Resolution of regional seismic models: Squeezing the Iceland anomaly

• Main Authors: Richard M. Allen, Jeroen Tromp
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.411.6033; http://seismo.berkeley.edu/~rallen/pub/2004icesqueeze/2005_AllenTromp_SqueezingIceland_GJI.pdf

We present a resolution study of the velocity structure beneath Iceland as constrained by teleseismic traveltime tomography using data from the HOTSPOT seismic network. This temporary PASSCAL network and the tomographic technique that was used to generate the ICEMAN velocity models are typical of regional seismic studies. Therefore, this study also provides a basis for understanding the resolution of other regional seismic experiments. A suite of tests is used to constrain the range of velocity models that satisfy the traveltime observations on Iceland. These include ray-theoretical squeezing experiments, which attempt to force velocity anomalies into specific geometries while still satisfying the data set, and finite-frequency experiments, which use the spectral-element method (SEM) to simulate full waveform propagation through various 3-D velocity models. The use of the SEM allows the verification of the ray-theoretical ICEMAN models without the assumption of ray theory. The tests show that the ICEMAN models represent an end-member of the range of velocity models that satisfy the data set. The 200-km-width Gaussian-shaped upwelling beneath Iceland, imaged in the ICEMAN models, is at the broadest end of the allowed model range; the peak −2 per cent compressional and −4 per cent shear wave perturbations are lower bounds on the amplitude