In seismology, a seismic zone or seismic belt is an area of seismicity potentially sharing a common cause. It can be referred to as an earthquake belt as well. It may also be a region on a map for which a common areal rate of seismicity is assumed for the purpose of calculating probabilistic ground motions. An obsolete definition is a region on a map in which a common level of seismic design is required.
>>>PUT SHARE BUTTONS HERE<<<
👉 Seismic zone in the context of Hunga Tonga–Hunga Haʻapai
Hunga Tonga–Hunga Haʻapai () is a submarine volcano in the South Pacific located about 30 km (19 mi) south of the submarine volcano of Fonuafoʻou and 65 km (40 mi) north of Tongatapu, Tonga's main island. It is part of the highly active Kermadec-Tonga subduction zone and its associated volcanic arc, which extends from New Zealand north-northeast to Fiji, and is formed by the subduction of the Pacific Plate under the Indo-Australian Plate. It lies about 100 km (62 mi) above an active seismic zone. The volcano rises around 2,000 m from the seafloor and has a caldera which on the eve of the 2022 eruption was roughly 150 m below sea level and 4 km at its widest extent. The only major above-water part of the volcano are the twin uninhabited islands of Hunga Tonga and Hunga Haʻapai, which are respectively part of the northern and western rim of the caldera. As a result of the volcano's eruptive history, the islands existed as a single landmass from 2015 to 2022: they were merged by a volcanic cone in a volcanic eruption in 2014–2015, and were separated again by a more explosive eruption in 2022, which also reduced the islands in size. The Hunga Tonga–Hunga Haʻapai volcano has seven historical recorded eruptions.
The most recent eruption, in January 2022, triggered a tsunami that reached the coasts of Japan and the Americas, along with a volcanic plume that soared 58 km (36 miles) into the mesosphere. It was the largest volcanic eruption since the 1991 eruption of Mount Pinatubo and the biggest explosion recorded in the atmosphere by modern instrumentation, far surpassing any 20th-century volcanic event or nuclear bomb test. NASA determined that the eruption was "hundreds of times more powerful" than the atomic bomb dropped on Hiroshima. It is believed that the 1883 eruption of Krakatoa is the only eruption in recent centuries that rivaled the atmospheric disturbance it produced. The January 2022 eruption is the largest volcanic eruption in the 21st century.
In this Dossier
Seismic zone in the context of Wadati–Benioff zone
A Wadati–Benioff zone (also Benioff–Wadati zone or Benioff zone or Benioff seismic zone) is a planar zone of seismicity corresponding with the down-going slab in a subduction zone. Differential motion along the zone produces numerous earthquakes, the foci of which may be as deep as about 670 km (420 mi). The term was named for the two seismologists, Hugo Benioff of the California Institute of Technology and Kiyoo Wadati of the Japan Meteorological Agency, who independently discovered the zones.
Wadati–Benioff zone earthquakes develop beneath volcanic island arcs and continental margins above active subduction zones. They can be produced by slip along the subduction thrust fault or slip on faults within the downgoing plate, as a result of bending and extension as the plate is pulled into the mantle. The deep-focus earthquakes along the zone allow seismologists to map the three-dimensional surface of a subducting slab of oceanic crust and mantle.