Title: Joan%20Gomberg,%20Bill%20Schulz,%20Paul%20Bodin,%20Aaron%20Wech,%20Roland%20Burgmann,%20Jason%20Kean,%20Patricia%20MacQueen,%20Katie%20Foster,%20Bob%20Nadeau,%20Chuck%20Wicks,%20Wes%20Thelen
1Sleuthing 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)
2Slow Slip
inter-slip motion
Dragert et al. (2004)
3 THE PHENOMENA Tremor
Earthquake
seconds
4Tremor Envelopes
24 hours (9/11/2005)
5Hallmarks 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
6Slow seismic signals depleted in high-frequencies
(relative to earthquakes)
7Premise 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.
8Plate-scale Observations
9The basic model Subduction Zones
10The basic model Subduction Zones
Dilatant Stabilization vs Thermal Pressurization
Control on Slow vs Fast Fault Slip? Segall and
Bradley, SCEC Annual Mtg., 2009
11The basic model Transform Faults
Transitional?
12The 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
13The 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
14Clues from a shallow creeping segment of the
San Andreas fault, an earthquake swarm in
eastern Washington, a translational landslide in
southwest Colorado.
15The Wooded Island Swarm (Hanford, WA)
from W. Thelen, Univ. of Washington
16InSAR-detected uplift of several cm!
from C. Wicks, USGS
17Earthquake Rate Uplift
18Earthquake Rate Uplift
Cascadia Tremor Rate, 2008 ETS Event
19Earthquake 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.)
20Shallow 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
21Shallow Slow Slip at San Juan Bautista - No
tremor?
NO clear tremor for 4 slow slip events, but
increased earthquake rates clearly correlate.
22Shallow Slow Slip at San Juan Bautista - No
tremor?
Slow slip and seismicity not co-located. seismic
m0 ltlt geodetic m0
23The Slumgullion landslide - a Natural Laboratory.
Basal Slip
Transform-fault Slip
24Seismic Network Installation
Robotic Displacement Meter
25Slumgullion Instrumentation
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29Ide et al. (2007) propose 2 distinct slip modes,
with differing m0 vs. duration scaling.
30Swarms scale like slow (or slower) slip events.
Roland McGuire, GJI, 2009 This study.
31Is there a gap between slow regular seismic
slip?
?
Beroza Jordan, JGR, 1990 Matsuzawa et al., JGR,
2009 Harrington Brodsky, GRL, 2009
32Aftershocks scale like slow (or slower) slip
events.
Savage et al., JGR, 2007
33The geodetic m0 gtgt seismic m0.
Savage et al., JGR, 2007
34What about landslides other slip events?
Ekstrom et al., Science, 2003 Nettles Ekstrom,
BSSA, 2004
35Inference 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?
36THANK YOU! Questions?