blue dot = midpoint between source and receiver
With funding from NSF and IRIS we are picking absolute and differential times of a variety of seismic phases. These observations are available to the community for further analysis.
The two primary goals of this project are to provide quality control for waveform data at the IRIS DMC and to routinely pick times for stations that may not otherwise be picked. Our focus is to pick P-wave travel times and amplitudes from BHZ and SHZ channels of all stations from all Networks that are in the IRIS FARM/POND. Click here to obtain the data, find out more about the status of this project or to read about our analysis of picking from broadband records versus short-period records.
We have picked differential times of PKP phases using cross correlations. Short-period PKP differential-time data sets we have used for imaging the inner core and the lower-most mantle are available for PKP(BC) minus PKP(DF) and PKP(AB) minus PKP(DF). This is the high-quality subset of observations picked and analyzed by:
Creager, K. C., 1999, Large-scale variations in inner-core anisotropy, J. Geophys. Res., 102, 23127-23139.
The data were picked and used in these other studies:Creager, K. C., 1992. Anisotropy of the inner core from differential travel times of the phases PKP and PKIKP, Nature, 356, 309-314.
Creager, K. C., 1997, Inner core rotation rate from small-scale heterogeneity and time-varying travel times, Science, 278, 1284-1288.
McSweeney, T. J., K. C. Creager, and R. T. Merrill, 1997, Depth extent of inner-core seismic anisotropy and implications for geomagnetism, Phys. Earth Planet. Interior., 101, 131-156.
van der Hilst, R. D., S. Widiyantoro, K. C. Creager, and T. J. McSweeney, 1998, Deep subduction and aspherical variations in P- wave speed at the base of Earth's mantle, in The core mantle boundary region, edited by M. Gurnis, M. E. Wysession, E. Knittle, and B. A. Buffett, pp5-20, Amer. Geophys. Union
Creager, K. C., 1999, Large-scale variations in inner-core anisotropy, J. Geophys. Res., 104, 23127-23139.
Creager, K. C., 2000, Inner core anisotropy and rotation, Mineral Physics and Seismic Tomography, edited by S. Karato, L. Stixrude, R. Lieberman, G. Masters, A. Forte, Geophys. Monograph Series, Amer. Geophys. Union, in press.
Tanaka, S. and H. Hamaguchi, 1997, Degree one heterogeneity and hemispherical variation of anisotropy in the inner core from PKP(BC) and PKP(DF) times, J. Geophys. Res., 102, 2925-2938.
Vinnik, L., B. Romanowicz and L. Breger, 1994, Anisotropy in the center of the inner core, Geophys. Res. Lett, 21, 1671-1674.
Song, X., 1996, Anisotropy in the central part of the inner core, J. Geophys. Res., 101, 16089-16097.
We plan to pick teleseismic P and PKIKP times for selected PASSCAL experiments and from data in the FARM.