Earthquake Data!

Saturday, July 27, 2013
First earthquake data from Eastern Caldera subnet
Leveling a Seismometer

Part of the work required to properly install a seismometer on the seafloor is to ensure that the instrument is level. The yellow disk, shown here, is placed on the seismometer by ROPOS. The legs of the seismometer platform are then adjusted until a level reading is achieved. VISIONS '13 Dive 1617


There’s excitement ricocheting around the ship as word spreads that our small network of instruments—two seismometers and one bottom-pressure and tilt meter—has captured an earthquake. The colorful and eye-catching patterns of the data (shown above) represent a small, but nonetheless, significant milestone for the OOI regional cabled observatory: the first in situ real-time earthquake data from Axial Seamount. And it happened within an hour of turning on this subnet using ROPOS power and communications.

The engineers and ROPOS team worked from about 2 pm yesterday, through the night, to install and test the subnet. University of Washington seismologist, Wiliam Wilcock, was watching the seismometer installation via the live stream, consulting with chief systems engineer, Dana Manalang of the UW Applied Physics Laboratory, who was “driving” this dive. With the seismometers installed in their two different locations, the ROV “flew” over to the bottom-pressure and tilt (BOTPT) instrument that had been delivered to the seafloor a couple days ago. BOTPT developer William Chadwick of Oregon State University and NOAA, consulted on the installation via the live stream and the telephone line into the ROPOS control room. Once all instruments were plugged in to the cables, the system was tested and found to be working as designed. At that point, a 6-hour time period of data collection began. It was within the first hour of that period that the earthquake data shown above was captured from the two seismometers.

In some ways, we are lucky to be on the seafloor working with ROPOS right now. At the time of launch yesterday, the wind had kicked up and there were big enough swells to consider postponing. However, because ROPOS was carrying only its tool basket, with the two seismometers, the vehicle was not burdened by the heavy weight of a spool of cable. The ROPOS team was willing to give the launch a try. The ROV was deployed over the side, held securely by its launch-and-recovery system just above the water until the practiced eye and intuition of the team leaders caught just the right moment between sets of waves, and the ROV was quickly and safely lowered by its umbilical wire into the water and sent on its way to the seafloor 1 mile below for this 32-hour-long dive.

Getting this type of live data is a big part of what cabled ocean observatories are all about. Today's success is only a first tiny push into the next-generation ocean science made possible by cabled networks of instruments. Nonetheless, for all involved, this is a moment to celebrate.

Contributed by Nancy Penrose, RSN Communications Coordinator