Short-period ocean-bottom seismometers (OBSSP) detect vibrations from small earthquakes ranging from 0.1 Hz to 100 Hz. These earthquakes are caused by local phenomena, such as melt movement beneath Axial Seamount and upward flow of hydrothermal fluids in the conduits that feed the black smoker chimneys. These instruments, built by Guralp (CMG-1 sec) enable imaging of the seismic energy traveling through the seafloor.
Five short-period seismometers are now installed at the summit of Axial Seamount at the Eastern Caldera subsite (MJ03E), near the ASHES (MJ03B) hydrothermal field, at the Central Caldera Site (MJ03F), and at the International District Hydrothermal Field (MJ03D). The short-period instrument OBSSPA304 is located in the Eastern Caldera site and is connected to the MJ03E J-Box by a 500 m-long extension cable. Other instruments in the Eastern Caldera include a second short period seismometer, a Bottom Pressure and Tilt meter, a broadband seismometer, and a low-frequency hydrophone.
All seismic instruments are streaming data live to IRIS (Incorporated Research Institutions for Seismology) and are available to the public. Daily and hourly updates on the number of earthquakes occurring at Axial Seamount can be accessed through Dr. William Wilcock's web site.