The heterogeneity of a tectonic fault interface controls both the spatial features of seismicity and the locations of the foci of shallow earthquakes. Strong earthquakes are associated with ruptures of asperities. We present the Seismogenic Patches Detection (SPAD) algorithm to analyze background seismicity to reveal tectonic asperities. In the first stage, the algorithm detects background seismicity based on the nearest-neighbor method. In the second stage, fuzzy clustering of the background mode is performed. Dense clusters of background seismicity, called seismogenic patches, can be interpreted as tectonic asperities. The SPAD algorithm does not use a priori data about the localizations of strong earthquakes. Using SPAD, we analyzed the seismicity of the Kamchatka segment of the Kuril–Kamchatka subduction zone for the period from 1 January 1990 to 23 September 2025. The Kamchatka regional seismic catalog includes 39,104 events, and the magnitude of completeness Mc equals 3.0. We have identified seven seismogenic patches with a size of 170–270 km. Seismogenic patches correlate with the tectonic asperity determined by the maps of the slip distributions for the four largest earthquakes—Mw7.5 (8 June 1993), Mw7.8 (5 December 1997), Mw8.8 (30 July 2025), and Mw7.8 (13 September 2025).
Остапчук et al. (Sun,) studied this question.