Coupling of Hawaiian volcanoes only during overpressure condition

Mauna Loa and Kilauea volcanoes, Hawaii, are thought to be coupled by pore pressure diffusion through an asthenospheric melt layer. However, abundant observations of independent activity of these volcanoes suggest a more complicated relationship. Here we analyze surface deformation data, deep seismicity and gas measurements, to reveal strong coupling of these volcanoes between 2003 and 2008. In early 2005, we find a shift from anticorrelation to correlation of magma-chamber inflation. The shift is preceded by a seismic swarm in the mantle beneath Mauna Loa and accompanied by a large silent slip event beneath the south flank of Kilauea. This suggests that these volcanoes are coupled during mantle-driven surges and that the 2005 silent slip event was triggered by accelerated magma supply at Kilauea.