WHAT’S GOING ON IN THE
PACIFIC NORTHWEST?
CHANCE FOR A MEGATHRUST EARTHQUAKE
Stefany Sit, UIC

ABOUT ME:
 Observational
Seismology / Geoscience Education
 Finished my 2nd year teaching at UIC
 Max & I  Develop “Assessing Hazard through Big
Data” Course at UIC

About THIS ACTIVITY
 Introductory
Geophysics Course for Upper Level
Students (teaching this Fall)
Instructor Background - Recent Research
Locked Zone – friction accumulates and is released as a megathrust EQ
Aseismic Creep – where plates slide freely past each other
New Observations from the Past
10 Years
due to More Instrumentation
Adapted from
Brudzinski, 2010
Instructor Background - Recent Research

Discovery - New and More Dense Instrumentation


GPS signal: Slow Slip Event (SSE)
Seismometer signal: Tremor
Additional Resources

Episodic Tremor and Slow Slip
 Other


lessons for more introductory level courses
http://www.iris.edu/hq/inclass/lesson/investigating_episodic_t
remor_and_slip
https://www.unavco.org/education/resources/educationalresources/lesson/ets-mystery-earthquakes/ets-mysteryearthquakes.html
Overview

Multiple datasets for students to explore and make
observations
 GeoMapApp?


Excel?
Individual student groups focus on either a location or
time period
Each member of the group to come up with a figure
and text for presentation
Dataset - Earthquakes
IRIS – www.ieb.org
2859 epicenters
for 1.5 years
Available for
DOWNLOAD
Earthquakes – Analysis Questions

Is there any pattern to the
earthquakes?
 Based

on location? timing? etc.?
Can you identify the plate
boundary(s)?
 What
additional data do you
need to identify the plate
boundaries?
Earthquakes – Analysis Questions


Compare
EQs
with Japan
Do you believe that a megathrust
earthquake, like the 2011 Japan
EQ could occur in the Pacific
Northwest?

How can we possibly monitor or assess the hazard
in the Pacific Northwest?
 Paleoseismic
data
 Geodesy – GPS signals
 Seismology – Non-EQ tectonic signals
Datasets - GPS
UNAVCO - www.unavco.org
GPS Velocity Vectors
Overall plate
motion per year
Datasets – Tectonic Tremor
Tremor Catalog –
http://pnsn.org/tremor
74,283 epicenters
for 1.5 years
Available for
DOWNLOAD
More Tectonically Active than we
Previously Thought…

Analyzing datasets – Location and Time
GPS Data
Tremor Epicenters
More Tectonically Active than we
Previously Thought…
GPS Data
Tremor Data
Any Observations, Patterns?
More Tectonically Active than we
Previously Thought…
GPS Data
Tremor Data
EPISODIC TREMOR AND SLOW SLIP
Does this motion lead to or
prevent a megathrust EQ?
Conclusion Questions for Students



How are GPS Slow Slip and Seismic Tremor signals
related?
What is their relationship to regional earthquakes?
What is their relationship to potential megathrust
earthquakes?