2024 CSDMS meeting-055


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Identifying active uplift across fault strands in the southern San Bernardino mountains: a TL thermochronology based Approach

Ayush Joshi, University of Texas Arlington Arlington Texas, United States. ayush.joshi@uta.edu
Nathan Brown, University of Texas Arlington Arlington Texas, United States. nathan.brown@uta.edu
Seulgi Moon, University of California Los Angeles LOS ANGELES California, United States. sgmoon@g.ucla.edu
Marina Argueta, University of California Los Angeles LOS ANGELES California, United States. moargueta@ucla.edu

In the southern San Andreas Fault zone, the San Gorgonio Pass (SGP) stands as a region of intricate structural complexity, pivotal for the assessment of seismic hazards due to its potential role in modulating earthquake rupture propagation. This investigation delves into the SGP's crucial function in earthquake dynamics amid ongoing discussions on slip partitioning among its fault strands, aiming to fill a substantial knowledge gap concerning fault activity spanning the last 1 to 100 thousand years. The challenge of estimating slip rates, exacerbated by a dearth of datable materials within the SGP's challenging terrain, calls for innovative methodologies to assess uplift rates along previously overlooked fault segments. In our study, we use thermoluminescence (TL) thermochronology to evaluate differential uplift by analysing bedrock erosion rates. Although AHe dating sheds light on thermal histories and erosion rates across millions of years, it falls short in detailing the recent uplift history vital for grasping Quaternary fault dynamics. In contrast, cosmogenic 10Be dating proves effective in measuring surface erosion rates over millennial timescales, providing insights into contemporary geological activities. TL dating, with its capacity to discern bedrock exhumation over 10-100 ka, acts as a bridge between the temporal scales of AHe thermochronology (Ma) and cosmogenic 10Be denudation rates (ka). By juxtaposing erosion rates across different faults within the SGP, our research aims to pinpoint active fault segments, thereby enriching our understanding of fault dynamics and seismic risk in the southern San Bernardino Mountains.