Two Magma Reservoirs Detected Under Masaya via Six-Year InSAR Record

Six years of Sentinel-1 radar acquisitions processed with InSAR revealed initial subsidence followed by uplift at a site several kilometers from the active Santiago crater, while the crater itself continued to subside. The pattern indicates magma injection into a deeper reservoir decoupled from a shallower one feeding persistent degassing and lava-lake activity. Lead author Lizzie Johnson and co-author Young Cheol Kim attribute the signals to distinct plumbing levels rather than a single connected chamber previously assumed.

Masaya's location 13 miles from Managua and its status as a national park with high tourist traffic make these observations directly relevant to hazard planning. Persistent sulfur dioxide emissions already create health risks; any shift in reservoir connectivity could alter eruption style or gas output without classic precursory seismicity. The study therefore supplies a new baseline for distinguishing routine fluctuations from escalation.

Context from earlier ground-based campaigns and older InSAR studies shows that single-reservoir models under-predicted deformation complexity at Masaya and similar basaltic systems such as Kilauea. Continuous satellite monitoring now allows separation of deep recharge from shallow drainage, improving the ability to flag changes that might warrant evacuation alerts.

Next steps include integration of the InSAR time series with seismic and gas-flux networks plus forward modeling to test reservoir connectivity thresholds. If the deep uplift signal accelerates beyond 3 cm per year while shallow subsidence persists, the authors recommend elevating alert levels within the next monitoring cycle.