Particle‐Based Modeling of Pull‐Apart Basin Development

Abstract

A scale‐independent modeling approach based on the discrete element method has been established to investigate the development of pull‐apart basins. The main findings can be summarized as follows. Thirty degree underlapping models produce pull‐apart basins that evolve from spindle‐shaped through lazy‐Z‐shaped to rhomboidal and stretched rhomboidal basin. Ninety degree nonoverlapping and 150° overlapping models generate rhomboidal pull‐apart basins without going through spindle‐shaped and lazy‐Z‐shaped stages. The shape of a pull‐apart basin is the consequence of both the initial strike‐slip fault geometry and its various evolution stages. Rhomboidal basins, which have larger basin length than the amount of motion, form in overlapping systems and do not progress through the spindle‐shaped and lazy‐Z‐shaped stages such as the Dead Sea basin. Rhomboidal basins with cross‐basin faults tend to form in underlapping systems. All the numerical models show nearly the same trend for maximum principal stress versus relative extension εx* (horizontal opening divided by fault separation). Peak stress and onset of crack propagation are observed for εx* of ~0.035. The relative extension to form the first depression is ~0.155. Therefore, for a pull‐apart to form in nature, the displacement and time needed to form the first cracks and depression area can be estimated from the corresponding εx* and the slip rate of the strike‐slip faults. The time needed to form the first depression can be considered as the minimum age of initiation for the pull‐apart basin. This method to deduce the starting age of pull‐apart basin development can be used for basins which are still active.

Particle‐Based Modeling of Transtensional Pull‐Apart Basins

“…The 5° transtensional model with two parallel master faults in 30° underlapping sidestep produces a pull‐apart basin evolving from spindle‐shaped through lazy Z‐shaped to the rhomboidal basin. This basin evolution history is similar to that of the pure strike slip (Liu & Konietzky, ). However, a slight change of the two master faults from pure strike slip to 5° transtension causes changes of crack pattern and basin geometry (Figures A and B).…”

“…From the modeling point of view, as displacement increases, particles in the model are carried outward, the area bounded by the cracks becomes empty, and the simulation results for crack propagation in this area are not so important. However, the basin sidewalls and the depression area geometries are still meaningful (Liu & Konietzky, ). The boundaries between the particles and the empty areas are the basin sidewalls.…”

“…Tectonics geometries are still meaningful (Liu & Konietzky, 2018). The boundaries between the particles and the empty areas are the basin sidewalls.…”

Influence of nodular structures on fracture development in fine-grained rocks: numerical simulations based on the discrete element method

“…The discrete element method has been extensively used for addressing problems in structural geology across a wide range of scales, such as the modelling of normal/ reverse faults (Saltzer, 1992;Strayer and Suppe, 2002;Yamada and Matsuoka, 2005;Abe et al, 2011;Smart et al, 2011;Hardy, 2011Hardy, , 2013Schöpfer et al, 2006Schöpfer et al, , 2007Schöpfer et al, , 2016Schöpfer et al, , 2017Finch and Gawthorpe, 2017), strikeslip fault (Liu and Konietzky, 2018), relay structures (Imber et al, 2004), fault gauge Mair, 2005, 2009;Morgan, 2006, 2007), detachment fold (Hardy and Finch, 2005;Vidal-Royo et al, 2011), fault-related fold (Finch et al, 2003(Finch et al, , 2004Cardozo et al, 2005;Finch, 2006, 2007;Benesh et al, 2007;Hughes et al, 2014), fold and thrust belt (Burbidge and Braun, 2002;Naylor et al, 2005;Hardy et al, 2009;Dean et al, 2013;Morgan, 2015;Morgan and Bangs, 2017), and salt tectonics (Pichel et al, 2017). In particular, the discrete element models can produce realistic fractures with a finite displacement due to the particle-based nature (Schöpfer et al, 2011;Virgo et al, 2013Virgo et al, , 2014Virgo et al, , 2016Spence and Finch, 2014), and provide a promising tool for fracture modelling and prediction.…”

Controls on structural styles and decoupling in stratigraphic sequences with double décollements during thin-skinned contractional tectonics: insights from numerical modelling

“…The particle stiffness (normal and shear) of the bulk rock was set to be 1 x 10 7 N/m, which has been effectively used to represent sedimentary rocks (Liu and Konietzky, 2018). A bonding cohesion of 1.0, 2.5 and 5.0 MPa was prescribed to the three types of materials 1, 2 and 3.…”