Skip to main content
U.S. flag

An official website of the United States government

November 30, 2022

A new Science for Everyone web article: Before a volcano erupts, there are typically precursory activities that can be detected on seismometers. Thus, monitoring volcanoes with nearby seismometers is a good way to know when a volcanic eruption may be imminent. However...

map of study area with bathymetry showing earthquake and seismic station locations
(a) The three closest seismic stations (red inverted triangles) to the Tonga eruption are more than ~760 km (~472 mi) away. (b) The timeline of earthquakes (yellow circles) at the Tonga eruption site shows the increase of seismicity immediately after the M5.8 during the initial eruption, followed by decreasing seismicity after the first couple of weeks. (from Kintner et al., 2022)

There are more than 1000 active volcanoes on the planet that are not locally monitored, and some of them are very near potentially impacted populations. One such location is the Tongan capital of Nukuʻalofa, where the only warnings before the nearby (70 km south; 44 mi) Hunga Tonga-Hunga Haʻapai (HTHH) volcano violently erupted on January 15, 2022, were some observed low-energy eruptions starting December 20, 2021, on the islands that form the northwest rim of the submerged caldera.

Without any local seismometers, seismologists at the National Earthquake Information Center (NEIC) had to rely solely on data recorded on the distant seismometers. Although not as straightforward as using nearby recordings, the scientists were able to glean important information about the activity going on beneath and around the caldera before, during, and after the main eruption. The methods they developed could be used for other volcanoes that do not have local monitoring in the event they become more active and threaten a local population.