The Central Caldera Medium-Power Jbox supports geophysical instruments in the north central portion of the Axial Seamount caldera at a water depth of ~1523 m. The instruments are attached to a Medium-Power J-Box and are mounted on the seafloor. A broadband seismometer at this site is enclosed in bags of pea-sized gravel to dampen acoustic signals associated with currents in the area. The instruments are designed to measure local seismic events associated with migration of melt and volatiles within the volcano, as well as far-field seismic events. The instruments also measure uplift and deflation of the seafloor associated with ingress of melt within the underlying magma chamber, and collapse of the seafloor during diking-eruptive events. This site was chosen because Axial has erupted in 1988, 2011, and again in 2015. During the 2015 event, over 8,000 earthquakes were measured with the cabled geophysical array, and data were streamed live back to shore in real-time.

Seafloor instruments at Central Caldera are attached to a Medium-Power J-Box (MJ03F) through a series of extension cables. An ~ 4.7 km long extension cable from Primary Node PN3B provides the JBox with significant power (375 v) and bandwidth (1 Gbs) to operate the instruments and transmit data to shore.


This site includes following instruments. To learn more about an instrument type, select its name on the left. To see the relevant data streams for a particular instrument, select the instrument code in the first column which will take you to the OOI Data Portal.

Instrument Depth Node Instrument
Make & Model
RS03CCAL-MJ03F-05-BOTPTA301 1,526m Medium-Power JBox (MJ03F) Bottom Pressure and Tilt (BOTPTA) PMEL/Chadwick - PMELcabled BPR/Tilt
RS03CCAL-MJ03F-06-OBSBBA301 1,526m Medium-Power JBox (MJ03F) Broadband Ocean Bottom Seismometer (OBSBBA) Guralp - CMG-1T/5T
RS03CCAL-MJ03F-06-HYDLFA305 1,526m Medium-Power JBox (MJ03F) Low Frequency Acoustic Receiver (Hydrophone) (HYDLFA) HTI - 90-U