Here is my simplified design for Lehman, , and accelerometer electronics. If your computer has a dedicated web connection, you can set this software to reset the time every 10 or 15 minutes, and that keeps your computer clock in synch. And of course you could still carry out the earthquake-simulation experiments that the author describes. You can download a free copy of jAmaSeis from 5. I generally use a cutoff of 1 Hz for a Lehman and 4. Figure 7: Earthquake signals recorded with our homemade seismograph.
If you have too little seismic activity in your region to make it worth building your own seismograph, you could visit the suggested websites to download earthquake data to analyse with your students. I purchased these at Lowes Home Improvement in the U. Depending on where you live you can expect a event every 3 to 10 days on average. Three time measurements in seconds are needed: the time that P waves arrive t p , the time that S waves arrive t s and the time that vibrations end t c Image courtesy of Panteleimon Bazanos; image source: Seismic Logger, Helicorder and Dataviewer software, Seismology Laboratory of the University of Patras Figure 4: How a geophone works. How do you get a voltage out of them? The weighted pencil should stay put and will make a mark on the paper strip you have moved through the cardboard base. If you live in a city, you may have noticed that buildings sometimes shake when a big truck or a subway train rolls by. I used a 30 lb.
It requires a smaller physical footprint that the Lehman horizontal sensor design, and hence requires a smaller thermal isolating cover. At the end of the long arm is a crosspiece, Q, of foil, whose two ends are bent up to form a support for the needle V' whose pointed ends rest in depressions in the foil. Seismic Waves: How Earthquakes Move the Earth Students learn about the types of seismic waves produced by earthquakes and how they move the Earth. He has degrees from the University of California, Irvine and New York University, including a masters degree in science journalism. Could they make it stronger? The pivot, K, is a common sewing needle, rather fine, whose point rests in a conical depression at. Most of the seismic circuit designs that I have seen do not use microprocessors and they use filter designs that require lots of precision components. The other end is bent up and to one side, and cut off half an inch long.
Faults are usually near the edge of a plate. Then write a paragraph explaining how your design works. Adjustment Of The Steady Mass By tapping the bar F to one side or the other, the bearing C' is brought exactly over C. This page copyright © 2001-2016 by , all rights reserved. The seismograph is based on an array of three geophones — devices that respond to the seismic waves and convert them to electrical signals. This article briefly describes the mechanism of earthquakes and especially the propagation of the different waves running through Earth. Be patient, it may take several days to a week or more for you to record your first earthquake.
This format can be read by the seismic data acquisition program. Above that Rs, the data sheet says the noise is significantly higher. Fasten the lower spring to the arm with a non-magnetic angle connector. On the Richter scale, anything below 2. The support from which this weight is hung can be adjusted, so as to bring more or less pressure on the strut as needed.
The paper is blackened by revolving the drum over a large, smoky flame, such as a kerosene torch. Earthquakes measuring more than 6. Virtually every object that you see around has been mechanically engineered or designed at some point, requiring the skills of mechanical engineering technicians to create drawings of the product, or to build and test models of the product to find the best design. Scientists and engineers use a seismograph measuring device to determine the strength of an earthquake. V is soldered along the minute hand, and also to its bushing and pivot, so that it will rotate rigidly with the minute hand.
Due to its position at the boundary of the African and European tectonic plates, several earthquakes occur in Greece every day Image courtesy of Panteleimon Bazanos; data source: the automated alert system of the Institute of Geodynamics at the National Observatory of Athens Figure 2: The 1886 earthquake ruined Filiatra, while the 1986 earthquake damaged Kalamata. For Trial 1, they should shake the paper dispenser a lot, and for Trial 2, they should shake it just a little. Now, you can easily hold the string and suspend the book in such a way that it is hanging over the paper and on the table. All of these parts can be purchased at RadioShack. The pendulum, when disturbed, should swing back and forth once in forty or fifty seconds. If the initial deflection goes up instead of down, reverse the leads from your unit to the amplifier. As the waves travel, they lose energy and the ground vibrates less.
The take-up spool should rotate when you crank its wood dowel; the paper roll can turn either with its wood dowel or separately from the dowel. When the ball strikes the hard surface, it produces vibrations that travel through the solid — just as an earthquake produces waves that travel through Earth. To do this, we used speakers and a computer equipped with a sound card and audio processing software, as before. Note that this page does not cover long-period seismometer designs other than the Lehman because I don't know much about them yet. So my op amp output is 2. To minimise interference from sound vibrations, we removed the cone of the loudspeaker. During an earthquake, the seismometer remains still while the case around it moves with the ground shaking.
Monitoring local earthquakes Earthquakes are a daily occurrence in Greece figure 1 , sitting as it does at the boundary of two tectonic plates. Thus when the point is down, it rests on the drum very lightly, and when swung- up. When you are confident that you have detected an earthquake, you can calculate its magnitude on the Richter scale and your distance in km from the epicentre figure 7. It is a logarithmic scale, meaning that the numbers on the scale measure factors of 10. If you do not have a drill, saw two slots into the upper edge of each wood support block and then drop the dowels into these slots. It rocked Chile on May 22, 1960.
Seismographs can detect quakes that are too small for humans to feel. The amplitude of the resultant signal is in the low microvolt region since the motion is quite small and very slow and not visually perceptible. Each of the three geophones monitors waves in the up-down, east-west or north-south directions. The smooth can rotates when you crank the nail at one end of its wood dowel; the paper roll can turn either with its wood dowel or separately from the dowel. They move rock particles perpendicular to the direction the wave is traveling in. Then have the students record the secret code, which trial they think it was and the height they measured in their science notebook or a separate piece of paper. Figure 5: How a loudspeaker works.