Episodic Tremor and Slip (ETS)

Slow slip events are earthquakes that occur along subduction zones (and other faults) and are usually associated with low amplitude tremor activity. Unique from regular earthquakes, which occur over seconds, these events can last anywhere from several days to several years. Because of this long duration of slip, these events are generally not felt, but can be observed with various geodetic and seismic techniques.

My research focuses on slow slip events in Cascadia, which occur below the locked zone of the subducting Juan de Fuca slab and have recurrence intervals of 10-20 months. I use a combination of GPS and strainmeter observations to quantify the kinematic properties of these events by inverting the surface observations to calculate how the fault is slipping at depth. I am particularly interested in the relationship between tremor and slip, as well as developing methods to utilize the highly sensitive network of strainmeters in Cascadia.

Slip distribution of the August 2010 slow slip event

Long-term Strain Accumulation in the Cascadia Subduction Zone

The last large tsunami-generating mega-trust earthquake in Cascadia was in 1700. As was seen in the recent events in Sumatra, Japan, and Chile, these type of events can have catastrophic consequences. Current surface deformation rates can be used to create estimates of the location and magnitude of a future mega-thrust event in Cascadia, which in turn helps inform the general population of the hazard associated with this future event.

I use a combination of uplift rates from historic tide gauge and leveling records, along with long-term GPS site velocities to quantify the current strain accumulation along the Cascadian subduction zone. The depth and distribution of locking along the fault can be estimated by matching the observed surface deformation with predictions from computer models. One focus of this project is how the region of episodic tremor and slip (ETS) relates to the updip locked zone.

Earth and Planetary Science Letters paper

Map of Cascadia with leveling uplift rates and horizontal GPS velocity vectors

Backslip rates along Cascadia with secondary locking zone in relation to tremor distribution.

Leveling survey along the Washington coast