Eastern

The Guralp broadband seismometer, hosting an accelerometer, and a low-frequency hydrophone rest atop pillow basalts. Bags filled with pea gravel enclose the seismometer to help dampen noise caused by currents atop the seamount. Credit: UW/NSF-OOI/V14_R1722.

The Eastern Caldera site, hosting the medium-powered junction box MJ03E, is located ~ 400 m southwest of Primary Node 3B. This site is focused on geophysical instruments that monitor seafloor deformation at the summit of Axial Seamount and seismicity, similar to the Central Caldera site. A broadband seismometer and low frequency hydrophone are “nestled” between pillow basalts, as is a bottom pressure-tilt instrument. The image of the bottom pressure-tilt instrument, shown at the top of this page, was taken prior to leveling of the tripod by a remotely operated vehicle (ROV), as indicated by the small bearing in the leveling bullseye being off center. T-handles on the “feet” of the platform are turned by the ROV manipulator to raise and lower the feet. Both instruments are connected to MJ03E by 50 m extension cables. Two short—period seismometers on 581 m- and 1262 m-long cables are located to the north and southwest of MJ03E, respectively. These cabled geophysical instruments are highly robust and have not required maintenance to date. Hence, the site has not been visited since 2014 when the Regional Cabled Array installation was completed during the 85-day long VISIONS’14 program using the R/V Thompson and remotely operated vehicle ROPOS. ROPOS, operated by the Canadian Scientific Submersible Facility (CSSF), installed  33,000 m of extension cables on the Regional Cabled Array – all have been operational since installation.

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