Relationships of Earthquake Moment Magnitude with Body and Surface Waves Using MCMC Approach

TL;DR

This study uses MCMC to analyze the relationship between body, surface, and moment magnitudes of earthquakes across global regions, providing new transition relationships to improve earthquake monitoring.

Contribution

It introduces a novel application of MCMC for modeling earthquake magnitude relationships, addressing error distribution deviations and regional variations.

Findings

MCMC provides more accurate parameter estimates than least squares.

Regional variations in magnitude relationships are quantified.

Transition relationships enhance earthquake monitoring capabilities.

Abstract

Due to the saturation of the body ($m_b$) and surface ($M_S$) earthquake magnitudes, the moment magnitude ($M_W$) is a more convenient parameter for representing earthquake energies. We use the HRVD data, including 18,569 earthquakes recorded from 1976 January 1 to 2010 December 31, for five regions on the Earth (\textbf{Asia}-Oceania, Europe, Africa, North America, and South America). Applying the error propagation technique on the moment tensor, we estimate the standard error for $M_W$ showing a distribution that deviates from Gaussian errors which recommends using the Monte Carlo Markov chain (MCMC) to obtain model parameters instead of the least square approach. We investigate the linear relationship between the body and surface waves in small ($\le$ 6.1) and large ($>$6.1) magnitudes via MCMC. The slope varies from 0.811 to 1.565 ($m_b - M_W$) and 0.566 to 0.971 ($M_S - M_W$) across five regions. For 18,569 global earthquakes, we obtained the slope for $m_b \le 6.1$ ($m_b>$6.1) 0.863 (1.374), while we find the slope for $M_S\le$6.1 ($M_S >$ 6.1) 0.581 (0.921). These transition relationships of the magnitude moments are useful for increasing earthquake monitoring capacity.