Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Abstract

Broadband seismometers, ground-based Global Navigation Satellite Systems (GNSS), and magnetometers that were located within an epicentral distance of approximately 150 km consistently observed the novel anomalous behaviors of the common-mode ground vibrations approximately 5–10 days before the M6.6 Meinong earthquake in Taiwan. The common-mode ground vibrations with amplitudes near 0.1 m at frequencies ranging from 8 × 10−5 to 2 × 10−4 Hz were generated near the region close to the epicenter of the impending earthquake. The common-mode vibrations were consistently observed in seismic and GNSS data associated with five other earthquakes in four distinct areas. The results reveal that the common-mode vibrations could be a typical behavior before earthquakes. The causal mechanism of common-mode vibrations can be attributed to crustal resonance excitations before fault dislocations occur. Potential relationships with other pre-earthquake anomalies suggest that the common-mode vibrations could be ground motion before earthquakes, which was investigated for a significant length of time.

Spatiotemporal changes of seismicity rate during earthquakes

“…The superimposition process, a statistical tool utilized in data analysis, is capable of either detecting periodicities within a time sequence or revealing a correlation between more than two data sequences (Chree, 1913). The process is known as the superposed epoch analysis (Adams et al, 2003;Hocke, 2008).…”

Lithosphere–Atmosphere–Ionosphere Coupling Effects Based on Multiparameter Precursor Observations for February–March 2021 Earthquakes (M~7) in the Offshore of Tohoku Area of Japan

“…In the future, we highly need data on the surface deformation (including GPS data, etc.) as performed by [98][99][100] as the initial agent of the LAIC process for the two EQs, especially because no lithospheric pre-EQ effect, such as lithospheric ULF radiation, was not clearly detected for the two EQs. This work is a relative multiparameter observation, but we require a much more elaborated multiparameter observation in the future.…”

“…This difference in the temporal appearance of anomalies may give us some hint on the elucidation of the LAIC process with taking into account the expected temporal changes for possible LAIC hypotheses [29,34,35,51,52]. Of course, the way of excitation of AGW is still unclear, even though there are a few possible ways of AGW modulation, such as the direct deformation of the earth's surface, the presence of an AGW resonator in the lithosphere [98,99], or local disturbances in the lithospheric conductivity by the modulation due to the emanation of charged gases in the EQ preparation phase [31,92,95]. Finally, we cannot say any definite conclusion on the LAIC mechanism.…”

“…In the old days, when we proposed the AGW hypothesis, we were always criticized that there is no evidence of surface deformation before an EQ. Recently, there have been several important published papers on the pre-EQ surface deformation based on the GPS, seismic measurements [55,[98][99][100][101]. Chen et al (2020) [99] found clear fluctuations in the frequency range in the earth's surface deformation before large EQs, and suggested the presence of an AGW resonator in the lithosphere.…”

“…Recently, there have been several important published papers on the pre-EQ surface deformation based on the GPS, seismic measurements [55,[98][99][100][101]. Chen et al (2020) [99] found clear fluctuations in the frequency range in the earth's surface deformation before large EQs, and suggested the presence of an AGW resonator in the lithosphere. Even if we accept their idea, how to relate this idea to the observational facts for our two EQs is open for discussion.…”