Map showing earthquake epicenters for the period January 1976-December 1984, in the vicinity of Mauna Loa summit caldera. Cluster of epicenters to the northwest of Mokuaweoweo caldera occurred as earthquake swarm in September 1983, prior to the March 1984 eruption. Earthquake activity beneath the summit caldera increased dramatically in early March 1984 leading into the eruption in late March. The vectors on the map above show the amount of tilt that was measured at sites near the summit between the 1975 and 1984 eruptions. The tilting of all sites away from an area just southwest of the caldera indicates the inflation of a magma chamber located beneath that area. Along with other geodetic data, tilt measurements allow us to estimate the amount of magma moving into the magma chamber, as well as its location. (More information about geodetic monitoring of volcanoes)

Map showing earthquake epicenters for the period January 1974-December 1975, in the vicinity of Mauna Loa summit caldera. Clusters of epicenters to the northwest of the summit caldera and near the intersection of the southwest rift zone and the summit caldera show the locations of earthquake swarms occurring prior to the July 1975 eruption.