Slow slip and tremor in the Cascadia Subduction zone

The Cascadia subduction zone in the U.S. Pacific Northwest  experiences giant (M 9) earthquakes approximately every 500 years. During the past decade data from continuous GPS networks have revealed episodic transient slip events that are believed to occur below the seismically active fault. The GPS transients are accompanied by low frequency seismic "tremor".  In an effort to elucidate the mechanical relationship between the aseismic slip and the tremor the Crustal Deformation and Fault mechanics group inverted the GPS data to determinethe slip-rate distribution in space and time on the plate interface. They find the highest slip-rates correspond well with the tremor locations, revealing that tremor comes from the rapidly slipping part of the fault. (more)