Geological Society of America

132 D29. Recent Advances in Structural Geology

Tuesday, 12 October 2021
8:00 AM - 12:00 PM
A106

FORE-LIMB AND BACK-LIMB FOLDING OF THE PUENTE HILLS BLIND-THRUST FAULT WITH IMPLICATIONS FOR PLEISTOCENE-HOLOCENE SLIP-RATE ESTIMATES AND SEISMIC HAZARD ANALYSIS IN THE LOS ANGELES BASIN, SOUTHERN CALIFORNIA

Paper number: 132-8
Program: Technical Sessions
Time: 9:35 AM – 9:50 AM

Authors

Christoffel Anthonissen Presenting Author
University of Southern California, Los Angeles, CA
Franklin Wolfe
Harvard University, Faculty of Arts and Sciences, Cambridge, MA
Lorraine Leon
University of Southern California, Los Angeles, CA
Jessica Don
Harvard University, Faculty of Arts and Sciences, Cambridge, MA
James Dolan
University of Southern California, Los Angeles, CA
John H. Shaw
Harvard University, Faculty of Arts and Sciences, Cambridge, MA
Tammy Rittenour
Utah State University, Logan, UT
Edward J. Rhodes
University of Sheffield, Sheffield
Andrew Ivester
University of Sheffield, Sheffield

Abstract

Using a combination of high-resolution and industry seismic reflection profiles, historical well logging data, and luminescence and ¹⁴C ages, we determine a detailed Pleistocene-Holocene slip history for the Santa Fe Springs segment of the Puente Hills blind-thrust fault (PHT), beneath metropolitan Los Angeles. Deep thrust displacement on the PHT is consumed updip in the creation of a hanging-wall fault-bend fold. We analyze the geometry of correlative stratigraphic units in the fore-limb and back-limb of this fold, using seismic reflection data and drilling data, and determine the uplift of several discrete units. These uplift measurements are converted to thrust displacements on the underlying PHT using a novel structural method, developed by Don et al. (in Review), that accounts for the precise geometry of the fault surface. Historical well logs, luminescence ages, and ¹⁴C ages collected from growth strata on the fore-limb and back-limb provide age constraints for folding and thrusting on the underlying PHT. A comparative slip history for the fore-limb and back-limb fold is determined from at least four discrete growth horizons, recording incremental deformation rates at four time intervals spanning the past ca. 450 ka. This study provides a direct comparison of fore-limb and back-limb slip rates determined for the same structure, facilitating accurate determination of the proportion of thrust displacement that is consumed in the development of different parts of the hanging-wall fold. Additionally, these new data provide more detailed constraints on both average slip rate of the PHT, a major seismic threat to the highly urbanized Los Angeles metropolitan region, as well as the variability of slip rate through time on this large thrust fault. These slip-rate data will also facilitate comparisons with similar rate data from other faults within the southern California plate boundary fault network.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-369848

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