Low-frequency (LF) hydrophone data, when collocated with a broadband seismometer, can be used to better distinguish between seismic signals, such as tremor and acoustic arrivals such as the tertiary phases of T waves of oceanic earthquakes, and enable optimal corrections for tilt noise on vertical seismometer channels.

Low-frequency acoustic pressure time series can be retrieved from EarthScope Data Services. Below are links to the station summaries, listed by site. 

For tools to access the data, select the "Data" tab at the top of the EarthScope Station Summary page.

PN1A (Slope Base)

OO HYSB1 - HTI-90-U LF Hydrophone; Sample rates: 1 Hz, 200 Hz

PN1B

COSZO instrument (coming in 2026) - HTI-90-U LF Hydrophone; Sample rates: 1 Hz, 8 Hz, 40 Hz, 200 Hz

Southern Hydrate Ridge

OO HYS14 - HTI-90-U LF Hydrophone; Sample rates: 1 Hz, 200 Hz

PN1C (Offshore)

COSZO instrument (coming in 2026) - HTI-90-U LF Hydrophone; Sample rates: 1 Hz, 8 Hz, 40 Hz, 200 Hz

PN1D

COSZO instrument (coming in 2026) - HTI-90-U LF Hydrophone; Sample rates: 1 Hz, 8 Hz, 40 Hz, 200 Hz

Oregon Shelf

COSZO instrument (coming in 2026) - HTI-90-U LF Hydrophone; Sample rates: 1 Hz, 8 Hz, 40 Hz, 200 Hz