Comparing Hawaii and South Carolina’s Devastating Earthquakes

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MYRTLE BEACH, SC (WMBF) – The tropical paradise of Hawaii is being shaken to its core with a cataclysmic combination of volcanoes and earthquakes. While our state doesn’t have any volcanoes in our backyard, South Carolina is the epicenter of the largest earthquake ever to strike the Eastern U.S.

“The earthquakes in Hawaii is different from the earthquakes we normally sense.”

Dr Zhixiong Shen, a CCU professor of coastal hazards, explains the culprit behind Hawaii’s recent earth-shaking activity.

“Those earthquakes are not generated by plate tectonics. Instead it is generated by the rising magma. When magma is rising upwards, it will push rocks around, and it will try to get into the cracks of rocks and then it will eventually break the rocks, and this breaking of the rocks will generate an earthquake.”

According to Dr. Shen, these volcano-generated quakes usually remain between a magnitude 4.0 and 6.0, meaning shaking and minor damage.

It’s not just volcanoes and tectonic plate boundaries, but also ancient fault lines that can awaken to cause major earthquakes. This includes South Carolina, and the devastation of the 1886 Charleston earthquake that killed 60 people.

“The earthquake is a so called, “intra-plate earthquake” and geologists have been struggling to explain why these earthquakes occur. The idea is generally that we believe that there were some deeply seeded faults that is occurring in the crust, probably 5 to 10 kilometers deep,” Dr. Shen says.

He adds it’s even more difficult to predict these types of earthquakes because they don’t occur regularly.

Dr. Shen, adds, “From my understanding, the type of earthquake that occurred in Charleston 1886 occurs once every 500 to 600 years. That’s based on geologic record that’s been collected goes back 5,000 to 6,000 years.”

On average, the USGS says South Carolina sees 10 earthquakes a year, most with minor shaking between a magnitude 2.0 and 4.0.

So far in the past 2 weeks the USGS has reported 1200 quakes, the highest being magnitude 6.9. Hawaii’s yearly average is over 100 quakes, with a magnitude 6.0 or greater occurring every 7 to 8 years.

So, what exactly does that number mean?

Seismographs all over the world measure the force of the ground waves that determine the earthquake’s rating. Professor of Coastal Harzards at CCU describes the process of finding the rating and epicenter.

“Seismic waves from the earthquake would be detected by at least 3 seismographs. Then we can workout the exact location of the epicenter and then with more data we can work out the magnitude of the earthquake.” Dr. Shen says.

The US Geological Survey, or USGS, rates earthquakes using the Moment Magnitude scale, similar to the well-known Richter scale.

Anything below a 2 is known as a microearthquake, normally only detected by seismographs

Between 2.0 and 4.0, most people will begin to feel shaking

Between 4.0 and 7.0, the varying degrees of damage begin to be noticed, especially closer to the epicenter

Above 7.0 is destruction and even objects thrown into the air. A 7.0 or greater usually occurs somewhere on earth once a year. South Carolina sees an average of 10 earthquakes a year, most being below a 4.0, in the Midlands and LowCountry.

The radar feature on our WMBF First Alert Weather App has an earthquake layer to get you the latest USGS info for any recent earthquake, anywhere in the world.

APPLE: http://apple.co/1ew0w0h

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