For a little more than three days this week, Kilauea volcano went through what scientists believe was an earthquake in slow motion.

From late Sunday night through early Thursday morning, scientists recorded 144 small earthquakes under the volcano, most too faint to be felt.

About 100 of those earthquakes were part of what scientists call a "slow-slip" or silent earthquake.

Michael Poland, a geophysicist with the Hawaiian Volcano Observatory, estimated that the south flank of Kilauea moved about an inch and a half toward the ocean.

If the movement had been a regular or "fast" earthquake, the magnitude would have been 5.5 or even 6.0, Poland said.

That kind of earthquake could have damaged buildings. Instead, the energy was released over several days and was barely felt.

"It’s very similar to a fast earthquake," Poland said. "It just takes a lot longer. Instead of sliding very quickly, the faults slide very slowly."

In fact, the ground movement is about a trillion times slower than a regular earthquake, where the slip happens within a few seconds or even fractions of a second.

These slow earthquakes are also called silent earthquakes because the slip does not create seismic waves. Instead, the smaller earthquakes are apparently triggered by the slow movement of the earth.

The phenomena of slow earthquakes was discovered at Kilauea about 10 years ago when scientists in Hawaii noticed that the small earthquake swarms were associated with the movement of the volcano along a fault where the volcano rests on the ocean floor.

The discovery of slow-slip earthquakes in Hawaii led to other discoveries that similar earthquakes happen all over the world, including on the San Andreas fault on the U.S. West Coast.

Scientists also figured out that these slow-motion earthquakes happen regularly in Hawaii, roughly every 21⁄2 to three years. This predictability makes these kind of earthquakes especially interesting for researchers, Poland said.

"You can put your ear to the ground because you know when it’s going to happen and where it’s going to happen," he said. "We can’t do this with the big earthquakes."

In January, scientists at the Hawaiian Volcano Observatory and the University of Wisconsin placed an array of instruments around the south flank hoping to record this week’s event.

"The hope is by spending a lot of time studying these events, we can learn more about how faults move in general." Poland said.

Scientists know why earthquakes happen under the volcano.

"The weight of Kilauea, plus the push from the magma pressure, pushes the south flank (of Kilauea) toward the ocean," Poland said.

But what they don’t know is why some earthquakes are slow and why some are fast, or why the slow earthquakes happen so regularly.

Over the next several weeks and months, scientists will look at the data gathered from this week’s event. They will plot movement of the earth and the measureable earthquakes to try to figure out exactly what happened and why, and look for tremors that may have preceeded the slow-motion earthquake.

"The Holy Grail of this is learning how ‘fast’ earthquakes work," Poland said. The research could lead to a better understanding of earthquake faults, perhaps even data that could help scientists predict earthquakes in the future.