en تخصصي Special پژوهشي Research <p dir="ltr" style="text-align: justify;">We have built a vertical seismometer that works based on the moir&eacute; technique. One grating is attached to the suspended mass and one to the frame of the instrument. The two gratings are in relative motion, and the resulting moir&eacute; pattern magnifies this motion. The intensity of a light beam passing through the moving moir&eacute; fringes changes with time, and a light detecting system converts this power fluctuation into a voltage signal. From this voltage signal the time series of ground motion is obtained. We investigated the performance of the instrument theoretically, as well as experimentally. Our instrument can measure the amplitude of oscillation through moir&eacute; magnification. It is free from EM environmental noise, has adjustable sensitivity and dynamic range, and has simple and straightforward design. Furthermore, we introduce a novel way of data acquisition from moving moir&eacute; patterns.</p> Moiré pattern, seismometer, recording system, ground displacement, transmission function, time series 3 10 http://ijop.ir/browse.php?a_code=A-10-231-2&slc_lang=en&sid=1 Saifollah Rasouli rasouli@iasbs.ac.ir 10031947532846001519 10031947532846001519 Yes Institute for Advanced Studies in Basic Sciences (IASBS) Shamsedin Esmaeili 10031947532846001521 10031947532846001521 No Institute for Advanced Studies in Basic Sciences (IASBS) Farhab Sobouti fahads@iasbs.ac.ir 10031947532846001520 10031947532846001520 No Institute for Advanced Studies in Basic Sciences (IASBS)