Cascading magmatic unrest and aseismic faulting in the Aegean Sea enabled by elastic stress relay.

Magma reservoirs commonly exist in clusters and situate within complex fault networks, yet sequential triggering of unrest at multiple reservoirs and faults is rarely observed. We show that the 2025 earthquake swarm in the Christiana-Santorini-Kolumbo complex of the Aegean Sea was driven by elastic stress transfer between two magma reservoirs, a 9-kilometer-long dike, and a 17-kilometer-long, southeast-dipping fault. Pressurization of the magma reservoir under Santorini triggered a dike intrusion originating from a separate magma reservoir under the Kolumbo volcano. The dike, in turn, triggered a moment magnitude ([Formula: see text]) 6.2 aseismic slip transient on a SW-NE trending branch of the Amorgos fault. Episodic bursts of upward-propagating seismicity within the geodetically constrained dike potentially indicate buoyancy-driven, segmented dike opening. We suggest that unrest in rift zones can propagate over spatial scales much larger than individual magma reservoirs and faults via sequential relay of elastic stress.