Wide Versus Narrow Back‐Arc Rifting: Control of Subduction Velocity and Convective Back‐Arc Thinning

Back-arc basins such as the ones behind island-arcs of Western Pacific Ocean or in Mediterranean Sea are ubiquitous structures Earth. They extensional forming overriding plate subduction zones and similarly to continental rifts, they can exhibit different structural styles from narrow, localized rifting wide-rift extension. While these have been long recognized, factors controlling style extension not explored properly. We use thermo-mechanical models investigate how relative rates progressive build-up slab-pull force convective thinning thermal weakening control back-arc rifting. Following subduction-initiation, a high subducting velocity results rapid force. The relatively low rate convectively associated moderate require build up close its maximum value overcome integrated strength resulting narrow rift. In turn comparison with timescale allows for significant before becomes large enough drive this case, exhibits wide occurs at significantly reduced strength. Our model provide an explanation why some wide, distributed instance observed Pannonian basin.