Open Access

, 1:11http://dx.doi.org/10.4172/scientificreports.506

Research Article Open Access

Open Access Scientific ReportsScientific Reports

Open Access

Volume 1 • Issue 11 • 2012

Keywords: Mercury; Seismometer; Electrical charge changing

IntroductionSeismograph is another Greek term from seismós and γράφω,

gráphō, to draw. It is often used to mean seismometer, though it is more applicable to the older instruments in which the measuring and recording of ground motion were combined than to modern systems, in which these functions are separated. Both types provide a continuous record of ground motion; this distinguishes them from seismoscopes, which merely indicate that motion has occurred, perhaps with some simple measure of how large it was [1]. In 1800s the theory of elastic wave propagation in solid The theory of elastic wave propagation in solid materials is developed by Cauchy, Poisson, Stokes, materials is developed by Cauchy, Poisson, Stokes, Rayleigh, and others. They describe primary and, and others. They describe primary and secondary body waves (P- and S-waves) and surface secondary body waves (P- and S-waves) and surface waves. (Theory is way ahead of observation) [2]. In 1857 R. Mallet, an Irish engineer, travelled to Italy to study damage caused by an earthquake near Naples. His work is generally considered to be the first serious work at observational seismology. In the 1960s, seismologists were able to show that the focal mechanisms (the type of faulting as inferred from the radiated seismic energy) of most global earthquakes are consistent with that expected from plate tectonic theory, thus helping to validate the still emerging paradigm [3]. Human ability to collect, process, and analyze earthquake data has been aided by rapid advance in electronics digital computers. Seismograms were mostly recorded using analog technique up to a few decades ago. Modern digital seismograph systems consist of analog and digital stages. The analog part of system involves the seismometer. Digital seismograph are merely sequences of numbers that must be processed in the context of analyze [4]. In 1961 the Worldwide Standardized Seismograph Network (WWSSN) was established, consisting of well-calibrated instruments with both short- and long-period seismometers. The 1960s and 1970s saw the development of the field of normal mode seismology, which gives some of the best constraints on the large-scale structure, particularly in density, of Earth’s interior [3]. Modern instruments use electronics. In some systems, the mass is held nearly motionless relative to the frame by an electronic negative feedback loop. The motion of the mass relative to the frame is measured, and the feedback loop applies a magnetic or electrostatic force to keep the mass nearly motionless. The voltage needed to produce this force is the output of the seismometer, which is recorded digitally. In other systems the weight is allowed to move, and its motion produces a voltage in a coil attached to the mass and moving through the magnetic field of a

*Corresponding author: Mohammad Mehdi Masoumi, Department of Civil

Azad University, Fars, Iran, E-mail: m.masoumi@rocketmail.com

Received November 12, 2012; Published December 03, 2012

Copyright: © 2012 Masoumi MM, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits un-restricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

AbstractThe Mercury Seismometer (MS) proposed for this paper was supposed to be worked by electrical charge and

electrical discharge such as capacitors and included mercury, copper wire, power supply, LC meter. The MS was more sensitive in the recording of vibrations. Vibrations could change the capacitor capacity or cause changes in the capacity of the capacitor which showed on the LC meter set. The charge changes of the capacitor were the major target, which show vibration. By increasing charge, the MS worked as a seismometer and if charge decrease worked as seismic acceleration recorder, accelerograph. The thermal effects are ineffective on the MS.

magnet attached to the frame [5]. Totally simple current seismometer works with electromagnetic [6].

In this present research, it has been attempted to show another seismometer for records quakes and seismic better and more sensitive. In contrast to work of other types of seismometers which mentioned above mercury assumed as mass that allow motion or motionless [7]. The mercury seismometer (MS) proposed for the present project was supposed to be worked by electrical charge and electrical discharge in order to gain more sensitivity and better in recording seismic for all ranges of ground motion and major part of the MS was mercury.

ExperimentA simple design of seismometer was built with a test tube of 1.8cm

interior diameter, 50cm lacquer copper wire with 0.5mm diameter, mercury, signal generator, LC meter, power supply and an auto switch. In the experiment, 20ml of mercury was poured into the test tube then the lacquer copper wire change to spiral shape (when the copper wire was connected to the sets such as power supply or the LC meter without lacquer and when proximity of the mercury it had lacquer) then put in the test tube somehow some parts were pushed in the mercury a little and tried to motionless all mounted parts on plate. The power supply made electric current equal 6.5v which on side connected to the lacquer copper wire and other side of electric current connected to the mercury that it is electrically conductive (Figure 1a), then the power supply disconnected then connected to the LC meter or the power supply was replaced by the LC meter (Figure 1b) that the LC meter showed capacity of electrical charge. When weak vibrations were happed manually (by one finger beat on the plate) in distance of 30cm, eventually the number of the LC meter was changing between 24 nμ and 19 nμ. While the intensity of vibrations increase manually, numerical range changing showed on the LC meter expanded. The Mercury Seismometer (MS) was simulated in this project, the test tube was filled by mercury and the copper wire was fixed there which was approximately spiral in

Seismometer Working with MercuryMohammad Mehdi Masoumi1* and Fatemeh Habibi Ardekani2

1Department of Civil Engineering, Young Researchers Club, Science and Research Branch, Islamic Azad University, Fars, Iran2Civil Engineering Department, Shiraz University, Fars, Iran

