Smaller Earthquakes

On October 22nd, 2018, three fairly large earthquakes (two M6.5 and one M6.8) struck off shore, SW of Port Hardy, Canada. They occurred at 9:39 pm, 10:16 pm, 10:22 pm (PST), respectively. Each sent a notification to my phone. Seeing one earthquake in the region this size doesn’t phase me much. Seeing three this large back-to-back had my heart racing. This page was born out of that night’s anxiety, it’s research illuminating the frequency of the relatively ‘smaller earthquakes’ offshore.

Some perspective:
Since 1980, the region has had 43 earthquakes ranging from magnitude 6.0-6.9. We have also had 5 in the M7 range near the Mendocino triple junction where the Gorda plate, the North American Plate and the Pacific Plate all meet (very active region!). Note:

These coordinates are used as ‘the region’ for all analyses derived from the USGS data.

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A look at all earthquakes in the region for magnitudes 4 and above (M4+)
Between 1/1/1990 & 9/9/2021, the region has experienced a range of these “smaller quakes” (i.e. not M8 or 9.0 megaquakes) from a mere 23 in 1993 to a whopping 156 in 2008!

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Below is a look at the number of M4+ earthquakes/month since 1980 (divided into 4 “decade” charts for easier viewing). Data derived from USGS queries.

Anything smaller than a magnitude 4 earthquake is so commonplace that I have turned off notifications for them in my earthquake alert phone applications. That said, curiosity had me running the data for magnitude 3 range earthquakes. Here are the yearly (top chart) and monthly counts (second chart) from 1990 through 2020. In them, we see that the past twelve years, while busy, look quieter than the previous nineteen.

USGS Query

I’ve added this page because I think it’s important to know when to be worried. Yes, history shows us we may not be far off from a major earthquake, but seeing articles in the paper about these smaller quakes should not be cause for alarm. Use the headlines as reminders that we live in earthquake country. Being 2-weeks-ready is just smart.