Extension induced by volcanic loading in regional strike-slip zones

Volcanoes and strike-slip pull-apart structures are commonly found together, We use theoretical predictions and analogue modeling to evaluate the effect of volcanic loading in strike-slip zones, and the converse effect of regional strike slip faults on volcano structure. Theoretical predictions indicate that regional stress is reoriented by volcano loading to cause extension. Analogue models indicate that volcanoes in strike-slip zones develop extensional pull-apart structures. A graben typically forms normal to the minimum regional stress axis (sigma 3) at a cone. Cones emplaced onto preexisting faults increase that fault's tensional component. If the substratum is weak enough to permit volcano spreading, thrusts form normal to the maximum stress axis (sigma 1), A feedback situation can arise, i.e., loading-related extension allows more magma influx, more eruption, and thus increased loading. This process can create large volcano-tectonic depressions. Volcano structures may also be used as indicators of regional strike-slip movements.