Amphibious Monitoring of Earthquake Cycle
Deformation at Subduction Zones
Kelin Wang, Earl Davis, Herb Dragert
Pacific Geoscience Centre, Geological Survey of Canada
We’ve come a long way in monitoring and modeling earthquake deformation
1973 (Bott and Dean)
Today
1984 (Thatcher and Rundle)
GPS
satellites
GPS sites after the M 9.0 Tohoku earthquake
GSI website
(Feb 26, 2012)
East component
North component
Vertical component
Japan and Sumatra: shortly after a great earthquake
All sites move seaward
GSI website
(Jan 29, 2012)
Grijalva et al (2009)
Alaska and Chile: ~ 40 years after a great earthquake:
Opposing motion of coastal and inland sites
M = 9.2
1964
Freymueller et al. (2009)
Wang et al. (2007)
M = 9.5
1960
Cascadia: ~ 300 years after a M ~ 9 earthquake:
All sites move landward
Wells and Simpson (2001)
Coast line
Inter-seismic 2
(Cascadia)
Inter-seismic 1
(Alaska, Chile)
Post-seismic
(Japan, Sumatra)
Co-seismic
Coast line
Rupture
Afterslip
Stress
relaxation
Viscoelastic
Stress relaxation
Characteristic timescales:
Afterslip – months to a few years
Viscoelastic relaxation (transient) – a few years
Viccoelastic relaxation (steady-state) – several decades
Locking – length of the earthquake cycle
ETS type transients – whatever it takes (weeks to years)
Hu and Wang
submitted
Central part
of Sumatra mesh


M
K
GPS observations and viscoelastic earthquake cycle model
A couple of years after
2004 M=9.2 earthquake
(also NE Japan)
Four decades after
1960 M=9.5 earthquake
(also Alaska)
Three centuries after
1700 M~9 earthquake
Wang, Hu, He, submitted
Coast line
Inter-seismic 2
(Cascadia)
?
Inter-seismic 1
(Alaska, Chile)
?
Post-seismic
(Japan, Sumatra)
?
Co-seismic
?
?
?
Coast line
Coast line
Tohoku Rupture from Inversion of GPS
Co-seismic
?
Coast line
Coast line
JCG website
Coseismic (contours) and 1-yr postseismic
(color) slip of 2005 Nias-Simeulue earthquake
GPS
stations
coseismic
slip (2 m
contours)
Post-seismic
?
Hsu et al. (2006)
Coast line
Coast line
GPSA off Peru (Gagnon et al., 2005)
?
Inter-seismic
?
Updip segment not slipping. Locked or fully relaxed?
Coast line
Coast line
?
Inter-seismic
Tilt and pressure,
(MaGuire & Collins,
Funded project)
?
Moored Buoy/GPS,
(Chadwell et al.
Poster, this meeting)
Coast line
Fluid pressure during an ETS episode
Pressure decrease:
Dilatation
Site 1253
Incoming plate
Coast line
?
?
Pressure increase:
Contraction
Site 1255
Overriding prism
Davis, Heeseman
& Wang (2011)
Tremor beneath
Nicoya Peninsula
(minutes of activity per day)
Coast line
Fluid pressure during an ETS episode
Coast line
?
?
Davis, Heeseman
& Wang (2011)
Coast line
Very-low-frequency earthquakes in
Nankai accretionary prism
Coast line
?
?
Coast line
Coast line
Fluid pressure during a VLF episode
?
Site 808
Acc. Prism
Near-trench
boreholes
off Mutoto
?
Site 1173
Incoming Plate
VLF events
Davis et al. (2006)
Coast line
ODP Hole 1173 ACORK, Just Seaward of Nankai Trench
Volumetric strain
(dashed: Dilatation,
pressure decrease)
Scientific targets for amphibious monitoring
1. Coseismic behaviour of the shallow, tsunamigenic part of the
subduction fault. Strengthening or weakening? Slip gradient?
2. Postseismic motion of the shallow subduction fault. Is afterslip
common? Does the rupture zone itself exhibit afterslip?
Coseismic stress drop or increase?
3. Interseismic motion of the megathrust.
4. Strain transients during the interseismic period. Nature of “partial
locking”? Modes of creeping? Connection with deep slow slip?
5. Interseismic deformation of incoming plate.
6. Rheology of the oceanic mantle in earthquake-cycle
deformation. More viscous than mantle wedge in steady state?
Similar transient behaviour to mantle wedge?
Cascadia tsunami warning using land and seafloor geodesy
Vancouver
Victoria
Cherniawsky et al., (2007)
Seafloor pressure during Tohoku-earthquake tsunami propagation
(ERI, U Tokyo website)
NEPTUNE Canada pressure sensors for tsunami detection/warning
Tsunami warning using land GPS
Vancouver
Victoria
Tsunami warning using land GPS
Vancouver
Victoria
Tsunami warning using land GPS
Vancouver
Victoria
Tsunami warning using land and seafloor geodesy
Vancouver
Victoria
Tsunami warning using land and seafloor geodesy
Vancouver
Victoria
McGuire and Collins, funded project
Cascadia since the 1700 earthquake
1702
1741
1778
2012
First Nations people
of Nootka Sound
traded with Captain
Cook who was sailing
along west coast of
North America.
Scientists discuss
seafloor geodesy at
UNAVCO workshop.
Nootka
Sound
England and France
began to fight in
eastern North
America (Queen
Anne’s War).
First Europeans
(Chirikov of Russia)
landed on northwest
coast of North
America (Prince of
Wales Island).