Joan%20Gomberg,%20Bill%20Schulz,%20Paul%20Bodin,%20Aaron%20Wech,%20Roland%20Burgmann,%20Jason%20Kean,%20Patricia%20MacQueen,%20Katie%20Foster,%20Bob%20Nadeau,%20Chuck%20Wicks,%20Wes%20Thelen - PowerPoint PPT Presentation

Title: Joan%20Gomberg,%20Bill%20Schulz,%20Paul%20Bodin,%20Aaron%20Wech,%20Roland%20Burgmann,%20Jason%20Kean,%20Patricia%20MacQueen,%20Katie%20Foster,%20Bob%20Nadeau,%20Chuck%20Wicks,%20Wes%20Thelen


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Sleuthing Slow Slip Phenomena
Joan Gomberg, Bill Schulz, Paul Bodin, Aaron
Wech, Roland Burgmann, Jason Kean, Patricia
MacQueen, Katie Foster, Bob Nadeau, Chuck Wicks,
Wes Thelen (from USGS, University of Washington,
University of California Berkeley)
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Slow Slip
inter-slip motion
Dragert et al. (2004)
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THE PHENOMENA Tremor
Earthquake
seconds
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Tremor Envelopes
24 hours (9/11/2005)
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Hallmarks of Tremor ( other Slow Phenomena)
Earthquakes

• Duration Moment1/3
• Amplitude grows with moment.

Slow Slip, Tremor

• Duration Moment0.85
• Amplitude doesnt grow with moment, is limited.

Houston, 2008
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Slow seismic signals depleted in high-frequencies
(relative to earthquakes)
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Premise To identify key controls narrow the
range of viable models requires a broad search
for clues. Conclusion Slow slip is nothing
new, and tremor isnt so special either.
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Plate-scale Observations
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The basic model Subduction Zones
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The basic model Subduction Zones
Dilatant Stabilization vs Thermal Pressurization
Control on Slow vs Fast Fault Slip? Segall and
Bradley, SCEC Annual Mtg., 2009
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The basic model Transform Faults
Transitional?
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The basic model Transform Faults
Transitional?
On the Mechanics of Earthquake Afterslip, Marone
et al., JGR, 1991 A Two-layer Model for Slip on
the Superstition Hills Fault, California, Bilham
and Behr, BSSA, 1992
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The basic model Landslides
Evidence of Dilatant Strengthening as a Mechanism
Controlling Landslide Velocity, Schulz et al.,
AGU Annual Mtg., 2008 The Transition from Stable
Creep to Stick-slip Instability in Gravity-driven
Landslide Motion, Iverson and Schaeffer, AGU
Annual Mtg, 2009
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Clues from a shallow creeping segment of the
San Andreas fault, an earthquake swarm in
eastern Washington, a translational landslide in
southwest Colorado.
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The Wooded Island Swarm (Hanford, WA)
from W. Thelen, Univ. of Washington
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InSAR-detected uplift of several cm!
from C. Wicks, USGS
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Earthquake Rate Uplift
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Earthquake Rate Uplift
Cascadia Tremor Rate, 2008 ETS Event
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Earthquake Rate Uplift
Cascadia Tremor Rate, 2008 ETS Event
Swarms tremor share irregular energy
release, limited max. amplitudes, temporal
migration, seismic m0 ltlt geodetic
m0. (Propagation paths differ.)
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Shallow Slow Slip at San Juan Bautista - Is there
tremor?
shallow creep is controlled by sediment depth,
perhaps due to high pore pressures, Wei et al.,
JGR 2009
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Shallow Slow Slip at San Juan Bautista - No
tremor?
NO clear tremor for 4 slow slip events, but
increased earthquake rates clearly correlate.
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Shallow Slow Slip at San Juan Bautista - No
tremor?
Slow slip and seismicity not co-located. seismic
m0 ltlt geodetic m0
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The Slumgullion landslide - a Natural Laboratory.
Basal Slip
Transform-fault Slip
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Seismic Network Installation
Robotic Displacement Meter
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Slumgullion Instrumentation
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Ide et al. (2007) propose 2 distinct slip modes,
with differing m0 vs. duration scaling.
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Swarms scale like slow (or slower) slip events.
Roland McGuire, GJI, 2009 This study.
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Is there a gap between slow regular seismic
slip?
?
Beroza Jordan, JGR, 1990 Matsuzawa et al., JGR,
2009 Harrington Brodsky, GRL, 2009
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Aftershocks scale like slow (or slower) slip
events.
Savage et al., JGR, 2007
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The geodetic m0 gtgt seismic m0.
Savage et al., JGR, 2007
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What about landslides other slip events?
Ekstrom et al., Science, 2003 Nettles Ekstrom,
BSSA, 2004
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Inference Tremor, swarms, aftershocks all
represent relaxation of residual slip are
driven by slow slip. These responses differ in
the degree to which ruptures are quenched (size
limited) their spectral contents. Variations
in quenching may be due to the slow slip, pore
pressure changes, /or environment. Could
spectral differences be due to propagation?
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THANK YOU! Questions?