Research On The Theory And Method Of Detecting Seismic Wave With Grating Vibrator

In seismic prospecting, seismograph receives geological information carried by seismic waves through geophone. The quality of seismic data records and precision of geological target interpretation are directly dependent on the characteristics of geophone. Based on analyzing and researching the characteristics of seismic wave and current seismic wave detected method in more detail, adopting a grating vibrator as sensor element, the topic has completed the fundamental research on seismic wave detection and the method with grating vibrator to detect, as well as designing a device and the experimental study of the detector. It mainly contains:1. A device on detecting seismic wave by grating vibrator is designed. It mainly includes: 1) a structure case; 2) grating vibrator; 3) optical system; 4) damping system and so on. The case is designed with light aluminum alloy material,"spring-quality system"of grating vibrator is composed of the main grating, spring with limited on lateral and cylinders. The grating vibrator uses the aluminous grating bracket to fix the main grating and detects the measured signal of seismic wave through a moment on case and spring that with limited on lateral. The optical system is made of source system, indicative gratings and photovoltaic devices. The optical system uses the fluorescent lamp with the collimation mirror, incident the grating surface by the parallel light, in order to produce the moiréfringe through the grating.2. Using the principle of eddy drag, a damping system is designed by studied thoroughly. It is integrated design on damping tube and vibrator grating support bracket, the magnet steel is fixed on the damping adjustment device connected with the case, according to the requirement, the ratio of damping can be adjusted precisely, the system has realized adjustment of the elastic system damping continuously.3. The method of enhancing the system sensitivity based on the grating multiplication technology is studied. Using the main grating with different parameters and the indicative grating to compose the vibrator, a blazed grating is used in indicative grating to enhance contrast of the moiréfringe, the main grating is amplitude with thick grating.4. The constitution of grating vibration detection system and the signal recovery is realized. The test system is constituted combining the grating sensor, the hardware differentiation, the segmentation circuit, the PIC microcontroller subdivided unit and the computer, using the software to realize the recovery of the measured vibration signal, and completed performance analysis of the grating vibration system.5. The experimental study on the device of grating vibrator detection seismic wave is implemented. The performance test system of the grating geophone is the essential method to guarantee the detector performance analysis. In this article, the static state and the dynamic characteristic test system of grating digital seismic detector have been designed, and the performance of grating digital seismic detector can be tested. In order to confirm that the device of the grating vibrator detected seismic wave can be re-constructed back to the seismic wave signal without distortion, this article has completed the measured signal reconstruction system and the data telemetry technology with the existing seismic data acquisition station.The achievement of this topic can be widely used in seismic exploration such as oil, mineral resources, terrestrial heat, engineering and hydrogeology, etc. especially in geophysical prospecting of high precision and resolution.