original setup is still running 30+ years later! Have you had to redo or repair worn parts or electronics? Wonder if this one will last another 30+ years.
barkergk (author)  joen1 year ago
I ran the Lehman seismometer at my school for my students for 25 years. We recorded hundreds of events including the Loma Prieta (World Series) earthquake.
I made sure that my students were well versed in seismology. A seismogram is worth a thousand words :)
kelseymh1 year ago
What an outstanding project! Like all good instruments, you have to spend some amount of money on it, but I am really impressed at how inexpensive it is. There's a part that I think I must have missed, though. How do you calibrate the amplitude?

One minor criticism -- you refer to "acceleration" of 50 um/s. Either you meant "ground motion" or "velocity", or you missed out a "2" on your units.
barkergk (author)  kelseymh1 year ago
Amplitude calibration can be done using the AS-1 software with the data from the lift test if you know the mass of the filecard cutout and the distance from the hinge when it is lifted off the arm. A more practical way to do it is to graph the p-wave amplitude of your trace against the reported magnitude of the earthquake. There are a lot of variables in extracting magnitude from a single seismometer. The USGS collects data from hundreds of seismometers and feeds it into a super computer at the Earthquake Information Center on the Campus of the Colorado School of Mines in Golden, Co.
Regarding your acceleration correction, you are of course correct and I will update the page. Thanks for your input. Always appreciated.
Ah, thank you! That first sentence answered my question. The lift test, with a known load, gives you the vertical scale.

Of course, you can't properly get an earthquake magnitude out of a single seismometer trace, unless you just happen to have been sitting at the epicenter (and your collapsing house didn't break the instrument :-). You need to know the distance to the hypocenter, you need to know something about the different formations the waves traversed, and so on.

With a sufficently large number of stations, over a large enough area, you can not only solve for the magnitude, but you can even invert the transport problem and derive the internal structure of the Earth from the pattern of signals.

(Yes, it's clear you already know that stuff! I'm writing for the same reason you did -- for the benefit of anyone else reading this.)
barkergk (author)  kelseymh1 year ago
Thanks kelseymh. Yes seismic tomography I think it is called. As you probably know, moment magnitude is used today which is based on the seismic moment, a function of the surface area of the slippage interface, the distance it slips and the rigidity of the rock involved. I also have a horizontal long-period unit running simultaneously that gives me two legs of an x,y,z monitoring station that would allow me to not only determine distance, but direction as well. Sigh! So little time, so much to do.
flavrt1 year ago
Outstanding project. I need this to monitor my neighbors' activities.
Kiteman1 year ago
I always love real science projects.