← Back to Sessions

Long-Lived Aftershocks in the New Madrid Seismic Zone and the Rest of the Stable North America

Description: 

Seismicity in the New Madrid seismic zone and the rest of the stable North America has been intensively studied and debated. Some workers view present-day earthquakes there as long-lived aftershocks of historical mainshocks, while others think that they are background earthquakes concentrated in weak zone. Separating aftershocks from background seismicity, however, can be challenging. Here, we used the nearest-neighbor method to identify aftershocks. This method calculates the distance between pairs of events in the space-time-magnitude domain. If the distance is too close to be expected for independent background events that follow the Gutenberg-Richter law and Poisson distribution, they are taken as clustered events (aftershocks). Our results suggest that, depending on the size and location of the 1811-1812 New Madrid mainshocks, 10.7% - 65.0% of the M ≥ 2.5 earthquakes in the New Marid region between 1980 and 2016 are long-lived aftershocks. Similarly, most present-day earthquakes in South Carolina are long-lived aftershocks of the 1886 Charleston earthquake. On the other hand, most contemporary seismicity in Charlevoix, Québec are background seismicity. These results reaffirm the existence of long-lived aftershock sequences in stable North America and suggest that, in stable continents, present seismicity usually includes both background earthquakes and aftershocks. Identifying long-lived aftershocks from background seismicity is important for assessing seismic hazard in the stable North America and other intraplate seismic zones.

Session: Tectonics and Seismicity of Stable Continental Interiors

Type: Oral

Date: 4/19/2023

Presentation Time: 04:30 PM (local time)

Presenting Author: Mian Liu

Student Presenter: No

Invited Presentation: 

Authors