2012 IRIS Workshop
Extraction of Ambient-Field Green's Functions From Asynchronous US Array Data
Shuo Ma: San Diego State University, Gregory C. Beroza: Stanford University
Conceptual diagram of a new approach to observational seismology showing possibility of linking all stations occupied at all times with asynchronous Green’s functions through a backbone, or fiducial, seismic network. The networks occupied at different times are equivalent to occupy simultaneously. Measurements, shown schematically in green, between two temporary networks shown in black and blue, could be made through our approach.
Full-resolution graphics file in original format: 0043.png
We demonstrated that the coda of station-to-station Green’s functions extracted from the ambient seismic field in southern California reach stability in the microseism band (5 – 10 s) after correlating six months of noise data (Ma and Beroza, GRL, 2012). The coda stability makes it possible to retrieve Green’s functions between stations that operate asynchronously through scattered waves as recorded by a network of fiducial stations that operate during all observing periods. The Green’s functions extracted from asynchronous and synchronous data in southern California have comparable quality as long as stable virtual coda are used, and both show good convergence to the Green’s functions extracted from 1 year of seismic noise with ~50 fiducial stations. In this work, we will extend this approach to the US Array data and explore the stability of the virtual coda and the number and spacing of fiducial stations that are required for the robust asynchronous Green’s functions to be retrieved.
Acknoweldgements: This work was supported by NSF grant EAR-0943885. This research was also supported by the Southern California Earthquake Center. SCEC is funded by NSF Cooperative Agreement EAR-0529922 and USGS Cooperative Agreement 07HQAG0008.
For further reading: Ma, S., and G. C. Beroza (2012), Ambient-field Green’s functions from asynchronous seismic observations, Geophys. Res. Lett., 39, L06301, doi:10.1029/2011GL050755. doi: 10.1029/2011GL050755
Keywords: ambient-field_greens_function, asynchronous_data