Earthquake Engineering is a branch of Civil Engineering which covers the investigation and solution of problems to structures created by earthquakes. It includes planning, designing, constructing and managing earthquake-resistant structures and facilities.
Seismology: Study of Earthquakes
Seismology, basically, the science of earthquakes, involving observations of natural ground vibrations and artificially generated seismic signals, with many theoretical and practical ramifications (see Earthquake). A branch of geophysics, seismology has made vital contributions to understanding the structure of the earth’s interior.
Longitudinal, transverse, and surface seismic waves cause vibrations at points where they reach the earth’s surface. Seismic instruments have been designed to detect these movements through electromagnetic or optical methods. The main instruments, called seismographs, were perfected following the development by the German scientist Emil Wiechert of a horizontal seismograph about the turn of the century.
Some instruments, such as the electromagnetic pendulum seismometer, employ electromagnetic recording; that is, induced tension passes through an electric amplifier to a galvanometer. A photographic recorder scans a rapidly moving film, making sensitive time-movement registrations. Refraction and reflection waves are usually recorded on magnetic tapes, which are readily adapted to computer analysis. Strain seismographs, employing electronic measurement of the change in distance between two concrete pylons about 30 m (about 100 ft) apart, can detect compressional and extensional responses in the ground during seismic vibrations. The Benioff linear strain seismograph detects strains related to tectonic processes, those associated with propagating seismic waves, and tidal yielding of the solid earth. Still more recent inventions used in seismology include rotation seismographs; tiltmeters; wide-frequency-band, long-period seismographs; and ocean-bottom seismographs.