Smaller Earthquakes

On October 22nd, 2018, the Juan de Fuca plate SW of Port Hardy, Canada had two earthquakes with magnitude’s measuring 6.5 and one 6.8! The three earthquakes (shown below) 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’ off shore.

Some perspective:
Just since 1980, we have had 43 earthquakes in the region shown below 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.

A look at all earthquakes in the region for magnitudes 4 and above (M4+)
Between 1990 & 2020, 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! 2020 ended with just 30 for the year.

Here 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.

Fun Fact: From June 2020 to now (see chart below for a close up of this timeframe), activity in the region has been a bit quiet with only 12 magnitude 4+ earthquakes, averaging just over 1 per month. Similar behavior occurred between April & December of 1993 (14 magnitude earthquakes in 9 months). The average for each of the four decades I ran falls between 4 & 6 of the M4+ earthquakes per month.

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 are overdue, 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.