1. Models for Fault Behavior
Elastic Rebound:
Pre-earthquake strain is gradual in space and time
Earthquake strain is abrupt in space and time
Author: Mike Brudzinski

2. Our Classic View of Fault Behavior
A New View of Fault Behavior
Fast Slip Earthquake
(minutes)
Slow Slip Tremor
(days)
I’m going to start by using some simple animations to contrast our classic view of fault behavior with new views that have emerged through EarthScope.
This shows a cross-section of subduction zone fault, like the one that caused the devastating Indian Ocean Earthquake and Tsunami in 2004.
It shows the displacement that occurs at the surface of the earth leading up to an earthquake that releases the accumulated strain.
The earthquake represents fast slip that produces energy release on the scale of minutes, as seen on this network of seismometer recordings.
In the past few years we’ve learned a lot more about another type of fault behavior that we call slow slip.
In this case the release of accumulated strain takes place gradually over many days and is accompanied by a subtle seismic tremor.
This plots shows the tremor waxing and waning over the course of a day, whereas small earthquakes are these thin vertical lines.

3. 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

4. Cross-Section of Fault Behavior
Dragert et al., 2000
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
Thrust fault!

5. Sumatra, Indonesia Aftershocks Locked Fault Dec. 26, 2004 event
Mar. 28, 2005 event
Earthquakes from

6. This Is Why It Is Important
Sumatra
Cascadia