Towards continuous 4D microgravity monitoring of volcanoes: Geophysics, 73, this issue

Four-dimensional or time-lapse microgravity monitoring has been used effectively on volcanoes for decades to characterize the changes in subsurface volcanic systems.With measurements typically lasting from a few days to weeks and then repeated a year later, the spatial resolution of theses studies is often at the ex-pense of temporal resolution and vice versa. Continuous gravity studies with one to two instruments operating for a short period of time weeks to months have shown enticing evidence of very rapid changes in the volcanic plumbing system minutes to hours and in one case precursory signals leading to eruptive ac-tivity were detected. The need for true multi-instrument net-works is clear ifwe are to have both the temporal and spatial reso-lution needed for effective volcano monitoring. However, the high cost of these instruments is currently limiting the implemen-tation of continuous microgravity networks. An interim ap-proach to consider is the development of a collaborative network of researchers able to bring multiple instruments together at key volcanoes to investigatemultitemporal physical changes in a few type volcanoes. However, to truly move forward, it is imperative that new low-cost instruments are developed to increase the number of instruments available at a single site. Only in this way can both the temporal and spatial integrity of monitoring be maintained. Integration of these instruments into a multiparame-ter network of continuously recording sensors is essential for ef-fective volcanomonitoring and hazardmitigation