coFE

33.4147 degN

115.7985 degW

The site was selected in 2004 in the hope that its depth would offer a noise free-coupling to the weak rocks flanking the San Andreas Fault. We have subsequently found that the walls of the cutting converge slightly following heavy rain giving the appearance of left lateral slip (see data).

Episodic creep events (usually doublets) have twice propagated southward along the fault, arriving at the Salt Creek and Durmid creepmeters several hours or days later.

The rail lines have been offset 10-15 cm where they cross the red to the grey clays flanking the San Andreas Fault at the end of the cutting.

Data

A least squares fit to the long term creep at Ferrum indicates a rate of 1.9 mm/yr, however, this includes a 5 mm left-lateral signal associated with rain. If precipitation events are excluded the slip rate is closer to 3 mm/yr. Triggered slip occurred twice in 2009, and again 4 April 2010.


Numerical data 2004->Feb 2011 may be downloaded here.