Gaiacode has just delivered 20 Theta medium motion seismic sensors to China. The instruments will be used to collect data for the investigation of the crustal structure beneath the earthquake prone areas in the Southwest of the country. The sensors are part of one of the temporary networks installed within the framework of a decade long project loosely translated as "Transparent Crust".
Active Seismic Sources
One of the many ways to gain information about the otherwise inaccesible outer layer of the Earth, the crust, is to set off artificial seismic sources. The seismic waves can originate from small explosions, from air-guns in water bodies or from heavy trucks which shake the ground in a controlled, rhythmic fashion. To detect such waves one needs sensitive compact sensors, which are easy to install and can run reliably for long times. Gaiacode's Theta sensors perfectly fulfill these requirements.Temporary Installations
The Chinese scientists plan to deploy the Theta sensors in small seismic network for up to two years in one place. Once retrieved the instruments will be deployed at different locations for similar lengths of time. During the various deployment phases, the sensors will record natural earthquakes as well as waves from artificial sources. Using such sources, researchers can focus on questions of specific interest, for instance of how rock parameters change during a natural earthquake cycle. One parameter to look for are very small changes in the velocity of seismic waves travelling through specific sections of the crust. Mechanical stresses induced into the rock prior to large earthquakes may change this velocity.