Title | Marine sediment shear velocity structure from the ratio of displacement to pressure of Rayleigh waves at seafloor |
Publication Type | Journal Article |
Year of Publication | 2014 |
Authors | Ruan Y, Forsyth DW, Bell SW |
Journal | Journal of Geophysical Research: Solid Earth |
Volume | 119 |
Pagination | 6357–6371 |
ISSN | 2169-9356 |
Keywords | admittance, D/P ratio method, marine sediment, microseism noise, Rayleigh waves, shear wave speed |
Abstract | AbstractThe complex ratio of vertical displacement to pressure (D/P) at seafloor is a function of frequency. It is sensitive to the subsurface elastic properties, particularly the shear modulus, and therefore can be used to determine the shear velocity and thickness of marine sediments. Instead of using compliance in response to loading of long-period infragravity waves as in previous studies, we investigate the transfer function from pressure to displacement using Rayleigh waves generated by microseisms and earthquakes. We find that at frequencies between 0.1 and 0.2 Hz, the Rayleigh wave transfer function is very sensitive to marine sediments and can be reliably obtained from microseism noise. Using a surface wave mode method, we calculate synthetic D/P ratios and examine their sensitivity to water depth, shear wave speed, and thickness of sediments. We develop a method to invert the Rayleigh wave D/P ratio for a regional 1-D profile of sediment shear wave speed and associated sediment thickness beneath each ocean bottom seismograph (OBS). We apply our method to a group of deep water OBSs deployed in the Cascadia Initiative and obtain a well-resolved depth-dependent shear wave speed for sediments on the Juan de Fuca plate and shear wave traveltime delays caused by sediments at each station. |
URL | https://onlinelibrary.wiley.com/doi/abs/10.1002/2014JB011162 |
DOI | 10.1002/2014JB011162 |