Global Investigation of Seismic Wave Propagation on a Regional Scale

摘要

Th Middle East study is focused on the Turkish and Iranian plateaus and the surrounding regions. Sn amplitude variations are very striking in these areas. Efficient Sn propagation is observed across a major part of the Turkish and Iranian plateaus. However, Sn is strongly attenuated in the northernmost part of the plateaus south of the Black and Caspian Seas, and in the area between these two areas. These regions are characterized, in general, by active tectonism, including volcanism, faulting, and folding. However, this active tectonism is not restricted to the areas of high Sn attenuation, but appears to extend, though with somewhat less apparent activity, beneath a major part of the Turkish and Iranian plateaus. Patterns of lateral variations in the propagation of Lg are not as consistent as those for Sn. Lg propagates efficiently across Turkey, Iran and adjacent regions, but the Lg waves that cross the Turkish and Iranian plateaus are, in general, weak and have relatively long predominant periods of about 2-5 seconds. The Lg phase is not observed when the path of propagation crosses the southern Caspian and the Black Seas, consistent with the available evidence of oceanic-type crustal structure beneath these seas. (Author)