Canyon Dam is built to withstand quakes
A May 13 article, “Professor says Thursday’s earthquake took place in fault zone not considered active” regarding the May 11, Magnitude M 5.5 Lake Almanor earthquake contains some inaccuracies regarding the local fault systems and activity levels, and potential risk to Canyon Dam and other nearby Pacific Gas and Electric Company (PG&E) assets. I appreciate that the professor quoted in the article took the time to follow up with the paper to retract some of his statements after doing some additional research.
This newspaper earlier and fairly reported that the quakes caused no damage to Canyon Dam or other PG&E hydropower facilities in Plumas and Butte counties. However, the information in a follow-up article about these quakes being unexpected or surprising are not accurate. Had we been contacted, we would have noted such information is in U.S. Geological data bases and that when a similar earthquake (Magnitude 5.7) occurred in nearly the same area 10 years ago (2013), it was widely reported in the media.
Canyon Dam can withstand quakes more powerful than faults at the lake can produce. PG&E’s most recent seismic hazard assessment for regional hydropower dams (2021) estimated maximum earthquake magnitude potential of between M 6.0 and M 6.7 for several faults in the Lake Almanor fault system that are mapped beneath the reservoir in the vicinity of the May 11 earthquake epicenter. Our analyses of record show the Canyon Dam in the epicentral area is stable for a Magnitude M 7 earthquake at a distance of less than 2 miles from the dam, conservatively enveloping the estimated potential earthquake magnitudes. (The earthquake magnitude scale is logarithmic, meaning the difference between each whole number is a magnitude of 10.)
PG&E collaborates and publishes regional fault and earthquake studies with various government and academic organizations. Interest in this earthquake event has made us aware of a need for greater collaboration between PG&E and Chico State University Earth and Environmental Sciences Department; we have reached out to arrange initial discussions to identify potential areas of mutual research interest.