Analysis Of Background Noise Of The Basement Gravity Observation Station Based On HHT

Continuous gravity stations are divided into three types: cave, basement, surface stations.According to observation experiences for many years, cave is best for observation, basementis better and surface is final choice. And the cave always make cave in the rock, that is a large,difficult, high cost project, so it’s necessary to study background noise level of continuousgravity stations and whether basement can instead of cave. This paper introduces a method basedon HHT algorithm to analyze background noise by using gPhone gravimeter seconds samplingdata, shows characteristics and advantages of HHT on high frequency time-frequency analysis.Besides, this paper studies how to apply the method to background noise analysis of continuousgravity stations, then primarily apply that in basement stations background noise analysis,finally, compare with two other types.This paper mainly analysis basement continuous gravity observation stations backgroundnoise by using gPhone gravimeter seconds sampling data, the following contents are discussed:1. Expounds the role of tidal gravity in geophysical and earthquake monitoring andprediction, and reviews the tidal gravity and continuous gravity observation technologydevelopment trends.2. Explores the tidal gravity theory algorithm, and influence factors of continuous gravityobservation and data processing method in detail.3. Introduces some common continuous gravity data processing software, and combineswith data processing method for gravity observation stations get gravity stations residue.4. Discusses the HHT (Hilbert-Huang) basic principle and significance, firstly, does HHTtime-frequency analysis with residual data and original observation data respectively, andconcludes differences between them to show HHT’s properties; then get advantages of HHTcompares with wavelet analysis method in time-frequency analysis.5. For the research purpose, studies how to apply the method to background noise analysisof basement continuous gravity stations by a example of Qiongzhong surface station, and sumsup basement stations’ background noise characteristics by analyzing that in the seismic networkand mainland monitoring network based on HHT algorithm. Then, use this method to the cavestations background noise analysis to obtain the characteristics of them. For the last, comparesthe three different types of the station background noise.6. This paper shows that, HHT method only extracts high frequency information; there is alittle effect after data to correct. HHT is more real, clear, easy to compare various components than Wavelet transform proved by experiments in background noise analysis. It can obviouslytell that the size of background noise level, the cave is smallest, the basement take second place,and the surface is the largest. At the same time, the basement of the station background noiseclose to the cave stations, far less than the surface stations, so basement stations may instead ofcave stations if condition is not allowed to construct the cave in the future.