Conjugate faulting and structural complexity on the young fault system associated with the 2000 Tottori earthquake

Young faults display unique complexity associated with their evolution, but how this relates to earthquake occurrence is unclear. Unravelling the fine-scale complexity in these systems could lead to a greater understanding of ongoing strain localization in young fault zones. Here we present high-spatial-resolution images of seismic sources and structural properties along a young fault zone that hosted the Tottori earthquake (Mw 6.8) in southwest Japan in 2000, based on data from a hyperdense network of similar to 1,000 seismic stations. Our precise micro-earthquake catalog reveals conjugate faulting over multiple length scales. These conjugate faults are well developed in zones of low seismic velocity. A vertically dipping seismic cluster of about 200m length occurs within a width of about 10m. Earthquake migrations in this cluster have a speed of about 30m per day, which suggests that fluid diffusion plays a role. We suggest that fine structural complexities influence the pattern of seismicity in a developing fault system.

Automated summary

Research indicates that young faults exhibit complex evolutionary characteristics, and fine structural complexities may impact seismic activity within fault zones. High-spatial-resolution images and a micro-earthquake catalog reveal the development of conjugate faults and earthquake cluster migration.