Anatomy of a megathrust
earthquake rupture:
The 2010 Mw 8.8 Maule, Chile quake
Stephen Hicks, Andreas Rietbrock, Isabelle Ryder
Liverpool Earth Observatory, University of Liverpool, UK
Chao-Shing Lee National Taiwan Ocean University,
Taiwan
Matt Miller Universidad de Concepción, Chile
Email: [email protected] @seismo_steve
The overriding / underlying question…
scientific aims community response rupture zone imaging megathrust properties lessons learnt
The overriding / underlying question…
scientific aims community response rupture zone imaging megathrust properties lessons learnt
The overriding / underlying question…
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Seamount
Fracture zone RidgeCrustal
faults
Batholiths
Subduction
channel
sediments
The overriding / underlying question…
Can we physically identify asperities and barriersalong the megathrust?
scientific aims community response rupture zone imaging megathrust properties lessons learnt
The overriding / underlying question…
Can we physically identify asperities and barriersalong the megathrust?
Megathrust
dynamics
Material
properties scientific aims community response rupture zone imaging megathrust properties lessons learnt
Earthquake
segmentation
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Maule segment
Recognised as a
mature seismic
gap (Ruegg et al., 2009, PEPI)
Longest-standing seismic
gap in Chile
Historic rupture areas from Métois et al (2012), JGR
Nazcaplate
SouthAmerican
plate
Earthquake
segmentation
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Maule segment
Recognised as a
mature seismic
gap (Ruegg et al., 2009, PEPI)
Longest-standing seismic
gap in Chile
Historic rupture areas from Métois et al (2012), JGR
Nazcaplate
SouthAmerican
plate
Closing the gap: 27 Feb
2010
6th largest recorded
earthquake
magnitude 8.8
rupture length 500 km
Concepción
Constitución
Pichilemu
SANTIAGO
Arauco
Peninsula
Image from Google EarthTM, Landsat (2013)
scientific aims community response rupture zone imaging megathrust properties lessons learnt
International Maule Aftershock
DeploymentSeismic instruments provided by
Universidad
de Concepción
Field & logistics support from
scientific aims community response rupture zone imaging megathrust properties lessons learnt
From the Pacific coast to the Andes …
International Maule Aftershock
Deployment
scientific aims community response rupture zone imaging megathrust properties lessons learnt
International Maule Aftershock
Deployment160 land stations
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Data available through IRIS repository
Virtual network code _IMAD
XS – French
3A – British
XY - United States
German data: www.webdc.eu
network code - ZE
International Maule Aftershock
Deployment160 land stations
37 OBS stations
+
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Data available through IRIS repository
Virtual network code _IMAD
XS – French
3A – British
XY - United States
German data: www.webdc.eu
network code - ZE
The overriding / underlying question…
Can we physically identify asperities and barriersalong the megathrust?
Megathrust
dynamics
Material
properties scientific aims community response rupture zone imaging megathrust properties lessons learnt
Modelling slip on the megathrust
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Modelling slip on the megathrust
scientific aims community response rupture zone imaging megathrust properties lessons learnt
most slip between trench
and coastline
max slip 16m at northern
asperity
Modelling slip on the
megathrust
Coseismic slip model from Moreno et al. (2012), EPSL
scientific aims community response rupture zone imaging megathrust properties lessons learnt
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Aftershock
seismicityLocations from Rietbrock et al. (2012), GRL
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Aftershock
seismicity
A’
C
C’D
D’E
E’
Locations from Rietbrock et al. (2012), GRL
A
B
B’
Distance from trench (km)
Aftershock
seismicity
A’
C
C’D
D’E
E’
Locations from Rietbrock et al. (2012), GRL
Gap in
seismicit
y
Distance from trench (km)
A
scientific aims community response rupture zone imaging megathrust properties lessons learnt
B
B’
The overriding / underlying question…
Can we physically identify asperities and barriersalong the megathrust?
Megathrust
dynamicsscientific aims community response rupture zone imaging megathrust properties lessons learnt
Material propertiesLocal earthquake tomography
Imaging the subsurface: seismic
tomography
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Tomographic inversion steps
P- & S-wave
arrival times
Initial event
locations
1-D starting
model
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Tomographic inversion steps
P- & S-wave
arrival times
Initial event
locations
1-D starting
model
Updated event
locations
Least squares
inversion
2-D velocity model (vp & vp/vs ratio)
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Tomographic inversion steps
P- & S-wave
arrival times
Initial event
locations
1-D starting
model
Updated event
locations
Least squares
inversion
Final 3-D
velocity
model
Final
event
locations
Least squares
inversion
2-D velocity model (vp & vp/vs ratio)
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Tomographic inversion steps
Resolutio
n?
