Scaling and spatial complementarity of tectonic earthquake swarms

Abstract

Tectonic earthquake swarms (TES) often coincide with aseismic slip and sometimes precede damaging earthquakes. In spite of recent progress in understanding the significance and properties of TES at plate boundaries, their mechanics and scaling are still largely uncertain. Here we evaluate several TES that occurred during the past 20 years on a transform plate boundary in North Iceland. We show that the swarms complement each other spatially with later swarms discouraged from fault segments activated by earlier swarms, which suggests efficient strain release and aseismic slip. The fault area illuminated by earthquakes during swarms may be more representative of the total moment release than the cumulative moment of the swarm earthquakes. We use these findings and other published results from a variety of tectonic settings to discuss general scaling properties for TES. The results indicate that the importance of TES in releasing tectonic strain at plate boundaries may have been underestimated.

Dual Seismic Migration Velocities in Seismic Swarms

“…Such velocity analysis is applied on the outermost events, but migrating sequences inside the swarms may bring new constrains on the swarm driving processes. Such dual migrations were observed in different natural swarms (Hainzl et al., 2012; Hatch et al., 2020; Hensch et al., 2008; Ruhl et al., 2016; Passarelli et al., 2018; Yoshida & Hasegawa, 2018) and reservoir stimulations (Bourouis & Bernard, 2007; Diehl et al., 2017; Eyre et al., 2019). Based on such dual migration behaviors observed in the Corinth Gulf (De Barros et al., 2020), we here propose a new model that conciliates fluid diffusion and slow slip and may successfully explain the observations of many of the swarms cited above.…”

Intermittent Slip Along the Alto Tiberina Low‐Angle Normal Fault in Central Italy

“…Examining the magnitude distribution within each ATF cluster with more than 10 events allow us to understand their development in time and space better. Swarms, more sensitive to changes of the tectonic loading (e.g., Passarelli et al, 2018; Shelly et al, 2016; Toda et al, 2002), persist over time compared with typical foreshock sequences and are characterized by a significantly higher number of events. Few clusters classified as swarms revealed a complex mixed behavior with bursts repetitions in a few days.…”

Distributed Deformation in an Oceanic Transform System: Applying Statistical Tools to Structural and Paleomagnetic Data Near the Húsavík‐Flatey Fault, Northern Iceland

“…In central Tjörnes, the fault system curves to join the Þeistareykir fissure swarm of the Northern Volcanic Zone (Gudmundsson, ; Gudmundsson et al, ) where there is evidence for complex deformation (Hjartardóttir et al, ; Tibaldi et al, ). Seismicity along this fault consists of small earthquake swarms, seen primarily with strike‐slip focal mechanisms (Passarelli et al, ).…”