Fault near Kendall now deemed active

David Lewis
Tribune reporter

  WHATCOM -- A recently revised seismic hazard map from the U.S. Geological Survey now includes the Boulder Creek Fault that runs north-northeast along the Mount Baker Highway near Kendall.
  The USGS revised its previous assertion that this fault line had been dormant for approximately 30 million years, instead saying that the fault has been active in the last few thousand years.
  “There has been a lot of confusion surrounding this fault,” said Craig Weaver, the USGS’s Pacific Northwest earthquake coordinator who participated with the agency teams that prepared the new seismic hazard map. “It is by no means new, as has been reported.”
  Weaver stated that the Boulder Creek Fault has been under investigation since 2006, when it was located in the Nooksack River valley. The reason that the Boulder Creek Fault is receiving so much attention now, Weaver said, is its inclusion on the new USGS seismic hazard map that is the basis for the entire country’s building codes.
  Weaver believes that the Boulder Creek Fault, once more research is done, could represent major progress in the understanding of plate tectonics in the Pacific Northwest. This is because the Boulder Creek Fault, which is thought to be at least 10 to 12 miles long, may actually be much larger and it is suggested by elevation changes of the Whatcom County shoreline that it actually extends to the Pacific Ocean.
  Additionally noteworthy, according to Weaver, is the Boulder Creek Fault’s repeated breaching of the earth’s surface. This is one of many pieces of evidence suggesting that three earthquakes have occurred at the Boulder Creek Fault within the last 7,500 years. The estimated magnitudes of the three Boulder Creek quakes fall between 6.5 and 6.8 on the Richter Scale.
  Although the fault is noteworthy for being very near the earth’s surface -- an estimated depth of less than one kilometer -- that fact also means that there is greater potential for damage. “These earthquakes can come with extreme consequences,” said Weaver. If the fault is discovered to be much longer than is currently presumed, “the earthquakes produced there could easily climb into the 7 (Richter) range.”
  Northwest Whatcom County, including Bellingham north to Lynden, would likely escape “extreme consequences,” although any earthquakes occurring at Boulder Creek would produce “strong shaking.” For residents of Sumas, Kendall and Abbotsford, B.C., any quake “would have a lot of consequences,” according to Weaver.
  Dr. Garry Rogers of the Geological Survey of Canada described the faults as a “non-event as far as buildings and damage and what we would expect to see.” However, he conceded that older buildings could be more heavily damaged.
  The new maps, released on April 21, really reinforce a commonly known fact: Washington state residents stand a high risk of earthquake-related damages. There are at least 100 acknowledged fault lines within western Washington and Oregon, with the possibility of countless more still being undiscovered.