Insurance Journal-By Khosrow Shabestari and Claire Pontbriand | September 9, 2013
It was June 15, 1990, when Mount Pinatubo, on the island of Luzon in the Philippines, awoke from its 500-year slumber to produce the second largest volcanic eruption of the 20th century.
Nearly a year before, Luzon was shaken by a magnitude 7.8 earthquake epicentered about 60 miles northeast of the volcano. Thousands of smaller earthquakes also occurred in the months leading up to the eruption as magma moved toward the surface from more than 20 miles below the volcano. Like most volcanoes, Mount Pinatubo is located along the boundary of tectonic plates. It is here where massive pieces of the Earth’s rigid outer shell, or lithosphere, converge or diverge, producing most seismic and volcanic activity.
But volcanoes and seismic hazards exist as well in the interior of tectonic plates. The Hawaiian Islands, for example, sit well within the interior of the vast Pacific Plate. On Hawaii, earthquakes accompany the movement of magma within and under active volcanoes such as Mauna Loa, Kilauea, and Hualalai, and sometimes release the strain that accumulates along the flanks of these volcanoes.
These and other volcanoes also influence Hawaii’s seismicity, as their heavy weight can stress the Pacific lithosphere to the point of triggering an earthquake. The culmination of these risks produces seismic hazard on the south side of Hawaii Island that is comparable to that of coastal California, even though Hawaii is far from any plate boundary.
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