Classification of Background Noise and Gravity Disturbance Signals

Summary:

In order to cope with the huge challenge of artificial-based processing and analysis brought by the surge of continuous gravity data, this paper attempts to use deep scattering network to extract features from gravity data, and use unsupervised Gaussian mixture model to classify earthquake-related signals and background noise. The results show that under the condition of simple preprocessing of the original gravity data, the identification of various source signals in the gravity signal is completed, including the background noise signal, the co-seismic gravity signal and the pre-earthquake gravity anomaly disturbance signal.

Background

The broadband seismometer or gravimeter installed on the surface of the earth can not only record the seismic wave signal excited by the big earthquake, but also the continuous weak high-frequency vibration signal, which is the earth background noise.

Analysis the background noise level of Gravimeter installed in china

Spatial distribution of PET/gPhone gravimeter Seismic Background Noise in Mainland China.
Spatial distribution of PET/gPhone gravimeter Seismic Background Noise in Mainland China.

We find that SNM (seismic noise level) of gravimeters in coastal areas generally larger than inland, indicating that ocean noise may be the main reason for the greater noise of coastal stations. And SNM in North China, eastern and northern Qinghai-Tibet Plateau is huge, which may be related to the frequent tectonic activities in these areas.

The possible relationship between earthquake event and background noise level changes

noise level spatial distribution of gravity station network.
noise level spatial distribution of gravity station network.

The Yangbi MS6.4 and Maduo MS7.4 Earthquake occurred successively on May 21-22, 2021 in Dali, Yunnan Province and Guoluo, Qinghai Province of China.

We find that the background noise had a clear upward trend from two months(early March) to the Earthquake occurred; The spatial distribution of SNM indicates that from March to May before the earthquake, the background noise of the gravimeter located in the northern Qinghai-Tibet Plateau and the Bayan Har block has a significant increase.

We preliminarily speculate that the preseismic gravity disturbance is the low-frequency tremor generated by the slow slip of seismogenic fault, and the increase in background noise before the earthquake may be related to the increased activity of seismogenic tectonic block.

Jianing Gou
Jianing Gou
PhD candidate