1872 North Cascades Earthquake Aftershocks

It is necessary to also consider the possibility that felt events **UNRELATED** the the mainshock may have occurred, and that not all felt accounts in the hours, days, weeks and months after the mainshock are due to aftershocks.

Nonetheless, it seems quite clear that the main shock was followed within a half-hour by several major aftershocks that were widely felt, and that additional widely felt shocks occurred later during the night.

The largest of the later aftershocks occurred on January 29, 1873, and was likely felt from Yale, B.C. to Walla-Walla.

The verbatim accounts of aftershocks are best separated in the following manner:

• Timed information about specific aftershocks
• Two or three shocks, presumably close together in time and immediately after the main shock.
  
  • Fort Lapwai ID (two shocks separated by a very slight interval)
  • Kittitas Valley W.T. (two more, lighter and shorter than first)
  • Klickitat, W.T. ( Second and third shocks of shorter duration)
  • Matsqui, Brit. Col. (Two distinct shocks, second less severe and shorter)
  • O'Hamet, Brit. Col. (Two distinct shocks, second lighter and shorter duration)
  • Reed's Ferry ID (Two others of less duration and violence)
  • Steilacoom, W.T. (Two distinct shocks [this includes the main shock??? RSL] accompanied by several minor shivers)
  • Walla Walla, W.T. (Two distinct shocks [this includes the main shock RSL])
  • Umatilla, Oregon (Three shakes [this includes the main shock RSL])
• Multiple aftershocks during the night of December 14-15, no specific time given:
  • Colville W.T. (several lighter shocks in the next five hours)
  • Fort Simcoe W.T. (Almost every half-hour until 5 A.M.)
  • Texas Ferry, W.T. (Ten to twelve more shocks during the night, none as severe as the first
  • Wallula, W.T. (Main shock followed by five lighter shocks at 15 minute intervals. Continued at irregular intervals until 4 A.M.
  • Wenatchee, W.T. Lasted until 5:00 Sunday morning, 64 shocks in all, eight severe. Six distinct shocks
  • Snoqualamie W.T. (13 before daylight; one as heavy as the first)
  • The Dalles, OR (Four or five shocks)
  • Walla Walla, W.T. (during the night others were felt)
• Aftershock activity from Dawn Dec. 15-Dec. 17, without definite times.
  • Colville W.T. ("trembling continued at intervals, for two or three days"; "continued at brief intervals for ten days")
• Aftershock activity from Dec. 17- end of December, without definite times.
• Aftershock activity from Dec. 14 - March, 1873 , Dates vague, without definite times.
• Persistant aftershock activity, without definite times, was reported for a few places.