Earthquake sensor

[elcano]

There has been a series of small earthquakes in the local area (Puerto Rico) reported in the newspaper last week. I didnt feel them nor know anybody that noticed them, but apparently were big enough to show up in the news.

We are supposed to have a major earthquake every 70 years. The last one was in 1910, so we have been waiting for it since 1980. And every day the accumulated energy is supposed to be higher, so the next one is going to be big. These little tremors might be the precursors to the big one.

In addition to the typical measures, I was wondering what happens if the earthquakes surprises my family while sleeping. Just having 4-8 seconds to run to my children's rooms would make a difference. Turning off electrical appliances to prevent short circuits are an value added.

I found this sensor, but it is stand alone. I wonder if I tinker with it to connect it to my M1 I might damage or take it out of calibration. There are other vibration/seismic sensors around, but I would better buy something made or tuned specific for the early notification of earthquakes (and reduced false alarms).

I wonder if the Californians in this forum know any other sensor for this purpose.
Thanks.

 

[Rupp]

Have a look at Geophones. These are used in homemade seismic monitoring solutions. The HS BB had some info on using these a while back for detecting when the washing machine had completed it's cycle and other uses as well.

Just do a search on Geophone on the HomeSeer BB and there's some interesting reading.

 

[smee]

Have a look at Geophones. These are used in homemade seismic monitoring solutions. The HS BB had some info on using these a while back for detecting when the washing machine had completed it's cycle and other uses as well.

Just do a search on Geophone on the HomeSeer BB and there's some interesting reading.

Here's a link to the geophone hardware:
geophone at bgmicro

These are supposed to be pretty sensitive. You will pick up normal house vibrations and possibly people just walking around.

To detect true seismic events, you may need something like a separate concrete pad located away from other activities - and then mount the sensor to that.

 

[jay]

Darn it! If I can remember, I'll post the circuit. I built one for my son's science class in 7th grade using RadShack parts. I mounted a spike like a ground rod into the earth and class kids had to jump up and down to trigger the thing. I remember it had a LED bar graph array to visually depict relative strength of the ground vibrations. That could easily be changed to trigger an annunciator with a simple comparitor circuit. This thing worked well and the cost was a couple of bucks max.
Maybe I used a phono cartrage with the needle in contact with the ground spike and amped and rectified the output.

I'll see if I can find any record of it. Was cheap, EZ and sensitive.

 

[BraveSirRobbin]

Wow, a lot of great suggestions. The only thing I am wondering is how would you go about calibrating such a system. I mean, think about what would happen when this thing went off at night. You would wake up, grab your kids, and go running out onto the street!

I guess you could always try it and see what happened (for instance see if it gets triggered by large trucks going down your road). Just wish there was a way to get some relevance of geophone vibration to earthquake detection scaling.

 

[elcano]

These are supposed to be pretty sensitive. You will pick up normal house vibrations and possibly people just walking around.

To detect true seismic events, you may need something like a separate concrete pad located away from other activities - and then mount the sensor to that.

That might not be a problem in my case. My house is 100% concrete, so any vibration will certainly come from really strong forces.

I certainly want something that focuses in detecting the horizontal seismic P waves (I read a little about this today) instead of vibration of other frequencies/directions. And given that I'll not be able to trigger an earthquake myself it will be difficult to test a home made sensor.

 

[elcano]

BSR, you read my mind.

 

[jay]

Certainly a valid point. In the meantime, you can always err on the side of caution.

 

[elcano]

The only thing I am wondering is how would you go about calibrating such a system.

It might not be that difficult if you live in an active area.

Check the USGS Recent Earthquake Program here.

I might try first with the QuakeAlarm since it is not too expensive. I could try to open the housing to tap into the circuit without damaging the mechanical sensor.

Nevertheless the geophones have many applications as a security/automation sensors.

 

[BraveSirRobbin]

Check out some of these links on building your own system:

http://www.infiltec.com/seismo/#cost

http://www.seismicnet.com/atod.html

 

[jay]

Just to follow up. I used a cantilevered piezoelectric sensor mounted on the side of my home's concrete foundation. The sensor arm was epoxied to the top of the 'ground rod'.

 

[elcano]

Its funny.

Even that my first language is Spanish, sometimes the translations are so bad that I prefer to navigate in English, even when Spanish is available.

However yesterday I checked the Spanish version of the QuakeAlarm page and found a distributor in Puerto Rico. It only had a phone number. Hmmmm...Who is this people?

I did a search in Google for Quake Alarm Puerto Rico. And found another vendor offering it (different number).

So today I called the first one. He was asking $49.95!!! The regular price in the web is $22.95.

So I called the second one. He asked $60!! What a rip!!

I was going to hang up, but told the guy that I preferred to buy in internet at $22.95 (shipping difectly or a relative in US). He challenged again the price - how are you going to get it cheaper?. I said "dont worry", and then he offered them for $20. Cheaper than unshipped price via internet!

Incredible, no?

 

[electron]

Now, that's what I call haggling lol, great job, you might want to stock up on those, and resell them for $30

 

[Dean Roddey]

I certainly want something that focuses in detecting the horizontal seismic P waves (I read a little about this today) instead of vibration of other frequencies/directions.

I've not lived in CA long enough to experience a big quake. But I felt a smallish one. It was wierd because I felt the fast tremor and I immediately thought, P wave since I'd been reading about earthquakes not to long before, and I should feel the S way next, and sure enough about 3 seconds afterwards I felt them. They were clearly very different even at that low magnitude.

I would think that you could get some sort of very small and inexpensive accelerameter type device to use for this. They have to have quite inexpensive ones these days I would think. You might have to mount three of them to catch movement in any axis, but I assume that both P and S waves are perpendicular to the ground, right?

 

[elcano]

I read a lot yesterday and there are several other waves in addition to P and S. P is the most useful because it is the fastest and S is the most important because it causes the most damage.

If I remember well (and do not mix up waves), the P waves are analog to sound waves. The wave movement and vibration are in the same direction. They are horizontal (assuming the earthquake center is not just below you, in that case they would be vertical).

The S waves are analog to the movement of water when you drop something on it. They travel horizontally along the surface of the ground, but the vibration is vertical.