Seismic sensors

Our Laboratory developed different types of seismic sensors such as very broadband high resolution seismometers KS-1, strong ground motion seismometers KSM-1 and seismic gyrotiltmeters KST-1. In addition to reception of regional and teleseismic signals, these seismic sensors could record strong ground motions, which enables the stations to be used to record aftershocks in the epicentral area of a large earthquake. Also, such seismometers record rotational ground motion, in addition to translation, which makes it possible to recover the true ground motion under the seismometer, which, as is known, is necessary for representing undistorted, "true" wave paths of ground particle motion. This problem is rather urgent at present for several, fast evolving scientific and engineering areas in seismology such as the study of source physics and earthquake precursory processes, engineering seismology and earthquake-resistant design, detection and identification of underground nuclear explosions.

Important metrologic characteristics of the superbroadband seismometer developed for this system include a low threshold of system noise and long-term drift achieved by protecting the seismic sensor from ambient excitations such as fluctuations of ambient temperature and air pressure; when a seismic gyrotiltmeter with a threshold resolution of order 10^-12 Rad/sec is used, the above measures reduce the background noise on records of the superbroadband seismometer due to ground tilts of baric origin (including those due to wind). The degree of tilt noise suppression in the range of medium to long seismic periods when recorded at the Earth's surface may prove to be as effective as in borehole observations, thereby lowering the magnitude level of recordable low amplitude seismic signals excited by earthquakes and explosions.

The strong motion seismometer KSM-1 developed for this system expand the dynamic range of recordable seismic events towards greater peak acceleration, including signals excited by large earthquakes when observed in the epicentral zone.

The superbroad frequency passbands of these seismic sensors enable observation of long period ground motions near earthquake epicenters during the generation of the wave field and far from the epicenter.