University of Manchester
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DEM: Normal faulting 3. The effect of prograding hangingwall derived deltas on faulting in pre- and syn-kinematic stratigraphy

posted on 2023-09-27, 15:48 authored by Emma FinchEmma Finch

An understanding of the interaction between sedimentation and fault displacement and resulting stratigraphy is key to improve interpretation of seismic data. A modification of one parameter such as sedimentation impacts fault propagation in the syn-tectonic stratigraphy and, as a result, local accommodation space and subsequent deposition locations creating variation in overburden thickness which then affects faulting in the pre- and syn-tectonic layers. A complicated feedback loop that is sometimes hard to unravel. Here, the relationship between a prograding delta with hangingwall-derived sediment and the resulting stratigraphy and faults in both pre- and syn-tectonic layers during basement fault propagation is shown. This is investigated in relation to a pair of domino faults with constant displacement. Initially, the fault planes dip at 50o which rotate to 33o at the end of an experiment.

The modelling is carried out using the discrete element method where the methodology and experiment set-up are described in the file HW.deltas.introduction.pdf. These pages and movies show results from 12 experiments where the location of the initial delta front is changed. Propagation of a delta assumes a sediment source on the right-hand side of the model. Experiments with two different sediment fill amounts per input are shown. All other parameters (for example: fault displacement, the mechanical properties of elements, timing of sediment addition) are constant.

Experiments run to 3,000,000 timesteps and sediment is input 25 times (every 120,000 timesteps), divided into 5 intervals. Data is output every 40,000 timesteps (75 files) to generate the movies. Sediment is added to a defined elevation which remains fixed at 0.25 unit/fill or 0.50 unit/fill for keeping pace with, or outpacing the left-hand fault crest respectively.

The intention of this data is not to provide full interpretation and discussion of the results but to provide an indication of the complexity within observed stratigraphy when only sedimentation changes. When presented with only a static representation of stratigraphy it is sometimes tricky to understand what is observed, hopefully, these movies and images will help in some way.