We propose a new probabilistic scheme for the automatic recognition of underwater acoustic signals generated by teleseismic P‐waves recorded by hydrophones in the ocean. The recognition of a given signal is based on the relative distribution of its power among different frequency bands. The signal's power distribution is compared with a statistical model developed by analyzing relative power distributions of many signals of the same origin and a numerical criterion is calculated, which can serve as a measure of the probability for the signal to belong to the statistical model. Our recognition scheme was applied to 6‐month‐long continuous records of seven ocean bottom hydrophones (OBH) deployed in the Ligurian Sea. A maximum of 94% of all detectable teleseismic P‐waves recorded during the deployment of the OBHs were recognized correctly with no false recognitions. The proposed recognition method will be implemented in autonomous underwater robots dedicated to detect and transmit acoustic signals generated by teleseismic P‐waves.

Scientists get a window into deep Earth structures by using a method called seismic tomography. Similar to computed tomography (CT) scans of the brain, seismic tomography uses delays in the arrival times of seismic P waves to make scans and three‐dimensional images of the variations in seismic wave speed in the Earth's interior. Patterns in the delays indicate thermal or compositional anomalies in the Earth's mantle and core, such as those caused by sinking cold oceanic lithosphere or rising hot thermal plumes. A large number of observations of such delays are available for continental regions; the number of observations for the United States is especially high due to a dense deployment of stations currently being installed temporarily and moved across a large area as part of the USArray project, a branch of the U.S. National Science Foundation's EarthScope program. In contrast, no comparable sensor density has been available in the oceans

We propose a new method to study the response of a hydrophone at very low frequencies. In our method, the hydrophone is placed in a calibration chamber filled with water and, by instantaneously changing the water height, an abrupt pressure increase of about 1000 Pa is produced. The pressure variation mathematically corresponds to an input signal close to a step function. The response is recorded after filtering and digitizing so that we obtain the response of the complete system.We also report on the development of an automatic method to determine the number of poles and zeros and their values that describe the observed response. We apply our method to the RAFOS II