Acoustic wave fields in an ocean waveguide with a sediment layer having continuously varying density and sound speed overlying an elastic subbottom is considered in this analysis. The objective of this study is to investigate the effects of seabed acoustic properties,including the density and sound speed of sediment layer and subbottom, on the characteristics of the wave fields. This geometry offers a good environmental model which closely resembles a realistic ocean waveguide. This noise model was first proposed by Kuperman and Ingenito in the study of surface-generated ambient noise using normal mode approach.Recent experimental data provided by Hamilton have shown that the sediment layer in the seabed experiences a transitional change in which the density and the sound speed vary continuously from one value at the top to another at the bottom of the layer. Traditionally, in treating wave propagation in a such environment,the medium is represented by a series of layers,each of which has a uniform property within the layer.While this approximation may reasonably describe the variations of the medium as a whole,the details of the acoustic constituent may only be seen when these variations are properly accounted for. Moreover, the subbottom is taken to be a uniform elastic medium that is capable of supporting both compressional and shear waves. For the study of reflection from seabed, various kinds of sound speed and density profiles are employed.The wavenumber spectrum has clearly shown the various kinds wave components in the waveguide,in particular, the Scholte wave mode.The noise intensity in the water column is dominated by the modal and continuous spectrum.For the set of parameters chosen,the horizontal correlation lengths of the noise field tend to increase as the noise sources becomes more correlated, however, the vertical correlation tends to reduce. This indicates that the coherency of the noise field is controlled both by the noise sources and waveguide properties.

An abnormally high number of explosion quakes were noted during the monitoring effort for the 2007 eruption of Pavlof Volcano on the Alaskan Peninsula. In this study we manually counted the explosion quakes from their characteristic ground-coupled air waves. This study makes an effort at better quantifying the number of explosion quakes and how the characteristic ground-coupled air waves are affected by wind direction and wind speed. Additionally this study investigates how the ground coupled air waves might be used in a monitoring or analysis effort by calculating energy release and gas mass release. Over 3.2x104 quakes were recorded. It was found that wind direction affects the travel time of the air wave by up to 0.7 seconds depending on station location and wind direction. Wind direction and speed, however, are demonstrated not to cause an appreciable difference in ground-coupled air wave frequencies or amplitude ratios. The energy release from the explosions is calculated to be 3.04x1011 J. and the total gas mass (assuming 100% water) released was 729 metric tons. These values are compared to other volcanoes in the literature and found to be somewhat lower. Nevertheless, the tracking of explosion quakes has the potential to become a valuable member of the seismic monitoring arsenal.