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The 2022-23 Reno, Northern Alberta Earthquake Sequence

Description: 

Although geographically part of western Canada, tectonically, most of Alberta is located within the North American craton and experiences relatively low levels of seismic activity. On 23 November 2022, a very active earthquake sequence began near Reno in northern Alberta with the largest event (M_W 5.1) occurring on November 30. It was the largest earthquake in Alberta in the last twenty years and one of the largest ever recorded there. To date there have been several hundred events in the ongoing sequence including 13 of magnitude greater than 4. We have studied these events to better understand the regional seismotectonics. Our regional centroid moment tensor inversions (RCMT) of the largest events indicate thrust faulting on a NW-SE striking plane at shallow depths (< 5km) and are consistent with the regional NE-SW maximum compressive stress field. Additionally, the surface displacement of the largest event was captured by INSAR and is consistent with our RCMT solutions and points to the NE-dipping plane as the probable fault plane. The maximum displacement is 5 cm. RCMT M_Ws for these events obtained in this analysis are generally significantly smaller than the ML magnitudes routinely used for small earthquakes in Alberta, more typical of cratonic than tectonic Canada. Although RCMT inversions provide robust MWs for moderate and large earthquakes, the relatively long periods modeled render the method unsuitable for small earthquakes. Instead, we are using the coda envelope moment magnitude method, to calibrate the region through the use of ground truth events and then calculate M_W (M_WC) for smaller earthquakes. We also consider how our results may aid in the discrimination of the source of the earthquake sequence.

Session: Tectonics and Seismicity of Stable Continental Interiors

Type: Oral

Date: 4/19/2023

Presentation Time: 11:30 AM (local time)

Presenting Author: Allison L. Bent

Student Presenter: No

Invited Presentation: 

Authors