Ambient-noise tomography study of northwestern Canada: Preliminary results

English Abstract:

Due to the ongoing collision of the Yakutat block onto the North American continental plate in south-eastern Alaska, a significant amount of deformation is occurring in the northern Canadian Cordillera. The stress transfer associated with the accretion of this terrane is believed to be responsible for the seismicity in the area. Estimates of crustal thickness within the mountain belt provide constraints on models describing the evolution of crustal roots responsible for supporting such belts that transmit tectonic stresses over long distances (>1000 km); unfortunately, current models have low resolution due to sparse coverage by seismograph networks Here we use data from a new regional seismograph network (Yukon-Northwest Seismograph Network – YNSN) as well as permanent stations to map out crustal structure. The crustal thickness can be resolved through the use of ambient noise tomography in the determination of the shear wave velocity structure. In this work we present preliminary results of a regional ambient noise tomography study of northwestern Canada, encompassing the northern Canadian Cordillera. First we collected all available vertical component seismic data from stations located in the Yukon and surrounding regions, including stations belonging the YNSN. Using this data set, we cross-correlated hour-long segments of the ambient seismic noise between all available station pairs that share common data availability and obtained virtual Rayleigh waves traveling between the stations, from which we measured group velocity. Our preliminary results will also include group velocity maps over the region of interest.