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Rapid magnitude estimation of earthquakes using single-station empirical relationships for the early warning system.

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Bibliographic Details
Title:	Rapid magnitude estimation of earthquakes using single-station empirical relationships for the early warning system.
Authors:	Lavasani, Mahdiye¹ (AUTHOR), Heidari, Reza² (AUTHOR) r.heidari@srbiau.ac.ir, Mirzaei, Noorbakhsh¹ (AUTHOR)
Source:	Journal of Seismology. Dec2025, Vol. 29 Issue 6, p1673-1690. 18p.
Subject Terms:	Magnitude estimation, Earthquake magnitude measurement, Earthquakes, Accelerometers, Empirical research, Earthquake prediction
Geographic Terms:	Japan
Abstract:	In the traditional method of rapid magnitude estimation based on the predominant period in the earthquake early warning systems, the magnitude of the occurring earthquake is estimated online by the empirical relationship between the magnitude and the maximum predominant period of the P wave ( τ p max ) average of accelerograph stations. This study determines the empirical relationship between the magnitude and τ p max for each accelerograph station to reduce the local effects in estimating the earthquake magnitude. The final earthquake magnitude will be estimated by averaging the magnitudes obtained at the individual stations, a method we refer to as the mean magnitude method (3M), where "3M" represents the three initial letters of the method's name. The dataset used in this study consists of more than 25,000 accelerograms (both vertical and horizontal components) from the 1,852 earthquakes with magnitudes ranging from MJMA 3 to 7.4 recorded. These data were collected eight accelerograph stations in Japan's KiK-net and K-NET networks. Results demonstrate that the estimated magnitudes using the 3M correlate better with the reported magnitudes than those estimated using the traditional method and provide a more accurate earthquake size, especially for small to moderate events. In contrast to the traditional method, which requires numerous waveforms from many stations with varying local effects to develop a magnitude empirical relationship, the 3M reduces scattering by using station-specific empirical relationships. We also investigated the efficiency of using horizontal components in the first 4 s of the P-wave in the study. After reducing site effects, the horizontal components provided additional useful information alongside the vertical component, improving magnitude estimation accuracy. Although magnitude residuals decrease with increasing number of recording stations in both methods, the 3M achieves greater bias reduction. In addition to the primary analyses conducted using MJMA, we further evaluated our method with moment magnitude (Mw) values converted from MJMA using an established empirical relationship. The results revealed notable improvements in residuals across all magnitude ranges, particularly for larger events. The findings indicate that the proposed approach not only performs effectively for Japanese magnitude scales but also shows strong agreement with the internationally recognized Mw scale, highlighting its potential applicability to seismic events worldwide. [ABSTRACT FROM AUTHOR]
Database:	Energy & Power Source

Description
Abstract:	In the traditional method of rapid magnitude estimation based on the predominant period in the earthquake early warning systems, the magnitude of the occurring earthquake is estimated online by the empirical relationship between the magnitude and the maximum predominant period of the P wave ( τ p max ) average of accelerograph stations. This study determines the empirical relationship between the magnitude and τ p max for each accelerograph station to reduce the local effects in estimating the earthquake magnitude. The final earthquake magnitude will be estimated by averaging the magnitudes obtained at the individual stations, a method we refer to as the mean magnitude method (3M), where "3M" represents the three initial letters of the method's name. The dataset used in this study consists of more than 25,000 accelerograms (both vertical and horizontal components) from the 1,852 earthquakes with magnitudes ranging from MJMA 3 to 7.4 recorded. These data were collected eight accelerograph stations in Japan's KiK-net and K-NET networks. Results demonstrate that the estimated magnitudes using the 3M correlate better with the reported magnitudes than those estimated using the traditional method and provide a more accurate earthquake size, especially for small to moderate events. In contrast to the traditional method, which requires numerous waveforms from many stations with varying local effects to develop a magnitude empirical relationship, the 3M reduces scattering by using station-specific empirical relationships. We also investigated the efficiency of using horizontal components in the first 4 s of the P-wave in the study. After reducing site effects, the horizontal components provided additional useful information alongside the vertical component, improving magnitude estimation accuracy. Although magnitude residuals decrease with increasing number of recording stations in both methods, the 3M achieves greater bias reduction. In addition to the primary analyses conducted using MJMA, we further evaluated our method with moment magnitude (Mw) values converted from MJMA using an established empirical relationship. The results revealed notable improvements in residuals across all magnitude ranges, particularly for larger events. The findings indicate that the proposed approach not only performs effectively for Japanese magnitude scales but also shows strong agreement with the internationally recognized Mw scale, highlighting its potential applicability to seismic events worldwide. [ABSTRACT FROM AUTHOR]
ISSN:	13834649
DOI:	10.1007/s10950-025-10339-3