John Cassidy

@Earthquakeguy
671 Followers
152 Following
81 Posts
NRCan earthquake seismologist and University of Victoria (Earth and Ocean Sciences) Adjunct Professor. Works with engineers, emergency managers, and communities to minimize the impact of #earthquakes. My thoughts/posts.
ResearchGatehttps://www.researchgate.net/profile/John-Cassidy-5
Geological Survey of Canadahttps://profils-profiles.science.gc.ca/en/profile/dr-john-f-cassidy
Did you feel shaking in the San Francisco Bay area this evening?
Thousands did!
That was a M3.7 earthquake about 18 km south of San Francisco at 6:38 p.m. PT.
Details (USGS): https://earthquake.usgs.gov/earthquakes/eventpage/nc73952475/executive
#Earthquake 13 mi SW of #Camano (#Washington) 22 min ago (local time 19:21:08). Updated map - Colored dots represent local shaking & damage level reported by eyewitnesses. Share your experience via:
📱http://www.emsc-csem.org/lastquake/information_channels/lastquake_app/
🌐http://m.emsc.eu/?id=1563689
LastQuake application

Learn more about EMSC LastQuake application.

EMSC - European-Mediterranean Seismological Centre
Did you feel shaking on the northern #California coast this morning?
That was a M4.7 #earthquake near Ferndale, CA at 8:26 a.m. PT.
Details from the USGS (and report shaking here):
https://earthquake.usgs.gov/earthquakes/eventpage/nc73943821/executive
No tsunami threat.
https://www.tsunami.gov/
@BJDeming
Thanks for your kind words. I always enjoy the posts that you share - thank you!
@BJDeming
Thanks for this. Also - it is great to see you here!
For original notes, photos and damage reports from the Canadian side for the 1944 earthquake - see:
https://articles.adsabs.harvard.edu//full/1945JRASC..39....5H/0000005.000.html
1945JRASC..39....5H Page 5

@Earthquakeguy They still remember this in Massena, as I recall from living in upstate New York. And it was in the Adirondacks that I felt a three-pointer in the early 1980s, though that was centered in New Hampshire (I was in Paul Smiths, attending the college with that name and, believe it or not, living off campus on Easy Street!). Very poorly constructed housing (an old tourist cabin) and the shaking opened kitchen cabinet doors 😎 .

Different source from this, though:

https://www.adirondackalmanack.com/2012/10/the-massena-earthquake-of-1944.html

The Massena Earthquake of 1944 -

Twice within a week recently, earthquakes were felt across the North Country, and just a few minutes later, folks were chattering about it on social media. Mainstream news outlets quickly picked up the story and posted it on their websites. That’s quite a contrast to the early morning hours of September 5, 1944, when the Associated Press agent in Albany received information about an earthquake in northern New York. “Anybody killed?” he asked. When informed no one had been hurt, he showed little interest. Likewise, when the state geologist in Albany was notified that a whole lotta shakin’ was goin’ on, he said, “There is no need to be alarmed. It is improbable they » Continue Reading.

The Adirondack Almanack
#Earthquakes continue ~120 km off the northern end of #VancouverIsland.
Following a few dozen M3-4 earthquakes last Thursday, a M5.5 struck at 4:28 a.m. today.
No damage, no tsunami.
Details:
https://earthquakescanada.nrcan.gc.ca/recent/2023/20230917.1128/index-en.php
If you felt shaking please report it here:
https://earthquakescanada.nrcan.gc.ca/dyfi-lavr/form-en.php?eventid=20230917.1128
See live ground shaking:
https://earthquakescanada.nrcan.gc.ca/stndon/wf-fo/index-en.php#/CN.HOLB..
Earthquake Details (2023-09-17)

@Nazani
Thanks, you are exactly right - the older structures in the east are more susceptible to damage.
There are also differences in the earth - in the East the old and stable rocks transmit seismic waves more effectively (especially the high-frequency shaking that impacts smaller, rigid structures). In the West the younger and more complicated earth structure is better at absorbing seismic waves. If you haven't seen this USGS webpage, you might be interested!
https://www.usgs.gov/news/featured-story/east-vs-west-coast-earthquakes
East vs West Coast Earthquakes | U.S. Geological Survey

Why was an earthquake in Virginia felt at more than twice the distance than a similar-sized earthquake in California? The answer is one that many people may not realize. Earthquakes east of the Rocky Mountains can cause noticeable ground shaking at much farther distances than comparably-sized earthquakes in the West.

Damaging earthquakes in eastern #NorthAmerica ?
Not so often - but, yes.

On this day in 1944 a damaging M5.8 #earthquake struck near Cornwall, #ON and Massena, #NY. Chimneys came crashing down and many masonry structures were damaged. Felt from Quebec City to New York City to Toronto. Details: http://earthquakescanada.nrcan.gc.ca/historic-historique/events/19440905-en.php… http://adsabs.harvard.edu/full/1945JRASC..39....5H

Time flies!
Today marks 125 years of seismic recording of #earthquakes in #Victoria, Canada!
On September 3, 1898, a Milne #seismograph began operation in the basement of the old Customs House building on the Victoria waterfront. It was one of the first seismographs in Canada (and one of very few operating in the world at the time):
http://science.gc.ca/eic/site/063.nsf/eng/97237.html…
48. First Seismographs (1897)

175 objects tell the story of the Geological Survey of Canada and its contributions to the development of Canada since 1842