Variation in the crustal structure across central Iceland

• Published in: Geophysical Journal International
• Main Authors: Du, Zhijun, Foulger, G. R.
• Format: Text
• Language: English
• Published: Oxford University Press 2001
• Subjects: Articles; Iceland
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/145/1/246; https://doi.org/10.1111/j.1365-246X.2001.00377.x

We determine the crustal structures beneath 12 broad‐band seismic stations deployed in a swath across central Iceland along and around the ICEMELT explosion seismic profile by combining teleseismic receiver functions, surface wave dispersion curves and the waveforms of a large, local event in Iceland. By using teleseisms that approach from different backazimuths, we study lateral structural variability out of the line of the ICEMELT profile. Beneath Tertiary areas, the thickness of the upper crust, as defined by the 6.5 km s−1 velocity horizon, is ∼8 km and the depth to the base of the lower crust, as defined by the 7.2 km s−1 velocity horizon, is ∼29–32 km. Beneath the currently active rift zone the upper crust thins to ∼6.0 km and the depth to the base of the lower crust increases to ∼35–40 km. A substantial low‐velocity zone underlies the Middle Volcanic Zone in the lower crust, which may indicate anomalously high geothermal gradients there. This suggests that the large‐scale thermal centre of the hotspot may be more westerly than northwest Vatnajokull, where it is generally assumed to lie. Simplified description of the results notwithstanding, there is substantial variability in the overall style of crustal structure throughout Iceland, and a clear, tripartite division into upper and lower crusts and a sharp Moho is poorly supported by many of our results. The nature, distinctiveness and continuity of the Moho is variable and in many areas the crust–mantle transition is a zone with enhanced velocity gradients several kilometres thick.