The Mw 7.5 Noto Peninsula earthquake illuminates a past shift in tectonic plate boundaries across Central Japan

能登半島地震(Mw7.5)で浮き彫りになった中部日本の過去のプレート境界の移動

Malatesta, L.*; Weiss, N.-M.*; 塚本 すみ子*; 末岡 茂   ; 石村 大輔*; Gailleton, B.*; 西村 卓也*; 高橋 直也*; 片岡 香子*; 小松 哲也  ; 岩佐 佳哉*

Malatesta, L.*; Weiss, N.-M.*; Tsukamoto, Sumiko*; Sueoka, Shigeru; Ishimura, Daisuke*; Gailleton, B.*; Nishimura, Takuya*; Takahashi, Naoya*; Kataoka, Kyoko S.*; Komatsu, Tetsuya; Iwasa, Yoshiya*

On January 1st, 2024, the Mw 7.5 Noto Peninsula earthquake ruptured on a series of coastal offshore reverse faults in the back arc of central Japan. Recent Holocene terraces mapped along the northern coast, where coseismic uplift was greatest on January 1st 2024, suggest that they may be attributable to similar past ruptures. The Peninsula itself is remarkable for its 4767 unique terraces ranging in age from Holocene to 1.02 Ma. We digitized all terraces and recorded the elevation of their landward edge, and derived a rock uplift rate for each based on their age and the corresponding original sea level. The southeast-tilting crustal deformation recorded by the terraces associated with the last two interglacial high stands strongly resembles that caused by the Mw 7.5 earthquake. Older terraces, on the contrary all record a spatially uniform rate of uplift across the Peninsula. We conclude that the faults that caused the most recent earthquake became the dominant structures on the Peninsula over a quarter million year ago. This onset of seismogenic activity informs us about the regional plate tectonics of the area. The boundary separating Eurasia from the North American Plate currently runs south of the Noto Peninsula, linking the cities of Niigata and Kobe along a northeast-striking Tectonic Zone (NKTZ). Immediately east of the Peninsula lies another north-striking Tectonic Line, from Itoigawa to Shizuoka (ISTL). East of the ISTL and north of the NKTZ is the Island of Sado, which terraces also suggest a change in deformation with strong southeast tilting synchronous and similar to Noto. Together, Noto and Sado act as a railroad switch, indicating which of the ISTL or the NKTZ is the active plate boundary. When the ISTL is active, the sites are on different tectonic plates and evolve differently. When the NKTZ takes over, Sado Island becomes part of Eurasia and is more likely to evolve similarly to the Noto Peninsula.