While borehole geodetic instruments have existed for over 50 years, in the last decade there has been an exponential increase in their number and substantial refinements in engineering techniques. Coupled with the drive to combine observations across the deformation spectrum into single observatories: strainmeter, atmospheric, seismic, tilt and GPS there has been an explosion of data to synthesize and interpret. Large investments in borehole networks in China, Japan, and the
US and smaller networks in Europe have begun to produce data with exciting discoveries such as short-term strain transients in both seismogenic zones and volcanic areas, hydrological signals, e.g., tsunamis and seiches and the connections between atmospheric pressure changes and slow slip.

This session is open to all aspects of borehole geophysics, with emphasis on borehole geodesy, ranging from installation and operations, through data analysis and synthesis with other observations.