Dip Angles of Mountain‐Front Facets Encode Long‐Term Slip Rates Along the Wasatch Normal Fault, USA | CU Experts

Abstract; Mountains bounded by seismogenic normal faults are commonly decorated with facet slopes: planar slopes made of bedrock, or bedrock mantled by regolith, that rise above the fault. The steepness of such slopes is thought to reflect a balance between fault slip and erosion rate. We show that facet dip angles along the Wasatch fault zone (WFZ), USA, positively correlate with fault slip rates, such that relative variations in slip rate can be estimated from facet angle, and that by constraining millennial‐scale facet erosion rates, absolute slip rates can be estimated. We calculate 100‐ka average vertical slip rates of mm/yr (mean and 90% confidence interval) along the central WFZ, consistent with estimates from features offset over similar timescales, but lower than Holocene rates. Our results provide evidence of slip rate acceleration on the WFZ, and demonstrate the potential of facet‐angle analysis to estimate slip rates on range‐bounding normal faults.

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