The Nankai Trough has a 1300-year record of generating large earthquakes(M_w>8)with a recurrence time of～100-200 a,but unfortunately,we don’t know the frequency of earthquakes before.Results from recent expeditions of NanTroSEIZE Stage 1 IODP 314/315/316 recovered many cycles of turbidites since late Pleistocene,which are triggered during the past earthquake shaking.Our purpose is
Tao Jiang~1,Shenghua Li~2,Chunfeng Li~3,Xinong Xie~1,Xin Su~4,Jianye Ren~1 1.Key Laboratory of Tectonics and Petroleum Resources,China University of Geosciences(Wuhan),Wuhan 430074,China. 2.Department of Earth Sciences,University of Hong Kong,Pokfullam Road,Hong Kong,China 3.School of Ocean and Earth Sciences,Tongji University,Shanghai 200092,China 4.School of Marine Geosciences,China University of Geosciences(Beijing),Beijing 100083,China
Through reduction to the North Pole and upward continuation of the total field magnetic anomalies, we analyze magnetic patterns and spatial distributions of different tectonic blocks and crustal faults in eastern China and adjacent seas. Depths to the Curie isotherms are further estimated from radially averaged amplitude spectra of magnetic data reduced to the pole. Data reductions effectively enhance boundaries of regional tectonic belts, such as the Dabie ultra-high metamorphic belt, the Tanlu Fault, and the Diaoyudao Uplift. Curie depths are estimated at between 19.6 and 48.9 km, with a mean of 31.7 km. The Subei Basin and the south Yellow Sea Basin in the lower Yangtze block show relatively deep Curie isotherms, up to about 35 km in depth, whereas in the surrounding areas Curie depths are averaged at about 25 km. This implies that the lower Yangtze Block has experienced a unique tectonic evolution and/or has unique basement lithology and structures. From a regional perspective, sedimentary basins, such as the Subei Basin, the south Yellow Sea Basin, and the East China Sea Basin, normally show deeper Curie isotherms than surrounding uplifts such as the Diaoyudao Uplift and the Zhemin Uplifts. Curie isotherms also upwell significantly in volcanically active areas such as the Ryukyu Arc and the Cheju Island, confirming strong magmatic and geothermal activities at depth.
