Hurricanes arise because of the warm seas of the tropics and subtropics, large amounts of water evaporates. Over the course of days, they gain more and more power. When they hit land, they are threatened with severe damage - by the winds that sweep over the affected regions at up to 300 kilometers per hour, heavy rainfall and murderous waves that hit the shores.
The noise of storms can even be measured with earthquake sensors, researchers have known for a long time. So even the path can track a hurricane across the ocean reasonably well. Now, a team of scientists led by Wenyuan Fan of the Florida State University in Tallahassee has described an unprecedented effect: In offshore marine areas, the storms can cause light earthquakes that are widely measurable on land.
Stormquakes , so the storm quake, call the researchers these tremors, about which they report in an article in the journal "Geophysical Review Letters". These are caused by the waves whipped up by the storm causing the earth's crust to vibrate. On the Atlantic coast off the US and Canada, the Canadian Pacific coast and the Gulf of Mexico, concrete evidence for the resulting surface waves, so-called Rayleigh waves.
Not every hurricane - and certainly not anywhere
Altogether one could prove about 10,000 single small Stormquakes in the data of the years 2006 to 2019, so the team. "The exciting thing is that seismic sources can last from hours to days due to hurricanes," Fan said. There are hurricanes caused by earthquakes, such as the hurricanes "Ike" (2008), "Bill" (2009) and "Irene "(2011) found.
The phenomenon of the Stormquakes, however, does not occur with every hurricane - and by no means in every location. Quakes occur at certain points on the edge of the continental shelf or on benches in the sea. Usually the events are weak, but they can reach a magnitude of up to 3.5.
This is a quake that even inexperienced people just feel when they are at the scene, explains Birger Lühr from the German Geo Research Center in Potsdam, who was not involved in the study. He calls the results "quite interesting scientifically", also because they showed the benefits of large seismic networks for research. Fan and his colleagues evaluated the data from the USArray, a network of mobile seismic stations that had collected data along the US and Canada.
The earth's crust is constantly under tension, explains researcher Lühr. Even small voltage changes were enough to cause quakes. These usually occur in tectonic zones of weakness of the earth's crust. That's not the case with the stormquakes.