Borehole Strainmeters Observe M4.9 Baja Earthquake

Overview

February 07, 2010

The Borehole Strainmeter (BSM) stations in Southern California observed an interesting sequence of earthquakes located in the Baja region on 12/30/2009. As with previous larger magnitude events there are smaller but with visible areal and shear strain signals. The lower plot shows unfiltered strain data clearly showing the event and the upper plot is low pass filtered to highlight the transient strain signal.

The initial ten boreholes were installed as a baseline for the rest of the project. Extensive reengineering of the surface enclosure and racks were committed to at that time. The original ten sites are being brought to these standards starting with B010.