Recent studies suggest that current seismic activities in the central and eastern regions of the United States may be repercussions of major earthquakes from the 1800s. This research, which examined seismic data from three historical earthquakes, posits that these present-day tremors could be a combination of prolonged aftershocks and regular seismic occurrences.
Understanding the Nature of Aftershocks
Aftershocks, which are smaller quakes following a major earthquake, can persist for days or even years, gradually diminishing over time. They are part of the natural adjustment of the earth’s crust post-earthquake. Although less powerful than the main event, aftershocks can still cause structural damage and hinder recovery efforts.
Reevaluating Seismic Activity
Yuxuan Chen, a geoscientist at Wuhan University and the lead author of the study, explains that current seismic activities in parts of stable North America are believed by some to be aftershocks, while others see them as normal seismic occurrences. The team approached this issue with a new statistical method.
Historical Seismic Events and Their Long-Lasting Impact
In the 1800s, several of the most significant earthquakes in U.S. history occurred in North America’s continental interior. Almost two centuries later, these areas might still be feeling the effects of those past events.
In particular, the 1886 Charleston, South Carolina earthquake, with a magnitude between 6.7 and 7.3, is highlighted. The recent study, published in AGU’s Journal of Geophysical Research: Solid Earth, suggests that this and other historical earthquakes might still be triggering aftershocks in the United States.
Challenges in Distinguishing Between Earthquake Types
The difficulty lies in differentiating between foreshocks, aftershocks, and normal seismic activities. While it’s impossible to identify foreshocks or regular seismic activities until a larger earthquake occurs, scientists can recognize aftershocks. This distinction is crucial for evaluating the future risk of disasters in these regions.
Focusing on Three Major Historical Earthquakes
The research centered on three significant quakes: one in southeastern Quebec, Canada in 1663, a series near the Missouri-Kentucky border from 1811 to 1812, and the 1886 Charleston earthquake. These events, among the largest in stable North America, likely generated numerous aftershocks due to their magnitudes.
Methodology and Findings of the Study
The research involved identifying modern earthquakes likely connected to these historic events, focusing on those within a 250-kilometer radius of the epicenters and with a magnitude of at least 2.5. Using a statistical method called the nearest neighbor method on USGS data, the team analyzed whether recent earthquakes were aftershocks or unrelated seismic activities.
Their findings indicated that while the aftershock sequence from the 1663 earthquake in Quebec has ended, the other two events might still be causing aftershocks centuries later. In the Missouri-Kentucky area, about 30% of earthquakes from 1980 to 2016 were likely aftershocks of the 1811-1812 quakes, and in Charleston, about 16% of recent quakes were probably aftershocks of the 1886 event.
Implications for Seismic Risk Assessment
This study underscores the importance of understanding historical seismic events to accurately assess current and future seismic risks. While background seismicity remains the primary cause of tremors in these regions, the possibility of ongoing aftershocks from historical earthquakes suggests a complex interplay of factors influencing seismic activities.
Reference: “Long-Lived Aftershocks in the New Madrid Seismic Zone and the Rest of Stable North America” by Yuxuan Chen and Mian Liu, published on November 7, 2023, in the Journal of Geophysical Research: Solid Earth.
DOI: 10.1029/2023JB026482
Table of Contents
Frequently Asked Questions (FAQs) about Historic Earthquakes Impact
What is the main finding of the recent seismic study in the U.S.?
The study indicates that current seismic activities in central and eastern U.S. may be aftershocks from major earthquakes in the 19th century.
How do aftershocks work according to the study?
Aftershocks are smaller quakes that follow a major earthquake, potentially lasting for years, and are part of the earth’s natural adjustment process post-earthquake.
What historical earthquakes are considered in this study?
The study focuses on three historical earthquakes: one in southeastern Quebec in 1663, a series near the Missouri-Kentucky border from 1811-1812, and the 1886 Charleston earthquake.
What is the significance of distinguishing between aftershocks, foreshocks, and normal seismic activities?
Distinguishing between these types of seismic activities is crucial for assessing the future disaster risk in the affected regions.
What methodology was used in the study to analyze seismic activity?
The study used a statistical approach called the nearest neighbor method on USGS earthquake data to determine whether recent earthquakes were likely aftershocks or unrelated seismic activities.
What were the key findings regarding the 1663, 1811-1812, and 1886 earthquakes?
The study suggests that the aftershock sequence of the 1663 Quebec earthquake has ended, but the 1811-1812 and 1886 earthquakes may still be causing aftershocks.
Why is understanding historical seismic events important for current seismic risk assessment?
Understanding historical seismic events helps in accurately assessing current and future seismic risks, as past events can influence present-day seismic activities.
More about Historic Earthquakes Impact
- Earthquake Aftershock Research
- Historic Earthquake Impact Study
- Seismic Activity Analysis Methods
- USGS Earthquake Data and Research
4 comments
I think they could’ve explained the methodology a bit more clearly, kinda got lost there…
wow this is really interesting stuff, didnt know that earthquakes from so long ago could still be affecting us today?
Is it just me or does the focus on the 1886 Charleston earthquake seem a bit too narrow? there’s gotta be more examples right?
it’s amazing how science keeps uncovering these hidden connections from the past, never thought about earthquakes this way before!