Development of Large-scale Rock Friction Apparatuses and Their Contribution to Earthquake Source Physics

Development of large-scale rock friction apparatus started around 2010 at National Research Institute for Earth Science and Disaster Resilience. Three generations of the apparatus have already been developed, whose sliding area ranges from 1.5 m to 6.0 m in length. Many kinds of large-scale rock friction experiments were conducted. Through such experimental research, the following results were reported. 1) Strength on the fault surface is not spatially uniform, which has been difficult to resolve in small-scale experiments. 2) Such spatial heterogeneity of strength on the fault surface could contribute to the fault-size dependence of the rock friction as well as the rich spectrum of rupture behaviors, which are quite important for the modeling of earthquake generation process. Especially, such ten-centimeter-scale heterogeneity on the fault surface, which was generated by high-speed (~1 mm/s) and long-distance sliding (~40 cm), is found to play an important role in large-scale friction experiments. In the near future, we sincerely expect that such large-scale rock friction experiments contribute to seismology, especially, physics of earthquake generation process, by establishing new constitutive law on the rock friction through the usage of large-scale friction experiment data.