Crustal thickness variation in south-central Alaska

Crustal thicknesses have been determined by receiver function analysis of broadband teleseismic waveforms recorded during the Broadband Experiment Across the Alaska Range (BEAAR). Typical crust beneath the northern lowlands is 26 km thick, while beneath the mountains it is 35-45 km thick. The transition from thick to thin crust coincides with the location of the Hines Creek fault, a major tectonostratigraphic boundary. Crustal thicknesses determined by receiver functions agree with those predicted from topography assuming Airy type isostasy, suggesting that the Alaska Range is compensated by its crustal root. North of the range, however, the crust is systematically thinner than predicted by simple Airy isostasy. A crustal density contrast of 4.6% across the Hines Creek fault, 2700 kg m(-3) to the north and 2830 kg m(-3) to the south, explains the observed difference between the crustal thicknesses predicted by simple Airy isostasy, and the crustal thicknesses determined by receiver function analysis.