Using ambient seismic noise to monitor ocean bottom pressure

Ambient seismic noise (ASN) recorded by ocean bottom seismometers allows us to perform coda wave interferometry without using active sources. We analyzed two-year ASN recordings from five ocean bottom stations in the northwestern Pacific Ocean basin (depth > 5,500 m), and measured the relative velocity variation ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" alttext="δ" display="inline"><m:mi>δ</m:mi></m:math> v/v ) near the seafloor. The most important finding is an extremely low variation in <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" alttext="δ" display="inline"><m:mi>δ</m:mi></m:math> v/v (around -0.05%), which likely responds to a significant pressure drop at sea level and subsequently affects an anomaly at the ocean bottom (over -400 Pa) in December 2013. Furthermore, several major phases of the velocity change show delayed-correlation with the sea level pressure variations. A poroelastic simulation with adjusted ocean bottom variables supports the pressure factor mainly drives the variation in <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" alttext="δ" display="inline"><m:mi>δ</m:mi></m:math> v/v . Our study suggests the potential use of seismic signals to monitor oceanic and atmospheric processes by tracking variations in the oceanic pressure field.