Ayush Joshi / Earth & Environmental Sciences / Faculty Mentor: Nathan Brown
The San Gorgonio Pass (SGP) in the southern San Andreas Fault Zone plays an important role in modulating earthquake ruptures. This region remains poorly understood largely due to its structural complexity and lack of datable materials in its mountainous terrain. In this study, we try to characterise SGP’s crucial function in earthquake dynamics amid ongoing discussions on slip partitioning among its multiple fault strands. Our aim is to fill a knowledge gap concerning the fault activity spanning the last 100 – 10 thousand years. Previous studies in the region have utilised low temperature thermochronometers like Apatite U-Th/He (hereafter, AHe) cooling ages and cosmogenic 10Be catchment wide erosion rates to inspect the activity of faults in the vicinity of SGP. Traditional thermochronometers like AHe can resolve uplift rates across a fault strand on million-year (Ma) time scale. On the other hand, cosmogenic 10Be dating can successfully measure activity across fault segments on thousand years (ka) time scale, but the observations carry significant spatial and temporal biases. In this study, we use thermoluminescence (TL) thermochronology, a novel technique, to measure in-situ erosion rates from bedrock samples obtained from the Yucaipa Ridge Block (YRB) across the Galena Peak-Mill Creek Fault configuration in the SGP region. By juxtaposing erosion rate estimates across the Galena Peak-Mill Creek Fault configuration, our research aims to pinpoint which fault segments are active to improve the understanding of fault dynamics and seismic risk in the southern California.
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