2007年能登半島地震の震源域陸域の地質

概要

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Stratigraphy and geologic structure in the onshore epicentral area of the 2007 Noto Hanto earthquake was studied to reveal the relationship between the earthquake source fault and geologic structure. The epicentral area is located in the southern part of the Yamato basin rift-system and thick syn-rift succession is exposed on the Noto peninsula. Exposed Paleogene to Miocene rocks overlying the Jurasic granitic rocks are divided in ascending order into Daifukuji, Ohkadoma, Anamizu, Nawamata, Touge, Sekinohama, Maehama Formations, and Kurosaki Andesite. The Dai-fukuji and Okadoma Formations consist of sedimentary rocks deposited at the Paleogene pre-rifting stage. More than 1,400m thick, Oligocene to lower Miocene andesitic volcanic rocks and fluvial sediments (Anamizu, Nawamata and Toge Formations) were deposited, filling half grabens bounded by ENE-WSW- and NS-trending faults. They are syn-rift sediments formed at the rifting and open-ing stage of the Sea of Japan. Middle Miocene shallow marine sedimentary rocks (Sekinohama and Maehama Formations) unconformably cover the syn-rift succession. A major geologic structure was formed by rifting associated with the opening of the Sea of Japan. The source fault of the 2007 Noto Hanto earthquake trending NE to ENE coincides with the fault bounding the Miocene halft graben, and its eastern end corresponds to the NS-trending fault, a probable transfer fault during the rifting stage.
2008-03-26