eric kirby penn state university collaborators:
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Late Pleistocene Slip Rate Along the Owens Valley Fault. Eric Kirby Penn State University Collaborators: Sridhar Anadankrishnan, Fred Phillips, Shasta Marrero, Nancye Dawers, Doug Burbank. SCEC Fault System History January 31, 2008. Geodynamics of deformation in the ECSZ. - PowerPoint PPT PresentationTRANSCRIPT
SCEC Fault System SCEC Fault System History History
January 31, 2008January 31, 2008
Eric KirbyEric KirbyPenn State UniversityPenn State University
Collaborators:Collaborators:Sridhar Anadankrishnan, Fred Sridhar Anadankrishnan, Fred Phillips, Shasta Marrero, Nancye Phillips, Shasta Marrero, Nancye Dawers, Doug BurbankDawers, Doug Burbank
Late Pleistocene Slip Rate Along the Late Pleistocene Slip Rate Along the Owens Valley FaultOwens Valley Fault
Geodynamics of deformation in the ECSZGeodynamics of deformation in the ECSZ
What is the significance of differences between geodetic velocities and geologic deformation rates?
– Characteristic timescales of Characteristic timescales of transient deformationtransient deformation
Postseismic relaxationPostseismic relaxation Seismic clustersSeismic clusters Fault switchingFault switching
– Role of spatial variations in Role of spatial variations in fault slipfault slip
Fault growth and interactionFault growth and interaction
Requires understanding the evolution of fault slip through space and timeRequires understanding the evolution of fault slip through space and time
Interseismic deformation in Owens ValleyInterseismic deformation in Owens Valley
Malservisi et al (2001) - data from Gan, Dixon
Fault parallel velocities range from Fault parallel velocities range from ~ 3 - 6 mm/yr~ 3 - 6 mm/yr
Savage, DixonSavage, Dixon
Geodetic data from Gan, Dixon Thatcher
Co-seismic deformation in Owens ValleyCo-seismic deformation in Owens Valley
1872 rupture ~ 100km– Mw 7.5-7.8
– 6 ± 2 m dextral slip– 1 ± 0.5 m vertical
Long-term slip rates ~1 - 2 mm/yr
Looking north along the Lone Pine fault scarp
How to reconcile? How to reconcile?
Elastic dislocation models require 4 - 7 mm/yr slip at depth
Viscoelastic models suggest high velocity could be legacy of 1872 event
Dixon et al (2003)
How well do we How well do we know long-term slip know long-term slip
rate?rate?
Long-term slip rate along OVFLong-term slip rate along OVF
What do we know?– Beanland and Clark (1994)– Lubetkin and Clark (1985; 1988)– Bierman et al. (1995)– Lee et al. (2001)– Bacon and Pezzopane (2007)
Records restricted to Late Records restricted to Late Pleistocene - Holocene:Pleistocene - Holocene:– Lone Pine faultLone Pine fault
0.8 ± 0.4 m/kyr0.8 ± 0.4 m/kyr– Owens Valley faultOwens Valley fault
South - 1.0 ± 0.5 m/kyrSouth - 1.0 ± 0.5 m/kyr Central - 1.8 ± 0.3 m/kyrCentral - 1.8 ± 0.3 m/kyr
Bacon and Pezzopane (2007)
Long-term slip rate along OVFLong-term slip rate along OVF
Sources of uncertainty– Multiple fault strands– Restricted to 10 - 15 ka
2 - 3 events
– Assumptions of uniform recurrence, characteristic slip
Late Pleistocene - Holocene:– Lone Pine fault
0.8 ± 0.4 m/kyr
– Owens Valley fault South - 1.0 ± 0.5 m/kyr Central - 1.8 ± 0.3 m/kyr
Bacon and Pezzopane (2007)
Toward a budget of deformation…Toward a budget of deformation…
Long-term slip along northern OVFLong-term slip along northern OVF
Geology adapted from Bateman (1968)
Displacement at Crater MountainDisplacement at Crater Mountain
Color orthophoto courtesy of Google Earth
Displacement at Crater MountainDisplacement at Crater Mountain
Kirby et al., (2008 - GRL)
Displacement at Crater MountainDisplacement at Crater Mountain
East of OVF - abrupt transition East of OVF - abrupt transition across flow marginacross flow margin
Displacement at Crater MountainDisplacement at Crater Mountain
East of OVF - abrupt transition across flow margin
West of OVF - flow margin is West of OVF - flow margin is buried by Qfyburied by Qfy
Displacement at Crater MountainDisplacement at Crater Mountain
East of OVF - abrupt transition across flow margin
West of OVF - buried flow margin
Across fault - no evidence of Across fault - no evidence of buried flowburied flow
Displacement at Crater MountainDisplacement at Crater Mountain
Buried basalt flow235 ± 15m
Restoration of flow margin Restoration of flow margin yields ~ 235m of right-lateral yields ~ 235m of right-lateral slipslip
Age of the Crater Mountain flowAge of the Crater Mountain flow
K/Ar - 290 ± 40 kaK/Ar - 290 ± 40 ka– Turrin and Gillespie (1986)Turrin and Gillespie (1986)
Overlies alluvial fans ca. 130 kaOverlies alluvial fans ca. 130 ka– Zhefuss et al. (2001)Zhefuss et al. (2001)
33He - range from 35 - 115 kaHe - range from 35 - 115 ka– Stone/Gillespie (unpublished)Stone/Gillespie (unpublished)
290±40 ka
~110 ka
~130 ka
Production of Production of 3636Cl by cosmic raysCl by cosmic rays
35Cl40K
40Ca
high energy neutrons
36Cln
low energy neutrons
n
n
nn
spallation reactions
absorption reaction
3636Cl production “bulge”Cl production “bulge”
Gosse and Phillips (2001)
3636Cl exposure ages - Crater Mtn.Cl exposure ages - Crater Mtn.
