Release of mantle and crustal helium from a fault following an inland earthquake

摘要: Abstract Static stress changes caused by megathrust slip of the 2011 Mw 9.0 Tohoku-Oki earthquake considerably affected seismicity patterns in inland areas, resulting occurrence numerous earthquakes along several active faults Japan. On June 30, 2011, Mj 5.4 central Nagano occurred at a shallow depth 5 km, indicating reactivation Gofukuji fault Central This study was undertaken to elucidate spatial and temporal 3He/4He ratios around source region before after an using both existing new helium isotope data from hot spring drinking water wells. Gas samples near its surrounding are characterized increase postseismic ratios. In contrast, decreased up about 30% away mainshock epicenter. Episodic faulting could either release stored crustal (radiogenic) host rocks, or enhance transfer mantle volatiles through permeable zones, such that subsequent fluid flow then explain spatio-temporal variations