Preliminary Results from a Prototype Ocean-Bottom Pressure Sensor Deployed in the Mentawai Channel, Central Sumatra, Indonesia

We analyze data retrieved from an ocean floor pressure sensor continuously operated for 48 days in the Mentawai Strait during the Spring of 2016, as part of Project Hazard SEES. Initial processing through systematic spectrogram analysis has identified ten distant earthquakes recorded through the variation of pressure accompanying the passage of seismic waves on the bottom of the ocean. The analysis of the corresponding wavetrains allows the recovery of the standard magnitude M_s of seven of the events (two more being intermediate depth, and the tenth antipodal) with a residual not exceeding 0.3 logarithmic units. We also show that the classical energy-to-moment ratio computation can be successfully adapted by defining a response function of the pressure sensor to teleseismic P waves. In addition, six local earthquakes, occurring at distances of 58–670 km from the sensor, but with moment magnitudes less than 5.7, were also recorded. We show that an estimate of the seismic energy radiated by these events can be obtained from a simple integration of the square of the pressure signal. Thus our results indicate that meaningful quantitative estimates of the source characteristics of both teleseismic and regional events can be obtained through robust methods based on single-station pressure recordings on the ocean floor.