We analyze GPS and seismic data to examine the spatiotemporal evolution of a slow slip event (SSE) near Boso Peninsula, central Japan, from December 2013 to January 2014. The evolution of this SSE and its associated seismicity is divided into two distinct phases. Slip initially accelerated slowly with low slip rates, low propagation speeds, and no accompanying seismicity during the early phase and then accelerated more rapidly with higher slip rates, a higher propagation speed, and local earthquake swarm activity during the later phase. The seismicity was highly correlated in space and time with slip rate, suggesting that the swarm activity was triggered by stress loading due to the slow slip. The transition from the slow to faster phase shares some similarities with the nucleation of megathrust earthquakes inferred from foreshock activities, suggesting that SSEs may provide insights into the nucleation of large earthquakes.
- earthquake swarm activity
- slow slip event