ANALYSIS OF QUATERNARY FAULTS AND ASSOCIATED DEFORMATION OF SEDIMENTARY BASIN FILL: INNER CONTINENTAL BORDERLAND OF CALIFORNIA

ANALYSIS OF QUATERNARY FAULTS AND ASSOCIATED DEFORMATION OF SEDIMENTARY BASIN FILL: INNER CONTINENTAL BORDERLAND OF SOUTHERN CALIFORNIA

Jonathan Bennett

OVERVIEWBackground and ProblemQuestions to Be AddressedMethodsResultsConclusions

BackgroundComplex tectonic historyTranstension transpressionMultiple episodes of faulting

Fisher et al. (2009)

Fisher et al. (2009)BackgroundJennings et al. (2010)Ryan et al. (2009)This Study

N

BackgroundDating method for ICB sediment based upon radiocarbon dated cores Date calibration beyond those provided from the cores are obtained through sequence stratigraphy and extrapolation below the coreNormark et al. (2009)

Bottom:Covault and Romans (2009)

ControversyDifferent fault interpretations based upon dating techniques The results of which are significant in calculating fault activity and seismic hazard

Questions to be Addressed:Can the sedimentary basin fill in the ICB be reliably correlated regionally to dated rocks in a core hole in Los Angeles harbor? What would this information, paired with a more thorough interpretation of ICB faults do to resolve some of the controversies found in the ICB such as fault continuity and activity?

MethodsData analysis: Stratigraphic and structural interpretationGridding and depth conversionMeasurementsSlip modeling

AABBCCDDEEFFGG

IHS THE KINGDOM SUITE

Data Analysis Four Quaternary reflections named Quaternary 1 - Quaternary 4Based upon previously interpreted top Lower Pico

Quaternary 1 Quaternary 2 Quaternary 3Quaternary 4 Top Lower PicoH 4 CC

Data Analysis

Data Analysis: Stratigraphy

Stratigraphic Interpretation

Data Analysis: StructureFaults that we interpreted were imaged consistently in MCS dataBounded large basins or large offset/ deformation were deemed significant

N

Flower Structures

AABBCCDDEEFFGGData Analysis: Structure

AABBCCDDEEFFGG

Data Analysis: Structure

GG

AABBCCDDEEFFGG

Gridding and Depth Conversion

10 km

Gridding Process

Measurements

Slip ModelingSimple trigonometry is used to estimate slip direction and amountIt assumes that vertical deformation is due to oblique transport of the hanging wall block up or down a ramp of apparent dip

Where is the angle between the local slip vector and local fault strike and is the fault dip

Results

N

Results

AABBCCDDEEFFGGQ1-Q4 were correlated to dated rocks in Los Angeles harbor (A)

Results

Bottom: Covault and Romans (2009)

1 km corridors used for modeling (1-58)Structural Relief (meters)Measured Strike (azimuth degrees)-100-200Results: Top Lower Pico Structural Relief vs. Strike of San Mateo-Carlsbad Fault

Releasing step over

Restraining

ResultsPure Thrust SlipRelative to a fixed footwall

Structural Relief (meters)

Relative to a fixed footwall this graph shows motion of the hanging wall29

Results:162 slip orientation with motion to the south

Vertical Deformation(meters)

1 km corridors used for modeling (1-58)Structural Relief (meters)

Results:177 slip orientation with motion to the south

1 km corridors used for modeling (1-58)Structural Relief (meters)

80% right-lateral 20% reverse 31

Results:Q3 Q4 and TLP vs SMC Strike

1 km corridors used for modeling (32-58)Measured Deformation (Measured Strike (azimuth degrees)Structural Relief (meters)58

Restraining

Releasing step over

Results:Isochore maps TLP-Seafloor

030060090012001500

Meters Depth20 km

Top Lower Pico-Quaternary 4

0

450

20 kmVertical Thickness(meters)

Quaternary 4 Quaternary 3

20 km

0200

Vertical Thickness(meters)

Quaternary 3- Quaternary 220 km

0200Vertical Thickness(meters)

Quaternary 2- Quaternary 1

20 km

0200Vertical Thickness(meters)

Quaternary 1- Seafloor

030020 kmVertical Thickness(meters)

Bathymetric Grid of the Seafloor

03006009001200150018002100Meters Depth20 km

New Animation

Conclusions

ConclusionsThe -9km wide step-over in the San Mateo-Carlsbad fault marks a boundary between transpression in the north and transtension in the southThe SMC fault is modeled as kinematically continuous with a slip direction range of 162-177 of the hanging wall relative to the footwall towards (right-lateral)Average slip rate of ~0.44mm/year relative to the 5cm/year attributed to the plate boundary

ConclusionsSMC-Newport Inglewood positive flower structure steps right ~19km over to the Coronado Bank-Descanso negative flower structure adjacent to San Diego.These findings are consistent with right-lateral strike-slip being the dominant accommodation of stress.

ConclusionsIsochore maps indicate sedimentation is not constant and accumulation shifts spatially throughout the QuaternaryThe ~ 600ka Q4 sequence boundary can locally represent hundreds of meters of missing sectionSlip rates calculated from our new age model suggest that slip rates are a magnitude lower than if they were calculated using a recently published age modelPotentially indicating lower seismic hazard

AcknowledgementsNAMSS, JEBCO, WestenGeco, Chevron, USGS for the seismic reflection dataIHS The Kingdom SuiteBrian Campbell and Billy Alward for their workDr. Bauer, Dr. Cormier, and Dr. Sorlien, for advising me on this projectDr. Loehr for serving as the outside reader on my defense committee My family and friends for their supportMy girlfriend Amy for putting up with me

BONUS CLOSED DOOR SLIDES

Results