Analyses of earthquakes in the Western Quebec Seismic Zone using data from the United States Transportable Array

Abstract

The present research investigates the efficacy of the additional seismic stations that were deployed in the Western Quebec Seismic Zone (WQSZ) as part of the US Transportable Array (USTA) during 2013-2015 in the determination of earthquake source parameters in this zone. The study is concentrated on the determination of hypocentre locations of three sets of data: the aftershock sequence of the 2010 Val-des-Bois earthquake; the aftershock sequence of the 2013 Ladysmith earthquake; and, 18 events of magnitude 3.0 or greater that occurred in the WQSZ from January 2013 to mid-July 2015. An attempt is also made to estimate the focal mechanisms of all events with MN≥3 that occurred in the WQSZ during 2013-2015. The relocated hypocentres of the two aftershock sequences using the double-difference algorithm through the hypoDD program and the joint hypocentre determination through VELEST software shows insignificant changes in focal depths (toward shallower depths) and only slight variations in the trend of the seismicity (toward the southwest for the Val-des-Bois aftershock and toward the south-east for the Ladysmith aftershock). Relocation of 18 magnitude 3+ events using the standard travel times method demonstrates more reliable focal depths when both the Canadian National Seismograph Network and the USTA data are used. Although favourable coverage provided by the additional USTA can be slightly more effective in obtaining more accurate hypocentres for small earthquakes, the focal mechanism solutions are not remarkably changed when more data from the combined seismic network are used.ii ACKNOWLEDGMENTS I would first like to express my deep gratitude to my supervisors, Dr. Allison Bent and Dr.Dariush Motazedian, for their continuous support, patience, motivation and immense knowledge. They consistently allowed this study to be my own work, but steered me in the right direction whenever they thought I needed it.Also, I must express my very profound gratitude to my loved ones, my parents for providing me with unfailing support and continuous encouragement throughout my years of study and with special thanks to my husband who provided moral support and my lovely son for his patience and tolerance.