Quake Characteristics near Canada's Coasts

Ninety percent of earthquakes (EQs) that affect Canadians happen near Canada's coasts and it is crucial to characterize these EQs from coast to coast. A large majority of these EQs occur offshore, indicating potential for tsunamis that directly threaten the coastal population of Canada. Due to the lack of broadband ocean bottom seismometers (BBOBS) in Canada so far, very limited knowledge about any of these EQs has been accumulated. For the next 5 years, I propose to study the characteristics of Canada's coastal quakes (e.g., EQs and landslides) using state-of-the-art methods and unprecedented seismic data recorded by the new BBOBS from the National Facility for Seismic Imaging (NFSI) housed at Dalhousie University. I will focus on the Queen Charlotte Fault (QCF) offshore the west coast of Canada and the western Baffin Bay offshore northeastern Canada.

The QCF is located between the Pacific and North American tectonic plates offshore western Canada and southeast Alaska and sustains high deformation rate (>50 mm/yr). The mechanisms of strain accommodation and primary controls on brittle failure during EQ ruptures along this margin remain unknown due to the lack of modern geophysical data and advanced methods. I will take part in a comprehensive Canada-US seismic survey scheduled for 2020-2021 along ~450 km segment of the QCF that encompasses systematic variations in plate boundary obliquity. Sixty-two BBOBS will be deployed for 15 months. Small EQs will be detected and located using methods that I have developed. We will develop a state-of-the-art focal mechanism inversion method to determine relative source parameters of small EQs. Our EQs locations and focal mechanisms are anticipated to reveal spatial variations in the detailed seismic structure and deformation mechanism of the plate boundary.

Baffin Bay is situated in a zone of high EQ risk. On June 17, 2017, one of the tallest (100 m-high wave) tsunamis in recorded history devastated the remote settlement of Nuugaatsiaq in western Greenland, directly across Baffin Bay from Nunavut, Canada. I will participate in a multidisciplinary Canadian investigation of the western Baffin Bay. Using machine learning techniques, we will develop a start-of-the-art system for seismicity detection and classification using data from 30 BBOBS to be deployed in the western Baffin Bay during 2020-2021. Integrated with the results of the planned geological and archeological work, we will provide a detailed geohazard map for the study area summarizing the threat from landslides, EQs, and tsunamis.

Source characterization is fundamental but challenging in seismology, which is especially true for focal mechanism inversion of quakes and their classification. My proposed research not only conducts scientific observation but also provides geohazard prediction. I anticipate that our results will be used by multiple organizations such as NRCan, DRDC and local governments, ultimately to the benefit of many Canadians.