In 2004, a 9.1 to 9.3 magnitude earthquake rocked the Indonesian island of Sumatra. Releasing as much energy as a 100-gigaton bomb, the quake was felt around the world. A quarter of a million people perished or went missing in the tsunami that followed. Not only was it one of the strongest earthquakes recorded since the invention of the seismograph, but it was also one of the longest, at 10 minutes of shaking.
The 1960 Valdivia earthquake in Chile was the strongest ever recorded, with a magnitude from 9.4 to 9.6. The fault that ruptured was anywhere from 500 to 1,000 km long, and the resulting earthquake left about 2 million people homeless.
Both of these were what is called megathrust earthquakes, and they happen when one tectonic plate slips under another. As one plate sinks, sometimes it gets stuck. Tension builds as the plates accumulate energy. Eventually, this tension is released. The subducting plate jolts forward as the upper plate is forced upward in a powerful megathrust. These are the world’s most powerful earthquakes, and unfortunately, they are often some of the longest as well.
Duration is not always the best metric to describe an earthquake. That is because the timing is not always easy to pinpoint. You can define the duration of an earthquake by how long shaking is felt on the ground, but you can also define it by the length of the wavetrain on a seismograph.
In general, the stronger the earthquake, the longer it is. That is because “the rupture speed (how quickly the front of the rupture moves along the fault) does not vary too much, but the size of the fault that breaks during the earthquake does increase with magnitude,” William Frank, a professor specializing in earthquakes and tectonics at the Massachusetts Institute of Technology, explained to Big Think. “The rupture speed of the slip front… stays more or less the same because it depends on the material properties of the rock that hosts the fault. And because most continental rocks are pretty similar, we often see a rupture speed of around 2 km per second.”
As a general rule, the size and duration of an earthquake depend on the length of the fault that slips. When an earthquake begins, we do not necessarily know how big it will be or how long it will last, because the slippage still has to
In general, the stronger the earthquake, the longer it is. That is because “the rupture speed (how quickly the front of the rupture moves along the fault) does not vary too much, but the size of the fault that breaks during the earthquake does increase with magnitude,” William Frank, a professor specializing in earthquakes and tectonics at the Massachusetts Institute of Technology, explained to Big Think. “The rupture speed of the slip front… stays more or less the same because it depends on the material properties of the rock that hosts the fault. And because most continental rocks are pretty similar, we often see a rupture speed of around 2 km per second.”
As a general rule, the size and duration of an earthquake depend on the length of the fault that slips. When an earthquake begins, we do not necessarily know how big it will be or how long it will last, because the slippage still has to
In general, the stronger the earthquake, the longer it is. That is because “the rupture speed (how quickly the front of the rupture moves along the fault) does not vary too much, but the size of the fault that breaks during the earthquake does increase with magnitude,” William Frank, a professor specializing in earthquakes and tectonics at the Massachusetts Institute of Technology, explained to Big Think. “The rupture speed of the slip front… stays more or less the same because it depends on the material properties of the rock that hosts the fault. And because most continental rocks are pretty similar, we often see a rupture speed of around 2 km per second.”
As a general rule, the size and duration of an earthquake depend on the length of the fault that slips. When an earthquake begins, we do not necessarily know how big it will be or how long it will last, because the slippage still has to
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