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November 1975 Aftershock Sequence
The M7.7 earthquake is the largest local earthquake ever to be instrumentally recorded by the Hawaiian Volcano Observatory. Although most were too small to be felt, an intense period of aftershocks continued for several months, where thousands of earthquakes were recorded.
Hypocentral map of located earthquakes for the first month following November 29, 1975. The M5.7 foreshock and M7.7 mainshock are outlined in red.
Hypocentral map of located earthquakes for 1976, the year following the November 29, 1975, M7.7 earthquake.
1975 - 1985 daily count of aftershocks in the epicentral region of the M7.7 earthquake. The red dashed line indicates the approximate decay rate. The earthquakes above the red dashed line are associated with intrusive swarms, or shallow earthquakes, that indicate magma movement. The elevated level of counts from December 1982 are attributed to the on going Puʻu ʻŌʻō eruption, which began on January 3, 1983.
Contact: hvowebmaster@usgs.gov
Updated: 14 Dec 1998