Build the Bucket Seismograph 3
Some Modifications


seismograph antenna

On 10-23-2014 the seismograph was modified by mounting the antenna solidly against the side of the bucket to prevent detecting vibrations other than that from the suspended mass. The suspended mass was moved to one side (instead of hanging from the center) so it is close to the antenna. The piece of rope used for dampening, resting on the bottom of the bucket was changed and made to 12 inches long.

The PVC pipe was changed to a copper pipe for more stability.

This page shows how to make some other modifications to the bucket seismograph.

Shown below, September 13, 2014. At 19:47 UTC, running new experiment with a smaller glass jar to contain the magnets. The stack of magnets is now 4 inches long, centered in the jar, and the total weight of the mass with added sand is 39 ounces. The swing frequency is now 1.150 Hz. 1 piece of string dampens the motion of the mass. The experiment with this particular mass was ended on 10-20-2014. See new info posted above on next experimental setup.

This design works very well. Here are some photos:

October 12, 2014.

Placed seismograph on new concrete slab. Replaced CPVC pipe with copper pipe, to add more stability. No other changes. Same smaller glass jar to contain the magnets. The stack of magnets is now 4 inches long, centered in the jar, and the total weight of the mass with added sand is 39 ounces. 1 piece of string dampens the motion of the mass.

SHOWN BELOW ARE SOME MORE EXPERIMENTAL MODIFICATIONS WE HAVE TRIED OUT WITH THIS BUCKET DESIGN to help you choose the right mass weight. See other pages to compare seismograms - vs- mass weight used and distance to quakes....

September 4, 2014. The bucket seismograph has been re-updated to use a glass juice bottle. The bottle and magnets weigh 79 oz when filled with sand. A 6 inch long stack of magnets is centered in the bottle. The antenna used is the 8SR-0.1H-1K.

The length of rope between the suspension point and the cap is 4 inches.

The swing frequency is a clean 1.055 Hz with much less resonant spurs than the red bucket method below.

One piece of rope has been taped to the bottom of the bottle to cause swing decay as it drags on the clean dry bottom of the bucket.

The 8SR-0.1H-1K antenna has been placed in a sand-filled tall glass jar. The straightness of the tall glass jar allows closer placement to the suspended magnet bottle.

The intended application of this seismograph is detection of 6.0 magnitude or greater quakes up to 1000 miles away. This range depends on seismic wave propagation and how the quake pushed or pulled.

If you are looking for an instrument to detect actual strong shaking that can be felt at your location then you can:

(1) Reduce the length of the magnet stack, perhaps just use 1 magnet piece instead of a stack of magnets,

(2) Increase the distance between the suspended magnet bottle and the antenna.

(3) Or you can use a magnetometer antenna instead of a physical seismograph.

We are operating this seismograph along side a 24 inch long magnetometer antenna. Local ground shaking that swamps the seismograph will still be recorded faithfully on the magnetometer.

August 17, 2014. The bucket seismograph has been updated to use a small red beach pail filled with 110 oz of sand for weight instead of the bottle, and a 6 inch long stack of magnets. The antenna used is the 10SR-0.1H-100H.

The 7 pounds of sand for the weight mass gives this design higher sensitivity. Its also easier to do.

A pencil has been used as a wooden support to suspend the bucket, other materials could also be used (suggest a 1/4 inch solid metal rod instead of the pencil), however do not use the cheap plastic handle that comes with the red beach pail for suspending.

Update September 4, 2014: Don't use the pencil, it will eventually bend.

Two pieces of rope have been taped to the bottom of the small red beach pail to cause swing decay as they drag on the clean dry bottom of the bucket.


Using salt water to cause swing decay

The suspended magnet bottle's bottom can be placed down in a PVC cap full of salt water. Shown is a 4 inch diameter cap. This slows the swing period down to 0.840 Hz and also causes quick decay of motion for increased waveform resolution. Operating in this dampend mode, the seismograph will detect down to its swing period and also above it, just like a speaker or a microphone has a low frequency cut-off. Use table salt in the water to prevent algae growth.

The 8SR antenna is placed in a plastic cup and craft-store beach sand is used to fill the cup to hold the antenna vertical.

This page shows how to make some other modifications to the bucket seismograph.

You can boost sensitivity and create swing decay for improved resolution by using a metal plate and a magnet below the suspended bottle

A small stack (4 pieces) of the same type of magnets that are inside the bottle is stuck to a metal plate 1/2 inch below the suspended bottle. It is assumed the 4.75 inch stack of magnets inside the bottle are resting on the bottom of the bottle, and that the magnet on the plate is ATTRACTED to the magnets in the bottle.

Sit the glass holding the 8SR antenna on the steel plate. The steel plate will help conduct magnetic field to the antenna, boosting reception strength.

By changing the number of magnets below the bottle, (add one, take away one, etc) the swing frequency can be tuned without making any other adjustments.

The swing period WITHOUT the magnet is around 0.75 Hz. The swing period WITH the magnets and plate is 2.2 Hz, no change in the length of suspension rope. This results in a great increase in sensitivity. Seismic waves from distant earthquakes are best received in the range of 0.5 Hz to 3 Hz.


