Volcanic Origin of a Long‐Lived Swarm in the Central Bransfield Basin, Antarctica

Abstract

reported 128 earthquakes with magnitudes larger than 4.0 (Figure 1). The seismicity was not characterized by any large mainshock (Figure S1 in Supporting Information S1) that could potentially have triggered the prolific occurrence of earthquakes in the region. Similar observations were recently reported by Olivet et al., (2021).

Spatiotemporal Evolution of the Seismicity in the Alto Tiberina Fault System Revealed by a High‐Resolution Template Matching Catalog

“…In contrast to that, the seismicity with long interevent time intervals evolves with a nearly constant rate for the whole duration of our study period (Figure 6c). After the increase in occurrences in January 2014, the seismicity associated with shallow families decays in time, following an Omori law, without however being governed by a large mainshock (Figure 6d), similar to observations of other swarms (Poli et al., 2022).…”

“…The analysis of the interevent times (Figure 6a) and the time evolution of cumulative events (Figure 6d) reveal that the swarm seismicity mimics an Omori‐like sequence, without however any clear large mainshock controlling this behavior. Additionally, γ ∼ 0.26, obtained from Equation 1, does not support the hypothesis of stress transfer from large events to govern the evolution of the seismicity (Duverger et al., 2018; Poli et al., 2022).…”

“…For families of the shallow part (above 7 km depth; Figure 6a) the interevent times linearly decay over four orders of time magnitude and can be fitted (Equation 1) with $$\gamma \sim 0.26$$. This value of $$\gamma $$ is indicative of seismicity clustered in time (Duverger et al., 2018; Poli et al., 2022), but differs from classic aftershock sequence (e.g., Omori, 1894). The influence of different separation depths can be seen in Figure S7 in Supporting Information S1.…”

“…The simplest mechanism of time and space clustering of earthquakes is through interactions between events during co‐ and post‐seismic processes, like static or dynamic stress transfer triggering (Freed, 2005) or afterslip (Perfettini & Avouac, 2004), with additional modulation related to the asperity density (Dublanchet et al., 2013). Alternatively, enhanced interaction can result from external forcing as slow aseismic deformation (Frank et al., 2016; Lengliné et al., 2017; Poli et al., 2022), fluid fracturing (Obara, 2002; Seno & Yamasaki, 2003) or coupled fluid and rock interaction (Shelly et al., 2006), in complex fault systems (e.g., Dublanchet et al., 2013).…”

“…Their general shape can be described with a truncated gamma distribution: $$$\rho (\tau )=C{(\tau )}^{\gamma -1}\cdot {e}^{-\frac{\tau }{\beta }}$$$ where C and β are constant while $$\gamma $$ indicates the time clustering of the seismicity (Hainzl et al., 2006). For $$\gamma =1$$ the seismicity is Poissonian‐like and therefore occurs randomly in time, while for $$\gamma =0$$ it follows a power‐law decay similar to an Omori‐like sequence (Duverger et al., 2018; Omori, 1894; Poli et al., 2022).…”