The Atera fault is one of the most active both geomorphologically and geologically in Japan. In the southern part of the fault, the Sakashita body (Ueno volcano) erupted about 1.5 km southwest of the fault in a direction parallel to it (early Pleistocene). A local strike direction change, reversal of vertical displacement (SW uplift), and branching of the fault line occurred in the southern tip of the fault (in and around the Dendahara district). Our microgravity survey suggests that a high-density body (probably basaltic) prevents ordinary activity of the Atera fault (left-lateral and NE uplift).