Abstract Volcanic activity in submarine calderas recurrently generates characteristic earthquakes on ring‐fault systems driven by magma‐induced stress. At Sumisu Caldera, trapdoor faulting has recurred quasi‐regularly, roughly at ∼10‐year intervals, generating earthquakes of moment magnitude 5.4–5.7 and producing tsunamis due to meter‐scale co‐seismic uplift. To assess event similarity and infer controlling factors, we compare seismic and tsunami waveforms at broadband period range (0.2–500 s). The 1996, 2015, and 2024 events exhibit nearly identical waveforms, indicating rupture of a persistent major asperity with stable geometry and processes. Similar but non‐identical earthquakes suggest partial rupture or additional minor asperities. Comparable repeating sequences at other submarine calderas further support that trapdoor faulting is generally governed by major asperities, while variations in recurrence patterns may reflect differences in fault properties among calderas. These results demonstrate that trapdoor faulting recurrency is controlled by major asperities on ring faults, sustained by long‐term, stable magma supply.

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