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Slip rate uncertainty: Examples from the Calico and Lenwood faults. Dr. Mike Oskin Department of Geological Sciences University of North Carolina at Chapel Hill. Co-PI : Lesley Perg Students : Mike Strane, Emily Gurney, Eitan Shelef, Dylan Blummentritt - PowerPoint PPT Presentation
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Slip rate uncertainty: Examples from the Calico and Lenwood faults
Dr. Mike OskinDepartment of Geological SciencesUniversity of North Carolina at Chapel Hill
Co-PI: Lesley Perg
Students: Mike Strane, Emily Gurney, Eitan Shelef, Dylan Blummentritt
Collaborators: Alex Iriondo, Brad Singer, Sujoy Mukhopadhyay
Lesley
Eitan
Emily Mike
Geodesy12 ± 2 mm/yr
Paleoseismology5 to 7 mm/yr (Estimate)
Central Mojave Transect
Paleoseismic clusters from the ECSZ south of Barstow
From T. Rockwell, S. Lindvall, and C. Rubin
Well-constrained
Poorly-constrained
Earthquake Timing
Recent cluster began ~1000 ka
Average Earthquake Recurrence of 3 to 9 kyr
Alluvial Fan Markers of Fault Slip
Active Wash Surface
Alluvial Fill
Abandoned Wash Surface
Development of Alluvial Fan Stratigraphy
Desert Pavement
Soil Development
Central Mojave Transect
Lenwood
Calico
Helendale
Camp Rock
Pisgah-Bullion
Ludlow
Pipkin Cinder Cone 740±40 ka
Sheep Spring Wash
3 kmCalico Fault
Slip Rate Measurement
s
SRTM Topography
Area of LIDAR
CalicoFault
Oskin et al. (2007)
Q2a
K
F
Q2b
Q1 B
QTcg
SlipRates
Plio-Quaternary Growth Strata
Fanning Dips
Q1 Fan: First occurrence of ca. 740 ka basalt clasts in growth section
Tilted Q1 Alluvial Fan
661 ± 20 ka 3He Exposure Date on one basalt clast
Restorationof Q1 Fan
Displacement
900 ± 200 meters
Age: 650 ± 100 ka
1.4 ± 0.4 mm/yr
Today
~300 ka?
650 ka
Cosmogenic Exposure Dating
qtz
ol
nn
X
+
10Be: t1/2 = 1.5 Myr
3He: stable, rare
Q2b Fan Surface
Quartz and Basalt PebbleDesert Pavement
Quartz Monzonite & Basalt Boulders
Cosmogenic Dates from Q2b Terrace and Modern Wash
0
50
100
150
200
250
300
Age
(ka
) Quartz Monzonite 10Be Basalt 3He
Boulders
Pavement
Wash Boulders
BouldersPavement
Wash Boulders
10Be Age - Inheritance: 56.4 ± 7.7 ka (2)
Lithology-Dependent Hillslope Residence Time
Restoration of Q2a Terrace Displacement
100 ± 10 meters 1.8 ± 0.3 mm/yr(95% confidence, Errors summed as root mean square)
Central Mojave Transect
Lenwood
Calico
Helendale
Camp Rock
Pisgah-Bullion
Ludlow
Lenwood FaultSlope Map: Darker = SteeperQ2b
Slip Rate: 0.8 +0.2/-0.3 mm/yr
Central Mojave Transect
Lenwood Fault
Calico Fault
Helendale Fault
Camp Rock Fault
Pisgah-Bullion Fault
Ludlow Fault
0.8 ± 0.2 mm/yr 1.8 ± 0.3 mm/yr
≤0.8 ± 0.2 mm/yr ≤1.4 ± 0.6 mm/yr ≤0.4 ± 0.2 mm/yr
Total: ≤6.1 ± 1.9 mm/yr
1.0 ± 0.2 mm/yr
(95% confidence, errors summed as root mean square,10Be production rate uncertainty added after summation)