1 Half graben inversion tectonics revealed by gravity modeling in the Mikawa Bay 2 Region, Central Japan 3 Ayumu Miyakawa 1 4 Corresponding author 5 Email:
[email protected] 6 7 Tomoya Abe 1 8 Email:
[email protected] 9 10 Tatsuya Sumita 1 11 Email:
[email protected] 12 13 Makoto Otsubo 1 14 Email:
[email protected] 15 16 (Institutional addresses) 17 1 Geological Survey of Japan, AIST, AIST Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 18 Pref., 305-8567, Japan 19 20 21 Abstract 22 The Mikawa Bay Region, central Japan, is characterized by many active faults recording 23 Quaternary activity. It is, however, difficult to understand the overall tectonic character of the 24 region due to the thick sediments in this region. We estimated the depth and the structure of 25 the basement top in the Mikawa Bay Region through the analysis of gravity data, compiling 26 publicly available gravity data and our own gravity measurements in the central part of the 27 region. The gravity basement map shows the deepening of the basement top from the 28 Nishi-Mikawa Plain to the Chita Peninsula. Two-dimensional modeling constrains the 29 orientation of the Utsumi and Takahama faults. The fact that the basement top structure 30 related to the Kou Fault is insignificant in the gravity data indicates that the geometry of the 31 Kou Fault is small relative to that of the Utsumi Fault. The basement top structure from the 32 Nishi-Mikawa Plain to the Chita Peninsula reveals a half graben structure bounded by the 33 Utsumi Fault.