Abstract

We observe a unique temporal variation in crustal heterogeneity from the analysis of coda Q-1 for 14 years in the Tamba region, northeast to the rupture zone of the 1995 Hyogo-ken Nanbu earthquake (MJMA 7.3) in southwest Japan. The values of forumla at lower frequencies (1.5–4.0 Hz) that increased coseismically due to the static stress change decreased back to the preevent values in about two years. No such variations are found at higher frequencies (5.0–24.0 Hz). We confirm that no tectonic events that cause a significant stress change occurred during the recovery period. The time required for the recovery of the scattering environment observed here, such as the number density of cracks and cracks opened by the stress change, is consistent with those of previous studies focused on the brittle shallower crust. This suggests a possibility that a similar mechanism of the recovery operates in both the brittle and the ductile parts of the crust.

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