Echo sounding with the shock wave generated by the implosion of an instrument pressure housing

Abstract

In December 2014, what was intended to be a passive-acoustic experiment at the Challenger Deep, suddenly became an active-acoustic experiment. Two free-falling, passive-acoustic instrument platforms, each with a suite of hydrophones, a CTD, a sound speed sensor and a glass-sphere pressure housing containing the electronics, were deployed from the R/V Falkor. One of the platforms imploded at a nominal depth of 9000 m. The highly energetic, broadband shock wave created by the implosion was recorded by the surviving platform. The shock wave reflected multiple times from the seafloor and the surface and the arrival times of the multiple reflections were used to obtain a highly constrained estimate of the Challenger Deep: 10 983 ± 6 m. We will discuss the signal processing methods used and propagated uncertainty in this highly constrained estimate. We will also discuss how this estimate of the depth of the deepest part of the ocean compares with other estimates of the depth of the Challenger Deep, including an update on estimates obtained following the publication of this study.