Models for Fault Behavior

• Elastic Rebound:– Pre-earthquake

strain is gradual in space and time

– Earthquake strain is abrupt in space and time

Our Classic View of Fault Behavior

Fast Slip Earthqua

ke(minutes)

Slow Slip

Tremor(days)

A New View of Fault Behavior

Episodic Tremor and Slip• Discovered in 2003, observations near Vancouver

revealed the correlation in time and space of GPS detected slow slip (top) and tremor vibrations (bottom)

• These episodes typically last 2 weeks and recur in this region nearly every 14 months

Rogers and Dragert, 2003

Cross-Section of Fault Behavior

• What kind of fault is this?• Shallow fault: Locked -> Earthquakes• Deeper fault: Transition -> Tremor and Slip• Changes in temperature and dehydration

affect frictional properties of fault

Dragert et al., 2000

Sumatra, Indonesia

Earthquakes from 1964-2004

Dec. 26, 2004 eventMar. 28, 2005 event

Locked Fault Aftershocks

This Is Why It Is Important

CascadiaSumatra