By Beth Bartel - Fall 2016
Borehole strainmeters in the EarthScope Plate Boundary Observatory measure the shifting and compressing Earth, and are so sensitive they can measure changes in their shape of less than the width of a hydrogen atom. Station B030, in Fall Creek, Oregon, southeast of Eugene, has recorded the waves of many large earthquakes, including the 2011 Tohoku earthquake. Closer to home, it records the regional "silent earthquakes" produced by slow-slip events every 19 months or so. In these events, slip down deep along the subduction-zone interface shows up as a temporary change in the strain field at ~550 ft below the surface, where this instrument lives. Station B030 was installed to better understand how slow-slip events impact the seismic hazard in central Oregon. Some of the rock down its borehole is vesicular, or air-bubble-filled basalt, in which quartz crystals and other minerals grow into the voids. Perhaps most interestingly, station B030 is near an air-conditioned chicken coop!