Global synthetic seismograms using a 2-D finite-difference method
Two-dimensional (2-D) finite-difference (FD) synthetics, which fill the gap between fast 1-D analytic synthetics and time-consuming full 3-D synthetics in our ability to model seismograms, have been used in many studies. We address several issues involving 2-D FD methods in generating global synthetic seismograms. These include: (1) interfacing point source excitation for earthquakes with 2-D FD methods; (2) out-of-plane spreading corrections and (3) reducing the spherical Earth to the flattened models. The first issue is tackled using two methods, a 'transparent source box' approach and a moment tensor excitation approach, where each has its own advantages. Moreover, our 'source box' excitation does not have the late-time drift problem that occurred in previous studies. The out-of-plane geometric spreading correction is accounted for by estimating the ray parameter and applying a post-simulation filter to 2-D synthetics. Finally, parameters of the Earth-flattening transformation are discussed and validated. The effectiveness of this method is demonstrated by comparing our synthetics with frequency–wavenumber summation, normal-mode and 3-D spectral-element synthetics.
Additional Information© 2014 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society Accepted 2014 February 6. Received 2014 February 5; in original form 2013 September 20. First published online: March 1, 2014. We thank the Editor and two anonymous reviewers for their comments which greatly improved the manuscript. Data were provided by the IRIS data center and EarthScope USArray. This work was supported by NSF EAR-1053064 and CSEDI EAR-1161046 at Caltech, with partial support of D. Sun at USC under EAR-0809023.
Published - Geophys._J._Int.-2014-Li-1166-83.pdf