Emergence and disappearance of interplate repeating earthquakes following the 2011 M9.0 Tohoku‐oki earthquake: Slip behavior transition between seismic and aseismic depending on the loading rate

Abstract

We investigated spatiotemporal change in the interplate seismic activity following the 2011 Tohoku‐oki earthquake (M9.0) in the region where interseismic interplate coupling was relatively weak and large postseismic slip was observed. We classified earthquakes by their focal mechanisms to identify the interplate events and conducted hypocenter relocation to examine the detailed spatiotemporal distribution of interplate earthquakes in the mostly creeping area. The results show that many interplate earthquakes, including M ~ 6 events, emerged immediately after the Tohoku‐oki earthquake in areas where very few interplate earthquakes had been observed in the 88 previous years. The emergent earthquakes include repeating sequences, and the extremely long quiescence of small to moderate earthquakes before the Tohoku‐oki earthquake suggests that the source areas for the post‐M9 events slipped aseismically during the quiescence. The repeaters' magnitudes decayed over time following the Tohoku‐oki earthquake and some sequences disappeared within a year. The emergence of interplate earthquakes suggests that areas where aseismic slip had been dominant before the Tohoku‐oki earthquake started to cause seismic slip after the earthquake, probably due to the increased loading rate from the afterslip. The magnitude decrease and disappearance of repeaters can be interpreted as shrinkage in seismic areas around the repeaters' sources as the loading rate decreased due to the afterslip decay over time. These observations suggest that changes in the loading rate can cause slip behavior transition between seismic and aseismic. This indicates that such loading‐rate‐dependent slip behavior plays an important role in the spatiotemporal distribution of earthquakes in interplate seismogenic zones.

Streak and hierarchical structures of the Tohoku–Hokkaido subduction zone plate boundary

“…Therefore, it is likely that M2005 was also influenced by the afterslip. Similarly, the extended rupture area of A2012 may be due to the afterslip of the 2011 Mw9.0 Tohoku-Oki earthquake on the shallower part of the same plate interface (Ozawa et al 2011), since the aseismic-to-seismic transition in slip behavior has previously been reported in the Tohoku-Oki region after the 2011 Tohoku-Oki earthquake (Uchida et al 2015;Hatakeyama et al 2017). The effect of the Tohoku-Oki earthquake may be also responsible to the relatively large slip of M2011 compared to other group M earthquakes (Fig.…”

Earthquake Nucleation Size: Evidence of Loading Rate Dependence in Laboratory Faults

“…As the ASZ undergoes accelerated creep, the local loading rate on the smaller locked asperities increases, and this could trigger their seismic rupture during the preseismic interval. In the postseismic phase, as long as the accelerated creep continues, the small asperities may still undergo seismic rupture as observed in the seismic cycle (Yao et al, ), and aftershocks could appear in conditionally stable areas following the increase of loading rate as discussed by Hatakeyama et al ().…”

“…Contrary to the observations reported by Ruiz et al (), the conditions under which the experiments are conducted here do not appear to result in a large creeping patch with locked asperities, but rather in a locked fault with a localized preslip patch that grows into a dynamic rupture, corresponding rather to the observations of Tape et al () for a M3.7 asperity. We can therefore discuss the possible effects of a shrinking nucleation size under accelerated loading rate in some natural contexts, for example, linking the natural earthquake nucleations described by Ruiz et al () and Tape et al () or to explain the appearance of aftershocks following the 2011 M9.0 Tohoku‐oki earthquake, in places where only very few earthquakes had been observed during the last 88 years (Hatakeyama et al, ).…”

Seismicity Controlled by a Frictional Afterslip During a Small‐Magnitude Seismic Sequence (ML < 5) on the Chihshang Fault, Taiwan

“…Aseismic loading has increased by a factor of 6 during the first few hours following stage A2 comparing to stage A1 as evidenced by the strain evolution following the initiation of each stage (Figure a). Hatakeyama et al () found change of loading rate has controlled the emergence and disappearance of REs following the 2011 M 9.0 Tohoku‐oki earthquake.…”