P- & S-wave
arrival times
Initial event
locations
1-D starting
model
2-D velocity model (vp & vp/vs ratio)
Updated event
locations
Least squares
inversion
Least squares
inversion
Final 3-D
velocity
model
Final
event
locations
Inversion
algorithm:
SIMUL2000
(Thurber &
Eberhart-Phillips,1999) scientific aims community response rupture zone imaging megathrust properties lessons learnt
Imaging the rupture zone: data160 land + 37 OBS
stations
670 aftershocks
38,000 P-wave
picks14,000 S-
wave picks
scientific aims community response rupture zone imaging megathrust properties lessons learnt
2D velocity structure
Focal mechanisms from:
Agurto et al. (2012), EPSL
Hayes et al. (2013), GJI Coastline
Resolutio
n limits
scientific aims community response rupture zone imaging megathrust properties lessons learnt
2D velocity structure
Focal mechanisms from:
Agurto et al. (2012), EPSL
Hayes et al. (2013), GJI Coastline
Resolutio
n limits
scientific aims community response rupture zone imaging megathrust properties lessons learnt
2-D velocity structure
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Coastline
Resolutio
n limits
2-D velocity structure
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Coastline
Resolutio
n limits
3-D velocity structure
A
B
C
D
E
A’
B’
C’
D’
E’
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Event catalogue and
cross-section locations
3-D velocity structure
Coastline
Resolutio
n limits
Pic
hile
mu
Con
stitu
ció
nC
ob
qu
ecu
raC
on
ce
pció
nA
rau
co
A
B
C
D
E
A’
B’
C’
D’
E’
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Event catalogue and
cross-section locations
Distance from trench (km)
3-D velocity
structure
Pic
hile
mu
Con
stitu
ció
nC
ob
qu
ecu
raC
on
ce
pció
nA
rau
co
A
B
C
D
E
A’
B’
C’
D’
E’
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Coastline
Resolutio
n limitsEvent catalogue and
cross-section locations
Distance from trench (km)
Input model
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Forearc anomalies: imaging capability
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Input model Recovered model
Forearc anomalies: imaging capability
scientific aims community response rupture zone imaging megathrust properties lessons learnt
vp ~ 7.8 km/s; vp/vs ratio ~ 1.8
Observations
Forearc body: composition &
origin
scientific aims community response rupture zone imaging megathrust properties lessons learnt
vp ~ 7.8 km/s; vp/vs ratio ~ 1.8
Positive gravity anomaly
Observations
Ultramafic (weakly serpentinised?)
Christensen (2010), Int. Geol. Rev.
Composition
Forearc body: composition &
origin
vp at 25 km
depth
Origin
Subducted topographic anomaly?Hicks et al. (2012), GRL
Gravity anomaly from EGM2008 (Pavlis et al., 2012, JGR)Forearc gravity model from Hicks et al. (2012), GRL.
Forearc body: composition &
origin
Origin
vp at 25 km
depth
Subducted topographic anomaly?Hicks et al. (2012), GRL
Root of Paleozoic granite batholith?
Triassic extensional phase?Vásquez et al. (2011), J. Geol.
vp ~ 7.8 km/s; vp/vs ratio ~ 1.8
Positive gravity anomaly
Observations
Ultramafic (weakly serpentinised?)Christensen (2010), Int. Geol. Rev.
Composition
scientific aims community response rupture zone imaging megathrust properties lessons learnt
The overriding / underlying question…
Can we physically identify asperities and barriersalong the megathrust?
Megathrust
dynamics
Material properties
of the megathrustscientific aims community response rupture zone imaging megathrust properties lessons learnt
Megathrust
geometryGood agreement with
global / regional plate
interface models
Uniform megathrust
geometry throughout
Maule segment
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Moment tensors from:
Agurto et al. (2012),
EPSL
Hayes et al. (2013), GJI
Shedding light on megathrust properties
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Shedding light on megathrust properties
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Correlating with seismic cycle behaviour
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Preseismic locking• >70% contours: Moreno
et al., 2010
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Preseismic locking• >70% contours: Moreno
et al., 2010
Correlating with seismic cycle behaviour
Coseismic rupture• Slip: Moreno et al., 2012
• High freq: Kiser & Ishii
(2011)
Preseismic locking• >70% contours: Moreno
et al., 2010
Postseismic• Afterslip >1m: Lin et
al.,2013
• Relocated interface
aftershocksscientific aims community response rupture zone imaging megathrust properties lessons learnt
Correlating with seismic cycle behaviour
Coseismic rupture• Slip: Moreno et al., 2012
• High freq: Kiser & Ishii
(2011)
Aftershock
distribution
Pic
hile
mu
Con
stitu
ció
nC
ob
qu
ecu
raC
on
ce
pció
nA
rau
co
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Distance from trench (km)
Coseismic rupture• Slip: Moreno et al., 2012
• High freq: Kiser & Ishii
(2011)
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Preseismic locking• >70% contours: Moreno
et al., 2010
Correlating with seismic cycle behaviour
Postseismic• Afterslip >1m: Lin et
al.,2013
• Relocated interface
aftershocks
Down-dip segmentation of the
megathrust
scientific aims community response rupture zone imaging megathrust properties lessons learnt
1
2
3
Ultramafic bodies in forearc may inhibit
rupture propagation
Minimal slip (seismic or aseismic) where
vp > 7.5 km/s
High vp/vs correlates with up-dip limit of
seismogenesis
4 Afterslip may be compositionally-driven
Implications for the Maule megathrust
scientific aims community response rupture zone imaging megathrust properties lessons learnt
Can we physically identify asperities and barriersalong the megathrust?
Up-dip barrier:
Fluid-
saturated
sediments
Down-dip barrier:
Long-lived
ultramafic bodies
in crust
Lessons learnt
scientific aims community response rupture zone imaging megathrust properties lessons learnt
4
3
2
1
Involve OBS communities into future
rapid deployments
Lessons learnt from deployment
Ocean-bottom measurements can fully
explore seismogenic zone – further
investment and planning needed
Active-source experiments may reveal
megathrust structure in seismic gaps
Instrument pools needed for rapid
responsesscientific aims community response rupture zone imaging megathrust properties lessons learnt
From Maule to IquiqueEarthquake locations (Mw > 5.5) and preliminary
finite fault model from NEIC (USGS)
Image from Google EarthTM, Landsat (2013)
Shifting focus northwardEarthquake catalogue from Servicio Centro
Sismológico Nacional, Chilewww.sismologia.cl
Web:
http://pcwww.liv.ac.uk/~es0u719b
Use of slip models and high-res seismic
images gives unique view of subduction
faultsSeismic velocities could help estimate
rupture size potential of future
earthquakesDense ocean-bottom observations of
foreshock and aftershock sequences in
remaining seismic gaps
Email:
Future progress…