N=6
NE flows
SW flows
3636Cl exposure ages - Crater Mtn.Cl exposure ages - Crater Mtn.
N=6
Effect of erosion on calculated ageEffect of erosion on calculated age
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 100 200 300 400 500 600
Apparent Exposure Age (kyr)
Spallation Only
70% Spallation15%Spallation
54% Spallation(actual value)
(equivalent to 10Be or otherspallation-only nuclide)
F. Phillips
Influence of surface weathering - 1mm/kyrInfluence of surface weathering - 1mm/kyr
N=6
Influence of surface weathering - 2mm/kyrInfluence of surface weathering - 2mm/kyr
N=6
Influence of surface weathering - 3mm/kyrInfluence of surface weathering - 3mm/kyr
N=6
Influence of surface weathering - 4mm/kyrInfluence of surface weathering - 4mm/kyr
N=6
Most-likely ageMost-likely age
N=6
Significance of rapid Late Pleistocene slipSignificance of rapid Late Pleistocene slip
Owens Valley fault at Crater Owens Valley fault at Crater Mountain exhibits slip rates of Mountain exhibits slip rates of 3.5 (+1.0 / -0.7) m/ka3.5 (+1.0 / -0.7) m/ka – 235 ± 15 m235 ± 15 m– 67.5 ± 12.5 ka67.5 ± 12.5 ka
Possible explanations:Possible explanations:
Paleoseismic may Paleoseismic may underestimate slip inventoryunderestimate slip inventory
Significance of rapid Late Pleistocene slipSignificance of rapid Late Pleistocene slip
Owens Valley fault at Crater Owens Valley fault at Crater Mountain exhibits slip rates of Mountain exhibits slip rates of 3.5 (+1.0 / -0.7) m/ka3.5 (+1.0 / -0.7) m/ka – 235 ± 15 m235 ± 15 m– 67.5 ± 12.5 ka67.5 ± 12.5 ka
Possible explanations:Possible explanations:
Paleoseismic may underestimate slip inventory
Spatial variations in slip rateSpatial variations in slip rate
Significance of rapid Late Pleistocene slipSignificance of rapid Late Pleistocene slip
Owens Valley fault at Crater Owens Valley fault at Crater Mountain exhibits slip rates of Mountain exhibits slip rates of 3.5 (+1.0 / -0.7) m/ka3.5 (+1.0 / -0.7) m/ka – 235 ± 15 m235 ± 15 m– 67.5 ± 12.5 ka67.5 ± 12.5 ka
Possible explanations:Possible explanations:
Paleoseismic may underestimate slip inventory
Spatial variations in slip rate
Clustered strain release Clustered strain release sometime between 20 ka and sometime between 20 ka and 50-80 ka50-80 ka
Is there a discrepancy with GPS?Is there a discrepancy with GPS?
GPS data courtesy of P. LaFemina (unpublished)
Sierra pole of Dixon et al. (2000)
Velocity difference resolved Velocity difference resolved parallel to OVF ~ 4.5 mm/yrparallel to OVF ~ 4.5 mm/yr
Orthogonal component ~ 1.5 Orthogonal component ~ 1.5 mm/yrmm/yr
Is there a discrepancy with GPS?Is there a discrepancy with GPS?
Not necessarilyNot necessarily
Extension - 070°1.1 - 1.5 m/kyrGreene et al. (in prep)
RL Shear - 340°2.8 - 4.5 m/kyrKirby et al. (2008)
Patterns of strain release over ~ 100 kaPatterns of strain release over ~ 100 ka
Both major fault systems Both major fault systems exhibit decreases in slip exhibit decreases in slip rate toward northrate toward north
Requires…Requires…– Role for distributed Role for distributed
deformationdeformation– Slip farther east Slip farther east (Frankel (Frankel
et al., 2007)et al., 2007)– Temporal variations in Temporal variations in
slip slip (Kirby et al., 2006)(Kirby et al., 2006)
3.1 ± 0.4
2.5 ± 0.4
4.5 ± 1.53.5 ± 1.0
0.5 ± 0.2
Patterns of strain release over ~ 100 kaPatterns of strain release over ~ 100 ka
Similar variations toward Similar variations toward Garlock?Garlock?
– Possible, but Possible, but chronologic basis not chronologic basis not well establishedwell established
– Stay tuned…Stay tuned…
3.1 ± 0.4
2.5 ± 0.4
4.5 ± 1.53.5 ± 1.0
0.5 ± 0.2
~1.5 - 3
~3 - 4
Conclusions/ImplicationsConclusions/Implications Slip rate at Crater Mountain is 3.5 +1.0/-0.7 m/kyrSlip rate at Crater Mountain is 3.5 +1.0/-0.7 m/kyr
– Either previous estimates are missing slip, or slip is variable in Either previous estimates are missing slip, or slip is variable in space/timespace/time
Reduces geologic-geodetic ‘discrepancy’ across Owens ValleyReduces geologic-geodetic ‘discrepancy’ across Owens Valley– But, seems to require shallow locking and/or creepBut, seems to require shallow locking and/or creep
Emerging picture of systematic regional variations in slip rate Emerging picture of systematic regional variations in slip rate along ECSZalong ECSZ– Are these maintained by interaction with barriers (Garlock, Mina Are these maintained by interaction with barriers (Garlock, Mina
Deflection), or do they represent nascent lengthening faults?Deflection), or do they represent nascent lengthening faults?