We use the Love waves of local earthquakes on Iceland to constrain 3D crustal S-velocity variations and Moho depth. The data comes from the broadband HOTSPOT network, a PASSCAL network deployed in Iceland from June 1996 to August 1998.

We apply the method of Partitioned Waveform Inversion to the data set. This method has been shown to be very successful for both continental and oceanic environments at long wavelengths (typically 0.01 to 0.03 Hz), here we use it at a higher frequency band, 0.03 to 0.2 Hz. The scattered energy is larger at higher frequencies, however we are still able to obtain good waveform fits.

Iceland suffers form a large microseismic noise peak between 0.1 and 0.5 Hz. Three events during the HOTSPOT deployment, in the north, southwest and southeast, were sufficiently large that the microseismic noise effect is negligible. This allows simultaneous fitting of the lower frequencies (typically 0.03 to 0.1 Hz) for the bulk crustal velocity and Moho depth, and higher frequencies for upper crustal velocity. Additional events provide useful data in the lower frequency band.

The results of a preliminary analysis of single paths are consistent with an average crustal thickness of 30 km, varying between 20 and 35 km. We see a high velocity gradient in the upper 5 km of crust from ~2 km/s to ~3.5 km/s. The gradient then drops and there is a more steady increase in velocity to ~3.7 km/s just above the Moho. We expect to have a full 3D S-velocity model based on surface wave data for the meeting.