A network of sensitive seismometers has revealed a new source of earth tremor. Rather than emanating from deep in the Earth’s crust, this disturbance comes from above and is produced by storms at sea. Researchers at Florida State University dubbed the effect a stormquake in a paper in Geophysical Research Letters.
While most earth tremors are jolts lasting a matter of seconds, there is also seismic background noise over a longer time scale. The scientists were exploring these longer-duration events and discovered a type which was highly seasonal and never occurred in summer. Normally seismic activity is indifferent to the seasons, but the meteorological connection became obvious when the researchers found the mystery quakes coincided with major hurricanes and storms.
Stormquakes only occur in a particular set of conditions, requiring long ocean waves striking an ocean bank, an underwater hill on the continental shelf. It is not known yet exactly how waves produce the tremors, but they can continue for hours or days, reaching a magnitude of 3.5 on the Richter scale.
Researchers have long suspected that storms can sometimes trigger earthquakes. Tokyo experienced a magnitude 5.7 quake on 12 October, the day Typhoon Hagibis hit. The new work may help shed light on the complex interaction between weather and seismic activity.
