Master Thesis- defense by Christoffer Stangerup – Niels Bohr Institute - University of Copenhagen

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Master Thesis- defense by Christoffer Stangerup

Analysis of the 2009-07-07 Baffin Bay Earthquake 
The tectonic processes in the Baffin Bay region are poorly understood. Analysis of earthquakes in the passive margin of Baffin Bay are not prioritized due to the sparse population. Further it is very expensive and not very practical to set up seismographs in the arctic area, which in turn, makes the coverage of seismic stations is very poor. This makes thorough earthquake analysis extremely difficult. However in connection with a receiver function analysis study of the Greenland MOHO (Dahl-Jensen et. al., 2003), additional seismic stations were distributed around Greenland. These stations are not a part of any global seismic network, and data from them are therefore not available for any routine analysis by international datacenters.
In 2009-07-07 a magnitude 6.0 (GCMT) earthquake occurred along the passive margin of Baffin Bay. This thesis seeks to improve the routine processed hypocenter locations and focal mechanisms of the this earthquake. The hypocenter of the earthquake was in this thesis determined to 75.227° latitude, -72.591° longitude and 29.3 km depth. This solution was obtained using a flat layered Earth model and P and S wave arrivals from a total of nine seismic stations, including three stations not available to datacenters (TULE, NEEM and ALE). The epicenter location of this study is located between 15.9 and 11.8 km south of the routinely processed epicenters from the international datacenters: NEIC, EMSC and GCMT.
The focal mechanism of the earthquake was using four different programs (FOCMEC, FPFIT, HASH and PINV). Using first motion P wave polarities from 82 stations the programs calculated fault plane solutions with a maximal azimuthal gap of 42°. The four programs agreed to a primarily strike-slip focal mechanism, which contrast the moment tensor solutions from NEIC and GTMC, that found thrust faulting. It is suggested in this thesis, that the mechanism of the Baffin Bay earthquake started as a primarily strike-slip rupture in the hypocenter calculated in this study, and from there developed into a primarily thrust motion towards the GCMT hypocenter along a fault of approximately 14° strike. The result of this thesis, can contribute to a better understanding of the plate tectonic processes in the region.
Supervisors: Aksel Walløe Hansen, Tine B. Larsen