Discrete radiation sources of the 2024 Noto Peninsula earthquake: linking teleseismic pulses and near-field observations

Abstract Understanding the rupture process of large earthquakes is critical; however, standard rupture process inversions require stabilizing constraints, which can obscure which features are genuinely required by the data. The 2024 M w 7.5 Noto Peninsula earthquake, with its intricate rupture behavior, underscores these challenges. In this study, we adopted a step-by-step approach, progressing from teleseismic analysis to regional constraints, to characterize this earthquake with limited a priori assumptions. Using the waveforms of the 2023 M w 6.2 earthquake as empirical Green’s functions, we first obtained teleseismic apparent moment-rate functions (AMRFs) for the mainshock. This approach directly unveiled the rupture complexity, revealing a sequence characterized by at least four distinct peaks at t = 16, 24, 32, and 40 s. Time integration of the squared time derivative of the AMRFs yields a radiated energy of this earthquake of 2.15 × 10 15 J, and a scaled energy of 9.6 × 10⁻ 6 . The azimuthal variation of AMRFs provided direct constraints on the presence of offshore slip, which was not evident in near-field onshore records. However, they alone provided limited constraints on the source locations for other episodes; therefore, we incorporated near-field seismic and geodetic data to guide the spatial placement of candidate sources and found that the largest teleseismic peak is a composite of two simultaneous, spatially separated subevents. Overall, the entire rupture is characterized by five major subevents (M w 6.6–7.2), beginning with a series of failures near the hypocenter that cascaded westward and eastward as distinctive rupture episodes across adjacent fault segments. This complex growth pattern may reflect the combined influence of fault geometry—including its considerable along-strike extent and bends—coupled with lithological heterogeneities, structural maturity, slip history, and regional stress conditions. Our analysis highlights the strength of teleseismic waveform data for capturing the overall rupture complexity, while showing that incorporating near-field observations is essential for more robustly resolving simultaneous rupture episodes through improved spatial resolution. Graphical Abstract