Data Services Newsletter

Volume 16 : No 1 : Spring 2014

Source time functions

The DMC is now calculating source-time functions (STFs) for M7.0+ earthquakes at GSN and other stations automatically (without human review). The STFs are calculated using point-source synthetic seismograms (theoretical Green’s functions) along with vertical component (LHZ channel) recordings of short-arc Rayleigh waves (R1). STFs are estimated using a simple two-source forward modeling approach by sweeping through the parameter space of two smoothed triangle and/or trapezoid functions of various widths, offset and amplitude and retaining the best fitting solution.

Product overview:
http://ds.iris.edu/ds/products/sourcetimefunction

Results in SPUD:
http://ds.iris.edu/spud/sourcetimefunction

Kuril: STF durations versus Azimuth
STF event summary figure with results alighted by source-to-receiver azimuth. For large unilateral (in one direction) ruptures, an azimuthal pattern emerges where STFs will be compressed at stations in the direction of rupture and longer at stations away from the rupture direction.

by Alex Hutko and Chad Trabant (IRIS Data Management Center)