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[SSS12-09] Spatio-Temporal Distribution of Repeating Earthquakes in the Noto Peninsula Earthquake Swarm (2)
Repeating earthquakes (repeaters) are earthquakes that recur at the same location with the same rupture processes, producing similar waveforms. They are interpreted as the repeated rupture of asperities surrounded by a stable slip zone, driven by aseismic slip loading. Repeaters have been reported not only at plate boundaries but also in intra-crustal earthquakes, including aftershock sequences of large earthquakes. However, their detailed distribution remains poorly understood and requires further investigation to elucidate their generation mechanisms.
In this study, we attempted to detect repeaters in the Noto Peninsula earthquake swarm, which became active around December 2020. The presence of fluids in the source region of this earthquake swarm has been suggested, and elevated pore fluid pressure may promote aseismic slip, leading to the occurrence of a large number of repeating earthquakes. We conducted a detailed analysis of the spatio-temporal evolution of these events and discussed the mechanisms underlying intra-crustal repeater generation.
We analyzed M2–4 earthquakes that occurred in the northeastern Noto Peninsula from January 2020 to December 2023. After relocating hypocenters using the double-difference method, we identified repeating earthquakes based on criteria for waveform similarity and source overlap. As a result, we identified 102 repeater sequences comprising 236 earthquakes, accounting for approximately 13% of the analyzed events. Among the four swarm clusters, more than 60% of the repeater sequences were distributed in the N cluster, while none were identified in the S cluster, which was the first to become active.
The occurrence of repeaters began immediately after seismic activity intensified in each cluster, and they exhibited migration patterns similar to those of background earthquakes. Additionally, focusing on the first event in each repeater sequence, we observed that they often occurred in close succession with other sequences. This temporal clustering of repeaters may coincide with the timing of slow slip events (SSEs) on the source fault planes of the clusters.
The detected repeaters exhibited a wide range of recurrence intervals. Notably, repeaters in the deeper part of the N cluster tended to have longer recurrence intervals than those in shallower regions. This trend may be attributed to extremely high pore fluid pressure in the deeper sections, which could facilitate aseismic slip even on repeater patches, leading to prolonged recurrence intervals.
In this study, we attempted to detect repeaters in the Noto Peninsula earthquake swarm, which became active around December 2020. The presence of fluids in the source region of this earthquake swarm has been suggested, and elevated pore fluid pressure may promote aseismic slip, leading to the occurrence of a large number of repeating earthquakes. We conducted a detailed analysis of the spatio-temporal evolution of these events and discussed the mechanisms underlying intra-crustal repeater generation.
We analyzed M2–4 earthquakes that occurred in the northeastern Noto Peninsula from January 2020 to December 2023. After relocating hypocenters using the double-difference method, we identified repeating earthquakes based on criteria for waveform similarity and source overlap. As a result, we identified 102 repeater sequences comprising 236 earthquakes, accounting for approximately 13% of the analyzed events. Among the four swarm clusters, more than 60% of the repeater sequences were distributed in the N cluster, while none were identified in the S cluster, which was the first to become active.
The occurrence of repeaters began immediately after seismic activity intensified in each cluster, and they exhibited migration patterns similar to those of background earthquakes. Additionally, focusing on the first event in each repeater sequence, we observed that they often occurred in close succession with other sequences. This temporal clustering of repeaters may coincide with the timing of slow slip events (SSEs) on the source fault planes of the clusters.
The detected repeaters exhibited a wide range of recurrence intervals. Notably, repeaters in the deeper part of the N cluster tended to have longer recurrence intervals than those in shallower regions. This trend may be attributed to extremely high pore fluid pressure in the deeper sections, which could facilitate aseismic slip even on repeater patches, leading to prolonged recurrence intervals.