Implications of Fault‐Valve Behavior From Immediate Aftershocks Following the 2023 <i>M</i><sub><i>j</i></sub>6.5 Earthquake Beneath the Noto Peninsula, Central Japan
Aitaro Kato
Abstract
Abstract The M j 6.5 ( M w 6.2) event that occurred on 5 May 2023 near the northern shoreline of the northeastern tip of the Noto Peninsula, central Japan, is the largest event to date in a long‐lasting, intense earthquake swarm. Here we have created a more precise aftershock catalog associated with the 2023 M j 6.5 and the second‐largest 2022 M j 5.4 sequence to understand the rupture process of this largest earthquake. Most of the aftershocks are aligned along a ∼45° SE‐dipping plane. The mainshock initially ruptured the same deep section of the fault zone that had been ruptured by the 2022 M j 5.4 event, before propagating rapidly to shallow depths and to offshore along the ruptured fault plane. The aftershock front migrated at a speed of ∼20 km/hr. This rapid upward migration of the immediate aftershocks might be driven by upwelling of crustal fluids along the intensely fractured and permeable fault zone via mainshock dynamic rupture.