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An Ongoing Search for Active Faults in Major Seismic Zones of Québec, Eastern Canada

Description: 

Southern Québec lies in an intracratonic setting that has experienced historical damaging earthquakes (e.g. 1732 M5.8 Montréal, 1663 M7 Charlevoix, 1935 M6.2 Témiscamingue). Despite the fact that approximately half of Québec’s population lives within one of the identified seismic zones, no studies to date have identified surface-rupturing faults. The lack of paleoseismic datasets and specific earthquake source scenarios impedes hazard estimates and risk preparedness, and is due in part to the province’s very young geomorphic surface. Since the last glacial maximum at ~21 ka, marine and lacustrine deposition dominated until a few thousand years ago, removing much of the Quaternary record of fault activity.

The study aims to develop a systematic criteria for fault scarp identification in this low-relief, deglaciated landscape, by adapting criteria used in the Fennoscandian Peninsula. We manually searched 2016 lidar-derived digital elevation models (DEMs) within three populated seismic zones to identify potential post-glacial surface-rupturing faults. We present the first geomorphic map of possible post-glacial fault scarps in Québec. One scarp was investigated with geophysical surveys, and we excavated the first paleoseismic trench in Québec, which did not find evidence of Quaternary faulting. This study paved the way for paleoseismic studies in the province and created a network of geoscientists/governmental agencies aware of, and invested in, paleoseismic studies. We hope our study can be used to optimize future paleoseismic research in the province of Québec and similar intracratonic deglaciated landscapes.

Session: Cryptic Faults: Advances in Characterizing Low Strain Rate and Environmentally Obscured Faults - I

Type: Oral

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Aube

Student Presenter: Yes

Invited Presentation: Yes

Authors