Ground motion simulations for finite-fault earthquake scenarios on the Húsavík-Flatey Fault, North Iceland

• Main Authors: Abril, Claudia, Mai, Paul Martin, Halldórsson, Benedikt, Li, Bo, Gabriel, Alice-Agnes, Ulrich, Thomas
• Other Authors: Computational Earthquake Seismology (CES) Research Group, Earth Science and Engineering Program, Physical Science and Engineering (PSE) Division, Icelandic Meteorological Office - IMO, Reykjavik, Iceland, University of Iceland, Reykjavik, Iceland, Ludwig Maximilian University, LMU, Münich, Germany
• Format: Conference Object
• Language: unknown
• Published: Copernicus GmbH 2021
• Subjects: Kolbeinsey; Kolbeinsey Ridge; Mid-Atlantic Ridge; Tjörnes; Húsavík; Iceland; Flatey
• Online Access: http://hdl.handle.net/10754/667941; https://doi.org/10.5194/egusphere-egu21-15557

The Tjörnes Fracture Zone (TFZ) in North Iceland is the largest and most complex zone of transform faulting in Iceland, formed due to a ridge-jump between two spreading centers of the Mid-Atlantic Ridge, the Northern Volcanic Zone and Kolbeinsey Ridge in North Iceland. Strong earthquakes (Ms>6) have repeatedly occurred in the TFZ and affected the North Icelandic population. In particular the large historical earthquakes of 1755 (Ms 7.0) and 1872 (doublet, Ms 6.5), have been associated with the Húsavı́k-Flatey Fault (HFF), which is the largest linear strike-slip transform fault in the TFZ, and in Iceland. We simulate fault rupture on the HFF and the corresponding near-fault ground motion for several potential earthquake scenarios, including scenario events that replicate the large 1755 and 1872 events. Such simulations are relevant for the town of Húsavı́k in particular, as it is located on top of the HFF and is therefore subject to the highest seismic hazard in the country. Due to the mostly offshore location of the HFF, its precise geometry has only recently been studied in more detail. We compile updated seismological and geophysical information in the area, such as a recently derived three-dimensional velocity model for P and S waves. Seismicity relocations using this velocity model, together with bathymetric and geodetic data, provide detailed information to constrain the fault geometry. In addition, we use this 3D velocity model to simulate seismic wave propagation. For this purpose, we generate a variety of kinematic earthquake-rupture scenarios, and apply a 3D finite-difference method (SORD) to propagate the radiated seismic waves through Earth structure. Slip distributions for the different scenarios are computed using a von Karman autocorrelation function whose parameters are calibrated with slip distributions available for a few recent Icelandic earthquakes. Simulated scenarios provide synthetic ground motion and time histories and estimates of peak ground motion parameters (PGA and PGV) at low ...