The growth of fault‐bounded tilt blocks

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Abstract
A series of uniformly tilted fault‐bounded blocks is a common feature in actively extending regions, such as the Basin and Range province. If the tilted blocks were produced by rigid “domino‐style” rotation, one would predict large voids at either end of a series of these blocks. Using tilt data and a simple flexural calculation, we suggest that much of the apparent rigid behavior could also be produced by internal block deformation. In our model of normal fault growth, isostatic/elastic uplift of the footwall is coupled with hanging wall downdrop within the region between faults, resulting in the appearance of a tilted rigid block. We present tilt data sampled at varying distances from several block‐defining faults within the northeast Basin and Range province. Tilt measurements between a series of 30‐km spaced block‐defining faults are found to be uniform, while tilts between more widely spaced faults exhibit a pattern of tilt that diminishes to zero in less than 30 km. Using a simple flexural calculation for internal block deformation, we show that for this region the patterns of tilt are consistent with a flexural length scale of ∼8–12 km and deflections of 2–4 km. These estimates are compatible with both the lower limit to seismicity and basin depth determined from earthquake and seismic reflection studies.