MEMS devises
MEMS devises : Sensor devices based on micro electromechanical systems. Originally developed for use in airbags, they are nowadays build-in in iPhones, hard disks, Wii stations etc. Of special interest for seismic exploration, seismology and engineering seismology are accelerometers based on MEMS technology. Mechanical components and required electronic circuits are often integrated on a silicon chip that means small dimensions and often low costs. Low g chips have a resolution of about 1 mg at costs of a few $. They can be used for strong-motion sensing (e.g., early warning system SOSEWIN, see IS 8.8) There is also some progress in the development of high resolution accelerometers for different applications. The resolution is up to ~100ng/sqrt(Hz) Other applications are in strong-motion seismic sensing with high dynamic range of 120dB or more and in seismic prospection where MEMS accelerometers combined with 24 bit digititizer modules result in a modern replacement for classical geophones. Costs of these high resolution sensors are still high (several 100$ per unit), due to a more expensive technology. It is not likely that MEMS can replace broadband seismometer in near future since their sensitivity at very low frequencies is more than 2 orders less than for broadband velocity meters
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