What seems to be the complete run of the Secret Service dime novel magazine (1899-1912, home of the Bradys) is now available in full-text via Google Books. The juvenile Lovecraft was an avid reader in the second half of its run. Search Google Books for: “Secret service” “bradys” -bunch   The Bradys frequently ventured to Chinatown and its underground tunnels, into decaying swamp houses, at least once to the Arctic, several times to Africa, exposed numerous fraudluent magicians and spiritualists, and opium dealers — among other themes that Lovecraft fans will be familiar with.

Chris Perridas has details and photos of the St. Lawrence earthquake of 28th February 1925, which was so powerful that Lovecraft even felt it in New York [at magnitude 9:22]. The quake was experienced over a 2 million square-mile region. A press report is given in full by ChthulhuLives, including a line that makes it relevant to the idea that it may have influenced “The Call of Cthulhu”…

“There is a possibility that the earthquake may have taken place at sea.”

I’ve also found that there was apparently another major earthquake in the “New England-New York-Quebec” area on 9th October 1925. In fact, there seems to have been a whole series of them. For a complete summary of the 1925/26 earthquakes see “SUMMARY OF EARTHQUAKES IN NEW ENGLAND AND VICINITY” in The Spectator: Volume 118, 1927…

“Through the kindness of the Acting Director of the United States Coast and Geodetic Survey, Mr. RL Faris, I have come into possession of an extremely valuable summary of earthquakes in New England and vicinity”

The New England Galaxy wrote…

“There were, in fact, five earthquakes in New England in 1925, on January 7, February 28, April 24, October 9, and November 14.”

Lovecraft may well have linked the earthquakes with the Pickwick Club collapse, perhaps surmising that they had weaked the fabric of the building? Severe building collapse or being trapped under buildings features in a number of stories he wrote around this time.