This grant supports the cost of replacing failed and antiquated air conditioning equipment that is essential for the continuous operation of two long baseline interferometric laser strainmeters in southern California that have been collecting near-continuous strain records for over 20 years, in the case of the Pinon Flats Observatory (PFO), and over 10 years, in the case of the Durmid Hill (DH) instrument. These instruments provide unique and highly sensitive information on short-period transient and secular strain rates proximal to the active transform system of the North American-Pacific plate boundary. In addition, continued operation of these instruments will complement a planned continuous GPS and borehole strainmeter network of instruments that is now under construction along the west coast of the north American continent (the Plate Boundary Observatory (PBO) component of EarthScope). ***
