San Andreas Fault in Santa Cruz Mountains -- large quakes more frequent than previously thought

May 30, 2012

Recent paleoseismic work has documented four surface-rupturing earthquakes that occurred across the Santa Cruz Mountains section of the San Andreas Fault (SAF) in the past 500 years. The research, conducted by the U.S. Geological Survey, with assistance from the California Geological Survey, suggests an average recurrence rate of 125 years, indicating the seismic hazard for the area may be significantly higher than currently recognized. The observations help fill a gap in data on the seismic activity of the SAF in northern California, particularly south of San Francisco.

Geologists Thomas Fumal and Tim Dawson conducted paleoseismic studies at Mill Canyon, near Watsonville, California. They documented evidence for four earthquakes, the most recent being the 1906 M 7.8 San Francisco event. They conclude that each of the three earthquakes prior to the 1906 quake was a large magnitude event that likely ruptured most, or all, of the Santa Cruz Mountains segment, producing similar physical deformation as the 1906 quake.

In addition to filling in a data gap about the SAF in this region, this research adds to the understanding of how the SAF behaves, in particular whether individual segments of the can produce destructive earthquakes and how often. This study joins to a growing body of work that suggests the SAF produces a wider array of magnitudes than previously appreciated in the current models.

Explore further: LLNL scientists simulate 1906 earthquake and possible future tremblors along local faults

More information: "Timing of Large Earthquakes during the past 500 years along the Santa Cruz Mountains Segment of the San Andreas Fault at Mill Canyon, near Watsonville, California," published by BSSA, Vol. 102:3.

Related Stories

Recommended for you

A cataclysmic event of a certain age

July 27, 2015

At the end of the Pleistocene period, approximately 12,800 years ago—give or take a few centuries—a cosmic impact triggered an abrupt cooling episode that earth scientists refer to as the Younger Dryas.

'Carbon sink' detected underneath world's deserts

July 28, 2015

The world's deserts may be storing some of the climate-changing carbon dioxide emitted by human activities, a new study suggests. Massive aquifers underneath deserts could hold more carbon than all the plants on land, according ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

rwinners
not rated yet May 30, 2012
I lived for a time in that area during the 1970's and 80's. If I remember correctly, a more recent quake on the SF Peninsula also produced surface ruptures in the mountains NE of Santa Cruz. Sorry I can't remember which quake it was.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.