Since 1991, the Hawaiian Volcano Observatory (HVO) has maintained a seismic recording station east of Hualālai's summit to monitor the volcano. During this time, not a single earthquake swarm or harmonic tremor, indicative of activity at the volcano, has occurred. Although Hualālai does experience several magnitude-4 earthquakes per year, these are attributed to a deep source off the coast of the north-western rift zone and are not related to the movement of magma. The USGS is currently in the process of upgrading its aging monitoring and telemetry equipment, using American Recovery and Reinvestment Act funds. The agency plans to add another seismometer and three more sensors to help monitor activity. In addition, the HVO uses GPS to measure slight changes in tilt and slope of Hualālai, indicative of magmatic movement. A survey has been conducted every two years since 1986, but no changes have been recorded.