Citation: Masoumi MM, Habibi Ardekani F (2012) Seismometer Working with Mer-cury. 1:506. doi:10.4172/scientificreports.506

Masoumi and Habibi Ardekani

Engineering, Young Researchers Club, Science and Research Branch, Islamic

Page 2 of 3

Volume 1 • Issue 11 • 2012

shape. The copper wire was covered by lacquer to prevent short cut and worked as dielectric. In fact Mercury Seismometer (MS) was worked by electrical charging, and it was sensitive since the mercury is liquid and most part of the wire was floating on the mercury. The mercury density was more than copper so the wire could not sink or suspend in the mercury, the copper wire was fixed in the test tube by supports while little parts of wire near supports, were under the mercury due to adjusted wire’s firm. As the copper wire assumed spiral shape near the supports, the wire was under tension such as stretch of a spring and on the surface of the mercury the wire was normal. In figure 2 we illustrate Mercury Seismometer (MS) and showed the auto switch was adjusted to charging and discharging of the capacitor on each definite period of time automatically for example on each 15 minutes. The auto switch was cut off, and the electric current from the power supply then made short cut due to discharging the capacitor, then connected the capacitor to the power supply and the capacitor charged again. This process took less than one second and was repeated in the next period. The mercury seismometer worked as an electrical capacitor (each capacitor include two plates) which its plates had mobility because one of two plates was assumed mercury and another was copper which floated on the mercury and lacquer on the copper wire worked as a dielectric, so they were charged by the power supply. Quake could change the capacitor capacity which showed on the LC meter set. The LC meter showed the capacity charge and charge changing of capacitor. Amount of capacity of the capacitor was not important, charge changes of the capacitor were major target. The electrical charge was major factor that moving on interface between the mercury and the spiral wire (Figure 3). Figure 3 shows two zones which one of them green in the mercury and another red located in the spiral copper wire; they illustrated assumed electrical charges location on interface. During vibration, the positive charge and negative charge were moving on interface such that, one side assumed

mercury and another one assumed the spiral copper wire, therefore it worked as a seismometer sensor. Since that thermal effect does not have any influence on the MS, the best fixing for seismometers may be in deep boreholes generally, which avoid thermal effects and ground noise. So in this case to avoid ground noise effect, the MS was mounted in a deep borehole. This seismometer included some parts such as the LC meter, the power supply, the auto switch, seismometer sensor that they placed on the ground surface, but only the seismometer sensor (which included the mercury and the spiral copper wire) was embedded in the borehole that it needed only wire due to electrical current for the seismometer sensor. In the other experiments, electrical loads on interface reduced and less than usual in order decline density of interface electrical load. Consequently the LC meter showed reduced charge in comparison to usual charge, then it could record quakes as accelerogragh because the electrical load density reduced in vibration time a few electrical load just varied on the interface and for usual charge that it charged with normal electrical loads density, the MS recorded quakes as seismometer and recorded more sensible than lessen density of electrical loads, which is shown in figure 4. In figure 4, a vertical axis showed the LC meter data which they were capacity changing while the test tube was shaken for 5 seconds t showed via horizontal axis. As the density of the electrical loads was reduced, the recording of the LC meter data was more tangible than the usual density. On the vertical axis, this experiment was done in the same condition but on the usual density of the electrical loads for copper wire which recording the LC meter data was so difficult because it showed very quick and varying numbers. The MS never saturated because in serious seismic while copper wire shake, mercury start waving.

ConclusionAs mentioned, the MS was mobile because it is liquid, and the MS

Figure 1: Experimental Process.

Figure 2: MS, works as a capacitor.

Figure 3: The interface of mercury & wire.

Figure 4: Low electrical load density (accelerogragh) records.

Citation: Masoumi MM, Habibi Ardekani F (2012) Seismometer Working with Mercury. 1:506. doi:10.4172/scientificreports.506

Page 3 of 3

Volume 1 • Issue 11 • 2012

2. Shearer PM (2009) Introduction to Seismology, 2nd Edition. University of California, San Diego, Cambridge University Press 1-2.

3. Lee WHK, Jennings P, Kisslinger C, Kanamori H (2002) International Handbook of Earthquake & Engineering Seismology.

4. Wielandt E (2002) Seismic Sensors and their Calibration.

5. Bargi K (2009) Tehran University Press Fundamental of Earthquake Engineering. 7th edition 1-50.

6. Bozorgnia Y, Bertero VV (2004) Earth Quake Engineering from Engineering Seismology to Performance-Based Engineering. CRC Press, USA.

7. Halliday D, Resnick R, Walker J (2005) Fundamentals of Physics Extended. (8th edn), Wiley.

was motionless because the mercury has high density. It was able to record vibrations because of electrical charges on interface, change while vibration was happening even when it was weak, so it is very sensitive. Factors that influence on the capacitor are dielectric material properties, area of the mercury and the copper wire interface and distance between the mercury and the copper wire. So the thermal effects are ineffective on the MS.

References

1. Richter CF (1958) Elementary Seismology. San Francisco: WH Freeman.

Citation: Masoumi MM, Habibi Ardekani F (2012) Seismometer Working with Mercury. 1:506. doi:10.4172/scientificreports.506