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Development of Empirical Scaling Relationships Between Spectral Displacement Amplitudes Measured in the Time Domain and Earthquake Magnitudes in South Korea

Description: 

In South Korea, a local magnitude scale using the maximum amplitude of S waves has been proposed (Sheen et al., 2018). However, the time when the previous study was conducted, there were very limited number of observations within an epicentral distance of 50 km. For this reason, it is difficult to accurately determine the magnitudes of small earthquakes typically observed only at short distances, using the previous scaling relationship. The recent increase in the number of seismic stations in South Korea enables us to develop an empirical scaling relationship accounting for short distances. In addition, it is shown that the moment magnitude can be measured for earthquakes as small as M 2.0 using peak displacement amplitudes (Al-Ismail et al., 2023). In this study, we collected seismograms of 647 earthquakes occurred in and around South Korea from 2017 to 2022. Spectral displacement amplitudes of S waves were measured from vertical components in the time domain using multiple narrowband filters and in the frequency domain using the multitaper method. Then, we developed empirical relationships between displacement amplitudes and seismic moments, separately for each frequency band, and use them to measure magnitudes. To validate the empirical relationship proposed in this study, we estimated the magnitudes of earthquakes in the 2016 Gyeongju earthquake sequence. Consequently, we demonstrate that spectral amplitude estimation in the time domain is an effective method for determining the magnitude of small earthquakes.

Session: Understanding and Quantifying the Variability in Earthquake Source Parameter Measurements [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Yoontaek

Student Presenter: Yes

Invited Presentation: 

Authors