This electronic supplement contains Figure S1 showing stacks for four additional global stations. For Figure S1, the four stations were selected because they represent a variety of geological/tectonic settings and because continuous seismic data over a long time span (≥10 years) were available for all of them. It is evident that stations situated in old, stable continental interiors (KMBL, Yilgarn craton in Australia; RAYN, Arabian shield; HYB, Indian shield) feature relatively simple waveforms with clearly recognizable conversion and reverberation phases and low energy levels on the transverse component, whereas waveforms are significantly more complex in young orogens (WUS) or in the presence of sedimentary sequences in the shallow subsurface (UNM). Observed waveforms at station UNM, which is situated in Mexico City, are severely modified by the presence of shallow sediments beneath the station. Although the initial P pulse is sufficiently simple (hinting at rather short source time functions [STFs]), the R component shows long reverberations, and there is significant energy on the T component. This is characteristic of S-wave reverberations in shallow sediment sequences. Station WUS, situated in the northwest Chinese Tien Shan, shows higher-frequency reverberations that are present in both the vertical and radial component. Because this feature is present in the majority of observed waveforms, it is unlikely that it represents a source-side effect; lithospheric-scale structural complexity, for example, from the northward submergence of Tarim basin lithosphere under the Tien Shan, could be responsible for the observed complex P waveforms.
Figure S1. Representative stacks for four seismic stations around the world.
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