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We have developed an automatic regional focal mechanism inversion system based on the Earthquake Rapid Report (ERR) system and the real-time three-component seismic waveform stream of 1 000 broadband seismic stations provided by the China Earthquake Networks Center (CENC). The system can rapidly provide a double couple solution and centroid depth within 5-15 min after receiving earthquake information from the ERR system. The data processing is triggered by earthquake information obtained from the ERR system. The system is capable of determining the focal mechanism of all shallow-depth earthquakes in the Chinese mainland with a magnitude of 5.5-6.5. It utilizes waveform data recorded by seismic stations located within 500 km from the epicenter, enabling the reporting of a focal mechanism solution within 5-15 min of an earthquake occurrence. Additionally, the system can assign a corresponding grade (A B C) to the focal mechanism solution. We processed a total of 301 earthquakes that occurred from 2021 to June 2022, and after the quality control, 166 of them were selected. These selected solutions were manually checked, and 160 of them were compiled in a focal mechanism catalog. This catalog can be conveniently downloaded online via the Internet. The automatic focal mechanism solution of earthquakes in eastern China exhibits a good agreement with that provided by the Global Centroid Moment Tensor (GCMT), when available. The average Kagan angle between this catalog and GCMT is 22°, and the average difference in MW is 0.17. Furthermore, compared with GCMT, the minimum magnitude of our catalog has been reduced from approximately 5.0 to 4.0. The correlation between the centroid depth and crustal thickness in the Chinese mainland confirms the distribution of the centroid depth. [ABSTRACT FROM AUTHOR]

High precision gravity observation is an important tool of seismological research and has played an important role in earthquake prediction in China in recent years. This paper first briefly introduces the development status and classification of gravity observation instruments, then compares the seismic gravity observations and researches for seismic events between China and Japan from the aspects of the scale of the seismic gravity observation network, the gravity data processing process and the interpretation of gravity observation results, and finally systematically analyzes the challenges faced by the gravity observation re⁃ search in China. The aim of this paper is to provide some reference and enlightenment for the follow-up work. [ABSTRACT FROM AUTHOR]

This paper mainly introduces the layout of mobile gravity monitoring network in China, and the gravity measurement data processing and extraction method of gravity precursor information. Mobile gravity monitoring results can reflects the image of dynamic evolution of regional gravity field and its tectonic activity characteristic. Based on a large number of observation data, the relationship between gravity variation and earthquake preparation is studied, and the ideas, ways and methods of earthquake prediction research are explored. The mid-term earthquake risk prediction research is carried out by using gravity observation data, and its results are used for earthquake consultation and annual earthquake trend prediction in time, which provide basises for the prediction of strong earthquakes and the delineation of annual dangerous areas in China. this paper points out the existing problems in mobile gravity monitoring in China, and puts forward the idea and thinking of using time-varying gravity monitoring data to promote seismic prediction research. [ABSTRACT FROM AUTHOR]

We present the current status of seismic noise interferometry to reconstruct the seismic velocity and discuss the four phases from single-station data preparation to quality control of data processing procedures. Each phase of the processing procedure has been discussed in detail with salient examples using seismic data acquired in Changbaishan volcano region. In the end, we use continuous recordings in Jilin, China to track the temporal change of the seismic velocity variations with the method promoted in this paper. We filter the data between the frequency band 0.02 and 0.1 Hz, which the Rayleigh waves are most sensitive to the shear wave velocities in the crust and uppermost mantle. The long-term seismic variations present strong seasonal influence which may be caused by precipitation. We find clear evidence that the seismic velocity drops by up to ∼0.8% which may be caused by the dilatation of the volcanic edifice before the Mar. 11 2011 Japan earthquake. [ABSTRACT FROM AUTHOR]

The alternating electromagnetic (EM) field is one of the most sensitive physical fields related to earthquakes. There have been a number of publications reporting EM anomalies associated with earthquakes. With increasing applications and research of artificial-source extremely low frequency EM and satellite EM technologies in earthquake studies, the amount of observed data from the alternating EM method increases rapidly and exponentially, so it is imperative to develop suitable and effective methods for processing and analyzing the influx of big data. This paper presents research on the self-adaptive filter and wavelet techniques and their applications to analyzing EM data obtained from ground measurements and satellite observations, respectively. Analysis results show that the self-adaptive filter method can identify both natural- and artificial-source EM signals, and enhance the ratio between signal and noise of EM field spectra, apparent resistivity, and others. The wavelet analysis is capable of detecting possible correlation between EM anomalies and seismic events. These techniques are effective in processing and analyzing massive data obtained from EM observations. [ABSTRACT FROM AUTHOR]