Abstract In this paper we document the first exampleâthe southern Delaware Basinâwhere widespread induced triggered (as opposed to âdrivenâ) seismicity across a large area exhibits a maximum magnitude truncation. The most likely cause of this truncation is that although the shallow faults in this area are many km in length, they are structurally constrained and have limited downâdip widths, typically no more than approximately 1 km. Ruptures on faults of such limited width are not expected to attain high aspect ratios. As such, the ruptures on such faults would be limited to dimensions of roughly 1 km2, which corresponds to magnitudes which closely match the observed MMAX truncation. The MMAX truncation for induced earthquakes in the southern Delaware Basin has significant implications since it implies that downâdip fault widths may play an important role in constraining the maximum magnitudes of induced events.