Investigation of the Factors Controlling the Duration and Productivity of Aftershocks Following Strong Earthquakes in Greece

Abstract

Strong crustal earthquakes in Greece are typically followed by aftershocks, the properties of which are important factors in seismic hazard assessment. In order to examine the properties of earthquake sequences, we prepared an earthquake catalog comprising aftershock sequences with mainshocks of Mw ≥ 5.5 from 1995 to 2021. Regional aftershock parameters were estimated to highlight variations in aftershock decay and productivity among regions with similar seismotectonic characteristics. A statistically based method of estimating aftershock duration and a metric of relative aftershock productivity to examine the variations among the different cases were employed. From the detailed analysis of the selected seismic sequences, we attempt to unravel the physical mechanisms behind deviations in aftershock duration and productivity and resolve the relative contribution of background seismicity, the Omori–Utsu law parameters and the mainshock faulting properties. From our analysis, the duration of aftershock sequences depends upon the rupture process of the mainshock, independently of its magnitude. The same applies to aftershock productivity, however, other tectonic setting (e.g., seismic coupling) or source-related (e.g., focal depth, stress drop) parameters also contribute. The estimated regional parameters of the aftershock rate models could be utilized as initial ones to forecast the aftershock occurrence rates at the early stage following a mainshock.

Implementation and verification of a real-time system for automatic aftershock forecasting in China

“…Furthermore, regional variability in sequence types has been widely observed and analyzed globally (Chen et al 1987;Ben-Zion et al 1993, 2006Yamanaka and Kikuchi 2004;Kanamori and Rivera 2004). For example, Bonatis et al (2022) defined six distinct tectonic regions in Greece and estimated controlling factors of the duration and productivity. Similarly, China comprises five active blocks, 26 seismic zones, and dozens of seismic subregions based on brittle failure theory of seismogenic faults (Zhang et al 2005;Qin et al 2016).…”

“…To explore the mechanism of earthquake sequences, scientists have conducted in-depth research on the physical environment of seismic sources. There exists general agreement that any aftershocks triggered after the main shock are mainly induced by stress adjustment during fault slip (Freed 2005;Scholz 2019;Bonatis et al 2022), whereas the migration of swarms can be partly explained by pore fluid diffusion( and other similar phenomena as suggested by Hatch et al (2020). Statistical results for mainland China further suggest that the characteristics of earthquake sequences exhibit certain regional differences due to the specific tectonic setting (Zhou et al 2001;Tian et al 2004;Jiang et al 2006b;Li et al 2011;Cheng et al 2015;Wen et al 2020).…”