EARTHQUAKES-Bell

When a large earthquake occurs, not only does the ground under your feet rumble, but the entire earth resonates like an enormous gong, and the vibrations can last for weeks. I’m Jim Metzner, and this is the Pulse of the Planet, presented by DuPont.

We’re listening to the sound of a South American earthquake recorded half-way around the world in Ankara, Turkey.

Michael Brown is the chair of the geophysics program at the University of Washington in Seattle.

“This was the Great Bolivian Earthquake of 1994. And it’s unusual in that it’s a very, very deep earthquake, having a rupture about six hundred and thirty kilometers beneath the earth’s surface whereas most earthquakes occur in the upper twenty or so kilometers.”

The Bolivian Earthquake registered around 8.2 on the Richter scale. According to Brown, although quakes of this magnitude typically happen only once or twice every year, millions of smaller ones shake the earth’s surface annually.

“What is perhaps surprising to people is that a large earthquake with these megatons of energy can set the entire earth vibrating like a bell. So an earthquake is like the hammer hitting the bell and the entire planet then resonates with its natural frequencies for periods of weeks following the giant earthquake.”

So why can’t we hear the earth ring like a gong? Well in locations far from the quake, the ground may only moving a few centimeters, and it can take as long as one hour to complete one vibration. So because these vibrations are so slow, they can’t be detected by the human ear. To hear them, scientists speed up recordings of the quake, sometimes taking an hour of real time and compressing it into a fraction of a second. That’s how the recording we’re listening to was made

Pulse of the Planet is presented by DuPont, bringing you the miracles of science. With additional support provided by the National Science Foundation. I’m Jim Metzner.

EARTHQUAKES-Bell

When a large earthquake hits, the entire earth can vibrate for weeks.
Air Date:02/15/2000
Scientist:
Transcript:

When a large earthquake occurs, not only does the ground under your feet rumble, but the entire earth resonates like an enormous gong, and the vibrations can last for weeks. I'm Jim Metzner, and this is the Pulse of the Planet, presented by DuPont.

We're listening to the sound of a South American earthquake recorded half-way around the world in Ankara, Turkey.

Michael Brown is the chair of the geophysics program at the University of Washington in Seattle.

"This was the Great Bolivian Earthquake of 1994. And it's unusual in that it's a very, very deep earthquake, having a rupture about six hundred and thirty kilometers beneath the earth's surface whereas most earthquakes occur in the upper twenty or so kilometers."

The Bolivian Earthquake registered around 8.2 on the Richter scale. According to Brown, although quakes of this magnitude typically happen only once or twice every year, millions of smaller ones shake the earth's surface annually.

"What is perhaps surprising to people is that a large earthquake with these megatons of energy can set the entire earth vibrating like a bell. So an earthquake is like the hammer hitting the bell and the entire planet then resonates with its natural frequencies for periods of weeks following the giant earthquake."

So why can't we hear the earth ring like a gong? Well in locations far from the quake, the ground may only moving a few centimeters, and it can take as long as one hour to complete one vibration. So because these vibrations are so slow, they can't be detected by the human ear. To hear them, scientists speed up recordings of the quake, sometimes taking an hour of real time and compressing it into a fraction of a second. That's how the recording we're listening to was made

Pulse of the Planet is presented by DuPont, bringing you the miracles of science. With additional support provided by the National Science Foundation. I'm Jim Metzner.