Geological record of a Cretaceous seismic event paired with multiple volcanic eruptions

Explosive volcanic eruptions can occur within days to years after an earthquake, suggesting a causal relation between them. Such paired seismic-volcanic events in the past, which occurred on a human timescale, can only be confirmed by field relationship of eruptive products. The Southern Kusandong Tuff (SKT) is an ignimbrite in a Cretaceous backarc basin of Korea, which shows north-to-south variations in grain componentry, chemical composition, magnetic properties and palaeoflow patterns, suggesting that the tuff originated from two volcanic sources. Here we shows that the tuff resulted from two pyroclastic density currents (PDCs), which were generated by synchronous eruptions of two volcanoes in the nearby volcanic arc, most likely triggered by a regional seismic event, and then collided with each other in the backarc region within minutes. The paired seismic-volcanic event raises concerns for intensified volcanic hazards over large areas in regions of clustered volcanoes.