Estimating the energy of past earthquakes from brecciation in a fault zone

During a 2017 research field trip to the Ichinokawa Mine (Ehime prefecture), which is famous for beautiful, sword-shaped stibnite crystals, Noriyoshi Tsuchiya found something unexpected. Although most would be entranced by the glittering crystals, it was a sedimentary rock bundle called breccia that caught his eye.