Please join us for the following AOS Seminar on Thursday, April 27 at 4:00 PM in Spiess Hall Room 330:
Ludovic Tenorio, Scripps Institution of Oceanography
"Double-difference methods reformulated for high-resolution tracking using a vertical array in deep water"
Ray tracing can estimate an acoustic source’s depth and range in a waveguide by exploiting multipath arrival information on a vertical array. However, environmental mismatch in the model or array tilt can yield highly scattered trajectories when ray tracing multiple events. “Double-difference” methods have been used to localize earthquakes (Waldhauser and Ellsworth, 2000) and fin whales (Wilcock, 2012) by determining the relative locations of multiple events, rather than their absolute positions. This approach, which exploits changes in relative ray travel times between events, is reformulated to recover the dive trajectory of a source using a single multi-hydrophone vertical array. The method is also expanded such that changes in ray elevation angles between events can be used in addition to temporal information. This technique is tested on data recorded on a short aperture vertical array off the coast of Southern California in 4 km deep water. Trajectories from both a controlled towed source and a sperm whale dive are examined.
Madeleine Harvey, Scripps Institution of Oceanography
"Wave Induced Sediment Transport in Los Peñasquitos Lagoon, San Diego, CA"
Los Peñasquitos Lagoon in San Diego, CA like many other Southern California estuaries, is a small, shallow, low-inflow, bar-built estuary. Observations conducted in Los Peñasquitos Lagoon from 2014 to 2017 show that the amount of wave energy able to propagate into the lagoon depends on the wave height and direction offshore, the tidal amplitude and phase, and the estuary mouth morphology. Waves are able to propagate furthest into the system when the offshore tidal height is high and the inflowing currents are strong. Waves are blocked when the tidal height is low or the outflowing currents are strong (determined by a competition between tides and runoff). Inflowing currents and waves propagating into and dissipating in the lagoon drive sediment transport from the beach into the lagoon. Sand accretion forms a sill at the mouth that can intermittently limit or block the lagoon’s exchange with the ocean. The sill height affects the circulation, inundation, stratification, and dissolved oxygen content inside the lagoon.