BROADBAND SEISMIC NODE BASED ON LOW-NOISE HIGH-SENSITIVITY MOLECULAR-ELECTRONIC SENSORS

The developed wideband compact digital seismic module designed for use in ground nodal seismic systems with deployment assistance from unmanned aerial vehicle (UAV) is discussed. The operation frequency band is 1–300 Hz, which is by far wider than that of the seismic nodes based on using standard (10Hz) electrodynamic geophones. Such improvement was achieved through the use of highly sensitive seismic sensors with molecular electronic transfer (MET) that allow for covering a low-frequency part of the spectrum that is needed for broadband processing and receiving information on deep subsurface formation. Low self-noise of the MET seismic sensors used for this seismic station has been proven in special tests. According to the test results, measurements of the self-noise of the developed sensor turned out to be 27-30 dB lower than the self-noise of similar sensors with additional mass. Besides of the 3 mutually orthogonal wideband MET sensors the developed module consists of a digital electronics block enabling autonomous registration and featuring wireless data transmission capability; a battery compartment providing autonomous operation of the seismic module; a device for attaching the seismic module to UAVs and lowering it to the ground. The developed device ensures data time synchronization with satellites, records data at frequencies up to 1000 samples per second with 24 bits resolution and stores the recorded information on the internal 32 Gb storage. A distinctive feature of the presented seismic node is the implementation of quality control of seismic data using a drone. This function is implemented on a Raspberry Pi single-board computer installed on board of the UAV, which has the ability to retrieve portion of information from the node for data quality control and initiate calibration procedure.