Some users may prefer this horizontal magnet set up. Others may prefer the standard vertical magnet set up. The horizontal setup can allow added detection of geomagnetic storms. The magnet stack can be made to swing freely like a compass needle which greatly amplifies the small change in Earth's magnetic field. The unit still detects earthquakes too.

Instructions are given below on this page to allow added detection of geomagnetic storms and ELF magnetic events. One instrument doing 2 jobs at once.

For full instructions on building the standard (non-modified) vertical aligned bucket seismograph click here: Standard Vertical Magnet Bucket Seismograph 3.

Using a 2 inch PVC Tee fitting and 3 couplings, some rope and a 4.75 inch long stack of magnets, you can make a seismic sensor which works with the 8SR antenna to detect earthquakes.

Fill the unit with craft-store beach sand for extra weight and to keep the magnets from moving around.

Drill a hole in the PVC plug so the nylon rope can be placed through the hole for suspension.

Tie a knot in the rope to allow suspending the unit.

Place the 8SR antenna on the bottom of the bucket and place dry craft beach sand around it. This prevents the antenna from moving around and also weighs down the bucket.

Suspend the magnet weight assembly with the nylon rope 1/2 inch above the 8SR antenna. The magnet may want to turn to align with Earth's magnetic field. Allow it to do so and adjust the antenna position to be directly under like shown in the photo below. If the magnets will not align when the antenna is moved around, then slowly turn the knot at the top to adjust the rotation position slightly.

The magnets may rotate slightly when detecting a magnetic storm, however this type of nylon rope is stiff enough to prevent good rotational swing (like a compass needle). This cuts down on detection of geomagnetic storms. However if you WANT to detect geomagnetic storms in addition to earthquakes then use a piece of twine or cotton string instead of the nylon rope. The magnets will then be seen to swing back and forth slowly before aligning with Earth's magnetic field. One end of the unit will point North, the other South, and will always go back to the same position freely if moved off axis by hand.

Geomagnetic storms will usually be below 0.5 Hz. The seismic swing of the unit is around 1.030 Hz. The assembly as shown will detect up to 10 Hz allowing detection of large trucks moving down a road 100 feet away, a good test to check the operation. Background seismic activity is also detectable at 1.030 Hz, showing that the ground is always in motion.

The magnet weight assembly is suspended 1/2 inch above the 8SR antenna.

Place the unit on a level slab of concrete (we used a 16 x 16 inch square concrete block, weight about 30 pounds). Use a bubble level to check that there is no tilt in the slab. A 10 pound brick is placed on top of the bucket lid to hold it down and add weight.

The hole filled with bricks in the background was where the bucket was before. It was found that burying is not needed for the seismograph to work. It has been moved onto the concrete brick slab shown in this photo. Having the unit on a concrete block allows the grass to be cut around the unit without disturbing. It also allows for easy maintenance or changes to be made.


See photos below:

How it works: The Earth's magnetic field can be disturbed by solar flares and geologic events. The magnetic field strength is rather low, about 0.5 gauss. This level is difficult for the antenna to detect by itself. However when a magnet is suspended near the antenna, the total magnet stack having a gauss power greater than 1000 works like a magnetic-field amplifier when it moves around, boosting the tiny change. The moving magnet is far easier to detect, it is a powerful amplification as the tiny field of Earth is pushing around a much stronger local field (the magnet stack).

The unit will still respond to earthquakes but not as strongly because the suspended mass ( now only the magnets, no sand) weighs much less.

The 4.75 inch stack of 1 inch diameter round magnets is suspeded by a thin piece of string or a thick piece of sewing thread, allowing it to swing freely around. A large popicle stick is placed between the center of the magnets so as a way to suspend them without using any glue or tape. Carefully drill a small hole without cracking the wooden stick. There should be an even number of magnets on the right side and on the left side of the stick so there is no imbalance in the way it hangs.

Suspend the magnets 2 inches above the antenna. Do not allow the magnets to touch or be attracted to the antenna, they must swing freely back and forth (moving around just like a compass).

VERY IMPORTANT: Allow the magnets to freely align with Earth's magnetic field just like a compass. Mark this point before placing the antenna below the magnets, without disturbing the direction they are pointing. One end points NORTH, the other end points SOUTH. Check this with a compass. Do not place the installation near metal or vehicles as their magnetism may change the results.

You will notice the magnets are free to swing in all axis: X, Y, and Z, allowing detection of any magnetic disturbance.

The seismic swing period will be around 1 Hz. Geomagnetic storms will be detected at and BELOW this frequency point as slower waveforms down to 0.1 Hz, (the magnet will swing side to side or up and down when it is detecting geomagnetic storms). The magnets also have an X-Y peak. Tap down on the magnets and allow them to settle. You can find all resonance peaks using the FFT function on the software.

This setup will also detect local ground vibrations up to 10 Hz, so you may see some high-frequency detections if a large heavy ruck passes nearby.



DATAQ SOFTWARE AND HARDWARE (13 bit data resolution. Best unit, higher signal gain.)

DATAQ SOFTWARE AND HARDWARE (8 bit data resolution. Inexpensive PC data logger.)

Seismic waves have a frequency range between 0.3 Hz to 3 Hz. For best seismograph performance use the center of the band between 1 Hz to 1.5 Hz.