Marine Geoscience Data System
Cascadia_Janiszewski Seismic:Velocity:Model
Onshore-offshore phase velocity maps from Cascadia Initiative data
This data set contains phase velocity maps calculated from vertical component ambient noise cross correlations, and Helmholtz tomography of teleseismic earthquake Rayleigh waves. These are calculated from seismic stations deployed as part of the Cascadia Initiative program. Tilt and compliance corrections have been applied to the teleseismic earthquake data from OBS instruments prior to analysis. For the ambient noise data, phase velocity maps are calculated for 9, 10, 11, 12, 13, 14, 15, 17.5, and 20 s period. For the Helmholtz tomography, results are given at 20, 25, 32, 40, 50, 60, 80, 100, 115, 130, 145, and 160 s period. The data are given in ASCII format where the first column is latitude, the second is longitude, the third is phase velocity in km/s, and the fourth is the uncertainty for phase velocity in km/s. The value 999.000000 designates a NaN for that grid cell. Each of the .xyz files contains information for the phase velocity maps at each period. The files are either named ambphv_* or helmholtz_* designating which data set was used to calculate the results. That is, ambphv_* is calculated from ambient noise cross correlations, while helmholtz_* uses teleseismic earthquake Rayleigh waves in Helmholtz tomography. The number ending each file name indicates the period band for each file in seconds. The data files were generated as part of a project called Thermal structure, hydration and dehydration of the entire Juan de Fuca Plate. Funding for this project came from NSF grant OCE13-34831. The data set is referenced in Janiszewski et al., 2019; details related to processing steps and phase velocity map calculations can be found therein.
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The data have been processed/modified to a level beyond that of basic quality control (e.g. final processed sonar data, photo-mosaics).

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