P-wave residuals in Canada

Abstract

The aim of this study was to obtain station residuals for the Canadian network, hitherto unavailable, and relate them to tectonics across Canada, since Canada shows large variations in tectonics and has a uniform station net; 1692 short-period, vertical P-wave arrivals at the Canadian seismograph network from 82 events were reread and reduced to residuals with respect to the J–B tables. The epicentral distances of the data vary from 1° to 103°. The events occur mostly along the northern rim of the Pacific with a few sources in the Americas and Asia. For each event a baseline correction was determined and applied to the residuals. Station corrections and distance corrections for 2° intervals were obtained by the method of successive approximations which is shown to be a stable and convergent technique. Station corrections are found to decrease with tectonic age of the stations. In addition, for those stations in several tectonic provinces where heat-flow data exist, the station corrections increase with increasing heat flow. The residuals remaining after subtraction of the station and distance corrections exhibit a complex distribution that implies inhomogeneity in some source regions and beneath some parts of Canada.